An In-Vivo Study on Pulsed Low-Dose-Rate Radiotherapy for Prostate Cancer

Purpose: The objective of this study is to investigate the in-vivo tumor control efficacy of pulsed low-dose-rate (PLDR) radiotherapy for prostate cancer treatment. Materials & Methods:We implemented three in vivo murine models of prostate cancer, namely an orthotopic LNCaP tumor model, a flank PC-3 tumor model, and an orthotopic PC-3 tumor model.The tumor-bearing mice were treated with a daily radiation dose of 2 Gy with either PLDR or at a conventional dose rate.The tumor growth was monitored with magnetic resonance (MR) imaging.Results: For the orthotopic LNCaP tumor model and the flank PC-3 tumor model, we found that both PLDR and RT group tumors showed significant growth delay compared to the control group tumors.At two weeks after the first treatment, the difference between the mean tumor volume of the control group and the RT (PLDR) group was about 28% (25%) and 41% (43%) for the orthotopic LNCaP and flank PC-3 tumor models, respectively, with student t-test p values <0.05.However, there is no statistically significant difference between PLDR and RT groups.For the orthotopic PC-3 tumor model, we found that the PLDR treatment showed a better tumor control than conventional RT treatment.At two weeks after the first treatment, the difference between the mean tumor volume of the RT and the PLDR group tumors was about 31%, with student t-test p=0.02.Conclusion: This study showed that PLDR could control prostate tumors at least as effectively as conventional RT.Considering that PLDR could also lead to much less normal tissue toxicity than conventional RT, we expect PLDR to be a viable modality for the management of recurrent prostate cancers.