Computed tomography planned interstitial brachytherapy for recurrent gynecologic cancer.

PURPOSE: To report outcomes and identify predictors of toxicity in patients undergoing reirradiation with interstitial brachytherapy (ISBT) for recurrent cancers of the female reproductive tract.

METHODS AND MATERIALS: Twenty-one patients received ISBT performed using (192)Ir sources (10 low dose rate and 11 high dose rate) at our institution between 2009 and 2013. Demographic, disease specific, treatment, toxicity, and outcome data were collected. Kaplan-Meier and proportional hazard models were used to estimate survival and logistic regression to model toxicity. A least absolute shrinkage and selection operator penalty was used to identify relevant predictors of outcome and toxicity.

RESULTS: Eleven patients had uterine cancer, 7 patients had cervical cancer, and 3 patients had vulvar cancer. One-year actuarial freedom from local-regional failure, progression-free survival (PFS), and overall survival were 71.5%, 66.0%, and 82.2%, respectively. Tumor size was a significant predictor of worse PFS and overall survival (1 cm increase in tumor size = hazard ratio [HR], 1.61; 95% confidence interval [CI]: 1.16, 2.62 for PFS; HR, 2.02; 95% CI: 1.21, 3.38). Grade 3 or higher vaginal, urinary, and rectal toxicity occurred in 28.5%, 9.5%, and 19% of patients, respectively. Urethra D0.1cc predicted for grade 2 or higher urinary toxicity (one equivalent dose in 2 Gy fraction increase = HR, 1.156; 95% CI: 1.001, 1.335).

CONCLUSIONS: Reirradiation with ISBT is both safe and effective. In patients with recurrent cancer, urethra D0.1cc predicts for increased urinary toxicity. Increased tumor size is a negative prognostic factor in patients receiving ISBT for cancer recurrence.