Receipt of thoracic radiation therapy and radiotherapy dose are correlated with outcomes in a retrospective study of three hundred and six patients with extensive stage small-cell lung cancer

Abstract

Background: The importance of the thoracic radiation therapy (TRT) dose has not been clearly defined in extensive stage small-cell lung cancer (ES-SCLC) and it is unclear whether improved TRT dose translates into a survival benefit.

Methods: 306 patients with ES-SCLC were retrospectively reviewed, of which 170 received IMRT/CRT fractionation RT after ChT, and 136 received chemotherapy (ChT) alone. We adopted the time-adjusted BED (tBED) for effective dose fractionation calculation. Due to the nonrandomized nature of this study, we compared the ChT+RT with ChT groups that matched on possible confounding variables.

Results: Patients achieved 2-year OS, PFS and LC rates of 19.7%, 10.7% and 28.4%, respectively. After propensity score matching, (113 cases for each group), the rates of OS, PFS and LC at 2 years were 21.4%, 7.7% and 34.5% for ChT+TRT, and 10.3% (p<0.001), 4.6% (p<0.001) and 6.3% for ChT only (p<0.001), respectively. Among propensity score matching patients, 56 cases for each group received the high dose (tBED>50 Gy) TRT and received low dose (tBED≤50 Gy) TRT. Two-year OS, PFS and LC rates were 32.3%, 15.3% and 47.1% for the high dose compared with 17.0% (p<0.001), 12.9% (p=0.097) and 34.7% (p=0.029) for low dose radiotherapy.

Conclusions: TRT added to ChT improved ES-SCLC patient OS. High dose TRT improved OS over lower doses. Our results suggest that high-dose thoracic radiation therapy may be a reasonable consideration in select patients with ES-SCLC.

Keywords: Extensive stage; Prognosis; Radiation dose; Small cell lung cancer; Thoracic radiation therapy.