MedWire News: Prostate cancer patients treated with permanent prostate brachytherapy (PPB) who receive a biologically effective dose (BED) of more than 200 Gy achieve significantly better local control than patients who receive lower doses of radiation, researchers report.
Improved local control in turn increases biochemical freedom from failure (bFFF) and survival rates, say Nelson Stone (Mount Sinai School of Medicine, New York, USA) and colleagues in the International Journal of Radiation Oncology Biology Physics.
Stone et al analyzed data from 584 patients receiving PPB alone or PPB with external beam radiation therapy (EBRT) who agreed to undergo prostate biopsy 2 years after implantation and thereafter yearly if results were positive or if their prostate-specific antigen (PSA) level increased. Short-term hormone therapy was used by 280 patients.
Over a median follow-up of 7.1 years, prostate biopsy results were positive for 48 (8.2%) patients. In all, 3.1% of patients who received a BED of more than 200 Gy had positive biopsy results versus 6.1% of patients receiving >150–200 Gy and 18.2% of patients receiving no more than 150 Gy, giving significant differences among the groups.
Furthermore, bFFF rate by prostate biopsy result was 84.7% for patients with negative results versus 59.2% for those with positive results , and cause-specific survival was 99.2% for patients with negative prostate biopsy results versus 87.6% for those with positive findings. Again, both differences were significant.
Stone et al comment: “One of the advantages of using the BED to investigate the radiation effects on local control is that it allows other investigators to compare their outcomes regardless of the type of radiation used.”
For example, they explain that “a BED of more than 200 Gy can be achieved with postimplant D90s of I-125 of 188 Gy, Pd-103 of 167 Gy, and combination therapy with ERBT (25 fractions of 1.8 Gy) for I-125 of 110 Gy and for Pd-103 of 102 Gy.”
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