Radiotherapy; Breast Cancer

East Asian female breast cancer patients receiving radiotherapy have a higher risk of developing second primary lung cancer. Lung cancer is the leading cause of cancer deaths worldwide, causing more deaths than breast, colon and prostate cancers combined. The risk factors for developing lung cancer include tobacco smoking, age, family history, medical or occupational radiation exposure and other chronic inflammatory diseases such as pulmonary fibrosis and chronic obstructive pulmonary disease