Body composition, in particular excess adiposity, has been implicated in the risk for developing some types of cancer. However, few studies have investigated a role for lean tissue in incident cancers. The aim of this study was to explore lean tissue mass as a risk factor for bowel cancer.
This study is part of the Geelong Osteoporosis Study; from 1285 women aged 30+yr assessed at baseline (1994-7) and followed prospectively for 20yr, 165 were excluded because of pre-existing cancers or incomplete DXA scans. Post-baseline admissions to the University Hospital Geelong were identified for bowel cancer according to codes ICD-9 1530-48 and ICD-10 C18-21. Body composition was determined by whole body DXA (Lunar); relative appendicular lean mass was corrected for height (rALM kg/m2) and body fat mass expressed as a percentage of body mass. Health behaviours were documented by questionnaire. Associations between rALM and cancer were tested using multivariable binary logistic regression; models were adjusted for age and other potential confounders.
22 (2.0%) bowel cases were identified (baseline age range 33-85yr). Compared to those without bowel cancer, cases were older (mean±SD: 65.0 (±14.1) vs 57.6 (±16.8) yr, p=0.024), had a greater BMI (29.9 (±6.0) vs 26.7 (±5.3) kg/m2, p=0.024), greater %body fat (40.7 (±5.4) vs 38.4 (±13.5) %, p=0.067) and greater rALM (7.1 (±1.1) vs 6.6 (±0.8) kg/m2, p=0.032). The pattern of greater rALM persisted after adjusting for age (OR=2.19, 95%CI 1.43-3.34;p<0.001) and was independent of alcohol intake and physical activity (adjusted OR=2.61, 95%CI 1.65-4.13;p<0.001); the association was not confounded by body fat mass.
Our study suggests that greater lean tissue mass may increase the risk for bowel cancer. Findings should be interpreted cautiously because of small numbers, potential case misclassification and unaccounted confounding. However, the findings warrant further research, as cancer risk might be impacted by modifying lean tissue mass.