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Comments on: Intrahepatic Activity Distribution in Radioembolization with Yttrium-90-Labeled Resin Microspheres Using the Body Surface Area Method—A Less than Perfect Model
Volume 27
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Number 2
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February
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2016
297
Figure 4. Patent right prostatic artery with perfusion of the right hemiprostate. Figure 3. Image after crossing the occlusion shows the typical appearance of the left hemiprostate parenchyma; however, a large (unnamed) collateral to the left pudendal artery is seen (arrow). This vessel was subsequently catheterized, and embolization with Gelfoam was performed.
microspheres (Embozene; CeloNova BioSciences, Inc, San Antonio, Texas). Following left PAE, the right prostatic artery was catheterized, and embolization with 100-μm Embozene particles was performed in the usual manner (Fig 4). The patient was discharged the same day with no complications occurring immediately after the procedure. After 6 months, the patient had sustained symptom improvement with a reduction in his American Urological Society Symptom Index score to 10 and a quality-of-life score of 2. He did report any change in his erectile dysfunction. Crossing of CTOs is well described and used in complex peripheral arterial disease. The experience we describe highlights the technique of crossing a CTO in the setting of a technically challenging PAE. Vascular anatomy in elderly male patients may not always be suitable for catheterization; however, the use of basic peripheral vascular techniques may allow for clinical and technical success. Our patient exhibited multiple risk factors for atherosclerotic disease, including a history of erectile dysfunction, which can be a vascular in nature. We do not routinely perform computed tomography angiography for planning purposes before embolization. A pitfall of computed tomography angiography is that it may not easily reveal complete occlusive disease of heavily calcified and small arteries or arteries with short segment occlusions or small caliber.
Potential risks of crossing a prostatic artery CTO include dissection, vessel perforation or rupture, longer procedural time, and technical failure. Interventional radiologists performing PAE in men with greater risk for atherosclerotic occlusive disease may consider this technique.
REFERENCES 1. Bagla S, Martin CP, van Breda A, et al. Early results from a United States trial of prostatic artery embolization in the treatment of benign prostatic hyperplasia. J Vasc Interv Radiol 2014; 25:47–52. 2. Pisco JM, Tinto HR, Pinheiro LC, et al. Embolisation of prostatic arteries as treatment of moderate to severe lower urinary symptoms (LUTS) secondary to benign hyperplasia: results of short- and mid-term follow-up. Eur Radiol 2013; 23:2561–2572. 3. Schreuder SM, Scholtens AE, Reekers JA, et al. The role of prostatic arterial embolization in patients with benign prostatic hyperplasia: a systematic review. Cardiovasc Intervent Radiol 2014; 37:1198–1219. 4. Bilhim T, Pisco J, Tinto HR, et al. Unilateral versus bilateral prostatic arterial embolization for lower urinary tract symptoms in patients with prostate enlargement. Cardiovasc Intervent Radiol 2013; 36:403–411.
