Evaluating proton stereotactic body radiotherapy to reduce chest wall dose in the treatment of lung cancer

Abstract Stereotactic body radiotherapy (SBRT) can produce excellent local control of several types of solid tumor; however, toxicity to nearby critical structures is a concern. We found previously that in SBRT for lung cancer, the chest wall (CW) volume receiving 20, 30, or 40 Gy (V 20 , V 30 , or V 40 ) was linked with the development of neuropathy. Here we sought to determine whether the dosimetric advantages of protons could produce lower CW doses than traditional photon-based SBRT. We searched an institutional database to identify patients treated with photon SBRT for lung cancer with tumors within 20 was 364.0 cm 3 and 160.0 cm 3 ( p 30 was 144.6 cm 3 vs 77.0 cm 3 ( p = 0.0012), V 35 was 93.9 cm 3 vs 57.9 cm 3 ( p = 0.005), V 40 was 66.5 cm 3 vs 45.4 cm 3 ( p = 0.0112), and mean lung dose was 5.9 Gy vs 3.8 Gy ( p = 0.0001) for photons and protons, respectively. Coverage of the planning target volume (PTV) was comparable between the 2 sets of plans (96.4% for photons and 97% for protons). From a dosimetric standpoint, proton SBRT can achieve the same coverage of the PTV while significantly reducing the dose to the CW and lung relative to photon SBRT and therefore may be beneficial for the treatment of lesions closer to critical structures.