- Email: [email protected]
Can Fluorine-18 Fluoroestradiol Positron Emission Tomography–Computed Tomography Demonstrate the Heterogeneity of Breast Cancer In Vivo?
Original Study
Can Fluorine-18 Fluoroestradiol Positron Emission TomographyeComputed Tomography Demonstrate the Heterogeneity of Breast Cancer In Vivo? Zhongyi Yang, Yifei Sun, Yongping Zhang, Jing Xue, Mingwei Wang, Wei Shi, Beiling Zhu, Silong Hu, Zhifeng Yao, Herong Pan, Yingjian Zhang Abstract Clarifying the estrogen receptor extent is important for treatment. We investigated the heterogeneity of estrogen receptor expression in 32 breast cancer patients by using fluorine-18 fluoroestradiol positron emission tomographyecomputed tomography, which demonstrated a conspicuous number of patients with the heterogeneity. Aim: Our study was to investigate the heterogeneity of estrogen receptor (ER) expression among tumor sites by using fluorine-18 (18F) fluoroestradiol (FES) positron-emission tomographyecomputed tomography (PET-CT) imaging. Methods: Thirty-two breast cancer patients underwent both 18F-FES and 18F fluorodeoxyglucose (FDG) PET-CTs from June 2010 to December 2011 in our center (mean age, 53 years; range, 27-77 years). We used the maximum standardized uptake value to quantify ER expression and a cutoff value of 1.5 to dichotomize results into ERþ and ER. The difference of heterogeneity between the initial patients and patients with recurrent or metastatic disease after treatments was assessed by using the c2 test. Also, the 18F-FES uptake was compared with the 18F-FDG uptake by use of Spearman correlation coefficients. Results: A total number of 237 lesions in 32 patients were detected. Among them, most lesions (64.1% [152/237]) were bone metastasis. A striking 33.4-fold difference in 18F-FES uptake was observed among different patients (maximum standardized uptake value range, 0.5 to approximately 16.7), and a 8.2-fold difference was observed among lesions within the same individual (1.0 to approximately 8.2). As for 18F-FDG uptake, the difference was 11.6-fold (1.3 to approximately 15.1) and 9.9-fold (1.4 to approximately 13.8), respectively. In 28.1% (9/32) of the patients, both 18F-FESþ and 18F-FES metastases were present, which suggests partial discordant ER expression. After treatments, 37.5% (9/24) patients with recurrent or metastatic breast cancer showed heterogeneity, whereas no untreated patient was detected to exist discordant ER expression (c2, 4.174; P < .05). In addition, the 18 F-FES uptake showed a weak correlation with the 18F-FDG uptake (r ¼ 0.248; P < .05). Conclusion: 18F-FES and 18 F-FDG uptake varied greatly both within and among patients. 18F-FES PET-CT demonstrated a conspicuous number of patients with the heterogeneity of ER expression. Clinical Breast Cancer, Vol. 13, No. 5, 359-63 ª 2013 Elsevier Inc. All rights reserved. Keywords: Breast cancer, Estrogen receptor, Fluorine-18 fluorodeoxyglucose positron emission tomography, fluorine-18 fluoroestradiol positron emission tomography, Heterogeneity
Zhongyi Yang and Yifei Sun contributed equally to the paper. Department of Nuclear Medicine, Shanghai Cancer Center Department of Oncology, Shanghai Medical College Fudan University, Shanghai, China Submitted: Jul 16, 2012; Revised: Dec 28, 2012; Accepted: Feb 4, 2013; Epub: Jun 17, 2013 Address for correspondence: Yingjian Zhang, MD, Shanghai Cancer Center, Fudan University, no. 270, Dong’an Road, Xuhui District, Shanghai, China Fax: þ86-21-54520250; e-mail contact: [email protected]
1526-8209/$ - see frontmatter ª 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clbc.2013.02.012
Introduction Breast cancer is the most common nondermatologic cancer and the second leading cause of cancer death in women.1 The status of the estrogen receptors (ER) is of prime importance in breast cancer to choose the appropriate therapeutic approach and to determine the prognosis of the illness.2-4 Approximately 75% of the tumors express the ER at diagnosis.5 However, not all the patients respond to the endocrine therapy, and most initial responders later become refractory: the objective response rate to second-line endocrine
Clinical Breast Cancer October 2013
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Heterogeneity Detected by Fluorine-18 Fluoroestradiol therapy is less than 20%.6 One factor hypothesized to underlie unpredictable response and acquired resistance to endocrine therapy is heterogeneity of ER expression. Because the ER status may be discordant within the same patient, a single biopsy may not be representative of the ER characteristics of the tumor burden as a whole.7 In addition, ER expression may also change over time in the same patient, caused either by genetic or epigenetic loss of the receptor, such as ER promoter B associated factor 1.8 Thus, clarifying the extent of within-patient heterogeneity of ER expression is critically important for treatment decision making. Positron emission tomography (PET) with ER-targeting radiopharmaceuticals is a noninvasive method for assessing regional ER expression in vivo. Several studies have shown that fluorine-18 (18F) fluoroestradiol (FES) PET can reliably detect ERþ tumor lesions and that 18F-FES uptake correlates well with immunohistochemical scoring for ER.9-11 Furthermore, low 18F-FES uptake was a strong predictor for failure of antihormonal therapy.12 The advantages of in vivo assessment of ERs include avoiding sampling error and assessing the entire tumor volume receptor status rather than part of the tumor, and assessing the biologic activity of the receptor at diagnosis and in response to treatment.13 Based on the advantages mentioned above, our study was to investigate the within-patient and between-patient heterogeneity of ER expression among tumor sites by using 18F-FES PETecomputed tomography (CT) imaging.