Comments on: Intrahepatic Activity Distribution in Radioembolization with Yttrium-90-Labeled Resin Microspheres Using the Body Surface Area Method—A Less than Perfect Model A.S.P. reports grants from and is a paid consultant for Sirtex Medical (Woburn, Massachusetts). The other author has not identified a conflict of interest. http://dx.doi.org/10.1016/j.jvir.2015.10.016
298
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Letters to the Editor
From: Alexander S. Pasciak, PhD Austin C. Bourgeois, MD The Johns Hopkins University School of Medicine (A.S.P.) Baltimore, Maryland Department of Radiology (A.S.P., A.C.B.) University of Tennessee Graduate School of Medicine University of Tennessee Medical Center 1924 Alcoa Highway Knoxville, TN 37920 Department of Radiology (A.C.B.) Medical University of South Carolina Charleston, South Carolina
Editor: A recent article in JVIR described a retrospective evaluation of the body surface area (BSA) treatment planning method for yttrium-90 radioembolization using resin microspheres in a cohort of 283 treated patients (1). In this work, Grosser et al (1) used these data to point out potential shortcomings with the BSA model and suggest that its use could lead to “overdosage and underdosage … in individual patients.” Although we agree that the BSA method is far from perfect, as correctly pointed out by Grosser et al (1), we also believe there are several important points that the JVIR readership should be aware of when interpreting this paper. Grosser et al (1) present much of their results in terms of activity concentration (AC) averaged over the whole liver volume. Although the use of AC is similar to the average whole liver dose used in a previous article on the BSA method by Lam et al (2), there is one critical difference: The analysis by Lam et al included only patients treated with single-session, whole-liver radioembolization. The patient cohort described in Grosser et al (1) was not limited to whole-liver treatment, yet the authors explicitly state that “prescribed activities” were normalized by the total liver volume to obtain the AC figure of merit. In patients not treated in a single-session bilobar fashion, this normalization has the effect of artificially decreasing AC because the total liver volume normalization factor includes tissue that was not treated. The average absorbed dose to treated liver tissue would have been a more useful figure of merit, which might have resulted in a more favorable relationship (eg, in Figure 2b in the article) (1). Although the method by which AC was used was a point of potential confusion in the analysis by Grosser et al (1), we believe that their general results (ie, see Table 4 in the article) are correct and logical given the construction of the BSA model. The BSA model does not account for liver volume, which may be viewed as a “methodologic shortcoming” of the model, as suggested by the authors. However, the authors’ contention that the BSA model could result in “overdosage and underdosage … in individual patients” is not supported by their data except by pointing out differences in AC for individual
Grosser et al
’
JVIR
patients with outlying liver volumes within their cohort. To determine if underdosage or overdosage occurred in this study cohort (1), an analysis of tumor response, liver toxicity, and adverse events and, ideally, quantification of absorbed dose in the liver from imaging obtained after radioembolization would be required. Because no such data from the outcomes of these patients were included, these points from the authors’ discussion and conclusion should be interpreted with caution. That said, we agree that yttrium-90 radioembolization using resin microspheres has the potential to be more beneficial with a more patientspecific treatment planning method.
REFERENCES 1. Grosser OS, Ulrich G, Furth C, et al. Intrahepatic activity distribution in radioembolization with yttrium-90-labeled resin microspheres using the body surface area method—a less than perfect model. J Vasc Interv Radiol 2015; 26:1615–1621. 2. Lam MG, Louie JD, Abdelmaksoud MH, et al. Limitations of body surface area-based activity calculation for radioembolization of hepatic metastases in colorectal cancer. J Vasc Interv Radiol 2014; 25:1085–1093.
Drs. Grosser et al respond : We appreciate the opportunity to respond to the letter to the editor. We agree with the authors that the body surface area (BSA) method is far from a perfect model for activity calculation in radioembolization. Nevertheless, it is frequently used in clinical practice and has been approved by regulatory bodies for activity calculation in yttrium-90 radioembolization (RE) with resin-based microspheres. In order to improve RE, model-based limitations and constraints must be understood. The aim of our study (1) was therefore to assess the model-based effects in preradioembolization activity calculation. According to our data, we were able to show that the poor correlation of BSA and actual liver volume, combined with the negligibility of absolute liver and tumor volumes, may result in a high variability of the prescribed activity (see Equation 3 in the article [1]). To address a concern regarding the normalization of the prescribed activity expressed in the letter, we refer to the section of our paper entitled Determination of Activity Concentrations (ACs) (1). The normalized AC (see Equation 5 in the article [1]) was calculated from the activity prescribed by the BSA method for a whole-liver treatment (see Equation 3 in the article [1]), as all data necessary for dose calculation had been derived from the whole-liver evaluation. In the case of lobar/segmental RE in further clinical workup, the prescribed activity is reduced in proportion to the treated liver volume. O.S.G. and J.Ri. are paid consultants for Sirtex (North Sydney, Australia) outside the submitted work. H.A. received funding from Sirtex during the conduct of the study. J.Ri. has received funding from Sirtex outside the submitted work. The other author has not identified a conflict of interest. http://dx.doi.org/10.1016/j.jvir.2015.11.036
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Number 2
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February
’
2016
297
Figure 4. Patent right prostatic artery with perfusion of the right hemiprostate. Figure 3. Image after crossing the occlusion shows the typical appearance of the left hemiprostate parenchyma; however, a large (unnamed) collateral to the left pudendal artery is seen (arrow). This vessel was subsequently catheterized, and embolization with Gelfoam was performed.
