Rapidly Growing Locally Advanced Non-Small Cell Lung Cancer Treated with Definitive Chemoradiotherapy Using Adaptive Volumetric Modulated Arc Therapy Followed by Durvalumab Maintenance: A Case Report.

BACKGROUND It is difficult to reduce lung toxicity in chemoradiotherapy for locally advanced lung cancer. Volume-modulated arc therapy (VMAT) is a useful lung dose-lowering radiation technique, but it is time-consuming because of its complexity. We present a case of a rapidly growing bulky lung cancer treated with VMAT and intensive adaptation to volume change. CASE REPORT A 43-year-old man with chest pain was diagnosed with non-small cell lung cancer, cT4N3M0 stage IIIC (UICC 8th edition). Concurrent chemoradiotherapy with a VMAT of 60 Gy in 30 fractions and carboplatin/paclitaxel was performed. Despite initiating chemoradiation, monitoring with cone-beam computed tomography (CT) revealed tumor progression. The peak tumor volume was 1.5 times larger than that on CT simulation. The VMAT plan was recreated to cover the increased tumor size. After the irradiation field was enlarged, the tumor, on the contrary, shrank rapidly. Therefore, VMAT planning was performed again to further shrink the irradiation field. CT at the end of the treatment showed a good volume reduction response. Durvalumab therapy was continued for 1 year. After that, the patient was alive and showed no sign of progression. Only asymptomatic radiation pneumonitis was observed as a sub-acute adverse event. CONCLUSIONS We present a case in which proper adaptive VMAT and durvalumab for dramatically progressive non-small cell lung cancer were effective, resulting in 1-year progression-free survival. Even when rapid progression of bulky lung cancer is suggested, the combination of VMAT and adaptive radiotherapy with improved target coverage and reduced lung dose can be a treatment option.