Combined external beam radiation therapy (EBRT) with a brachytherapy boost plus androgen deprivation therapy (ADT) is associated with excellent disease-free survival among men with intermediate-risk prostate cancer (PCa), researchers reported. The treatment also is associated with acceptable acute and late toxicity.

That conclusion is based on a study in which 61 men with intermediate PCa received this combined treatment. After a median follow-up of 73 months, the six-year disease-free survival rate was 87%, 75%, and 85% using the study protocol definition, the 1997 American Society for Therapeutic Radiation and Oncology (ASTRO) consensus definition, and the Phoenix definition, respectively. Six-year overall survival was 96%, according to study findings published in Cancer (2011;117:5579-5588).

The protocol definition of biochemical recurrence was three consecutive rises in PSA greater than 1.0 ng/mL after 18 months from the start of treatment. The 1997 ASTRO definition is three consecutive PSA increases above nadir and the Phoenix definition is nadir plus 2 ng/mL. The protocol and subsequently the Phoenix definitions were developed because of the tendency of the 1997 ASTRO definition to falsely indicate biochemical failure, which can occur because of PSA rises resulting from testosterone rebound after ADT cessation.

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Subjects received 3-D conformal EBRT of the prostate and seminal vesicles. Brachytherapy was performed two to four weeks after completion of EBRT. Patients received ADT for six months.

Late grade 2 and 3 toxicity, excluding sexual dysfunction, occurred in 20% and 3% of patients, respectively. The investigators, led by Mark D. Hurwitz, MD, of Brigham and Women’s Hospital in Boston, noted that although treatment efficacy is important, “the impact of any treatment on disease control or eradication has to be considered in the larger context of toxicity and quality of life.”