Simultaneously modulated accelerated radiation therapy reduces severe oesophageal toxicity in concomitant chemoradiotherapy of locally advanced non-small-cell lung cancer

Objective: The aim of this study was to evaluate the potential of simultaneously modulated accelerated radiation therapy (SMART) to reduce the incidence of severe acute oesophagitis in the treatment of unresectable locally advanced non-small-cell lung cancer (LANSCLC). Methods: 21 patients were treated with SMART and concomitant platinum-based chemotherapy. The prescribed doses were limited to 54 Gy at 1.8 Gy per day to the zones of presumed microscopic extent while simultaneously maintaining doses of 66 Gy at 2.2 Gy per day to the macroscopic disease. The whole treatment was delivered over 30 fractions and 6 weeks. Dosimetric parameters of SMART and the standard technique of irradiation [intensity-modulated radiation therapy (IMRT)] were compared. Acute toxicity was prospectively recorded. Results: The highest grade of oesophagitis was 62% (13 patients) grade 1, 33% (7 patients) grade 2 and 5% (1 patient) grade 3. Three (14%) patients experienced acute grade 2 pneumonitis. There was no grade 4 oesophageal or pulmonary toxicity. Doses to the organs at risk were significantly reduced in SMART compared with IMRT [oesophagus: V-50Gy, 28.5 Gy vs 39.9 Gy (p=0.003); V-60Gy, 7.1Gy vs 30.7Gy (p=0.003); lung: V-20Gy, 27.4Gy vs 30.1Gy (p=0,002); heart: V-40Gy, 7.3Gy vs 10.7 Gy (p=0.006); spine: Dmax, 42.4Gy vs 46.4Gy (p=0.003)]. With a median follow-up of 18 months (6-33 months), the 1-year local control rate was 70% and the disease-free survival rate was 47%. Conclusion: SMART reduces the incidence of severe oesophagitis and improves the whole dosimetric predictors of toxicity for the lung, heart and spine. Advances in knowledge: Our study shows that SMART optimizes the therapeutic ratio in the treatment of LANSCLC, opening a window for dose intensification.