Purpose: To define the maximal tolerated dose of hypofractionated thoracic radiotherapy given with concurrent chemotherapy for limited-stage small cell lung cancer.
Materials and methods: Limited-stage small cell lung cancer patients were prescribed 54, 58, 62 or 65 Gy, all given in 25 daily fractions and commenced on or before the second chemotherapy cycle. Dose level accrual was performed sequentially. Conformal radiotherapy techniques were used and targeted gross disease plus margin. Four cycles of platinum-based chemotherapy were prescribed. Primary endpoint was the rate of acute RT toxicities according to NCI Common Toxicity Criteria scales. The dose which caused unacceptable acute radiotherapy toxicity rates according to pre-defined stopping rules defined the maximal tolerated radiotherapy dose.
Results: Six patients were accrued to each of the 54, 58 and 62 Gy dose levels. There were no radiotherapy-related deaths. No grade 3 toxicities occurred in the 54 and 58 Gy groups. There were 2 grade 3 RT toxicities in the 62 Gy group. There were 14 complete responses. Trial accrual has stopped at the 62 Gy group according to trial stopping rules.
Conclusions: The maximal tolerated hypofractionated thoracic radiotherapy dose in this trial was 58 Gy in 25 daily fractions.
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