Abstract: We found 1952 potential titles, with a most recent search date of February 2019, of which five RCTs of varying quality and size met the inclusion criteria. These studies assessed a total of 1713 women with stage IIIc/IV ovarian cancer randomised to NACT followed by interval debulking surgery (IDS) or PDS followed by chemotherapy. We pooled results of the three studies where data were available and found little or no difference with regard to overall survival (OS) (1521 women; hazard ratio (HR) 1.06; 95% confidence interval (CI) 0.94 to 1.19, I2 = 0%; moderate-certainty evidence) or progression-free survival in four trials where we were able to pool data (1631 women; HR 1.02; 95% CI 0.92 to 1.13, I2 = 0%; moderate-certainty evidence). Adverse events, surgical morbidity and quality of life (QoL) outcomes were poorly and incompletely reported across studies. There may be clinically meaningful differences in favour of NACT compared to PDS with regard to serious adverse effects (SAE grade 3+). These data suggest that NACT may reduce the risk of need for blood transfusion (risk ratio (RR) 0.80; 95% CI 0.64 to 0.99; four studies,1085 women; low-certainty evidence), venous thromboembolism (RR 0.28; 95% CI 0.09 to 0.90; four studies, 1490 women; low-certainty evidence), infection (RR 0.30; 95% CI 0.16 to 0.56; four studies, 1490 women; moderate-certainty evidence), compared to PDS. NACT probably reduces the need for stoma formation (RR 0.43, 95% CI 0.26 to 0.72; two studies, 581 women; moderate-certainty evidence) and bowel resection (RR 0.49, 95% CI 0.26 to 0.92; three studies, 1213 women; moderate-certainty evidence), as well as reducing postoperative mortality (RR 0.18; 95% CI 0.06 to 0.54:five studies, 1571 women; moderate-certainty evidence). QoL on the EORTC QLQ-C30 scale produced inconsistent and imprecise results in two studies (MD -1.34, 95% CI -2.36 to -0.32; participants = 307; very low-certainty evidence) and use of the QLQC-30 and QLQC-Ov28 in another study (MD 7.60, 95% CI 1.89 to 13.31; participants = 217; very low-certainty evidence) meant that little could be inferred. The available moderate-certainty evidence suggests there is little or no difference in primary survival outcomes between PDS and NACT. NACT may reduce the risk of serious adverse events, especially those around the time of surgery, and the need for bowel resection and stoma formation. These data will inform women and clinicians and allow treatment to be tailored to the person, taking into account surgical resectability, age, histology, stage and performance status. Data from an unpublished study and ongoing studies are awaited.

Plain-language summary: We found 1952 potential titles. From these we found five studies which met our inclusion criteria, including a total of 1713 women with advanced ovarian cancer. We were able to pool data from four studies. These studies compared women who were given chemotherapy prior to surgery (NACT) with women who underwent surgery first (PDS) prior to chemotherapy. We found little or no difference between the two treatments with respect to the time to death or the time to progression of the disease. We found that giving NACT probably reduces the risk of some complications of surgery, but these data were less well reported in the included studies and so we have low certainty about these results. The studies only enrolled women with stage IIIc/IV ovarian cancer i.e. those who had advanced disease; a large proportion of women in this review had very bulky tumours. We are currently awaiting results of two ongoing studies and one unpublished study that will hopefully contribute more evidence to guide clinical practice in this area in the future. Overall, the evidence was of moderate certainty. There is probably little or no difference in how long women with advanced epithelial ovarian cancer will survive, if they have chemotherapy or surgery first, where both treatments are planned. NACT may reduce some of the risks of surgery, and probably halves the risk of needing bowel removed and/or the bowel diverted through the abdominal wall via a stoma (a bag attached to the abdominal wall to collect bowel contents). NACT/IDS is an alternative to PDS followed by chemotherapy in women with bulky stage IIIc/IV disease. Individual decisions about which treatment to have first will depend on the individual woman's wishes, how well she is at the time of diagnosis, the risks of surgery and the burden and distribution of disease.