Methods Patient Selection From June 2010 to December 2011, 32 breast cancer patients underwent both 18F-FES and 18F-FDG PET-CTs in our center. The patients were enrolled through one of several protocols: by predicting response to endocrine treatment, the correlation of FES uptake to an in vitro assay of ER, and by using 18F-FES PET-CT as a diagnostic tool for the patients presenting with a clinical dilemma. Concomitant bisphosphonate therapy or trastuzumab was not an exclusionary criterion but concurrent cytotoxic therapy or radiotherapy was. Also, any patient with suspicious liver lesions was not enrolled due to 18F-FES metabolism in the liver. Additional technical requirements for inclusions were performance of a whole-body survey to evaluate all disease sites and access to an 18F-FDG PETCT conducted within 7 days of 18F-FES PET-CT to assist in locating lesions. Multiple scans for the same patient were not included. All of these patients met these criteria. Therefore, 32 patients were analyzed in this study. Our protocol strictly followed the clinical study rules established by our review board, and informed written consent was obtained from all these retrospectively enrolled patients.
PET-CT Imaging
360
-
Patients underwent both 18F-FES and 18F-FDG PET-CT. 18F-FES was prepared according to published methods14 and was modified by us, as reported in our prior study.15 18F-FDG was produced automatically by cyclotron (Siemens CTI RDS Eclips ST, Knoxville, TN) by using the Explora FDG4 module in our center. 18 F-FES and 18F-FDG PET-CT studies were performed on 2 separate days. For the FES study, ER antagonists were discontinued for a minimum of 5 weeks before FES study to prevent
Clinical Breast Cancer October 2013
false-negative results. The use of aromatase inhibitors was allowed. Approximately 6 mCi (222 MBq) of 18F-FES was administered intravenously over 2 minutes. Scanning was initiated 1 hour after administration of the tracer. The images were obtained on a Siemens biograph 16 HR PET-CT scanner. The transaxial intrinsic spatial resolution was 4.1 mm (full width at half maximum) in the center of the field of view. The data acquisition procedure was as follows: CT was first performed, from the proximal thighs to the head, with 120 kV, 80 to approximately 250 mA, pitch 3.6, rotation time 0.5. Immediately after the CT, a PET that covered the identical transverse field of view was obtained. Acquisition time was 2 to approximately 3 minutes per table position. PET image data sets were reconstructed iteratively by applying the CT data for attenuation correction; coregistered images were displayed on a workstation. Before the 18F-FDG PET-CT, all the patients were requested to fast for at least 4 hours. At the time of the tracer injection (dosage, 0.2 mCi/kg), the patients presented with a blood glucose level of less than 10 mmol/L. Before and after injection, the patients were kept lying comfortably in a quiet, dimly lit room. The parameters of PET-CT were the same as 18F-FES PET-CTs.
Image Interpretation Imaging analysis was performed retrospectively. A multimodality computer platform (Syngo; Siemens) was used for image review and manipulation. Two experienced nuclear medicine physicians evaluated the images for each patient independently. The reviewers reached a consensus in cases of discrepancy. Lesions in 18F-FES PET-CTs were identified by using paired 18F-FDG PET-CT images. Images from patients with extensive diseases or ER lesions were also coregistered with 18F-FDG PET-CTs to locate each tumor accurately. Only FDG-avid lesions, which could be detected definitely by PET-CT, were included in the analysis. All the patients were followed up for at least 6 months to confirm these lesions. In our study, only clinically confirmed metastatic lesions were analyzed. Quantification of tumor metabolic activity was obtained by using the standardized uptake value (SUV) normalized to body weight and the maximum SUV (SUVmax) for each lesion was calculated. In reference to other 18F-FES PET studies, we used the SUVmax to quantify ER expression and a cutoff value of 1.5 to dichotomize results into ERþ and ER.11,16 Lesions smaller than 1.5 cm were excluded because of partial-volume limitation and resolution restriction. In patients with widespread bone metastasis, up to 5 of the largest 18F-FES PET lesions that corresponded to the most 18 F-FDG-avid lesions were tabulated for each of 5 areas: skull, thorax (including sternum, scapula, clavicle, and ribs), long bones, spine, and pelvic. If the lesions presented in the same patient with discordant ER expression or the recurrent or metastatic lesions showed different ER status from primary tumor immunohistochemical results, then we considered that there was heterogeneity in these patients.
Statistic Analysis The difference of heterogeneity between initial patients and patients with recurrent or metastatic disease after treatments was assessed by using c2 test. Also, the 18F-FES uptake was compared
Zhongyi Yang et al with 18F-FDG uptake, and the results were reported by use of Spearman correlation coefficients (r). Data were analyzed by SPSS 13.0 software (SPSS Inc, Chicago, IL). All analyses were 2-sided. A 2P < .05 was taken to indicate a significant difference.
Table 1 Patient Characteristics Characteristic Mean (range) age, years
53 (27 to approximately 77)
Purpose of FES PET, no. (%)
Results Patient Characteristics The characteristics of the 32 18F-FES PET-CT studies analyzed for 32 breast cancer patients are summarized in Table 1. All the patients were women. Among them, 8 patients were initial ones, which meant that they did not have any treatment before the scans. The remaining 24 patients had recurrent or metastatic breast cancers after operations and adjuvant treatments.
