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In Vivo Studies On the Pulsed Low-Dose Hyper-Radiosensitivity in Prostate Cancer

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J Ren

J Ren1,2*, B Wang1, X Chen1, L Chen1, D Cvetkovic1, F Chen1, C Ma1, (1) Fox Chase Cancer Center, Philadelphia, PA, (2) Department of Radiation Oncology, Taihe Hospital Affiliated Hospital Hubei University of Medicine, Shiyan, Hubei Province, China

SU-E-T-313 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: In vitro radiation doses of below 0.5 Gy have been shown to be more effective than higher doses per unit dose in killing clonogenic cells of various tumor cell lines and can lead to better biological effects than predicted by the standard linear quadratic (LQ) model. This phenomenon is known as low-dose hyper-radiosensitivity (LD-HRS). To investigate the in vivo HRS effects of pulsed low-dose radiotherapy (PLDR) for prostate cancer treatment, we developed a human prostate PC3 cancer cell model in nude mice.

Methods:We developed an orthotopic murine model of human prostate tumor and evaluated the in vivo treatment efficacy using MRI. PC3 cells were implanted in the prostates of nude mice. The mice with tumor are randomly allocated into a PLDR group, a conventional fractionation (CF) group, and a control group. The mice in the PLDR and CF groups were both treated with 4Gy radiation dose, which was divided into two fractions of 2Gy treatments with a seven-day interval. For PLDR treatment, the fractional 2Gy dose was further divided into ten 0.2Gy pulses with an inter-pulse interval of 3 minutes.

Results:We have monitored the tumor growth on a weekly basis. Sizable delay of the tumor growth after the treatments have been observed, with the PLDR group showing better tumor control than the CF group. For example, the average relative tumor volumes are 1.33, 1.70, and 1.82 at one week after treatment, and 2.06, 2.19, and 3.40 at two weeks after the last treatment, for the PLDR, CF, and control groups, respectively.

Conclusion:According to our preliminary results, the PLDR could be more efficacious than the CF regimen for prostate cancer treatment.

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