microspheres (Embozene; CeloNova BioSciences, Inc, San Antonio, Texas). Following left PAE, the right prostatic artery was catheterized, and embolization with 100-μm Embozene particles was performed in the usual manner (Fig 4). The patient was discharged the same day with no complications occurring immediately after the procedure. After 6 months, the patient had sustained symptom improvement with a reduction in his American Urological Society Symptom Index score to 10 and a quality-of-life score of 2. He did report any change in his erectile dysfunction. Crossing of CTOs is well described and used in complex peripheral arterial disease. The experience we describe highlights the technique of crossing a CTO in the setting of a technically challenging PAE. Vascular anatomy in elderly male patients may not always be suitable for catheterization; however, the use of basic peripheral vascular techniques may allow for clinical and technical success. Our patient exhibited multiple risk factors for atherosclerotic disease, including a history of erectile dysfunction, which can be a vascular in nature. We do not routinely perform computed tomography angiography for planning purposes before embolization. A pitfall of computed tomography angiography is that it may not easily reveal complete occlusive disease of heavily calcified and small arteries or arteries with short segment occlusions or small caliber.
Potential risks of crossing a prostatic artery CTO include dissection, vessel perforation or rupture, longer procedural time, and technical failure. Interventional radiologists performing PAE in men with greater risk for atherosclerotic occlusive disease may consider this technique.
REFERENCES 1. Bagla S, Martin CP, van Breda A, et al. Early results from a United States trial of prostatic artery embolization in the treatment of benign prostatic hyperplasia. J Vasc Interv Radiol 2014; 25:47–52. 2. Pisco JM, Tinto HR, Pinheiro LC, et al. Embolisation of prostatic arteries as treatment of moderate to severe lower urinary symptoms (LUTS) secondary to benign hyperplasia: results of short- and mid-term follow-up. Eur Radiol 2013; 23:2561–2572. 3. Schreuder SM, Scholtens AE, Reekers JA, et al. The role of prostatic arterial embolization in patients with benign prostatic hyperplasia: a systematic review. Cardiovasc Intervent Radiol 2014; 37:1198–1219. 4. Bilhim T, Pisco J, Tinto HR, et al. Unilateral versus bilateral prostatic arterial embolization for lower urinary tract symptoms in patients with prostate enlargement. Cardiovasc Intervent Radiol 2013; 36:403–411.