Predict of response
10 (31.3)
Correlation with in vitro assay of ER
14 (43.7)
Assisting in clinical dilemma
8 (25.0)
Menopausal status, no. (%) Premenopausal
8 (25.0)
Postmenopausal
24 (75.0)
Primary tumor histology, no. (%) Ductal
27 (84.3)
F-FES
Lobular
3 (9.4)
The radiochemical purity of F-FES prepared by us was > 98%. Specific activity was available for 32 scans, with a mean of 137,936 GBq/mmol (range, 93,240-268,842 GBq/mmol) at the time of injection.
Others
2 (6.3)
The Quality Control of
18
18
Heterogeneity of
18
F-FES and
18
F-FDG Uptake
18
F-FES Uptake and
ERþ
28 (87.5)
PR
21 (65.6)
HER2/neuþ
13 (40.6)
Prior adjuvant treatment, no. (%)
Lesion-level characteristics of 18F-FES PET-CTs for the 237 lesions in 32 patients are described in Table 2. Among them, most lesions (64.1% [152/237]) were bone metastasis, and the remaining lesions were located in lymph node, lung, breast, soft tissue, pleura, and adrenal gland, successively. A striking 33.4-fold difference in 18 F-FES uptake was observed between different patients (SUVmax range, 0.5 to approximately 16.7), and a 8.2-fold difference was observed among lesions within the same individual (SUVmax range, 1.0 to approximately 8.2). As for 18F-FDG uptake, the difference was 11.6-fold (SUVmax range, 1.3 to approximately 15.1) and 9.9-fold (SUVmax range, 1.4 to approximately 13.8), respectively. In 28.1% of the patients (9/32), both 18F-FESþ and 18F-FES metastases were present, which suggests partial discordant ER expression (Figure 1). Among them, 6 patients showed discordant ER expression in bone metastasis and 2 patients demonstrated low ER expression in lung metastasis, whereas the other lesions were FES-avid; and 1 patient with lymph node metastasis was FES-absent but the rest of lesions had positive FES results. After treatments, 37.5% (9/24) patient with recurrent or metastatic breast cancer showed heterogeneity, whereas no untreated patient was detected to exist discordant ER expression. There was statistical difference of heterogeneity between these 2 groups (c2, 4.174; P ¼ .041).
The Correlation Between Uptake
Immunology, no. (%)
18
F-FDG
The 18F-FES uptake showed a weak correlation with 18F-FDG uptake as determined by Spearman analysis, r ¼ 0.248 (P < .05).
Discussion Breast cancer is a heterogeneous disease, and there is a continual drive to identify markers that will aid in predicting prognosis and response to therapy. To date, relatively few markers have established prognostic power. Among them, ER is probably the most powerful predictive marker in breast cancer management, both in determining prognosis and in predicting response to hormone
Chemotherapy
22 (68.8)
Radiotherapy
10 (31.3)
Endocrine treatment
20 (62.5)
Abbreviations: ER ¼ estrogen receptor; FES ¼ fluoroestradiol; HER2 ¼ human epidermal growth factor receptor 2; PET ¼ positron emission tomography; PR ¼ progesterone receptor.
Table 2 Lesion Characteristics of Tumor Site
n
Bone
18
F-FES PET-CTs
18
F-FESD
F-FESe
18
152
121
31
Lymph node Lung
54 12
33 2
21 10
Breast Soft tissue
10 5
7 1
3 4
3 1
3 1
0 0
237
168
69
Pleura Adrenal gland Total
Abbreviations: 18F ¼ fluorine 18; CT ¼ computed tomography; FES ¼ fluoroestradiol; PET ¼ positron emission tomography.
therapies.17 ER expression is routinely measured in clinical practice by in vitro assay of biopsy material. Although ER is the strongest predictor of response to hormonal treatment, it is far from perfect. The limitations could be concluded as follows: the technique is semiquantitative, which can result in interobserver variation, and ER scoring depends on the antibody used and delay-to-fixation time.18,19 The recent systematic review by the American Society of Clinical Oncology and the College of American Pathologists revealed that up to 20% of all immunohistochemical determinations worldwide are inaccurate.20 Discordant ER expression between primary tumor and metastatic lesions occurs in 18%-55% of the patients21,22 Hence, guidelines of the European Society for Medical Oncology and National Comprehensive Cancer Network recommend repeated biopsies to
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Heterogeneity Detected by Fluorine-18 Fluoroestradiol Figure 1 A 52-Year-Old Female Breast Cancer Patient (Primary Tumor: Estrogen Receptor [ER] Positive) Underwent Both Fluorine-18 (18F) Fluoroestradiol (FES) and 18F-Fluorodeoxyglucose Positron Emission TomographyeComputed Tomography (PET-CT). We Detected Multiple Bone Metastasis (C, F; CT Images). Both Thoracic Vertebra (Arrows in Left Column) and Right Ilium (Arrows in Right Column) Demonstrated Abnormal 18F-FDG Uptake (A, D; PET Images); Maximum Standardized Uptake Value (SUVmax) was 5.5 and 4.7, Respectively. However, They Showed Different 18F-FES Uptake: Thoracic Vertebra was a Low ER Expression With a SUVmax [ 1.3; Whereas, Right Ilium was High, SUVmax [ 2.7 (B, E PET Images), Which Suggested That she had Heterogeneity Metastatic Lesions
362
-
obtain ER expression.23 Despite these clear indications for rebiopsy, this may not always be feasible because of the characteristics of the lesion (such as location) or the patient (such as comorbidity). In addition, within a single tumor or across lesions within a patient, ER expression can be heterogeneous. Furthermore, physicians may be reluctant to perform biopsies given the invasive nature of the procedure. A noninvasive method to quantify ER expression in all metastatic lesions, therefore, would be valuable.16 As a molecular image modality, 18F-FDG PET can detect a wide variety of tumor sites,24 but it only focuses the glucose metabolism on tumor sites and cannot assist in receptor analysis. Up to now, 18 F-FES PET has been the most successful imaging for ER detection. Preliminary comparison of 18F-FES uptake to immunohistochemistry assay of biopsy material from patients with both primary and metastatic cancer showed a good correlation; and it could be used as a predictive assay for endocrine therapy.13 However, the studies of ER heterogeneity in breast cancer by using this ERtargeting molecular imaging are limited. According to these
