Stereotactic Ablative Radiation Therapy For Gynecological Malignancies In The Oligometastatic Setting

Stereotactic ablative radiation therapy (SABR) has recently emerged as an effective treatment option for cancer patients. It is non-invasive, provides excellent rates of local control (LC) and is associated with few serious side effects. In the metastatic setting, the population of patients expected to receive maximum benefit from SABR is not well defined, although those with oligometastatic disease (≤3 involved organs, ≤5 total metastases) are suspected. SABR data with respect to gynaecological malignancies is particularly limited. Here we report one of the largest single institution experiences on this subject. We performed a retrospective review of all patients with gynecological malignancies harboring oligometastatic disease treated with SABR at our institution. Collected information included patient demographics, malignancy characteristics and SABR details, as well as treatment outcomes including LC, progression-free survival (PFS), overall survival (OS) and toxicities. Between March 2011 and November 2013, 21 patients with oligometastatic disease were treated. Median age at time of stereotactic consultation was 61 years (43-85). Nine patients had uterine, nine had ovarian and three had cervical primaries. Adenocarcinoma was the most common histology (47.6%), followed by papillary/serous (33.3%) and squamous cell (9.5%) variants. Tumors were Grade 1, 2 and 3 in 19%, 19% and 42.9% of cases, respectively. Median PFS following initial treatment(s) was 29.6 months (2.9-171.3). Two-thirds of patients had a single metastasis treated with SABR (range = 1-3), located within nodal (55.2%), pulmonary (13.8%), intracranial (10.3%) and hepatic (10.3%) tissues. Average lesion size was 3.8 cm (0.8-7.6) and median prescription dose was 30 Gy over 5 fractions (ranging from 22-60 Gy/1-8 fractions). Median post-SABR follow-up time was 8.5 months (2.9-24.9) with a LC rate of 92.6% (25/27 targets). Eight patients (38.1%) remain alive with no evidence of disease progression. Of the 13 patients (61.9%) who did progress, their median PFS was 11.1 months (1.5-36.6). Two patients (9.5%) received additional SABR following progression, while 3 patients (14.3%) died from their metastatic disease. Not a single serious (≥ grade 3) toxicity was identified. The use of SABR to treat oligometastatic disease in patients with gynecological malignancies is safe and provides excellent LC. Progression outside of the treated area remains high and further research is needed to conclude which patients may benefit most from this approach.