Preliminary results of a U.S. trial indicate that increasing the dose of conformal radiation therapy produces fewer relapses in men with early stage prostate cancer than conventional dose. This advantage was achieved without any increase in either acute or long-term urinary or rectal morbidity (damage). These results were reported in the plenary session of the 46th annual meeting of the American Society of Therapeutic Radiology and Oncology (ASTRO) held in Atlanta GA, Oct 3-7, 2004.
Prostate cancer is one of the most commonly diagnosed cancers in men in the United States. The prostate is a walnut-sized gland that is located between the bladder and rectum and is responsible for the formation of components of semen. Patients with localized prostate cancer, or cancer that has not spread from the prostate, have 3 main different treatment options: surgery to remove the prostate and surrounding tissue; radiation therapy; or watchful waiting (no treatment until progression of disease).
Over 90% of patients with low-risk (stage I, PSA less than 10/ng/mL, Gleason less than 6) prostate cancer treated with radiation therapy will survive 5 years after treatment and most patients who die do so of causes other than prostate cancer. However, 40%-65% of patients with Gleason scores greater than 6 and high PSA levels will experience disease recurrence by 5 years following radiation. Because of the relatively poor outcomes of patients with adverse risk factors, researchers have evaluated more intensive treatments for this group of patients. A higher radiation dose to the prostate appears to improve outcomes.
In the March 2003 issue of the Journal of Urology, researchers from the William Beamont hospital in Royal Oak, Michigan have reported that adding a high-dose boost of conformal brachytherapy delivered in a conformal manner improves outcomes of patients with localized prostate cancer with high-risk features.
The trial presented at ASTRO involved 393 patients with early stage prostate cancer (T1b-T2b) and a PSA of <15ng/ml. The median age at diagnosis was 67 years and the median PSA was 6.3. Patients were randomized to receive an initial radiation boost to the prostate alone using conformal protons of either 19.8 Gy (conventional dose) or 28.8 Gy (high dose). All patients then received 3-D conformal photons to the prostate, seminal vesicles, and peri-prostate tissue. No patients received adjunctive androgen suppression therapy with their radiation.
The effectiveness of treatment was determined by clinical evaluation (palpation), evaluation of a biopsy sample, or by a PSA of > 1ng/ml at 2 or more years after treatment, the latter of which is the ASTRO definition of a “biochemical failure.”
Four years after treatment, more of the patients who received the higher dose of conformal radiation therapy were free from PSA progression and had lower PSA levels than those that received the conventional dose (see table).
. Zietman AL, DeSilvio M, Slater JD, et al. A randomized trial comparing conventional dose (70.2GyE) and high-dose (79.2GyE) conformal radiation in early stage adenocarcenoma of the prostate: results of an interim analysis of PROG 95-09. Proceedings from the 46th annual meeting of the American Society for Therapeutic Radiology and Oncology, Atlanta GA, Oct 2004, Abstract #4.
. Martinez A, Gonzalez J, Spenser W. Conformal high dose rate brachytherapy improves biochemical control and cause. The Journal of Urology . 2003; 169:974-980.
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