Comments on: Intrahepatic Activity Distribution in Radioembolization with Yttrium-90-Labeled Resin Microspheres Using the Body Surface Area Method—A Less than Perfect Model A.S.P. reports grants from and is a paid consultant for Sirtex Medical (Woburn, Massachusetts). The other author has not identified a conflict of interest. http://dx.doi.org/10.1016/j.jvir.2015.10.016
298
’
Letters to the Editor
From: Alexander S. Pasciak, PhD Austin C. Bourgeois, MD The Johns Hopkins University School of Medicine (A.S.P.) Baltimore, Maryland Department of Radiology (A.S.P., A.C.B.) University of Tennessee Graduate School of Medicine University of Tennessee Medical Center 1924 Alcoa Highway Knoxville, TN 37920 Department of Radiology (A.C.B.) Medical University of South Carolina Charleston, South Carolina
Editor: A recent article in JVIR described a retrospective evaluation of the body surface area (BSA) treatment planning method for yttrium-90 radioembolization using resin microspheres in a cohort of 283 treated patients (1). In this work, Grosser et al (1) used these data to point out potential shortcomings with the BSA model and suggest that its use could lead to “overdosage and underdosage … in individual patients.” Although we agree that the BSA method is far from perfect, as correctly pointed out by Grosser et al (1), we also believe there are several important points that the JVIR readership should be aware of when interpreting this paper. Grosser et al (1) present much of their results in terms of activity concentration (AC) averaged over the whole liver volume. Although the use of AC is similar to the average whole liver dose used in a previous article on the BSA method by Lam et al (2), there is one critical difference: The analysis by Lam et al included only patients treated with single-session, whole-liver radioembolization. The patient cohort described in Grosser et al (1) was not limited to whole-liver treatment, yet the authors explicitly state that “prescribed activities” were normalized by the total liver volume to obtain the AC figure of merit. In patients not treated in a single-session bilobar fashion, this normalization has the effect of artificially decreasing AC because the total liver volume normalization factor includes tissue that was not treated. The average absorbed dose to treated liver tissue would have been a more useful figure of merit, which might have resulted in a more favorable relationship (eg, in Figure 2b in the article) (1). Although the method by which AC was used was a point of potential confusion in the analysis by Grosser et al (1), we believe that their general results (ie, see Table 4 in the article) are correct and logical given the construction of the BSA model. The BSA model does not account for liver volume, which may be viewed as a “methodologic shortcoming” of the model, as suggested by the authors. However, the authors’ contention that the BSA model could result in “overdosage and underdosage … in individual patients” is not supported by their data except by pointing out differences in AC for individual
Grosser et al
’
JVIR
patients with outlying liver volumes within their cohort. To determine if underdosage or overdosage occurred in this study cohort (1), an analysis of tumor response, liver toxicity, and adverse events and, ideally, quantification of absorbed dose in the liver from imaging obtained after radioembolization would be required. Because no such data from the outcomes of these patients were included, these points from the authors’ discussion and conclusion should be interpreted with caution. That said, we agree that yttrium-90 radioembolization using resin microspheres has the potential to be more beneficial with a more patientspecific treatment planning method.
REFERENCES 1. Grosser OS, Ulrich G, Furth C, et al. Intrahepatic activity distribution in radioembolization with yttrium-90-labeled resin microspheres using the body surface area method—a less than perfect model. J Vasc Interv Radiol 2015; 26:1615–1621. 2. Lam MG, Louie JD, Abdelmaksoud MH, et al. Limitations of body surface area-based activity calculation for radioembolization of hepatic metastases in colorectal cancer. J Vasc Interv Radiol 2014; 25:1085–1093.
Drs. Grosser et al respond : We appreciate the opportunity to respond to the letter to the editor. We agree with the authors that the body surface area (BSA) method is far from a perfect model for activity calculation in radioembolization. Nevertheless, it is frequently used in clinical practice and has been approved by regulatory bodies for activity calculation in yttrium-90 radioembolization (RE) with resin-based microspheres. In order to improve RE, model-based limitations and constraints must be understood. The aim of our study (1) was therefore to assess the model-based effects in preradioembolization activity calculation. According to our data, we were able to show that the poor correlation of BSA and actual liver volume, combined with the negligibility of absolute liver and tumor volumes, may result in a high variability of the prescribed activity (see Equation 3 in the article [1]). To address a concern regarding the normalization of the prescribed activity expressed in the letter, we refer to the section of our paper entitled Determination of Activity Concentrations (ACs) (1). The normalized AC (see Equation 5 in the article [1]) was calculated from the activity prescribed by the BSA method for a whole-liver treatment (see Equation 3 in the article [1]), as all data necessary for dose calculation had been derived from the whole-liver evaluation. In the case of lobar/segmental RE in further clinical workup, the prescribed activity is reduced in proportion to the treated liver volume. O.S.G. and J.Ri. are paid consultants for Sirtex (North Sydney, Australia) outside the submitted work. H.A. received funding from Sirtex during the conduct of the study. J.Ri. has received funding from Sirtex outside the submitted work. The other author has not identified a conflict of interest. http://dx.doi.org/10.1016/j.jvir.2015.11.036