Development of second primary small‐cell lung cancer within the irradiated field after chemoradiotherapy: a report of two cases

Two male smokers developed small-cell lung cancer (SCLC) as the second primary malignancy (SPM) in the irradiated field after concurrent chemoradiotherapy for locally advanced cancer, which could also be considered as a radiation-induced tumour. A 70-year-old man received cisplatin and S-1 and irradiation at 60 Gy for lung adenocarcinoma eight years previously and an 81-year-old man cisplatin and 5-fluorouracil and at irradiation 60 Gy for oesophageal cancer five years previously. They sequentially received chemotherapy for SCLC, the effects of which were limited, and a refractory course was noted. Chemoradiotherapy is an effective treatment strategy for locally advanced cancer but may be relevant to the onset of SCLC as SPM.