Abstract: We included four multicentre RCTs involving 1269 women with primary FIGO stage III/IV endometrial cancer. We considered the trials to be at low to moderate risk of bias. All participants received primary cytoreductive surgery. Two trials, evaluating 620 women (83% stage III, 17% stage IV), compared adjuvant chemotherapy with adjuvant radiotherapy; one trial evaluating 552 women (88% stage III, 12% stage IV) compared two chemotherapy regimens (cisplatin/doxorubicin/paclitaxel (CDP) versus cisplatin/doxorubicin (CD) treatment) in women who had all undergone adjuvant radiotherapy; and one trial contributed no data. Overall survival (OS) and progression-free survival (PFS) was longer with adjuvant chemotherapy compared with adjuvant radiotherapy (OS: hazard ratio (HR) 0.75, 95% confidence interval (CI) 0.57 to 0.99, I² = 22%; and PFS: HR 0.74, 95% CI 0.59 to 0.92, I² = 0%). Sensitivity analysis using adjusted and unadjusted OS data, gave similar results. In subgroup analyses, the effects on survival in favour of chemotherapy were not different for stage III and IV, or stage IIIA and IIIC (tests for subgroup differences were not significant and I² = 0%). This evidence was of moderate quality. Data from one trial showed that women receiving adjuvant chemotherapy were more likely to experience haematological and neurological adverse events and alopecia, and more likely to discontinue treatment (33/194 versus 6/202; RR 5.73, 95% CI 2.45 to 13.36), than those receiving adjuvant radiotherapy. There was no statistically significant difference in treatment-related deaths between the chemotherapy and radiotherapy treatment arms (8/309 versus 5/311; Risk Ratio (RR) 1.67, 95% CI 0.55 to 5.00). There was no clear difference in PFS between intervention groups in the one trial that compared CDP versus CD (552 women; HR 0.90, 95% CI 0.69 to 1.17). We considered this evidence to be of moderate quality. Mature OS data from this trial were not yet available. Severe haematological and neurological adverse events occurred more frequently with CDP than CD. We found no trials to include of adjuvant chemotherapy versus chemoradiation in advanced endometrial cancer; however we identified one ongoing trial of this comparison. There is moderate quality evidence that chemotherapy increases survival time after primary surgery by approximately 25% relative to radiotherapy in stage III and IV endometrial cancer. There is limited evidence that it is associated with more adverse effects. There is some uncertainty as to whether triplet regimens offer similar survival benefits over doublet regimens in the long-term. Further research is needed to determine which chemotherapy regimen(s) are the most effective and least toxic, and whether the addition of radiotherapy further improves outcomes. A large trial evaluating the benefits and risks of adjuvant chemoradiation versus chemotherapy in advanced endometrial cancer is ongoing.

Plain-language summary: Women who received chemotherapy after surgery (starting within eight weeks of surgery) survived approximately 25% longer than those receiving radiotherapy after surgery. Assuming that 60% of women with stage III endometrial cancer usually survive at least five years after surgery and radiotherapy, this would increase to 75% if they receive surgery and chemotherapy instead, depending on other risk factors, such as age. The risk of death which might have been caused by treatment was low with both chemotherapy and radiotherapy but we could not be sure if one was more harmful than the other. Chemotherapy may be associated with more side-effects (low blood counts, nerve damage and hair loss) compared with radiotherapy. In the trial that compared two different chemotherapy treatments, there was no clear evidence that using three anti-cancer drugs was better than using two. However, the final overall survival results of this trial have not yet been reported. Severe side-effects were much more common in women treated with three anti-cancer drugs than two drugs. Chemotherapy appears to be more effective than radiotherapy after surgery for women with stage III and IV endometrial cancer but may cause more side-effects. More research is needed to determine whether the addition of radiotherapy to chemotherapy improves outcomes and which anti-cancer drugs are best.