Background: Prior observational studies have suggested that elevated body mass index (BMI) at the time of breast and colorectal cancer diagnosis is associated with worse prognosis. There are limited data for other cancer types. We examined the association between baseline BMI and survival across multiple cancer types using SWOG clinical trial data.

Methods: We selected previously published SWOG phase II and III clinical trials with ≥5 years of follow-up, baseline BMI and survival data. Patients with BMI <18.5 kg/m2 were excluded. Within a disease, analyses were limited to patients on similar treatment regimens. For a given treatment regimen, we combined study arms of similar histology and stage to increase power. We used variable cutpoint analysis to identify a BMI cutpoint of 25 kg/m2 to maximize differences in survival. Multivariable Cox regression analyses were used to compare survival between patients with BMI ≥ and <25 kg/m2, adjusting for age, race, sex, and major clinical prognostic factors for each disease.

Results: We identified a total of 11,724 patients in 22 eligible SWOG trials [acute myeloid leukemia, n=5; bladder, n=2; breast, n=3; colorectal, n=1; non-Hodgkin's lymphoma, n=2; non-small cell lung cancer (NSCLC), n=3; ovarian, n=1; prostate, n=2; renal, n=2; sarcoma-GIST, n=1] and performed 14 separate analyses by disease site and treatment regimen. Higher BMI was associated with better survival in bladder/BCG (HR=0.69, P=0.02), sarcoma-GIST/imatinib (HR=0.73, P=0.006), NSCLC/carboplatin+paclitaxel (HR=0.76, P=0.01), and prostate/androgen deprivation therapy (HR, 0.79, P=0.01). We did not observe difference in the following groups: prostate/docetaxel (HR=0.81, P=0.13), colorectal/5-FU (HR=0.88, P=0.12), NHL/CHOP (HR=0.89, P=0.47), renal/a-IFN (HR=0.98, P=0.90), AML/ara-C-DNR (HR=1.04, P=0.52), NSCLC/CDDP+vinorelbine (HR=1.05, P=0.65), breast/CAF (HR=1.18, P=0.28), ovarian/paclitaxel (HR=1.18, P=0.38), breast/AC+paclitaxel (HR=1.23, P=0.16), and breast/CMF (HR=1.27, P=0.42). Across all groups, we did not observe differences in survival (mean HR=0.96, P=0.06). However, in sex-stratified analyses, BMI ≥25 kg/m2 was associated with an overall protective effect among men (HR=0.86; P=0.003), but not among women (HR=1.04; P=0.86). This association was maintained when sex-specific cancers (breast, ovarian, prostate) were excluded, and among treatment regimens with dose based on body-surface area only.

Conclusions: Our findings suggest that sex-related hormonal factors may interact with BMI and affect cancer survival, and that higher BMI at the time of a cancer diagnosis may be protective for men. Among women there was much more variability in the association between BMI and overall survival.

Citation Format: Heather Greenlee, Joseph Unger, Michael LeBlanc, Dawn L. Hershman. Association between BMI at treatment initiation and cancer survival across multiple SWOG trials. [abstract]. In: Proceedings of the Thirteenth Annual AACR International Conference on Frontiers in Cancer Prevention Research; 2014 Sep 27-Oct 1; New Orleans, LA. Philadelphia (PA): AACR; Can Prev Res 2015;8(10 Suppl): Abstract nr A44.