Accelerated hypofractionated thoracic radiotherapy in limited disease small cell lung cancer : comparison with the results of conventionally fractionated radiotherapy

Purpose: To compare accelerated hypofractionated (A-HYPO) radiotherapy (RT) with conventionally fractionated (CF) thoracic RT in patients with limited-disease small-cell lung cancer (LD-SCLC). Methods: Out of 217 consecutive LD-SCLC patients, treated between 1997 and 2012, 82 received CF-RT (44-60 Gy. 2 Gy/fraction) sequentially to 4-6 cycles of platinum-based chemotherapy (CHT), and 100 received A-HYPO-RT (42 Gy, 2.8 Gy/fraction). Forty-two patients (42%) received "early" (before the 3rd cycle of CHT) A-HYPO-RT, and 58 (58%) patients received "late" A-HYPO-RT. Overall survival (OS), locoregional failure risk (LRFR) and toxicities were retrospectively evaluated and compared between CF-RT and A-HYPO-RT groups (also separately for "early" and "late" A-HYPO-RT). Results: Median survival times (MST) for CF-RT and A-HYPO-RT were 18 and 24 months, respectively; 3-year OS were 19.1 and 39.4%, respectively (p=0.004). Three-year LRFR in CF-RT was 47.3% and 34.0% in the A-HYPO-RT group (p=0.12). Statistically significant difference in OS (p=0.007) and LRFR (p=0.03) was observed, favoring "early" A-HYPO-RT (MST=27 months, 3-year OS=40.0%, 3-year LRFR=28.4%) over CF-RT. Use of CF-RT (relative risk/RR=1.65, p=0.02) and poor CHT compliance (RR=1.69, p=0.03) were independent prognostic factors for poor OS; "early" start of RT was a favorable although non-significant prognostic factor for LRFR (RR=0.42, p=0.05). No difference in toxicities was observed between the groups. Conclusions: A-HYPO-RT results in better outcomes than CF-RT. "Early" A-HYPO-RT provides additional benefit in locoregional control and survival, without increased toxicity. These results indicate the need for a randomized study on the efficacy of A-HYPO-RT.