LAUSR

OBJECTIVE Low-grade serous carcinoma of the ovary/peritoneum (LGSC) is relatively chemoresistant in the adjuvant, neoadjuvant, and recurrent settings. We sought to expand our prior work and evaluate response rates of women with LGSC to neoadjuvant chemotherapy (NACT) compared to women with high-grade serous carcinoma of the ovary/peritoneum (HGSC). METHODS Thirty-six patients with LGSC who received NACT were matched to patients with HGSC. A single radiologist re-reviewed pre- and post-NACT imaging for response using RECIST 1.1. Pre- and post-NACT CA-125 values were compared using paired t-tests. Kaplan-Meier estimates of progression free survival (PFS) and overall survival (OS) were performed. RESULTS All patients received neoadjuvant platinum-based regimens. LGSC patients received a median of 5 cycles (range 3-9), HGSC patients received a median of 4 cycles (range 3-9). Interval cytoreductive surgery was performed in 29/36 (81%) of LGSC and 32/36 (89%) HGSC patients. Complete cytoreduction was reported and achieved in 11/29 (38%) of LGSC patients and 24/32 (75%) of HGSC patients (p = 0.002). Median pre- and post-treatment CA-125 levels for LGSC patients were 295.5 U/mL and 144 U/mL (52% decrease) (p < 0.001). The median pre- and post-treatment CA-125 levels for HGSC patients were 767.5 and 35.6 (96% decrease) (p < 0.001). For LGSC patients, 4/36 (11%) had partial response (PR), 30/36 (83%) had stable disease (SD), and 2/36 (6%) had progressive disease (PD). In HGSC patients, 27/36 (75%) had PR, and 9/36 (25%) SD. Median PFS for LGSC patients was 18.5 months and median OS was 47.4 months. CONCLUSIONS This study provides further evidence of relative chemoresistance of LGSC in patients treated with NACT.