Main Session
Sep
27
PQA 01 - Gastrointestinal Cancer and Central Nervous System
Presenter(s)
Kavita Sehrawat, MD - Baptist Health, Miami, FL
K. Sehrawat1, C. Velten2, P. Brodin3, M. Gjini2, W. A. Tome4, N. Ohri5, S. Kalnicki5, M. K. Garg3, and R. Kabarriti3; 1Albert Einstein College of Medicine`, Bronx, NY, 2Department of Radiation Oncology, Montefiore Medical Center, Bronx, NY, 3Department of Radiation Oncology, Albert Einstein College of Medicine and Montefiore Medical Center, Bronx, NY, 4Department of Radiation Oncology, Montefiore Einstein Comprehensive Cancer Center, Bronx, NY, 5Montefiore Einstein Comprehensive Cancer Center, Bronx, NY
Purpose/Objective(s):
Concurrent chemoradiotherapy is the standard treatment for localized anal cancer; however, post treatment fecal incontinence adversely affects patients’ quality of life. This study investigates the association between radiation dose to pelvic muscles and post treatment fecal incontinence.Materials/Methods:
We retrospectively reviewed patients with stage I-III anal cancer treated with definitive intensity modulated chemoradiotherapy at our institution between 2006-2024 and examined medical charts for reports of fecal incontinence. Inclusion criteria included patients who were =18 years old, had no prior pelvic radiotherapy, without disease recurrence, and had =1 year follow-up. Pelvic muscles, including anal sphincter complex, levator ani, coccygeus, gluteus maximus, obturator, piriformis, pectineus and urogenital diaphragm, were manually contoured using axial images from the planning CTs. Dose volume histogram (DVH) metrics were calculated and assessed for association with fecal incontinence using Fisher exact test, Mann-Whitney U-test, logistic regression, and Cox regression.Results:
114 patients met inclusion criteria, with 45 patients (39%) noted to have at least one reported episode of fecal incontinence. The median prescription dose was 54 Gy (IQR: 50.4-54 Gy), and the median follow-up duration was 71 months. In the gluteus maximus muscle, several dose parameters showed statistically significant association with fecal incontinence, including Dmean, D90% (p=0.01), Dmax (p=0.04), V15Gy and V20Gy (p<0.01). On multivariate analysis, the odds ratio (OR) of experiencing fecal incontinence was 1.41 (95% CI: 1.08-1.83, p=0.01) per 10% increase in gluteus maximus V20Gy, independent of age, stage, or prescribed dose, and the hazard ratio for V20Gy > median was 2.61 (95% CI: 1.33-5.12, p=0.005).Conclusion:
Abstract 2207 – Table 1
Increase radiation dose to the gluteus maximus was independently associated with fecal incontinence following anal cancer radiotherapy. This finding supports a potential contributory role of the gluteus maximus in continence mechanisms and merits further prospective validation.| Cox regression model | HR (95% CI) | P-value |
| Gluteus maximus V20Gy > median | 2.61 (1.33, 5.12) | 0.005 |
| Age (per year) | 1.02 (0.99, 1.05) | 0.081 |
| Stage I | Ref | |
| Stage II | 0.35 (0.13, 0.95) | 0.04 |
| Stage III | 0.46 (0.17, 1.28) | 0.14 |
| Prescribed dose <54 Gy | Ref | |
| Prescribed dose =54 Gy | 1.41 (0.68, 2.93) | 0.36 |
| Prescribed dose (per 1 Gy increase) | 1.07 (0.94, 1.20) | 0.31 |