High Dose Rate Brachytherapy (HDR-BT) as Monotherapy for Favorable Prostate Cancer: Excellent 5-Year Control Rates and Low Toxicity

Article Outline

• Purpose/Objective(s)
• Materials/Methods
• Results
• Conclusions
• Appendix. Supplementary data
• Copyright

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Purpose/Objective(s) 

The radiobiology of prostate cancer appears to favor the use of large doses per fraction. Accelerated hypofractionation should therefore improve the therapeutic ratio, if doses to rectum and bladder are less than the prostate dose. We report our pooled 5-year clinical outcome and toxicity data with prostate HDR-BT as monotherapy from California Endocurietherapy (CET) and William Beaumont Hospital (WBH) in favorable (low or low intermediate risk group) prostate cancer.

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Materials/Methods 

From 1996 and 2005, 298 patients were treated with prostate HDR-BT alone at the 2 centers. Two hypofractionation schedules were utilized. The prescribed dose at WBH was 38 Gy in 4 fractions delivered twice daily (1 implant) based on an equivalent dose of 75.6 Gy delivered with external-beam RT (EBRT) at 1.8 Gy/fraction and assumed α/β ratio of 7. The planning target volume (PTV) was defined intra-operatively with trans-rectal ultrasound (TRUS) as being the prostate gland with no margins added. At CET the prescribed dose was 42 Gy in 6 fractions (2 implants 1-week apart) delivered to a CT-based PTV using a 5 mm margin beyond the prostate, based on an EBRT equivalent dose of 76 Gy at 2 Gy/fraction and a α/β ratio of 4.5. Patients were seen in follow-up and toxicity was scored using the Common Toxicity Criteria (CTC) version 3.

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Results 

The median study values were: follow up 3.9 years (range 0.6–10.9), age 64 years, stage T1c, Gleason 6, pre-treatment PSA 5.9 and 9 follow-up PSA tests. The 5-year results were 96% overall survival, 100% cause specific survival, 100% local control, 0% distant metastasis, and 94% biochemical control (Phoenix definition nadir +2). The chronic GU toxicity rates grade 1–3 were low and there was no grade 4 toxicity. Toxicity was scored per event, meaning that a single patient may be represented more than once in the table. Patients experienced mainly low grade frequency and/or urgency. Three percent of cases had a grade 3 episode of urinary retention. Chronic GI toxicity was <1%. The crude 5-year chronic GU toxicity ≥2 in 298 patients are shown in the table. There were no significant statistical differences in survival or complication rates between the two hypofractionated regimes.

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Conclusions 

Accelerated hypofractionated HDR brachytherapy as monotherapy for favorable risk prostate cancer yielded excellent 5-year clinical and biochemical disease control rates. HDR-BT was very well tolerated; it was associated with <1% chronic GI toxicity and the chronic GU toxicity profile was also low.

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Appendix. Supplementary data 

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Appendix. Supplementary data 

Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.ijrobp.2007.07.150