CONVERT Trial Shows No Advantage to Once-Daily Radiotherapy for LS-SCLC


The phase 3 CONVERT study suggests that twice-daily radiotherapy remains the standard for limited-stage small cell lung cancer due to its effectiveness and lower associated toxicity compared to the once-daily approach.

Small cell lung cancer: © Констянтин Батыльчук-

Small cell lung cancer: © Констянтин Батыльчук-

The phase 3 CONVERT trial (NCT00433563) comparing once-daily (OD) and twice-daily (BD) radiation therapy (RT) did not demonstrate the superiority of OD RT among patients with limited-stage small cell lung cancer (LS-SCLC), suggesting 45 Gy BD should remain the standard of care in this patient population.1

In the international, randomized clinical trial, 547 patients recruited across 73 centers were included. Those treated with OD RT at 66 Gy/33 fractions/6.5 weeks compared with BD RT at 45 Gy/30 fractions/3 weeks had a slightly worse toxicity profile after 80 months of follow-up, according to findings in an updated analysis describing the 6.5-year outcomes of these regimens.

While no treatment-related deaths were seen following the initial analysis that was performed in 2017, late toxicity findings showed that 7 patients given the OD regime developed grade 3 esophagitis vs no patients in the BD arm, and grade 3 pulmonary fibrosis was seen in 2 patients in the OD arm vs 3 patients in the BD arm, respectively.

Findings showed that the median follow-up for the surviving cohort, which consisted of 164 patients, was 81.2 months. In the OD and BD arms, the median survival rates were 25.4 months (95% CI, 21.1-30.9) and 30.0 months (95% CI, 25.3-36.5), respectively, with an HR of 1.13 (95% CI, 0.92-1.38; P =.247).

The CONVERT trial randomly assigned patients in a 1:1 fashion to receive either OD RT at a dose of 66 Gy/33 fractions for 6.5 weeks or BD RT at 45 Gy/30 fractions for 3 weeks, both delivered with concurrent cisplatin/etoposide. Treatment in both arms continues in the absence of disease progression or unacceptable toxicity.

For definitive treatment, a 3D conformal RT plan was mandatory. Intensity-modulated RT was allowed for improved plan conformity, while elective nodal irradiation was not. Prophylactic cranial irradiation (PCI) remained at the treating physician's discretion, and central quality assurance ensured adherence to treatment planning protocols.

On multivariate analysis, performance status and primary tumor volume emerged as significant prognostic factors for survival.

Of the 547 patients recruited, the median age was 62 years, more than 95% of patients had a performance score of 0 or 1, and one-third were current smokers. Additionally, 57% of patients were PET/CT-staged, and 78% had stage III disease.

The primary end point of the trial was to compare overall survival of patients with LS-SCLC treated with chemoradiotherapy comprising cisplatin, etoposide, and OD vs TD RT.2 This trial also evaluates several key secondary end points, including assessing local control of the disease by comparing local progression-free survival between the treatment groups, metastasis-free survival, patient tolerability as compared through a comprehensive analysis of treatment-related toxicities, overall response rates, and dose intensity achieved with the 2 different treatment schedules.

1. Walls GM, Mistry H, Barlesi F, et al. Long-term outcomes after concurrent once- or twice-daily chemoradiation in limited-stage small-cell lung cancer: a brief report from the CONVERT trial. Int J Radiat Oncol Biol Phys. Published online March 11, 2024. doi:10.1016/j.ijrobp.2024.02.063
2. Concurrent once daily versus twice daily radiotherapy for limited stage small cell lung cancer (CONVERT). Updated September 8, 2022. Accessed April 9, 2024. https://www.clinicaltrials.govshow/NCT00433563
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