Clinical Breast Cancer October 2013
studies, 18F-FES PET detected discordant ER expression in 10% to approximately 37% of breast cancer patients.25-27 In our study, we discovered discordant 18F-FES uptake in 28.1% [9/32] of patients; and this result was similar to the study that contained the largest number of patients so far (37%).25 Also, in a between-patient analysis, we found a great variation both in 18F-FDG and 18F-FES uptake, which suggested that they had different tumor glucose metabolism and ER status. In vitro ER expression predicts response to hormonal treatment in 30% to 70% of untreated patients; however, an objective response is seen in only 7% to 21% of previously treated patients.13 We noted in our study that patients with recurrent or metastatic breast disease after treatments were prone to have a greater incidence of ER heterogeneity compared with untreated patients. It may explain why treated patients were more difficult to benefit from hormonal therapy. Interestingly, we found that the 18F-FES uptake showed a weak correlation with 18F-FDG uptake. It may simply be a
Zhongyi Yang et al statistical fluke. Therefore, the further study should be performed to clarify their relationship. The present study had several limitations. The first was the retrospective nature of the study. Another limitation was the relatively small number of patients, which might have led to the selection bias. Third, because all the patients had malignant tumors, it was impossible for us to obtain immunohistochemistry assay of biopsy material in most patients; we could not compare 18F-FES uptake with the criterion standard. For these reasons, we suggest that further clinical trials should be undertaken, especially a prospective and multicenter study.
Conclusion 18
F-FES uptake and 18F-FDG uptake varied greatly both within and among patients. 18F-FES PET-CT demonstrated a conspicuous number of patients with the heterogeneity of ER expression. Because clarifying ER status in advanced breast cancer is crucial for treatment decision making, 18F-FES PET-CT is particularly promising in the metastatic setting in which patients have widespread lesions, especially bone lesions, which are difficult to biopsy.
Clinical Practice Points The status of the ER is of prime importance in breast cancer
to choose the appropriate therapeutic approach and to determine the prognosis of the illness. This retrospective study with a limited number of breast cancer patients demonstrated a relatively high prevalence of heterogeneity. It may explain why some patients with proven ERþ tumors at first presentation cannot benefit from the endocrine treatment. We strongly suggest that the breast cancer patients undergo an 18 F-FES PET-CT during follow-up, which might avoid some unnecessary endocrine strategy and its accompanying adverse reaction.
Disclosure The authors have stated that they have no conflicts of interest.
References 1. Siegel R, Naishadham D, Jemal A. Cancer statistics, 2012. CA Cancer J Clin 2012; 62:10-29. 2. Clark GM, Sledge GW, Jr, Osborne CK, et al. Survival from first recurrence: relative importance of prognostic factors in 1,015 breast cancer patients. J Clin Oncol 1987; 5:55-61. 3. Rose C, Thorpe SM, Andersen KW, et al. Beneficial effect of adjuvant tamoxifen therapy in primary breast cancer patients with high oestrogen receptor values. Lancet 1985; I:16-9.
4. Bertelsen CA, Giuliano AE, Kern DH, et al. Breast cancers: estrogen and progesterone receptor status as a predictor of in vitro chemotherapeutic response. J Surg Res 1984; 37:257-63. 5. Blamey RW, Hornmark-Stenstam B, Ball G, et al. ONCOPOOL: a European database for 16,944 cases of breast cancer. Eur J Cancer 2010; 46:56-71. 6. Buzdar A, Jonat W, Howell A, et al. Anastrozole, a potent and selective aromatase inhibitor, versus megestrol acetate in postmenopausal women with advanced breast cancer: results of overview analysis of two phase III trials. Arimidex Study Group. J Clin Oncol 1996; 14:2000-11. 7. Fisher B, Redmond CK, Fisher ER. Evolution of knowledge related to breast cancer heterogeneity: a 25-year retrospective. J Clin Oncol 2008; 26:2068-71. 8. Yoshida T, Eguchi H, Nakachi K, et al. Distinct mechanisms of loss of estrogen receptor alpha gene expression in human breast cancer: methylation of the gene and alteration of trans-acting factors. Carcinogenesis 2000; 21: 2193-201. 9. McGuire AH, Dehdashti F, Siegel BA, et al. Positron tomographic assessment of 16 alpha-[18F] fluoro-17 beta-estradiol uptake in metastatic breast carcinoma. J Nucl Med 1991; 32:1526-31. 10. Mintun MA, Welch MJ, Siegel BA, et al. Breast cancer: PET imaging of estrogen receptors. Radiology 1988; 169:45-8. 11. Peterson LM, Mankoff DA, Lawton T, et al. Quantitative imaging of estrogen receptor expression in breast cancer with PET and 18F-fluoroestradiol. J Nucl Med 2008; 49:367-74. 12. Mortimer JE, Dehdashti F, Siegel BA, et al. Metabolic flare: indicator of hormone responsiveness in advanced breast cancer. J Clin Oncol 2001; 19:2797-803. 13. Sundararajan L, Linden HM, Link JM, et al. 18F-Fluoroestradiol. Semin Nucl Med 2007; 37:470-6. 