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A Comparison of CT and MRI Imaging for the Staging of Cancer of the Anal Canal
I. J. Radiation Oncology d Biology d Physics
S378
2351
Volume 81, Number 2, Supplement, 2011
A Comparison of CT and MRI Imaging for the Staging of Cancer of the Anal Canal
B. J. Debenham1,2, K. Joseph1,2, D. G. Williams2, K. Tankel1,2, R. C. Hennig1,2 1
University of Alberta, Edmonton, AB, Canada, 2Cross Cancer Institute, Edmonton, AB, Canada
Purpose/Objective(s): Anal canal cancer is a relatively uncommon GI cancer, with an incidence of 1.6 new cases per 100,000 persons per year. Its incidence is rising in the female population, and HPV is recognized as a risk factor for the disease. The AJCC staging manual does not recommend any specific diagnostic imaging tests for the purpose of staging. Most clinical practice guidelines, including those from the NCCN, suggest a DRE, anoscopy, chest imaging, and a CT or MRI of the abdomen and pelvis to stage the disease. Our objective was to compare the benefit of using MRI versus CT in the staging of anal canal patients. Materials/Methods: After institutional ethics review, 24 patients were identified from 2007 to 2010 who received curative-intent treatment for anal canal cancer at the Cross Cancer Institute. All patients had a MRI and CT scan. Their charts were reviewed, and data from the CT report, MRI report, and initial consultation was tabulated. If any information was missing from the CT and MRI reports, the scans were reviewed by a radiologist and that information was tabulated. Results: Based on the CT scans, the anal canal lesion was seen only in 42% (10/24) of cases. The anal canal lesion was visible in 100% (24/24) of the MRI scans. The average largest dimension of the tumor, based on MRI scan, was 4.6cm (minimum 0.8cm, maximum 9.9cm). In comparison with clinical exam findings, MRI scans caused upstaging in 38% (9/24) of patients, and downstaging in 25% (6/24). In comparison with CT scan findings, MRI scans caused upstaging in 75% (18/24) patients, and caused down-staging in 4% (1/24) patients. The average difference between MRI and clinical exam size of tumor was 1.3cm (minimum 0cm, maximum 3.1cm). The average difference in the size of tumor between MRI and CT scan findings, when the lesion was visible on CT images, was 2.7cm (minimum 2.1cm, maximum 9.9cm). MRI detected pathologic lymph nodes in 33% (8/24) cases, while CT detected pathologic lymph nodes in 17% (4/24) cases. MRI was able to detect the depth of wall invasion in 92% of cases (22/24), while CT was able to detect the depth of wall invasion in 13% (3/24). MRI was able to determine the size of craniocaudal extension in 92% (22/24) cases, while this was able to be accurately determined on any CT scan. Conclusions: MRI appears to be a more sensitive test than CT, as it detected a lesion in all of the cases reviewed. MRI was superior to CT in detecting invasion through the bowel wall and for lymph node involvement. There was considerable upstaging of patients using MRI versus CT scans. In addition, MRI provides consistency in T stage assessment compared to clinical evaluation where subjective variation exists. Based on our data , we recommend that MRI should strongly be considered for staging of anal canal cancers. Author Disclosure: B.J. Debenham: None. K. Joseph: None. D.G. Williams: None. K. Tankel: None. R.C. Hennig: None.
