Abstract: We included three RCTs in the review, randomising a total of 161 overweight and obese women with endometrial cancer. All studies compared combined behavioural and lifestyle interventions to facilitate weight loss through dietary modification and increased physical activity. The included RCTs were of low or very low quality, due to high risk of bias by failing to blind participants, personnel and outcome assessors, and significant loss to follow-up (attrition rate up to 29%). Combined behaviour and lifestyle interventions were not associated with improved overall survival (risk ratio (RR mortality), 0.23 95% confidence interval (CI) 0.01 to 4.55, P = 0.34, one RCT, 37 participants; very low-certainty evidence) compared with usual care at 24 months. There was no evidence that such interventions were associated with improvements in cancer-specific survival or cardiovascular event frequency as no cancer-related deaths, myocardial infarctions or strokes were reported in the included studies. None of the included RCTs reported data for the outcome of recurrence-free survival. Combined behaviour and lifestyle interventions were not associated with significant weight loss at either six months (mean difference (MD) -1.88 kg, 95% CI -5.98 to 2.21 kg, P = 0.37, three RCTs, 131 participants, I2= 0%; low-certainty evidenc e)or 12 months (MD -8.98 kg, 95% CI -19.88 to 1.92 kg, P = 0.11, two RCTs, 91 participants, I2= 0%; very low-certainty evidence) when compared with usual care. Combined behaviour and lifestyle interventions were not associated with increased quality of life, when measured using either the SF-12 Physical Health questionnaire or FACT-G at six months (FACT-G MD 2.51, 95% CI -5.61 to 10.64, P = 0.54, two RCTs, 95 participants, I2= 83%; very low-certainty evidence), or by FACT-G alone at 12 months (MD 2.77, 95% CI -0.65 to 6.20, P = 0.11, two RCTs, 89 participants, I2= 0%; very low-certainty evidence) when compared with usual care. No serious adverse events, for example hospitalisation or deaths, were reported in included trials. Lifestyle and behavioural interventions were associated with a higher risk of musculoskeletal symptoms (RR 19.03, 95% CI 1.17, 310.52, P = 0.04, two RCTs, 91 participants; low-certainty evidence). There is currently insufficient high-quality evidence to determine the effect of combined lifestyle and behavioural interventions on survival, quality of life, or significant weight loss in women with a history of endometrial cancer compared to those receiving usual care. The limited evidence suggests that there is little or no serious or life-threatening adverse effects due to these interventions, although musculoskeletal problems were increased, presumably due to increased activity levels. Our conclusion is based on low- and very low-quality evidence from a small number of trials and very few patients. We therefore have very little confidence in the evidence: the true effect of weight-loss interventions in obese women with endometrial cancer is currently not known. Further methodologically-rigorous, adequately-powered RCTs are required with follow-up of 5 to 10 years duration. These should focus on the effects of varying dietary modification regimens, pharmacological treatments associated with weight loss and bariatric surgery on survival, quality of life, weight loss and adverse events.

Plain-language summary: We included three randomised controlled trials in which women were allocated at random to receive one of several interventions (treatments) and which involved 161 obese participants. The trials were conducted in the USA and the UK. All compared lifestyle advice (diet and exercise) plus self-help techniques (to encourage adherence to the advice) with usual care. The evidence is current to January 2018. We found no benefit for endometrial cancer survivors from receiving lifestyle advice in terms of survival, cardiovascular events or quality of life, though such interventions were not associated with significant or serious harms to participants. They did, however, report higher rates of musculoskeletal symptoms, presumably due to increases in physical activity. Whilst some women lost weight with these interventions, others did not, meaning that overall there was little or no benefit. The quality of included studies was, however, low or very low and all were small in terms of the number of participants and not designed to specifically look at the effect of their intervention on survival. Additional high-quality studies are required in this field and currently there are five ongoing trials.