Intensity Modulated Radiation Therapy For Vulvar Cancer: Predictors Of Local Control And Survival

Vulvar cancer is an uncommon disease and limited guidance is available from prospective trials. We reviewed our institutional experience treating vulvar cancer with intensity modulated radiation therapy (IMRT) within the last decade. We retrospectively reviewed patients with vulvar cancer receiving IMRT at our institution between 2005 and 2015. Patients with distant metastatic disease or recurrent disease were excluded. Age, FIGO stage, tumor size, histology, grade, radiation, surgery, number and size of involved LN, ECE, LVSI, surgical margin, depth of invasion, brachytherapy, and concurrent chemotherapy were assessed. Endpoints of interest were local recurrence and overall survival. SAS was used for Cox univariate and multivariate analysis. 44 patients were identified with mean follow-up of 23 months. Six patients were FIGO stage I, 7 patients were stage II, 23 were stage III, and 8 were stage IV. The included FIGO stage IV patients had AJCC T3 disease or positive pelvic LN but no distant metastases. Thirty-five (80%) patients received PET staging and 11 (25%) received MRI staging. Fourteen (32%) patients received definitive radiation, 24 (55%) received adjuvant radiation, and 6 (14%) received neoadjuvant radiation. Twenty-three (52%) patients received bilateral inguinal lymph node dissection and 2 (4.3%) received sentinel LN sampling. All patients received once daily external beam radiation by IMRT to doses ranging 50.4-70 Gy. 5 (11%) patients received RT to the vulva only, while the remainder received RT to the vulva, pelvic, and inguinal nodes. 8 (18%) patients received high dose rate brachytherapy with doses ranging from 10-20 Gy. 14 (32%) patients received concurrent chemotherapy; most commonly weekly cisplatin. 14 (32%) patients developed recurrence: 8 at the vulva (18%), 2 at the inguinal LNs (4.5%) and 4 at distant metastases (9.1%). On univariate and multivariate analysis, tumor size (HR 1.05, P = 0.01) and surgical excision of the vulva (HR 0.13, P<0.01) were the significant factors predicting local control. No significant difference in local control was seen in radiation dose, adjuvant vs neo-adjuvant RT, brachytherapy, or concurrent chemotherapy. Eight (18%) patients ultimately died of vulvar cancer in the follow-up period. Tumor size (HR 1.03, P = 0.03) was the only factor predictive of overall survival on multivariate analysis. Three (6.8%) patients developed lymphangitis as a consequence of treatment. Radiation, either alone or with surgery, plays an important role in achieving local-regional control of vulvar cancer. In this cohort who all received IMRT, tumor size and surgical treatment of the vulva are the major contributors to local control. We achieved a low rate of inguinal node recurrence. The use of concurrent chemotherapy was not correlated with local control or survival.