Long-term outcomes after concurrent once- or twice-daily chemoradiation in limited-stage small-cell lung cancer: a brief report from the CONVERT trial.

INTRODUCTION: CONVERT was a phase 3 international randomized clinical trial comparing once-daily (OD) and twice-daily (BD) radiation therapy (RT). This updated analysis describes the 6.5 year outcomes of these regimes delivered with conformal techniques.

METHODS: CONVERT (NCT00433563) randomized patients 1:1 between OD RT (66 Gy/33 fractions/6.5 weeks) and BD RT (45 Gy/30 fractions/3 weeks) both delivered with concurrent cisplatin/etoposide. Three-dimensional conformal RT was mandatory, intensity-modulated RT was permitted, and elective nodal irradiation was not allowed. Prophylactic cranial irradiation was delivered at the discretion of treating clinicians. RT treatment planning was subject to central quality assurance.

RESULTS: 547 patients were recruited at 73 centres. The median follow-up for the surviving cohort (n=164) was 81.2 months. The median survival for the OD and BD arms were 25.4 months (95%CI 21.1-30.9) and 30.0 months (95%CI 25.3-36.5), HR 1.13 (95%CI 0.92-1.38), p=0.247. Performance status and tumour volume were associated with survival on multivariate analysis. No treatment-related deaths occurred subsequent to the initial analysis performed in 2017. Regarding late toxicity, 7 patients in the OD arm developed grade 3 esophagitis, 4 of which went on to develop stricture or fistulation, compared with no patients in the BD arm. Grade 3 pulmonary fibrosis occurred in 2 and 3 patients in the OD and BD arms respectively.

CONCLUSIONS: As the CONVERT trial did not demonstrate the superiority of OD RT and this regime had a slightly worse toxicity profile after 80 months of follow-up, 45 Gy BD should remain the standard of care in limited stage small cell lung cancer.