14. Mori T, Kasamatsu S, Mosdzianowski C, et al. Automatic synthesis of 16 alpha[(18)F]fluoro-17beta-estradiol using a cassette-type [(18)F]fluorodeoxyglucose synthesizer. Nucl Med Biol 2006; 33:281-6. 15. Zhang YP, Zhang YJ, Wang MW, et al. Fully automated synthesis of 16a [18F] fluoro-17b-estrogen using Explora GN/LC dual module [in Chinese]. Zhonghua He Yi Xue Za Zhi 2011; 31:196-200. 16. van Kruchten M, Glaudemans AW, de Vries EF, et al. PET imaging of estrogen receptors as a diagnostic tool for breast cancer patients presenting with a clinical dilemma. J Nucl Med 2012; 53:182-90. 17. Payne SJ, Bowen RL, Jones JL, et al. Predictive markers in breast cancer: the present. Histopathology 2008; 52:82-90. 18. Sharangpani GM, Joshi AS, Porter K, et al. Semi-automated imaging system to quantitate estrogen and progesterone receptor immunoreactivity in human breast cancer. J Microsc 2007; 226:244-55. 19. Pusztai L, Mazouni C, Anderson K, et al. Molecular classification of breast cancer: limitations and potential. Oncologist 2006; 11:868-77. 20. Hammond ME, Hayes DF, Dowsett M, et al. American Society of Clinical Oncology/College Of American Pathologists guideline recommendations for immunohistochemical testing of estrogen and progesterone receptors in breast cancer. J Clin Oncol 2010; 28:2784-95. 21. Amir E, Clemons M, Purdie CA, et al. Tissue confirmation of disease recurrence in breast cancer patients: pooled analysis of multi-centre, multi-disciplinary prospective studies. Cancer Treat Rev 2011; 38:708-14. 22. Simmons C, Miller N, Geddie W, et al. Does confirmatory tumor biopsy alter the management of breast cancer patients with distant metastases? Ann Oncol 2009; 20:1499-504. 23. Cardoso F, Fallowfield L, Costa A, et al. Locally recurrent or metastatic breast cancer: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol 2011; 22:vi25-30. 24. Podoloff DA, Ball DW, Ben-Josef E, et al. NCCN task force: clinical utility of PET in a variety of tumor types. J Natl Compr Canc Netw 2009; 7:S1-26. 25. Kurland BF, Peterson LM, Lee JH, et al. Between-patient and within-patient (site-to-site) variability in estrogen receptor binding, measured in vivo by 18F-fluoroestradiol PET. J Nucl Med 2011; 52:1541-9. 26. Linden HM, Stekhova SA, Link JM, et al. Quantitative fluoroestradiol positron emission tomography imaging predicts response to endocrine treatment in breast cancer. J Clin Oncol 2006; 24:2793-9. 27. Mortimer JE, Dehdashti F, Siegel BA, et al. Positron emission tomography with 2-[18F]fluoro-2-deoxy-D-glucose and 16alpha-[18F]fluoro-17beta-estradiol in breast cancer: correlation with estrogen receptor status and response to systemic therapy. Clin Cancer Res 1996; 2:933-9.
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Can Fluorine-18 Fluoroestradiol Positron Emission TomographyeComputed Tomography Demonstrate the Heterogeneity of Breast Cancer In Vivo? Zhongyi Yang, Yifei Sun, Yongping Zhang, Jing Xue, Mingwei Wang, Wei Shi, Beiling Zhu, Silong Hu, Zhifeng Yao, Herong Pan, Yingjian Zhang Abstract Clarifying the estrogen receptor extent is important for treatment. We investigated the heterogeneity of estrogen receptor expression in 32 breast cancer patients by using fluorine-18 fluoroestradiol positron emission tomographyecomputed tomography, which demonstrated a conspicuous number of patients with the heterogeneity. Aim: Our study was to investigate the heterogeneity of estrogen receptor (ER) expression among tumor sites by using fluorine-18 (18F) fluoroestradiol (FES) positron-emission tomographyecomputed tomography (PET-CT) imaging. Methods: Thirty-two breast cancer patients underwent both 18F-FES and 18F fluorodeoxyglucose (FDG) PET-CTs from June 2010 to December 2011 in our center (mean age, 53 years; range, 27-77 years). We used the maximum standardized uptake value to quantify ER expression and a cutoff value of 1.5 to dichotomize results into ERþ and ER. The difference of heterogeneity between the initial patients and patients with recurrent or metastatic disease after treatments was assessed by using the c2 test. Also, the 18F-FES uptake was compared with the 18F-FDG uptake by use of Spearman correlation coefficients. Results: A total number of 237 lesions in 32 patients were detected. Among them, most lesions (64.1% [152/237]) were bone metastasis. A striking 33.4-fold difference in 18F-FES uptake was observed among different patients (maximum standardized uptake value range, 0.5 to approximately 16.7), and a 8.2-fold difference was observed among lesions within the same individual (1.0 to approximately 8.2). As for 18F-FDG uptake, the difference was 11.6-fold (1.3 to approximately 15.1) and 9.9-fold (1.4 to approximately 13.8), respectively. In 28.1% (9/32) of the patients, both 18F-FESþ and 18F-FES metastases were present, which suggests partial discordant ER expression. After treatments, 37.5% (9/24) patients with recurrent or metastatic breast cancer showed heterogeneity, whereas no untreated patient was detected to exist discordant ER expression (c2, 4.174; P < .05). In addition, the 18 F-FES uptake showed a weak correlation with the 18F-FDG uptake (r ¼ 0.248; P < .05). Conclusion: 18F-FES and 18 F-FDG uptake varied greatly both within and among patients. 18F-FES PET-CT demonstrated a conspicuous number of patients with the heterogeneity of ER expression. Clinical Breast Cancer, Vol. 13, No. 5, 359-63 ª 2013 Elsevier Inc. All rights reserved. Keywords: Breast cancer, Estrogen receptor, Fluorine-18 fluorodeoxyglucose positron emission tomography, fluorine-18 fluoroestradiol positron emission tomography, Heterogeneity
