Effect of tumor volume and radiation dose on the prognosis of hepatocellular carcinoma patients treated with whole body gamma knife

Objective: To examine the effects of gross tumor volume (GTV) and radiation dose on the prognosis of hepatocellular carcinoma (HCC) patients treated with whole body gamma knife. Methods: The clinical data of 69 HCC patients who underwent body gamma knife treatment from January 2012 to June 2015 in the Radiotherapy Center of the PLA General Hospital were retrospectively reviewed. Based on a 50% or 60% isodose coverage of the planning target volume (PTV), patients were treated with a radiation dose of 4-5 Gy per fraction, and a total marginal dose of 36-50 Gy (median dose 45 Gy). Short-term efficacy, overall survival (OS), and the adverse effect of the treatment were evaluated. The optimal cut-off tumor volume was identified using the receiver operating characteristic curve, and survival was determined by the Kaplan-Meier method. Univariate and multivariate analyses were performed using the log-rank test and Cox proportional hazards regression model, respectively. Results: The overall short-term response rate of the 69 patients was 67%. The 1- and 2-year OS rates were 62% and 40%, respectively, with a median survival of 18.6 months. The multivariate analysis showed that gross tumor volume (GTV) < 93 cm³(P = 0.013) and short-term efficacy of radiotherapy (P = 0.000) were significant independent prognostic factors for survival. When GTV was < 93 cm³, prognosis was significantly better in patients treated with a dose of ≥ 45 Gy than in those with < 45 Gy (P = 0.019). In contrast, radiation dose had no significant effect on survival among patients with GTV > 93 cm³(P = 0.665). Conclusions: GTV is an independent prognostic factor for overall survival of HCC patients. Although high-dose radiotherapy provides survival benefits to patients with small GTV, it is not necessarily suitable for patients with large GTV. (authors)