Abstract
Background: Lymphocytes play an important role in the cancer immune system. We investigated influences of irradiated doses and volumes of the bone on lymphopenia and survivals in chemoradiotherapy for stage III non-small cell lung cancer (NSCLC).Methods: Data from 41 patients with stage III unresectable NSCLC who received definitive proton beam therapy (PBT) of 74 GyE with concurrent chemotherapy between 2007 and 2017 were retrospectively reviewed. The correlation between dosimetry parameters obtained from dose-volume histograms (DVHs) of the bone, lung, and heart and lymphopenia during PBT were analyzed. Maximum and minimum absolute lymphocyte counts (ALCmax and ALCmin) and maximum neutrophil/lymphocyte ratio (NLRmax) were used as indicators of lymphopenia. Clinical factors, dosimetry parameters, and indicators of lymphopenia were also evaluated for the correlation with overall survival (OS), progression-free survival (PFS), and distant metastasis-free survival (DMFS).Results: Significant inverse correlations were observed between bone V5 and ALCmax (ρ = -0.377, p = 0.015) and ALCmin (ρ = -0.441, p = 0.003) during the treatment period. Also, significant correlation between bone V5 and NLRmax (ρ = 0.398, p = 0.010) was observed, but bone V5 exhibited no significant association with OS, PFS, or DMFS. On the other hand, heart V5 (Hazard ratio [HR]: 1.032, p = 0.023), ALCmax (HR: 0.999, p = 0.049), and NLRmax (HR: 1.035, p = 0.007) were significantly associated with OS in univariable analysis. Lung V5 tended to be associated with PFS in univariable analysis (HR: 1.047, p = 0.056) and was significantly associated with DMFS (HR: 1.075, p =0.005). In multivariable analysis, heart V5 was not associated with OS, whereas ALCmax was significantly associated with OS (HR: 0.999, p = 0.022). Lung V5 was not a factor associated with PFS, but it was significantly associated with DMFS (HR: 1.062, p = 0.027).Conclusions: In PBT with chemotherapy for stage III NSCLC, lymphopenia was correlate with irradiation doses to the bone and lung, and lung dose but not bone dose was associated with DMFS.
Results of Proton Beam Therapy without Concurrent Chemotherapy for Patients with Unresectable Stage III Non-small Cell Lung Cancer