2352
Gastrointestinal Normal Tissue Toxicity Prediction In Stereotactic Body Radiotherapy
J. D. Murphy, J. Abelson, M. P. Chung, D. T. Chang, A. C. Koong Stanford University Cancer Center, Stanford, CA Purpose/Objective(s): As the use of hypofractionated stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR) increases, there is a need to define dosimetric constraints to allow the safe delivery of this promising modality. Normal tissue complication probability (NTCP) models have been developed and validated for conventionally fractionated radiation regimens, and there is there is a tendency to extrapolate these models to SBRT. The purpose of this study was to examine the accuracy of conventionally fractionated NTCP models extrapolated to SBRT with esophageal and duodenal toxicity. Materials/Methods: 150 patients treated between 2002 and 2010 were included in this study, including 96 patients treated with abdominal SBRT for pancreatic cancer, and 54 patients (59 targetable lesions) treated with thoracic SBRT for tumors in the spine (n = 44) or lung (n = 10). All patients were treated with 1-5 fractions of SBRT. Lyman NTCP model parameters for conventionally fractionated radiation schedules were obtained from the published literature. Each patient’s SBRT dose was converted to the equivalent dose in conventional fraction sizes (2 Gy per fraction) prior to incorporation into the Lyman NTCP model. Two dose transformations were used including: the linear-quadratic (LQ) model (a/b = 3); and the universal survival curve or linear-quadratic-linear (LQL) model (a/b = 3, and DT = 6). The accuracy of the conventional fractionated NTCP models in predicting toxicity was assessed with a Monte-Carlo simulation. Results: The median follow up for all patients was 7.1 months (range 0.1-42). With esophageal toxicity, the three published conventionally fractionated NTCP models slightly under-predicted the observed toxicity. While three grade 2+ esophageal toxicity events were observed, the NTCP predictions ranged between 1.5 to 2.4 events when using the LQ transformation, and ranged between 0.95 and 1.3 events when using the LQL transformation. With duodenal toxicity, one published conventionally fractionated NTCP model significantly over-predicted toxicity. Thirteen grade 2+ duodenal toxicity events were observed in our population, yet the NTCP prediction was 60 events with the LQ transformation, and 28 events with the LQL transformation. Conclusions: This study demonstrates that conventionally fractionated NTCP models fail to predict toxicity when extrapolated to the hypofractionated regimens used with SBRT. These conventional NTCP models can both under- and over-predict toxicity. Improved models are needed. Author Disclosure: J.D. Murphy: None. J. Abelson: None. M.P. Chung: None. D.T. Chang: None. A.C. Koong: None.
2353
Perineural Invasion Predicts for Increased Recurrence, Metastasis, and Death from Prostate Cancer following Treatment with Dose-Escalated Radiation Therapy
N. S. Kapadia1, Y. Qian1, M. H. Stenmark1, S. Halverson1, K. Blas1, S. Vance1, H. Sandler2, D. Hamstra1, F. Feng1,3 1 The University of Michigan Cancer Center, Ann Arbor, MI, 2The Cedars Sinai Medical System, Los Angeles, CA, 3Veteran Affairs Medical Center, Ann Arbor, MI
Purpose/Objective(s): To assess the prognostic value of perineural invasion (PNI) for patients treated with dose-escalated external beam radiation therapy (EBRT) for prostate cancer.
S378
2351
Volume 81, Number 2, Supplement, 2011
A Comparison of CT and MRI Imaging for the Staging of Cancer of the Anal Canal
B. J. Debenham1,2, K. Joseph1,2, D. G. Williams2, K. Tankel1,2, R. C. Hennig1,2 1
University of Alberta, Edmonton, AB, Canada, 2Cross Cancer Institute, Edmonton, AB, Canada
Purpose/Objective(s): Anal canal cancer is a relatively uncommon GI cancer, with an incidence of 1.6 new cases per 100,000 persons per year. Its incidence is rising in the female population, and HPV is recognized as a risk factor for the disease. The AJCC staging manual does not recommend any specific diagnostic imaging tests for the purpose of staging. Most clinical practice guidelines, including those from the NCCN, suggest a DRE, anoscopy, chest imaging, and a CT or MRI of the abdomen and pelvis to stage the disease. Our objective was to compare the benefit of using MRI versus CT in the staging of anal canal patients. Materials/Methods: After institutional ethics review, 24 patients were identified from 2007 to 2010 who received curative-intent treatment for anal canal cancer at the Cross Cancer Institute. All patients had a MRI and CT scan. Their charts were reviewed, and data from the CT report, MRI report, and initial consultation was tabulated. If any information was missing from the CT and MRI reports, the scans were reviewed by a radiologist and that information was tabulated. Results: Based on the CT scans, the anal canal lesion was seen only in 42% (10/24) of cases. The anal canal lesion was visible in 100% (24/24) of the MRI scans. The average largest dimension of the tumor, based on MRI scan, was 4.6cm (minimum 0.8cm, maximum 9.9cm). In comparison with clinical exam findings, MRI scans caused upstaging in 38% (9/24) of patients, and downstaging in 25% (6/24). In comparison with CT scan findings, MRI scans caused upstaging in 75% (18/24) patients, and caused down-staging in 4% (1/24) patients. The average difference between MRI and clinical exam size of tumor was 1.3cm (minimum 0cm, maximum 3.1cm). The average difference in the size of tumor between MRI and CT scan findings, when the lesion was visible on CT images, was 2.7cm (minimum 2.1cm, maximum 9.9cm). MRI detected pathologic lymph nodes in 33% (8/24) cases, while CT detected pathologic lymph nodes in 17% (4/24) cases. MRI was able to detect the depth of wall invasion in 92% of cases (22/24), while CT was able to detect the depth of wall invasion in 13% (3/24). MRI was able to determine the size of craniocaudal extension in 92% (22/24) cases, while this was able to be accurately determined on any CT scan. Conclusions: MRI appears to be a more sensitive test than CT, as it detected a lesion in all of the cases reviewed. MRI was superior to CT in detecting invasion through the bowel wall and for lymph node involvement. There was considerable upstaging of patients using MRI versus CT scans. In addition, MRI provides consistency in T stage assessment compared to clinical evaluation where subjective variation exists. Based on our data , we recommend that MRI should strongly be considered for staging of anal canal cancers. Author Disclosure: B.J. Debenham: None. K. Joseph: None. D.G. Williams: None. K. Tankel: None. R.C. Hennig: None.
