Abstract
BACKGROUND: Few studies have investigated the association between adiposity and connective and soft tissue cancer, a rare and understudied cancer entity. We investigated this association in a large cohort of more than 1.7 million individuals in Norway. METHODS: The study cohort included 1,723,692 men and women aged 16-75 years at baseline in 1963-1975. Data on weight and height measurements from the Norwegian Tuberculosis Screening Programme were linked to the Cancer Registry. We estimated hazard ratios (HRs) and 95% confidence intervals (CIs) for the associations between body mass index (BMI) and risk of connective and soft tissue cancer, adjusting for age and sex. RESULTS: In total 1758 connective and soft tissue cancer cases were registered during 56.1 million person-years of follow-up. The HRs (95% CIs) for the BMI categories of 15-<18.5, 18.5-<25.0 (reference), 25.0-<30.0, 30.0-<35.0, ≥ 35.0 were 0.77 (0.50-1.20), 1.00 (reference), 1.15 (1.03-1.27), 1.28 (1.06-1.54), and 1.69 (1.21-2.37, p(trend)<0.0001). The HR per 5 kg/m(2) increment in BMI was 1.14 (1.07-1.22) overall, 1.10 (0.99-1.23) in men and 1.17 (1.08-1.27) in women. Obesity in early adulthood (age 16-29 years) showed a suggestive positive association with connective and soft tissue cancer risk with HR (95%CIs) of 1.73 (0.95-3.16), p(trend)=0.09) when compared to normal weight. No clear association was observed between BMI and early-onset (age < 50 years at diagnosis) connective and soft tissue cancer. Positive associations were observed between BMI and soft tissue sarcoma, fibrosarcoma, dermatofibroma, and lipoleiomyoma, but no clear associations were observed with fibrous histiocytoma and liposarcoma. CONCLUSION: These results suggest that higher BMI overall and in early adulthood may be associated with increased risk of connective and soft tissue cancer, but BMI seems not to influence early-onset disease. Large cohort studies with more detailed information on confounding factors and BMI trajectories over time are needed for further verification before firm conclusions can be made.