title: Body mass index does not influence post-treatment survival in early stage endometrial cancer: results from the MRC ASTEC trial.
abstract: Body mass index (BMI) is a major risk factor for endometrial cancer incidence but its impact on post-treatment survival is unclear. We investigated the relationships of BMI (categorised using the WHO definitions) with clinico-pathological characteristics and outcome in women treated within the MRC ASTEC randomised trial, which provides data from patients who received standardised allocated treatments and therefore reduces biases. The impact of BMI on both recurrence-free survival (RFS) and overall survival (OS) was analysed using the Cox regression models. An apriori framework of evaluating potential biases was explored. From 1408 participants, there were 1070 women with determinable BMI (median=29.1 kg/m(2)). Histological types were endometrioid (type 1) in 893 and non-endometrioid (type 2) in 146 women; the proportion of the latter decreasing with increasing BMI (8% versus 19% for obese III WHO category versus normal weight, p(trend)=0.003). For type 1 carcinomas, increasing BMI was associated with less aggressive histopathological features (depth of invasion, p=0.006; tumour grade, p=0.015). With a median follow-up of 34.3 months, there was no influence of BMI on RFS - adjusted HRs per 5 kg/m(2) were 0.98 (95% CI 0.86, 1.13) and 0.95 (0.74, 1.24), for type 1 and 2 carcinomas; and no influence on OS - adjusted HRs per 5 kg/m(2) were 0.96 (0.81, 1.14) and 0.92 (0.70, 1.23), respectively. These findings demonstrate an important principle: that an established link between an exposure (here, obesity) and increased incident cancer risk, does not necessarily translate into an inferior outcome following treatment for that cancer.
authors.affiliation: Gynaecology Oncology Research Group, School of Cancer and Enabling Sciences, University of Manchester, Manchester, UK.
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Crosbie
authors.forename: Chris
authors.initials: C
authors.lastname: Roberts
authors.forename: Wendi
authors.initials: W
authors.lastname: Qian
authors.forename: Ann Marie
authors.initials: AM
authors.lastname: Swart
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kitchener
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Renehan
mesh_terms: D000704:Analysis of Variance; D015992:Body Mass Index; D018269:Carcinoma, Endometrioid / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D016889:Endometrial Neoplasms / Q000401:mortality* / Q000473:pathology / Q000628:therapy; D005260:Female; D006801:Humans; D008875:Middle Aged; D016016:Proportional Hazards Models; D016019:Survival Analysis; D006113:United Kingdom / Q000453:epidemiology