Survival Outcomes of Extensive Stage Small Cell Lung Cancer Patients Treated with Consolidative Thoracic Radiotherapy at a Tertiary Cancer Center

PURPOSE/OBJECTIVE(S)

Most small cell lung cancer cases present as Stage IV (M1) or extensive stage (ES-SCLC), which are defined as tumor extending outside the hemithorax without a tolerable radiation portal. The CREST trial demonstrated improved local control with a modest overall survival (OS) benefit at the 2-year secondary endpoint of 14% survival with consolidative thoracic radiotherapy (CTRT) compared to 3% without CTRT. Low toxicity rates were also observed. This study reports our institutional ES-SCLC experience for patients treated with CTRT.

MATERIALS/METHODS

A retrospective review was conducted on ES-SCLC patients treated with CTRT at our institution between 2014 and 2019. CTRT was defined as ≥30 Gy of thoracic radiotherapy. OS and tolerability of treatment were assessed in this population. Chemotherapy details were also captured. OS rate was determined using the Kaplan-Meier method and the time from start of CTRT to last date of follow-up or death. CTRT tolerability was determined using incidence and grade of esophagitis and radiation pneumonitis as per CTCAE v5.

RESULTS

We identified 100 ES-SCLC patients treated with any thoracic RT at our institute, of which 45 received thoracic RT for palliative intent or with <30 Gy. The remaining 55 patients received ≥30 Gy CTRT and were included for analysis. The median age was 65.1 years (range 46.6-86.9) and 36 (65%) were male. The median follow-up for this sample was 0.8 (range 0.03-4.2) years. Median chemotherapy cycles were 6 (range 1-6), most receiving ≥4 cycles (87%) and completing chemotherapy prior to CTRT initiation (91%) with a minority concurrently receiving chemotherapy and CTRT (9%). Platinum chemotherapy was the most common (96%) with 2 patients receiving etoposide alone (4%). The most common CTRT regimens were 30 Gy in 10 fractions (80%) followed by 40 Gy in 15 fractions (9%) and 45 Gy in 30 twice-daily fractions (7%). Most patients (67%) were treated with IMRT/VMAT technique, while the remaining (33%) patients were treated with 3DCRT. The median survival time was 1.3 years with 1- and 2-year OS of 57.2% (CI 44.0 - 74.3%) and 26.1% (CI 12.9 - 52.7%), respectively. CTRT was well tolerated with no grade 4+ toxicities. The most common toxicity was esophagitis with 21 patients (39%), of which 15 were G1 (28%) and 6 were G2 (11%). Radiation pneumonitis was present in 5 patients (9.2%) with 1 G1 (2%), 3 G2 (6%), and 1 G3 (2%) cases.

CONCLUSION

Consolidative TRT for ES-SCLC in this institutional series was at least as good as the reported CREST outcome with modest acute toxicities in this cohort. Disease burden at diagnosis, chemotherapy response, patterns of failure, and subsequent therapies will be further investigated.