A population-based case-control study (Zahm et al, 1989) conducted in Kansas, USA and based on 133 cases showed that the risk of soft-tissue sarcoma (STS) increased with adult body weight, the odds ratio (OR) being 2.0 for people weighing more than 200 pounds. To provide further information on this issue, we analysed data from a large case-control study conducted in Italy.
SUBJECTS AND METHODSData were derived from a case-control study of STS, conducted between 1983 and 1998 in the greater Milan area and the province of Pordenone, northern Italy (Serraino et al, 1991;Tavani et al, 1997).Cases were 217 patients (113 men, median age 52 years, range 21-79; and 104 women, median age 54 years, range 16-79) with histologically confirmed incident (i.e. diagnosed within the year preceding the interview) STS (International Classification of Diseases IX Edition ICD-171) admitted to the cancer institutes and major teaching and general hospitals of the areas under surveillance.Controls were 1297 patients (792 men, median age 55 years, range 17-79; and 505 women, median age 57 years, range 17-79) admitted to the same network of hospitals for acute, nonneoplastic and non-immune-related conditions. Of the comparison group, 15% were admitted for traumas, 27% for other orthopaedic disorders (such as low back pain and disc diseases), 29% for acute surgical conditions (such as acute appendicitis or strangulated hernia), and 28% for other miscellaneous illnesses (such as ear, nose and throat, eye, dental or skin disorders). On average, fewer than 4% of the eligible cases and controls refused the interview.Trained interviewers used a structured questionnaire to collect data on socio-demographic characteristics, anthropometric measures (self-reported weight and height), personal and family history of selected medical conditions, a few selected occupational and environmental exposures, smoking status and consumption of alcohol, coffee and selected dietary items.
Data analysisBody mass index (BMI) was computed according to Quetelet's index (weight height -2 , kg m -2 ), which is essentially an indicator of weight unrelated to height (Benn, 1971). Odds ratios (OR) with their corresponding 95% confidence intervals (CI) were derived using unconditional multiple logistic regression analysis, fitted by the method of maximum likelihood (Breslow and Day, 1980). The regression models included terms for study centre, year of recruitment, age (8 levels plus a continuous term) and education. Table 1 gives the distribution of STS cases and controls by sex according to age and BMI, and the OR of STS according to BMI. The risk of STS rose with BMI, and the OR was 3.28 in subjects with a BMI > 30 compared to those with BMI ≤ 20. The OR was 3.49 for men and 3.26 for women. The risk estimates did not change after further adjustment for employment in agriculture and radiation therapy: the OR became 3.41 and 3.53 respectively for men and women with BMI > 30 compared to those with BMI ≤ 20.
RESULTSA separate analysis for broad categories of anatomical sit...