Phase 2 Trial Assessing Toxicity of Personalized Response-Based Radiation Treatment in Patients With Locally Advanced Non-Small Cell Lung Cancer.

Purpose: Local failure rates after treatment for locally advanced non-small cell lung cancer (NSCLC) remain high. Efforts to improve local control with a uniform dose escalation or dose escalation to midtreatment positron emission tomography (PET)-avid residual disease have been limited by heightened toxicity. This trial aimed to refine response-based adaptive radiation therapy (RT) and minimize toxicity by incorporating fluorodeoxyglucose-PET (FDG-PET) and ventilation-perfusion single-photon emission computed tomography (SPECT) imaging midtreatment.

Methods And Materials: A total of 47 patients with stage IIA to III unresectable NSCLC were prospectively enrolled in this single-institution trial (NCT02492867). Patients received concurrent chemoradiation therapy with personalized response-based adaptive RT over 30 fractions incorporating ventilation-perfusion single-photon emission computed tomography and FDG-PET. The first 21 fractions (46.2 Gy at 2.2 Gy/fraction) were delivered to the tumor while minimizing the dose to the SPECT-defined functional lung. The plan was then adapted for the final 9 fractions (2.2-3.8 Gy/fraction) up to a total of 80.4 Gy, based on the midtreatment FDG-PET tumor response to escalate the dose to the residual tumor while minimizing the dose to the SPECT-defined functional lung. Nonprogressing patients received consolidative carboplatin, paclitaxel, or durvalumab. The primary endpoint of the study was ≥ grade 2 lung and esophageal toxicities. Secondary endpoints included time to local progression, tumor response, and overall survival.

Results: At 1 year posttreatment, the rates of grade 2 and grade 3 pneumonitis were 21.3% and 2.1%, respectively, with no difference in pneumonitis rates among patients who received and did not receive adjuvant durvalumab (P = .74). Although there were no grade 3 esophageal-related toxicities, 66.0% of patients experienced grade 2 esophagitis. The 1- and 2-year local control rates were 94.5% (95% CI, 87.4%-100%) and 87.5% (95% CI, 76.7%-100%), respectively. Overall survival was 82.8% (95% CI, 72.6%-94.4%) at 1 year and 62.3% (95% CI, 49.6%-78.3%) at 2 years.

Conclusions: Response-based adaptive dose-escalation accounting for tumor change and normal tissue function during treatment provided excellent local control, comparable toxicity to standard chemoradiation therapy, and did not increase toxicity with adjuvant immunotherapy.