Practical Radiation Oncology: April-June Supplement 2013 phantom were generated via DIR method as described above and were compared to the true T2-w ‘4D-MRI’ of the phantom. Results: In phantom study, pseudo T2-w ‘4D-MRI’ matched well with true T2-w ‘4D-MRI’, with only minimal differences between the two that were potentially due to residual errors in DIR. Pseudo T2-w 4D-MRI improved tumor-to-tissue CNR (32.2 ± 5.9) as compared to those of original T2*/T1w 4D-MRI (16.1 ± 2.0), while both showed superior CNR over 4D-CT (1.4 ± 1.2). Pseudo T2-w 4D-MRI revealed similar motion patterns of organs and tumor as observed in T2*/T1-w 4D-MRI. Conclusions: Improvement in tumor-to-tissue CNR of 4D-MRI by combining T2-w MRI and DIR is feasible. Further validation of the proposed method is required. Author Disclosure Block: J. Cai: J. Funding Other; Golfers Against Cancer (GAC) Foundation. Z. Chang: J. Funding Other; Golfers Against Cancer (GAC) Foundation. B. Czito: J. Funding Other; Golfers Against Cancer (GAC) Foundation. F. Yin: J. Funding Other; Golfers Against Cancer (GAC) Foundation.

Poster Presentations

S9

bowel toxicity following XRT for prostate cancer in a larger cohort is warranted. If there is an association between baseline ARA and bowel toxicity, measuring the ARA on a pre-treatment CT scan could allow more informed counseling of patients regarding the risks for bowel toxicity following XRT. Author Disclosure Block: M. Gossweiller: None. A. Waggoner: None. S. Ninneman: None. R. Huang: None. G. Hughs: None. S. Wendt: None. M. Brown: None. B. Tinnel: None. D.M. Macdonald: None.

DIAGNOSIS, STAGING, AND RECURRENCE 109 See Oral Abstract Presentation #11

110 See Oral Abstract Presentation #9 108 Anorectal Angle Is Associated With Bowel Toxicity One Month Following Radiation Therapy for Prostate Cancer M. Gossweiller 1, A. Waggoner 2, S. Ninneman 3, R. Huang 1, G. Hughs 1, S. Wendt 3, M. Brown 4, B. Tinnel 1, D.M. Macdonald 1, 1 Madigan Healthcare System, Tacoma, WA, 2Pacific Northwest University of the Health Sciences, Yakima, WA, 3The Geneva Foundation, Tacoma, WA, 4University of Washington School of Medicine, Seattle, WA Purpose/Objectives: Bowel toxicity following radiation therapy (XRT) for prostate cancer can cause a significant decrease in patient quality of life. Some of this toxicity - such as rectal bleeding - seems to relate directly to damage to the rectal wall, while other elements of bowel toxicity - such as urgency, frequency, or fecal leakage - may be related to anal canal geometry and musculature. The anorectal angle (ARA) and the volume of the puborectalis muscle (VPRM) - which assists in maintaining the anorectal angle - are two image-based measurements which are known to be related to the maintenance of fecal continence. Here we explore whether a large pre-treatment ARA or a small VPRM are associated with increased bowel toxicity following XRT. Materials/Methods: We studied 10 consecutive patients with low-tointermediate risk prostate cancer treated on a prospective study with definitive intensity-modulated radiation therapy (IMRT). All patients completed the EPIC quality of life questionnaire at the end of treatment, and at 1 and 4 months post-treatment. We used the patients’ answers on the bowel section of these questionnaires to divide the patients into two groups: one with few side effects as reflected by a score within 10% of the most favorable score possible, and the other with more side effects as reflected by a lower score. The patients’ VPRMs were measured by contouring on planning CT scans. The anorectal angle was measured on sagittal CT scan reconstructions as the angle between the line down the center of the long axis of the anal canal, and the line down the center of the long axis of the rectum immediately superior to the anal canal. Both the VPRM and the ARA measurements were then categorized as “small” or “large” using the mean as the dividing line. We used Fisher's exact test to evaluate for a significant association between ARA and bowel toxicity and between VPRM and bowel toxicity. Results: EPIC bowel toxicity scores varied from a low of 56.7 to a high of 100, with a mean of 83.8 and standard deviation of 14.76. VPRM varied from 6.45cc to 15.87cc (std. dev. 3.13), and was not associated with bowel toxicity (p = 1.000 at all time points). ARA varied between 93.5 and 121.8 deg (std. dev. 9.69), and was correlated with bowel toxicity one month following completion of therapy (p = 0.048), but not at the end of XRT (p = 1.000) or at 4 months post-treatment (p = 0.524). Conclusions: These results are hypothesis-generating and based on a very small sample size. Further evaluation of the association of ARA with

111 Benefit of MRI Scanning in the Pretreatment Assessment of Anal Canal Carcinoma V.G. Swami, K. Joseph, D. Severin, K. Tankel, N. Usmani, T. Nijjar, University of Alberta, Edmonton, AB, Canada Purpose/Objectives: Anal canal carcinoma is an uncommon curable malignancy. The AJCC staging manual does not recommend any specific diagnostic tests for 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. It has still not been established whether MRI should be used routinely for local staging. We compared the benefit of MRI versus CT in the pre-treatment assessment and staging of anal canal carcinoma. Materials/Methods: This prospective cohort study included 31 consecutive patients from 2007 to 2011 with a histopathologically confirmed anal canal carcinoma who underwent curative-intent treatment at the Cross Cancer Institute. Patients underwent contrast-enhanced CT of the chest, abdomen and pelvis and pelvic MRI following clinical examination as part of the staging work-up. All the images were evaluated prospectively to record tumor size, extent and the TNM stage. Results: MRI visualized the primary anal canal lesion in all cases (31 of 31), while CT only visualized 39% (12 of 31) of lesions. Compared to CT, MRI altered T staging in 84% (26 of 31) of cases. MRI upstaged 81% (25 of 31) of cases and downstaged 3% (1 of 31) of cases. Compared to clinical examination, MRI altered T staging in 52% (16 of 31) of cases. MRI upstaged 35% (11 of 31) of cases and downstaged 16% (5 of 31) of cases. Pathologic lymph nodes were detected by MRI in 52% (16 of 31) of cases, CT in 19% (6 of 31) of cases, and clinical examination in 26% (8 of 31) of cases. Compared to N Staging by CT, MRI upstaged 32% (10 of 31) of cases and did not downstage. Compared to clinical examination N staging, MRI upstaged 32% (10 of 31) of cases and did not downstage. MRI was able to assess the depth of bowel wall invasion in all cases and detected positive wall invasion in 81% (25 of 31) of cases. CT was only able to assess the depth of wall invasion in 29% (9 of 31) of cases and detected positive wall invasion in only 6% (2 of 31) of cases. While CT did not detect involvement of the anal sphincter muscles, MRI detected involvement of the internal anal sphincter in 61% (19 of 31) of cases and the external anal sphincter in 48% (15 of 31) of cases. CT did not upstage any cases to T4, while MRI upstaged 6 cases to T4 by detecting vaginal invasion. Conclusions: MRI was more sensitive than CT in detecting primary anal canal lesions. MRI was superior to CT in detecting lymph node

See oral abstract presentation #11.

See oral abstract presentation #11. - PDF Download Free
58KB Sizes 1 Downloads 3 Views