2352
Gastrointestinal Normal Tissue Toxicity Prediction In Stereotactic Body Radiotherapy
J. D. Murphy, J. Abelson, M. P. Chung, D. T. Chang, A. C. Koong Stanford University Cancer Center, Stanford, CA Purpose/Objective(s): As the use of hypofractionated stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR) increases, there is a need to define dosimetric constraints to allow the safe delivery of this promising modality. Normal tissue complication probability (NTCP) models have been developed and validated for conventionally fractionated radiation regimens, and there is there is a tendency to extrapolate these models to SBRT. The purpose of this study was to examine the accuracy of conventionally fractionated NTCP models extrapolated to SBRT with esophageal and duodenal toxicity. Materials/Methods: 150 patients treated between 2002 and 2010 were included in this study, including 96 patients treated with abdominal SBRT for pancreatic cancer, and 54 patients (59 targetable lesions) treated with thoracic SBRT for tumors in the spine (n = 44) or lung (n = 10). All patients were treated with 1-5 fractions of SBRT. Lyman NTCP model parameters for conventionally fractionated radiation schedules were obtained from the published literature. Each patient’s SBRT dose was converted to the equivalent dose in conventional fraction sizes (2 Gy per fraction) prior to incorporation into the Lyman NTCP model. Two dose transformations were used including: the linear-quadratic (LQ) model (a/b = 3); and the universal survival curve or linear-quadratic-linear (LQL) model (a/b = 3, and DT = 6). The accuracy of the conventional fractionated NTCP models in predicting toxicity was assessed with a Monte-Carlo simulation. Results: The median follow up for all patients was 7.1 months (range 0.1-42). With esophageal toxicity, the three published conventionally fractionated NTCP models slightly under-predicted the observed toxicity. While three grade 2+ esophageal toxicity events were observed, the NTCP predictions ranged between 1.5 to 2.4 events when using the LQ transformation, and ranged between 0.95 and 1.3 events when using the LQL transformation. With duodenal toxicity, one published conventionally fractionated NTCP model significantly over-predicted toxicity. Thirteen grade 2+ duodenal toxicity events were observed in our population, yet the NTCP prediction was 60 events with the LQ transformation, and 28 events with the LQL transformation. Conclusions: This study demonstrates that conventionally fractionated NTCP models fail to predict toxicity when extrapolated to the hypofractionated regimens used with SBRT. These conventional NTCP models can both under- and over-predict toxicity. Improved models are needed. Author Disclosure: J.D. Murphy: None. J. Abelson: None. M.P. Chung: None. D.T. Chang: None. A.C. Koong: None.
2353
Perineural Invasion Predicts for Increased Recurrence, Metastasis, and Death from Prostate Cancer following Treatment with Dose-Escalated Radiation Therapy
N. S. Kapadia1, Y. Qian1, M. H. Stenmark1, S. Halverson1, K. Blas1, S. Vance1, H. Sandler2, D. Hamstra1, F. Feng1,3 1 The University of Michigan Cancer Center, Ann Arbor, MI, 2The Cedars Sinai Medical System, Los Angeles, CA, 3Veteran Affairs Medical Center, Ann Arbor, MI
Purpose/Objective(s): To assess the prognostic value of perineural invasion (PNI) for patients treated with dose-escalated external beam radiation therapy (EBRT) for prostate cancer.