Introduction The surgical approach for interval debulking surgery after neoadjuvant chemotherapy has been extrapolated from primary tumor reductive surgery for high-grade ovarian cancer. The study objective was to compare pathologic distribution of malignancy at interval debulking surgery versus primary tumor reductive surgery.

Methods Patients with a diagnosis of high-grade serous or mixed, non-mucinous, epithelial ovarian, fallopian tube or primary peritoneal cancer who underwent neoadjuvant chemotherapy or primary tumor reductive surgery and had at least 6 months of follow-up were identified through tumor registry at a single institution from January 1995 to April 2016. Pathologic involvement of organs was categorized as macroscopic, microscopic, or no tumor. Statistical analyses included Mann-Whitney and Fisher’s exact tests.

Results Of 918 patients identified, 366 (39.9%) patients underwent interval debulking surgery and 552 (60.1%) patients underwent primary tumor reductive surgery. Median age was 62.3 years (range 25.3–92.5). The majority of patients in the interval debulking surgery group were unstaged (261, 71.5%). In the patients who had a primary tumor reductive surgery, 406 (74.6%) had stage III disease. In both groups, the majority of patients had serous histology: 325 (90%) and 435 (78.8%) in the interval debulking and primary tumor reductive surgery groups, respectively. There was a statistically significant difference between disease distribution on the uterus between the groups; 31.4% of the patients undergoing interval debulking surgery had no evidence of uterine disease compared with 22.1% of primary tumor reductive surgery specimens (p<0.001). In the adnexa, there was macroscopic disease present in 253 (69.2%) and 482 (87.4%) of cases in the interval vs primary surgery groups, respectively (p<0.001). Within the omentum, no tumor was present in the omentum in 52 (14.2%) in the interval surgery group versus 91 (16.5%) in the primary surgery group (p<0.001). In the interval surgery group, there was no tumor involving the small and large bowel in 49 (13.4%) and 28 (7.7%) pathologic specimens, respectively. This was statistically significantly different from the small and large bowel in the primary surgery group, of which there was no tumor in 20 (3.6%, p<0.001) and 16 (2.9%, p<0.001) of cases, respectively.

Conclusion In patients undergoing interval debulking surgery, there was less macroscopic involvement of tumor in the uterus, adnexa and bowel compared with patients undergoing primary cytoreductive surgery.