Final report of a prospective randomized study on thoracic radiotherapy target volumes for limited-stage small cell lung cancer

Objective In view of the controversy over radiotherapy target volume for patients with limited-stage small cell lung cancer (SCLC), a prospective randomized controlled trial was conducted to compare the impact of different radiotherapy target volumes on prognosis. Methods After 2 cycles of EP chemotherapy, patients without progressive disease were randomly assigned to receive thoracic radiotherapy (TRT) to either the post-or pre-chemotherapy primary tumour extent as study arm or control. Involved field radiotherapy (IFRT) to the entire metastatic lymph node regions was applied for both arms. TRT consisted of 45 Gy/30Fx/19 d administered concurrently with cycle 3 chemotherapy. Prophylactic cranial irradiation was administered to patients achieved complete or partial remission. Kaplan-Meier method was used for survival analysis. Results Between June 2002 and December 2017, 159 and 150 patients were randomly assigned to study arm and control respectively. The 1-, 2-, and 5-year local/regional control rates were 79.4%, 61.5% and 60.1% respectively in the study arm versus 79.8%, 66.5%, and 57.3% in the control arm (P=0.73). The median OS time was 22.1 months in the study arm (95%CI, 18.2-26.0 months) and 26.9 months (95%CI, 23.5-30.3 months) in the control arm, the 1-, 3-, 5-, and 7-year OS rates were 81.1%, 31.6%, 23.9% and 22.2% respectively in the study arm versus 85.3%, 36.6%, 26.1% and 20.0% in the control arm (P=0.51). Grade 2-3 acute esophagitis was developed in 32.9% and 43.2% of patients respectively in study arm and control arm (P=0.01), while grade 2-3 pulmonary fibrosis was observed in 2.0% and 10.9% of patients (P=0.01) respectively. Conclusions For patients with limited-stage SCLC who received induction chemotherapy, thoracic radiotherapy can be limited to post-chemotherapy tumour extent and IFRT can be routinely applied. Key words: Lung neoplasms/radiotherapy; Radiotherapy target volume; Prospective study