P40.05 Radiation-Related Platelet Reduction in Patients With Stage IV Lung Cancer

Abstract

Platelet plays an important in multiple stages of cancer progression, cancer prognosis and treatment decisions. Many studies reported the prognostic significance of platelet or platelet/monocyte ratios at baseline in non-small cell lung cancer. The purpose of this study is to 1) exam whether radiotherapy reduces platelet, 2) study whether there is radiation dose associated with platelet decrease, and 3) explore the relationship between the reduction of platelet and overall survival and quality of life (QOL) in patients with metastatic lung cancer. This is part of a multicenter prospective study with close monitoring of quality of life and biomarkers. Patients with stage IV lung cancer patients treated with palliative radiotherapy were eligible. The variables of our interest included gender, age, stage, pathology, radiation dose, and platelet. The absolute differences of platelet, before and after radiotherapy were calculated. Associations between radiation dose, QOL（PROMIS-29 Profile v2.1）, and survival were analyzed. Data are presented as mean (95% confidence interval) unless otherwise specified. Statistical significances were tested using paired t-test. Disparities in patient survival were analyzed by multivariate Cox regression models. Multivariate correlation analysis was performed using Pearson models. Ps less than 0.05 were significant. A total of 80 patients enrolled, 43 patients with a minimum follow-up of 6 months were included in this analysis. All have stage IV lung cancer, 39 non-small cell lung cancer. There were 29 males and 13 females, with median age of 63 years (range 39 to 85 years). Paired t-test showed that platelet decreased significantly after radiotherapy (233.49, 95%CI: 193.11-282.73; 185.31, 95%CI: 145.29-225.32, P=0.002), though the absolute number in reduction is limited. The total radiation dose, ranged 20-60 Gy/3-30 fxs, was significantly and linearly correlated with the reduction in platelet during RT (r=0.47, P=0.005). Interestingly, the decreased of platelet was significantly associated with the increased T-score of depression (r=0.38, P=0.04) and pain intensity (r=0.48, P=0.009) of QOL after radiation, but not significantly associated with overall survival at 6 months. This study demonstrated that palliative radiation can significantly decrease platelet. It is interesting to note that platelet reduction during radiotherapy also has significant impact on QOL, including measures in depression and pain intensity. In addition to validate these findings, future study shall take platelets into consideration.