[Preventability estimates for colorectal and breast cancer in Germany. A methodological evaluation of the risk factors alcohol and overweight].

Population attributable fractions (PAFs) for the risk factors alcohol intake and overweight in the German population were calculated to estimate the preventability of colorectal and breast cancer attributable to these risk factors. Estimates were based on national alcohol consumption and overweight prevalence data in the German population. Comparative analyses were used to evaluate the variation of PAF estimates according to changes in the calculation parameters. PAFs quantify the preventive potential that could result from removing or reducing the risk factor exposure, respectively. Postmenopausal breast cancer was estimated to be preventable by 13-23% if the population were normal weight. Among German men, 10-25% of colon cancers were attributable to alcohol consumption and 7-13% of colorectal cancers to overweight. The comparative analyses demonstrated that preventability estimates vary considerably with the chosen data (risk estimates, reference categories) for PAF calculation and can differ by up to 50%. Thus, data selection should be evidence based, for example, based on meta-analyses, in order to increase the validity of preventability estimates.