The magnitude of the association between smoking and the risk of developing cancer in Brazil: a multicenter study

OBJECTIVES To estimate the magnitude of association and identify the aetiological fraction (AF) attributable to smoking in the development of different types of cancers in Brazil. SETTING We conducted a case-control study, including 231 102 patients registered in the Cancer Hospital Registries (CHR) in the period from 1998 to 2011. PARTICIPANTS A total of 204 131 cancer cases relating to 30 topographies were compared with 26 971 cases of non-melanoma skin cancer. PRIMARY AND SECONDARY OUTCOME MEASURES Smoking exposure was considered at the time of hospital registration. We calculated OR, unadjusted and adjusted for gender, age and alcohol consumption, with 95% CIs. RESULTS After adjustment, the risk of developing cancer associated with smoking was very high (piriform sinus, bronchi and lung, larynx, hypopharynx, oropharynx and oral cavity), high (oesophagus and bladder), moderate (anus and anal canal stomach, nasal cavity, middle ear and paranasal sinuses, pancreas, nasopharynx, other parts of the biliary tract and kidney and low (liver, gall)). There was no association between smoking and cancers of the central nervous system and myeloid leukaemia. For thyroid cancer there was a decreased risk of developing the disease. The AF was higher than 50% for hypopharynx, larynx, bronchi and lung, oropharynx, oral cavity and oesophagus cancers. CONCLUSIONS This study confirms a high risk of developing cancer of the hypopharynx, bronchi and lung, larynx, oropharynx and oral cavity, oesophagus and bladder cancer among smokers and establishes the AF attributable to smoking in the development of different types of cancer in Brazil.