High-dose-rate brachytherapy combined with hypofractionated external beam radiotherapy for men with intermediate or high risk prostate cancer: analysis of short- and medium-term urinary toxicity and biochemical control

The best management of localized and locally advanced prostate cancer remains controversial, but there are clinical evidences that for patients considered of unfavorable outcome that dose escalation radiotherapy has a significantly better outcome.

Methods: Between 2005-2009 a total of 39 unfavorable patients were treated in a phase I-II trial for dose escalation with high-dose rate (HDR)- 30 Gy given by 4 fractions BID, in two separated implants and hypofractionated conformal/tri-dimensional radiotherapy (hEBRT) - 45 Gy (3 Gy per fraction in 3 weeks), at Hospital AC Camargo, Sao Paulo, Brazil.

Results: Median age of patients was 69 (range, 58-80) years old. With a median follow up of 42.5 months the highest RTOG acute severe genitourinary toxicity (GU-TX) was grade 3 in two (5.1%) patients. Late severe GU-TX was observed in one (2.6%) patient. On univariate analysis the prostate volume > 45cc (p=0.024), <11 needles per implant (p=0.038) and urethral dose >130% of prescribed dose (p<0,001) were statistical significant predictive factors. Multivariate analysis showed urethral dose >130% as the only predictive factor for late severe GU-TX, p=0.017 (95%CI-1.39-29.49), HR-6.4. The actuarial overall survival, biochemical control and disease specific survival rates for the entire group at 3.5-years were 92.0%, 87.6% and 96.9%, respectively.

Conclusion: HDR combined to hEBRT is well tolerated in the short and medium term. Acute toxicity was minimal and improved outcomes in terms of reduced late toxicity can be achieved using at least 11 needles and prostate with no more than 45cc to be implanted. The maximum urethral dose should be kept bellow 130% of prescribed dose.