Chemotherapy-associated foam cell aggregates as a prognostic factor in patients with pelvic high-grade serous carcinoma receiving neo-adjuvant chemotherapy.

High-grade serous carcinoma (HGSC) tends to recur after treatment; therefore, the Chemotherapy Response Score (CRS) has been proposed as a histopathological prognostic scoring system for measuring the response to neo-adjuvant chemotherapy and the risk of recurrence. This study aimed to evaluate the CRS in only those with an R0 debulking status and to investigate new prognostic factors for progression-free survival (PFS). We reviewed the CRS of HGSC patients with R0 using surgical specimens of the omental sections. Patients were categorized according to foam cell change (FCC), defined as foam cells occupying more than half of the area of the chemotherapy-associated scar. In total, 100 HGSC patients were evaluated. PFS was significantly different according to the CRS. For CRSs of 1/2 and 3, the median PFS were 18 and 27 months, respectively (HR, 1.84; 95% CI 1.01-3.33, p = 0.045). Moreover, the FCC group showed significantly longer PFS than did the non-FCC group (20 vs 59 months; HR 2.43; 95% CI 1.15-5.14; p = 0.020). The present study validated the CRS of those in the R0 cohort. Furthermore, an increase in foam cells in the regression scar reflects the chemotherapy response and the FCC may be a useful novel prognostic factor for patients undergoing R0 resection. This finding must be further validated independently.