A study explored the joint effect of smoking or alcohol drinking, and radiotherapy on the risk of second primary cancer and overall mortality among Breast Cancer survivals.
10,676 breast cancer cases (stage 0-III) with data on smoking and alcohol consumption at time of diagnosis and clinical and therapeutics characteristics were included. Models were used to estimate Hazard Ratios [HRs] and 95% confidence interval [CI] of total and site-specific second primary cancer and mortality adjusting for demographic and cancer related characteristics.
The second primary cancer risk associated with radiotherapy was higher among ever-smokers than never-smokers. Compared to never-smokers/ unirradiated, the adjusted HR for ever-smokers/ irradiated was 1.79 (95%CI, 1.43-2.23), and for never-smokers/irradiated was 1.31 (95%CI, 1.06- 1.63). Analysis by cancer site showed that for eversmokers/ irradiated the risk for hematological, gastrointestinal, gynaecological urological and lung/pulmonary cancer was significantly increased by two to five-fold. Mortality was significantly higher for ever-smokers/irradiated (HR = 1.25; 95%CI, 1.06-1.47), but was lower for neversmokers/ irradiated (HR = 0.85; 95%CI, 0.73-0.99). Alcohol consumption did not alter the association between radiotherapy and second primary cancer risk, but was associated with lower mortality risk.
Patients who received radiotherapy and smoked before or at time of breast cancer diagnosis have an increased risk for specific second primary cancers; drinking alcohol did not alter the effect of radiotherapy. Smoking significantly increased mortality risk reducing the protective effect of radiotherapy treatment.
Source: Smoking and alcohol drinking effect on radiotherapy associated risk of second primary cancer and mortality among breast cancer patients. DiMarzio P, Peila R, Dowling O, Timony DM, Balgobind A, Lee LN, Kostroff KM, Ho GYF. Cancer Epidemiol. 2018 Oct 22;57:97-103.