External pelvic and vaginal irradiation vs. vaginal irradiation alone as postoperative therapy in women with early stage uterine serous carcinoma: Results of a National Cancer Database analysis.

PURPOSE: Adjuvant treatment in early stage uterine serous carcinoma (USC) usually consists of chemotherapy with vaginal brachytherapy (VB), pelvic external beam radiation therapy (EBRT), or combination. We compared survival outcomes across these various radiation treatment modalities using the National Cancer Database.

METHODS AND MATERIALS: The National Cancer Database was queried for adult females with histologically confirmed International Federation of Gynecology and Obstetrics 1988 Stage I-II USC diagnosed from 2003 to 2013 treated definitively with hysterectomy, adjuvant chemotherapy, and radiation therapy. χ(2) tests were used to assess differences by radiation type (VB, pelvic EBRT, and EBRT + VB) and various clinical variables. Kaplan-Meier and log-rank test methods were used to evaluate survival outcomes. Risk factors related to overall survival were identified by univariate and multivariate analysis.

RESULTS: We identified 1336 patients with USC who met our inclusion criteria. Most patients were treated with VB (66%) compared with EBRT (21%) or combination EBRT + VB (13%). The proportion of patients who received EBRT (including EBRT + VB) was higher for those who did not have a lymph node dissection or with fewer dissected lymph nodes. Patients treated with VB alone had longer 5-year survival rates (84% [95% confidence interval: 80, 90]) than those treated with EBRT (75% [95% confidence interval: 69, 80]) (p < 0.001). On multivariate analysis, the presence of lymphovascular space invasion (hazard ratio, 2.48; p < 0.001) and the absence of a lymph node dissection (hazard ratio, 2.24; p = 0.047) were independent predictors of overall survival.

CONCLUSIONS: This large hospital-based study suggests that VB alone may be sufficient for adjuvant radiation treatment in women with USC treated with adjuvant chemotherapy and who underwent an adequate surgical staging.