Will we still treat ED-SCLC patients with consolidation RT in the era of immunotherapy?

Abstract

Background. Consolidation radiotherapy (cRT) in extended disease small cell lung cancer (ED-SCLC) showed improved 2-year overall survival in patients who responded to chemotherapy (ChT) in CREST trial, however results of two meta - analysis were contradictive. Recently, immunotherapy was introduced to the treatment of ED-SCLC, making the role of cRT even more unclear.

Patients and methods. We retrospectively reviewed 704 medical records of patients with small cell lung cancer treated at the Institute of Oncology Ljubljana from January 2010 to December

2014 with median follow up of 65 months. We analyzed median overall survival (mOS) of patients with ED-SCLC treated with ChT only and those treated with ChT and consolidation radiotherapy (cRT). We also compared mOS of patients treated with different consolidation doses.

Results. We included 412 patients with ED-SCLC in our analysis. Of those 59 (14.3%) patients received only best supportive care (BSC) and 66 (16%) patients had only RT. Median OS of those patients was poor, 1.86 and 2.42 months, respectively. Chemotherapy only was delivered to 113 (31.6%) patients, while 173 (42%) patients had combination of ChT and RT. Consolidation radiotherapy was delivered to 74 patients. Patients with cRT had significantly longer mOS compared to patients with ChT only, 11.1 months (CI 10.1-12.0) vs 7.6 months (CI 6.9 - 8.5), p<0.001 and 1-year OS (44% vs 23%, p=0.0025) as well as 2-year OS (10% vs 5%, p=0.19). The cRT dose was not uniform. Higher dose with 45 Gy (in 18 fractions) resulted in better mOS compared to lower doses 30-36 Gy (in 10-12 fractions), 17.2 months vs 10.3 months (p=0.03) and difference was also seen for 1-year OS (68% vs 30%, p=0.01) and 2-year OS (18% vs 5%, p=0.11).

Conclusions. Consolidation RT improved mOS in ED-SCLC as compared to ChT alone. Consolidation RT, higher number of ChT cycles and prophylactic cranial irradiation (PCI) were independent prognostic factors for better survival in our analysis. For patients who received cRT, only higher doses and PCI had impact on survival regardless of number of ChT cycles received. Role of cRT in the era of immunotherapy is unknown and should be exploited in further trials.