Radiation therapy for vaginal and perirectal lesions in recurrent ovarian cancer

Abstract

<h3>Objectives:</h3> The role for radiation therapy (RT) to treat ovarian cancer (OC) patients with locally recurrent vaginal/perirectal lesions remains unclear, though we hypothesize that these patients may be salvaged locally and gain long-term survival benefit. We aimed to describe our institutional outcomes using vaginal brachytherapy±intensity modulated radiation therapy (IMRT) to treat this population and report our in-field control rate, RT-related toxicities, post-RT chemotherapy-free interval (CFI), RT-related toxicities, progression-free survival (PFS), and overall survival (OS). We also studied the prognostic impact of platinum status immediately prior to RT. <h3>Methods:</h3> This is a single institution retrospective case series of 17 recurrent OC patients treated with brachytherapy±IMRT for vaginal and/or perirectal recurrences between January 2006 and November 2019. Intent of RT (palliative or definitive) was determined collaboratively by the treating gynecologic and radiation oncologists. PFS and OS were defined from date of RT completion to either progression or death/last follow-up, respectively. <h3>Results:</h3> This was a heavily pre-treated cohort (median 3 prior lines of chemotherapy, range 1-9), with a median follow-up of 28.4 months (range 4.5-166.4) after RT completion (Figure 1). Most patients had high-grade serous histology (9 of 17) with the remainder of patients even distributed between low-grade serous, clear cell, mixed, and carcinosarcoma. Eleven patients were treated with definitive intent, including 4 with isolated vaginal/perirectal disease. Three patients received concurrent chemotherapy or immunotherapy and RT. Four (23.5%) patients had in-field failures at 2.3, 10.9, 23.2, and 25.7 months post-RT, all of whom had been treated with definitive intent. The 9 patients who were platinum-sensitive prior to RT had similar median PFS (8.1 vs. 10.4 months, log-rank p=0.91), but longer OS (53.9 vs 16.5 months, log-rank p=0.03) compared to their platinum-resistant counterparts. Excluding patients with low-grade histology or who were treated with palliative RT, the median CFI was 12.6 months (range 1.3-31.7). When including all patients, the two patients with the longest CFI post-RT included a <i>BRCA2</i> mutation carrier with an isolated vaginal recurrence and a patient with a <i>MLH1</i> somatic mutation treated with concurrent RT and pembrolizumab. RT was well tolerated with 2 (12%) experiencing grade 3/4 gastrointestinal/genitourinary toxicities. <h3>Conclusions:</h3> RT to treat locally recurrent vaginal and perirectal lesions in heavily pre-treated OC patients is safe and may effectively provide locoregional control.