High dose rate brachytherapy boost in the treatment of prostate cancer

This review analyzed a number of studies that evaluated the efficacy and safety of high dose rate brachytherapy in combination with external beam radiation therapy  for the treatment of localized prostate cancer.

Radiation therapy is used for treatment of localized prostate cancer (confined to the prostate gland).  Brachytherapy is a form of radiation therapy where a radiation source is placed inside the prostate and delivers focused radiation only to the prostate, while sparing the surrounding healthy tissues. External beam radiation therapy is a conventional prostate cancer therapy that delivers focused beams of X-rays from outside the body into the prostate. A combination of external beam radiation therapy with high dose rate brachytherapy is referred to as high dose rate brachytherapy boost. Recent trials have investigated the use this combination in the treatment of prostate cancer.

This review analyzed 38 studies with a total number of 8008 patients treated with high dose rate brachytherapy boost for prostate cancer. The study classified patients into different risk groups dependent on the extent and aggressiveness of the disease; patients with low-, intermediate- and high-risk of cancer growth and spread, and patients with locally advanced cancer. Biochemical failure is a rise in prostate-specific antigen levels at three consecutive measurements following treatment.

Several studies found that in a period of five years, men at low risk of cancer growth and spread showed rates of freedom from biochemical failure between 85–100%.Patients at intermediate risk showed rates of freedom from biochemical failure of between 80–98%. Patients at high risk showed rates of freedom from biochemical failure between 59–96%. Patients with locally advanced cancer showed rates of freedom from biochemical recurrence between 34–85%.

Over the period of five years, the overall survival rates were 99–100%. Cancer specific survival rates (the percentage of people who had not died from prostate cancer) were 85–100%. 0–8% of the patients had local recurrence (return of the cancer at or near the prostate) while 2–12% had distant metastases (spread of the cancer outside the prostate).

56% of the patients were free from genitourinary toxicities (toxicities relating to the genital and urinary organs) and 73% were free from gastrointestinal toxicities (toxicities relating to the stomach and intestines). Less than 6% of the patients experienced severe toxicity.

Compared to other conventional therapies such as external beam radiation therapy, low dose rate brachytherapy, low dose rate brachytherapy-boost and radical prostatectomy (surgical removal of all or part of the prostate gland), high dose rate brachytherapy boost may be more effective in patients with an intermediate or high risk of prostate cancer growth and spread.

The studies in this review were from single-institutional studies. To validate these findings, studies involving larger populations are necessary.