Background: The decrease in peripheral blood lymphocytes induced by radiation lessens the antitumour effect of\nthe immune response, which might cause immunosuppression. We aimed to investigate the correlation between\nthe decrease in peripheral blood lymphocytes during radiotherapy (RT) and the spleen irradiation dose in patients\nwith hepatocellular carcinoma (HCC).\nMethods: The subjects were 59 patients with HCC who had received RT from 2005 to 2014. The Min ALC\n(minimum value of absolute counts for peripheral blood lymphocytes) was collected from the routine workup for\neach patient prior to RT and weekly during RT. Spleen dose-volume variables, including the percentage of the\norgan volume receiving �n Gy (Vn) and the mean spleen dose (MSD), were calculated using Eclipse treatment\nplanning. Potential associations between dosimetric variables and the Min ALC were assessed by multiple linear\nregression analysis.\nResults: Peripheral lymphocytes decreased during RT (P < 0.001). The Min ALC correlated with the MSD (P = 0.005),\nspleen V5 (P = 0.001), spleen V25 (P = 0.026) and spleen V30 (P = 0.018). Controlling for the Karnofsky performance\nstatus (KPS), sex, age, Child-Pugh grade, total dose and tumour stage, a multiple linear regression model with\nbootstrap analysis of 1000 replicates showed that only the spleen V5 was correlated with the decrease in the Min\nALC (P < 0.05). According to the receiver-operating characteristic (ROC) curve analysis, the predictive cutoff values of\nthe MSD, V5, V25 and V30 of the spleen for the Min ALC were 227.72 cGy, 17.84, 0.98 and 0.42%, respectively\n(P = 0.002, P = 0.004, P = 0.007 and P = 0.002, respectively). Furthermore, an MSD � 227.72 cGy (OR = 14.39; 95% CI,\n12.18 to 16.60) and V5 (OR = 7.99; 95% CI, 6.91 to 9.07) of the spleen significantly predicted the Min ALC.\nConclusions: Higher spleen irradiation doses were significantly correlated with lower Min ALC during RT for HCC.\nV5 should be limited in clinical practice. Maximum sparing for spleen irradiation during RT is recommended to\npreserve peripheral blood lymphocytes, which may decrease immunosuppression.
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