Improved Seeds for Permanent Seed Implants for Prostate Cancer
(Mark Phillips)
Classic radiation biology has always categorized tumor response as having a high alpha/beta ratio, similar to that of acutely responding tumors. This has resulted in treatment strategies that make use of prolonged fractionation schedules in order to achieve the most separation between the tumor response and dose-limiting late responding tumors. Recent clinical results have indicated that for prostate tumors the alpha/beta ratio is probably less than 3, similar to late responding tissues. In addition, recently published data indicate that repair is much slower than previous thought. In a project done in collaboration with IsoRay, Inc., a company designing and developing novel isotope-seed combinations, I am investigating the potential advantages that would result from a shorter half-life isotope for permanent seed implants in light of the profound changes in the radiobiological modelling of prostate cancer.