Impact of Brachytherapy Boost and Dose-escalated External Beam Radiotherapy in Margin Positive Cervical Cancer Treated With Chemotherapy and Radiation

Objectives: We examined the impact of brachytherapy boost (BB) and external beam radiotherapy (EBRT) dose-escalation on overall survival (OS) for women with cervical cancer receiving postoperative chemotherapy and radiation (CRT) for a positive margin following hysterectomy. Materials and Methods: The National Cancer Database (NCDB) was queried from 2004 to 2015 for women with nonmetastatic squamous cell carcinoma or adenocarcinoma of the cervix who had a positive margin following hysterectomy and received postoperative CRT. Patient and treatment characteristics were assessed with multivariate logistic regression. Survival analyses were performed with univariate Cox regression and Kaplan-Meier analyses. Propensity-score weighted cohorts were generated with inverse probability of treatment weighting via generalized boosted regression modeling. Results: Of 630 women receiving CRT, 331 (53%) received EBRT alone and 299 (47%) received EBRT+BB. Eighty-two percent had chemotherapy initiation within 2 weeks of radiation, suggesting concurrent delivery. Median EBRT dose was 5040 cGy. Intracavitary high-dose rate was the most common BB (67%). Inclusion of BB was more likely with larger tumor sizes (odds ratio=1.03, P=0.002). Women receiving EBRT+BB had improved OS compared to EBRT alone for both unweighted (hazard ratio [HR], 0.72; P=0.020) and propensity-score weighted cohorts (HR, 0.70; P=0.017), and this finding was consistent across multiple patient subsets. EBRT dose-escalation >5040 cGy was not found to be associated with OS (unweighted HR, 1.38; P=0.065 and weighted HR, 1.16; P=0.450). Conclusion: The addition of BB to standard CRT improved OS for women with cervical cancer and a positive margin after hysterectomy. No consistent survival benefit was seen to EBRT dose-escalation beyond 5040 cGy.