Zhongyi Yang and Yifei Sun contributed equally to the paper. Department of Nuclear Medicine, Shanghai Cancer Center Department of Oncology, Shanghai Medical College Fudan University, Shanghai, China Submitted: Jul 16, 2012; Revised: Dec 28, 2012; Accepted: Feb 4, 2013; Epub: Jun 17, 2013 Address for correspondence: Yingjian Zhang, MD, Shanghai Cancer Center, Fudan University, no. 270, Dong’an Road, Xuhui District, Shanghai, China Fax: þ86-21-54520250; e-mail contact: [email protected]
1526-8209/$ - see frontmatter ª 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.clbc.2013.02.012
Introduction Breast cancer is the most common nondermatologic cancer and the second leading cause of cancer death in women.1 The status of the estrogen receptors (ER) is of prime importance in breast cancer to choose the appropriate therapeutic approach and to determine the prognosis of the illness.2-4 Approximately 75% of the tumors express the ER at diagnosis.5 However, not all the patients respond to the endocrine therapy, and most initial responders later become refractory: the objective response rate to second-line endocrine
Clinical Breast Cancer October 2013
- 359
Heterogeneity Detected by Fluorine-18 Fluoroestradiol therapy is less than 20%.6 One factor hypothesized to underlie unpredictable response and acquired resistance to endocrine therapy is heterogeneity of ER expression. Because the ER status may be discordant within the same patient, a single biopsy may not be representative of the ER characteristics of the tumor burden as a whole.7 In addition, ER expression may also change over time in the same patient, caused either by genetic or epigenetic loss of the receptor, such as ER promoter B associated factor 1.8 Thus, clarifying the extent of within-patient heterogeneity of ER expression is critically important for treatment decision making. Positron emission tomography (PET) with ER-targeting radiopharmaceuticals is a noninvasive method for assessing regional ER expression in vivo. Several studies have shown that fluorine-18 (18F) fluoroestradiol (FES) PET can reliably detect ERþ tumor lesions and that 18F-FES uptake correlates well with immunohistochemical scoring for ER.9-11 Furthermore, low 18F-FES uptake was a strong predictor for failure of antihormonal therapy.12 The advantages of in vivo assessment of ERs include avoiding sampling error and assessing the entire tumor volume receptor status rather than part of the tumor, and assessing the biologic activity of the receptor at diagnosis and in response to treatment.13 Based on the advantages mentioned above, our study was to investigate the within-patient and between-patient heterogeneity of ER expression among tumor sites by using 18F-FES PETecomputed tomography (CT) imaging.
Methods Patient Selection From June 2010 to December 2011, 32 breast cancer patients underwent both 18F-FES and 18F-FDG PET-CTs in our center. The patients were enrolled through one of several protocols: by predicting response to endocrine treatment, the correlation of FES uptake to an in vitro assay of ER, and by using 18F-FES PET-CT as a diagnostic tool for the patients presenting with a clinical dilemma. Concomitant bisphosphonate therapy or trastuzumab was not an exclusionary criterion but concurrent cytotoxic therapy or radiotherapy was. Also, any patient with suspicious liver lesions was not enrolled due to 18F-FES metabolism in the liver. Additional technical requirements for inclusions were performance of a whole-body survey to evaluate all disease sites and access to an 18F-FDG PETCT conducted within 7 days of 18F-FES PET-CT to assist in locating lesions. Multiple scans for the same patient were not included. All of these patients met these criteria. Therefore, 32 patients were analyzed in this study. Our protocol strictly followed the clinical study rules established by our review board, and informed written consent was obtained from all these retrospectively enrolled patients.
PET-CT Imaging
360
-
Patients underwent both 18F-FES and 18F-FDG PET-CT. 18F-FES was prepared according to published methods14 and was modified by us, as reported in our prior study.15 18F-FDG was produced automatically by cyclotron (Siemens CTI RDS Eclips ST, Knoxville, TN) by using the Explora FDG4 module in our center. 18 F-FES and 18F-FDG PET-CT studies were performed on 2 separate days. For the FES study, ER antagonists were discontinued for a minimum of 5 weeks before FES study to prevent
Clinical Breast Cancer October 2013
false-negative results. The use of aromatase inhibitors was allowed. Approximately 6 mCi (222 MBq) of 18F-FES was administered intravenously over 2 minutes. Scanning was initiated 1 hour after administration of the tracer. The images were obtained on a Siemens biograph 16 HR PET-CT scanner. The transaxial intrinsic spatial resolution was 4.1 mm (full width at half maximum) in the center of the field of view. The data acquisition procedure was as follows: CT was first performed, from the proximal thighs to the head, with 120 kV, 80 to approximately 250 mA, pitch 3.6, rotation time 0.5. Immediately after the CT, a PET that covered the identical transverse field of view was obtained. Acquisition time was 2 to approximately 3 minutes per table position. PET image data sets were reconstructed iteratively by applying the CT data for attenuation correction; coregistered images were displayed on a workstation. Before the 18F-FDG PET-CT, all the patients were requested to fast for at least 4 hours. At the time of the tracer injection (dosage, 0.2 mCi/kg), the patients presented with a blood glucose level of less than 10 mmol/L. Before and after injection, the patients were kept lying comfortably in a quiet, dimly lit room. The parameters of PET-CT were the same as 18F-FES PET-CTs.
