Population-based multicase-control study in common tumors in Spain (MCC-Spain): rationale and study design.

INTRODUCTION: We present the protocol of a large population-based case-control study of 5 common tumors in Spain (MCC-Spain) that evaluates environmental exposures and genetic factors.
METHODS: Between 2008-2013, 10,106 subjects aged 20-85 were enrolled in 23 hospitals and primary care centres in 12 Spanish provinces including 1,112 cases with a new diagnosis of prostate cancer, 1,738 of breast cancer, 2,140 of colorectal cancer, 459 of gastro-oesophageal cancer, 559 cases with chronic lymphocytic leukaemia and 4,098 population controls frequency matched to cases by age, sex and region of residence. Participation rates ranged from 57% (stomach cancer) to 87% (CLL cases) and from 30% to 77% in controls. Participants completed a face-to-face computerized interview on sociodemographic factors, environmental exposures, occupation, medication, lifestyle, and personal and family medical history. In addition, participants completed a self-administered food-frequency questionnaire and telephone interviews. Blood samples were collected from 76% of participants while saliva samples were collected in CLL cases and participants refusing blood extractions. Clinical information was recorded for cases and paraffin blocks and/or fresh tumor samples are available in most collaborating hospitals. Genotyping was done through an exome array enriched with genetic markers in specific pathways. Multiple analyses are planned to assess the association of environmental, personal and genetic risk factors for each tumor and to identify pleiotropic effects. DISCUSSION: This study, conducted within the Spanish Consortium for Biomedical Research in Epidemiology & Public Health (CIBERESP), is a unique initiative to evaluate etiological factors for common cancers and will promote cancer research and prevention in Spain.