2848 - The Role of the Sigmoid Colon in Late Gastrointestinal Toxicity in Cervical Cancer Patients Receiving Definitive Chemoradiation

10:45am - 12:00pm PT

Hall F

Screen: 5

POSTER

Presenter(s)

Phoebus Sun Cao, MD - SUNY Upstate Medical University, Syracuse, NY

P. Sun Cao, A. Ho, E. Hilliard, A. Marsallo, S. S. Hahn, P. D. Aridgides, and B. Simone; SUNY Upstate Medical University, Syracuse, NY

Purpose/Objective(s): Cervical cancer is the fourth most common cancer in women globally. Treatment of cervical cancer stage IB and above typically consists of definitive chemoradiation followed by brachytherapy. Clear dose constraints for the rectum and bladder exist, however, the role that radiation to the sigmoid colon plays in late gastrointestinal (GI) toxicity is not well defined. Hence, we sought to evaluate the association of sigmoid colon dose-volume data and GI toxicity.

Materials/Methods: We retrospectively identified patients with FIGO stage IB2-IVB cervical cancer at a single institution who underwent definitive chemoradiation followed by brachytherapy. All patients received intracavitary brachytherapy with or without interstitial needles. Both external beam radiotherapy (EBRT) and brachytherapy plans were examined and dosimetric data were collected. Sigmoid colon was contoured from the sigmoidodescending junction proximally to the rectosigmoid junction distally. EBRT dosimetric data included Dmax, Dmean, D2cc, D5cc, D10cc, and V40. Brachytherapy dosimetric data included D2cc, D5cc, and D10cc. The primary endpoint was late GI toxicity as defined by common terminology criteria for adverse events (CTCAE) v. 5.0. Additional factors evaluated included stage, smoking status, and weight. Univariate (UA) and multivariate analyses (MA) were performed using logistic regression.

Results: We identified 74 patients with complete dosimetric data for evaluation. Most patients had stage II (n=22) and III (n=29) disease. The most common histology was squamous cell carcinoma (n=54). 72.9% of patients were Caucasian. Median follow-up was 34 months. While no parameters were predictive of grade 1 & 2 toxicity under UA, the EBRT Dmean (p=0.004), D2cc (p=0.018), D5cc (p=0.010), D10cc (p=0.040), and V40% (p=0.013) were significant under MA. Only EBRT V40% (p=0.047) remained significant as predictor for = grade 3 toxicity under UA. Overall, the patient’s stage, smoking status, and weight did not correlate with GI toxicity. On MA assessing all examined dosimetric factors and demographic factors, only the EBRT dosimetric factors Dmean (p=0.009), D2cc (p=0.012), D5cc (p=0.011), D10cc (p=0.047), and V40% (p=0.038) were significant specifically for Grade 1 & 2 toxicity.

Conclusion: Radiation dose to the sigmoid from EBRT was found to correlate with physician-reported late GI toxicity. Future studies should routinely assess sigmoid radiation dose during treatment planning and incorporate patient-reported outcomes in follow-up.