Image Interpretation Imaging analysis was performed retrospectively. A multimodality computer platform (Syngo; Siemens) was used for image review and manipulation. Two experienced nuclear medicine physicians evaluated the images for each patient independently. The reviewers reached a consensus in cases of discrepancy. Lesions in 18F-FES PET-CTs were identified by using paired 18F-FDG PET-CT images. Images from patients with extensive diseases or ER lesions were also coregistered with 18F-FDG PET-CTs to locate each tumor accurately. Only FDG-avid lesions, which could be detected definitely by PET-CT, were included in the analysis. All the patients were followed up for at least 6 months to confirm these lesions. In our study, only clinically confirmed metastatic lesions were analyzed. Quantification of tumor metabolic activity was obtained by using the standardized uptake value (SUV) normalized to body weight and the maximum SUV (SUVmax) for each lesion was calculated. In reference to other 18F-FES PET studies, we used the SUVmax to quantify ER expression and a cutoff value of 1.5 to dichotomize results into ERþ and ER.11,16 Lesions smaller than 1.5 cm were excluded because of partial-volume limitation and resolution restriction. In patients with widespread bone metastasis, up to 5 of the largest 18F-FES PET lesions that corresponded to the most 18 F-FDG-avid lesions were tabulated for each of 5 areas: skull, thorax (including sternum, scapula, clavicle, and ribs), long bones, spine, and pelvic. If the lesions presented in the same patient with discordant ER expression or the recurrent or metastatic lesions showed different ER status from primary tumor immunohistochemical results, then we considered that there was heterogeneity in these patients.
Statistic Analysis The difference of heterogeneity between initial patients and patients with recurrent or metastatic disease after treatments was assessed by using c2 test. Also, the 18F-FES uptake was compared
Zhongyi Yang et al with 18F-FDG uptake, and the results were reported by use of Spearman correlation coefficients (r). Data were analyzed by SPSS 13.0 software (SPSS Inc, Chicago, IL). All analyses were 2-sided. A 2P < .05 was taken to indicate a significant difference.
Table 1 Patient Characteristics Characteristic Mean (range) age, years
53 (27 to approximately 77)
Purpose of FES PET, no. (%)
Results Patient Characteristics The characteristics of the 32 18F-FES PET-CT studies analyzed for 32 breast cancer patients are summarized in Table 1. All the patients were women. Among them, 8 patients were initial ones, which meant that they did not have any treatment before the scans. The remaining 24 patients had recurrent or metastatic breast cancers after operations and adjuvant treatments.
Predict of response
10 (31.3)
Correlation with in vitro assay of ER
14 (43.7)
Assisting in clinical dilemma
8 (25.0)
Menopausal status, no. (%) Premenopausal
8 (25.0)
Postmenopausal
24 (75.0)
Primary tumor histology, no. (%) Ductal
27 (84.3)
F-FES
Lobular
3 (9.4)
The radiochemical purity of F-FES prepared by us was > 98%. Specific activity was available for 32 scans, with a mean of 137,936 GBq/mmol (range, 93,240-268,842 GBq/mmol) at the time of injection.
Others
2 (6.3)
The Quality Control of
18
18
Heterogeneity of
18
F-FES and
18
F-FDG Uptake
18
F-FES Uptake and
ERþ
28 (87.5)
PR
21 (65.6)
HER2/neuþ
13 (40.6)
Prior adjuvant treatment, no. (%)
Lesion-level characteristics of 18F-FES PET-CTs for the 237 lesions in 32 patients are described in Table 2. Among them, most lesions (64.1% [152/237]) were bone metastasis, and the remaining lesions were located in lymph node, lung, breast, soft tissue, pleura, and adrenal gland, successively. A striking 33.4-fold difference in 18 F-FES uptake was observed between different patients (SUVmax range, 0.5 to approximately 16.7), and a 8.2-fold difference was observed among lesions within the same individual (SUVmax range, 1.0 to approximately 8.2). As for 18F-FDG uptake, the difference was 11.6-fold (SUVmax range, 1.3 to approximately 15.1) and 9.9-fold (SUVmax range, 1.4 to approximately 13.8), respectively. In 28.1% of the patients (9/32), both 18F-FESþ and 18F-FES metastases were present, which suggests partial discordant ER expression (Figure 1). Among them, 6 patients showed discordant ER expression in bone metastasis and 2 patients demonstrated low ER expression in lung metastasis, whereas the other lesions were FES-avid; and 1 patient with lymph node metastasis was FES-absent but the rest of lesions had positive FES results. After treatments, 37.5% (9/24) patient with recurrent or metastatic breast cancer showed heterogeneity, whereas no untreated patient was detected to exist discordant ER expression. There was statistical difference of heterogeneity between these 2 groups (c2, 4.174; P ¼ .041).
The Correlation Between Uptake
Immunology, no. (%)
18
F-FDG
The 18F-FES uptake showed a weak correlation with 18F-FDG uptake as determined by Spearman analysis, r ¼ 0.248 (P < .05).
Discussion Breast cancer is a heterogeneous disease, and there is a continual drive to identify markers that will aid in predicting prognosis and response to therapy. To date, relatively few markers have established prognostic power. Among them, ER is probably the most powerful predictive marker in breast cancer management, both in determining prognosis and in predicting response to hormone
Chemotherapy
22 (68.8)
Radiotherapy
10 (31.3)
Endocrine treatment
20 (62.5)
Abbreviations: ER ¼ estrogen receptor; FES ¼ fluoroestradiol; HER2 ¼ human epidermal growth factor receptor 2; PET ¼ positron emission tomography; PR ¼ progesterone receptor.
