A higher BID.

Top Line: Does dose escalation improve outcomes when using BID fractionation for limited stage small cell lung cancer?

The Study: Twice daily radiation is considered by many to be the standard when treating LS-SCLC. In the CONVERT trial (a superiority design), 66 Gy in 33 fractions was not superior to 45 Gy in 30 BID fractions. The ongoing CALGB 30610/RTOG 0528 trial is comparing 70 Gy in 35 fractions with 45 Gy in 30 BID fractions. Just to spice things up, here’s the randomized, phase 2 THORA trial that investigated whether dose escalation using BID fractionation improves overall survival. Patients with LS-SCLC (n = 170) received 4 q3 week cycles of cis/carbo and etoposide. They were randomized to 45 Gy in 30 BID fractions or 60 Gy in 40 BID fractions starting with the second chemo cycle and targeting the primary tumor and involved nodes. Dose constraints were comparable to those used for 60 Gy in 30 fractions. A dose reduction to 54 Gy was allowed in the 60 Gy arm if dose constraints were exceeded. Most patients (85%) also received PCI following completion of chemotherapy. At 2 years, 60 Gy/40 significantly improved the overall survival rate from 48.1→ 74.1% and median overall survival was improved from 23→ 37 months. Interestingly, there were no significant differences in local failure, distant failure, disease progression rates (63% vs 64%) or median PFS (18.6 vs 10.9 months) between arms. Toxicity was also surprisingly similar between arms with 21% vs 18% having grade 3 and 37% vs 44% having grade 1-2 esophagitis. Hmm. Looking forward to theMedNet commentary on this one.

TBL: According to the phase 2 THORA trial, dose escalation to 60 Gy in 40 fractions for LS-SCLC may improve overall survival without a significant increase in toxicity. | Gronberg, Lancet Oncol 2021


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