BACKGROUND

Lung cancer is the leading cause of cancer deaths in France. The number of deaths in 2018 is estimated at 33,117, of which 31% are women. The incidence is estimated at 46,363 cases for 2018 (33% women). The increase of this incidence in women is related to smoking. However, tobacco is not the only responsible. There is evidence on the risk of radiotherapy, used in the treatment of breast cancer. This risk is strongly related to smoking status (4% smokers vs. 0.3% non-smokers).

OBJECTIVES : and METHODS

A prospective longitudinal randomized multicenter study to evaluate the risk of lung cancer among former or current-smoking women undergoing irradiation for breast cancer will be conducted. Patients will be randomized in two groups: standard of care follow up or advanced follow up including "Liquid biopsy" consisting in the analysis of circulating biomarkers from peripheral blood (tumor cells and circulating tumor DNA). The primary endpoint is the rate of localized lung cancer. This rate is currently at 20%. The expected gain by adding biological markers is 10%. The number of required patients, with unilateral alpha risk of 5% and 80% power, with a 2:1 ratio, experimental (EG) compared to control group (CG), is 370 for EG and 185 for CG, corresponding to a total of 555 patients rounded up to 560. After correcting the rate of effective participation and knowing that 10% of the irradiated women will develop a lung cancer at 10 years, we therefore calculated that 7,000 former or current-smoking women, undergoing irradiation for breast cancer need to be recruited, with the following distribution: EG: 4,667 and CG: 2,333 patients.

RESULTS : and CONCLUSIONS

This study will provide data to establish whether the combined effect of irradiation and smoking status in women undergoing radiotherapy for breast cancer, is related to lung cancer.