Table 2 Lesion Characteristics of Tumor Site
n
Bone
18
F-FES PET-CTs
18
F-FESD
F-FESe
18
152
121
31
Lymph node Lung
54 12
33 2
21 10
Breast Soft tissue
10 5
7 1
3 4
3 1
3 1
0 0
237
168
69
Pleura Adrenal gland Total
Abbreviations: 18F ¼ fluorine 18; CT ¼ computed tomography; FES ¼ fluoroestradiol; PET ¼ positron emission tomography.
therapies.17 ER expression is routinely measured in clinical practice by in vitro assay of biopsy material. Although ER is the strongest predictor of response to hormonal treatment, it is far from perfect. The limitations could be concluded as follows: the technique is semiquantitative, which can result in interobserver variation, and ER scoring depends on the antibody used and delay-to-fixation time.18,19 The recent systematic review by the American Society of Clinical Oncology and the College of American Pathologists revealed that up to 20% of all immunohistochemical determinations worldwide are inaccurate.20 Discordant ER expression between primary tumor and metastatic lesions occurs in 18%-55% of the patients21,22 Hence, guidelines of the European Society for Medical Oncology and National Comprehensive Cancer Network recommend repeated biopsies to
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Heterogeneity Detected by Fluorine-18 Fluoroestradiol Figure 1 A 52-Year-Old Female Breast Cancer Patient (Primary Tumor: Estrogen Receptor [ER] Positive) Underwent Both Fluorine-18 (18F) Fluoroestradiol (FES) and 18F-Fluorodeoxyglucose Positron Emission TomographyeComputed Tomography (PET-CT). We Detected Multiple Bone Metastasis (C, F; CT Images). Both Thoracic Vertebra (Arrows in Left Column) and Right Ilium (Arrows in Right Column) Demonstrated Abnormal 18F-FDG Uptake (A, D; PET Images); Maximum Standardized Uptake Value (SUVmax) was 5.5 and 4.7, Respectively. However, They Showed Different 18F-FES Uptake: Thoracic Vertebra was a Low ER Expression With a SUVmax [ 1.3; Whereas, Right Ilium was High, SUVmax [ 2.7 (B, E PET Images), Which Suggested That she had Heterogeneity Metastatic Lesions
362
-
obtain ER expression.23 Despite these clear indications for rebiopsy, this may not always be feasible because of the characteristics of the lesion (such as location) or the patient (such as comorbidity). In addition, within a single tumor or across lesions within a patient, ER expression can be heterogeneous. Furthermore, physicians may be reluctant to perform biopsies given the invasive nature of the procedure. A noninvasive method to quantify ER expression in all metastatic lesions, therefore, would be valuable.16 As a molecular image modality, 18F-FDG PET can detect a wide variety of tumor sites,24 but it only focuses the glucose metabolism on tumor sites and cannot assist in receptor analysis. Up to now, 18 F-FES PET has been the most successful imaging for ER detection. Preliminary comparison of 18F-FES uptake to immunohistochemistry assay of biopsy material from patients with both primary and metastatic cancer showed a good correlation; and it could be used as a predictive assay for endocrine therapy.13 However, the studies of ER heterogeneity in breast cancer by using this ERtargeting molecular imaging are limited. According to these
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studies, 18F-FES PET detected discordant ER expression in 10% to approximately 37% of breast cancer patients.25-27 In our study, we discovered discordant 18F-FES uptake in 28.1% [9/32] of patients; and this result was similar to the study that contained the largest number of patients so far (37%).25 Also, in a between-patient analysis, we found a great variation both in 18F-FDG and 18F-FES uptake, which suggested that they had different tumor glucose metabolism and ER status. In vitro ER expression predicts response to hormonal treatment in 30% to 70% of untreated patients; however, an objective response is seen in only 7% to 21% of previously treated patients.13 We noted in our study that patients with recurrent or metastatic breast disease after treatments were prone to have a greater incidence of ER heterogeneity compared with untreated patients. It may explain why treated patients were more difficult to benefit from hormonal therapy. Interestingly, we found that the 18F-FES uptake showed a weak correlation with 18F-FDG uptake. It may simply be a
Zhongyi Yang et al statistical fluke. Therefore, the further study should be performed to clarify their relationship. The present study had several limitations. The first was the retrospective nature of the study. Another limitation was the relatively small number of patients, which might have led to the selection bias. Third, because all the patients had malignant tumors, it was impossible for us to obtain immunohistochemistry assay of biopsy material in most patients; we could not compare 18F-FES uptake with the criterion standard. For these reasons, we suggest that further clinical trials should be undertaken, especially a prospective and multicenter study.
Conclusion 18
F-FES uptake and 18F-FDG uptake varied greatly both within and among patients. 18F-FES PET-CT demonstrated a conspicuous number of patients with the heterogeneity of ER expression. Because clarifying ER status in advanced breast cancer is crucial for treatment decision making, 18F-FES PET-CT is particularly promising in the metastatic setting in which patients have widespread lesions, especially bone lesions, which are difficult to biopsy.
Clinical Practice Points The status of the ER is of prime importance in breast cancer
to choose the appropriate therapeutic approach and to determine the prognosis of the illness. This retrospective study with a limited number of breast cancer patients demonstrated a relatively high prevalence of heterogeneity. It may explain why some patients with proven ERþ tumors at first presentation cannot benefit from the endocrine treatment. We strongly suggest that the breast cancer patients undergo an 18 F-FES PET-CT during follow-up, which might avoid some unnecessary endocrine strategy and its accompanying adverse reaction.
Disclosure The authors have stated that they have no conflicts of interest.
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