Room: AAPM ePoster Library
Purpose: This work studies pulsed low-dose-rate (PLDR) treatment, and compares its effectiveness to conventional radiotherapy (CRT). The purpose of this study is to investigate the dose-rate effect on tumor growth of PLDR, consisting of multiple doses of radiation given at short intervals, using a mouse model.
Methods: Male nude mice were injected with human lung cancer (A549) cells subcutaneously bilaterally into their flanks. Two experiments were conducted. In the first experiment, mice were irradiated using total body irradiation without anesthesia and treated with 2 Gy daily using 6-MV radiation. Tumors were randomized into six groups: CRT and PLDR treatments, each using three total doses of 12, 14, and 16 Gy. In the second experiment, mice were irradiated using total body irradiation without anesthesia and given 6 Gy in one PLDR irradiation consisting of 24 fractions of 25 cGy. Tumors were divided into three groups by varying the time interval between treatments: 20 s, 1 min, and 3 min. Efficacy was monitored with weekly MR scans using a GE Signa 1.5T MR scanner.
Results: Tumors treated with CRT and PLDR showed statistically equivalent increase in size for each dose group examined; two weeks after treatment, tumors treated with CRT and PLDR increased in volume by a factor of 1.33±0.16 and 1.40±0.21 for 12 Gy, 1.25±0.24 and 1.51±0.32 for 14 Gy, 2.13±0.30 and 1.74±0.21 for 16 Gy, respectively. Tumors treated to 6 Gy with PLDR showed statistically equivalent increase in size: tumors increased by a factor of 2.79±0.32, 2.40±0.19, 2.73±0.27 for the 20 s, 1 min, and 3 min intervals, respectively.
Conclusion: There was no statistically significant difference in tumor growth delay between PLDR and CRT using this mouse model. Results suggest that varying the dose rate may produce a more significant tumor effect, warranting further studies with more mice.
Not Applicable / None Entered.