External validation of a 'response score' after neoadjuvant chemotherapy in patients with high-grade serous ovarian carcinoma with complete clinical response

OBJECTIVES: The chemotherapy response score (CRS) has been developed for measuring response to neoadjuvant chemotherapy in tubo-ovarian high-grade serous carcinoma. This study aimed to validate the ability of this three-tier scoring system of pathologic response on omental specimens to determine prognosis in a subgroups of patients who had clinical complete response to neoadjuvant chemotherapy. METHODS: This was a retrospective study, conducted in women receiving interval debulking surgery at the Division of Gynecologic Oncology, between December 2007 and April 2017. Inclusion criteria were: high-grade serous ovarian cancer, FIGO stage IIIC/IV, platinum-based neoadjuvant chemotherapy, and clinical complete response after neoadjuvant chemotherapy (normalization in CA125 levels, disappearance of all target and non-target lesions according to RECIST 1.1). CRS was defined by a single pathology review and classified as previously reported: CRS1, no or minimal tumor response with fibroinflammatory changes limited to a few foci ranging from multifocal or diffuse regression-associated fibroinflammatory changes with viable tumor in sheets, or nodules to extensive regression-associated fibroinflammatory changes with multifocal residual tumor; CRS2, appreciable tumor response with viable tumor readily identifiable; and CRS3, complete absence of tumor or nodules with maximum size of 2 mm. CRS was analyzed according to clinical variables and survival. RESULTS: A total of 108 patients were eligible for analysis. The average age was 65 (range 36-85) years. A total of 91 (84.3%) patients had stage IIIC disease and 17 (15.7%) patients had stage IV disease. No statistically significant differences were observed in terms of age, FIGO stage, CA125 serum levels, type of chemotherapy schedules, and number of cycles between the three groups. Patients in the CRS3 group had a longer median progression-free survival (25.8 months) compared with CRS2 or CRS 1 (20.3 vs 17.4 months, respectively; p=0.001). Median overall survival was 68.9 months for CRS3, 35.0 months for CRS2, and 45.9 months for CRS1 (p=0.034). CONCLUSION: Complete or near-complete pathologic response assessed in the omental specimens of advanced epithelial ovarian carcinoma patients after neoadjuvant chemotherapy (CRS3) is predictive of prolonged progression-free and overall survival. In particular, this is true in women with a clinical complete response.