Adjuvant High-dose Intensity Modulated Radiotherapy May Decrease Relapses After Radical Prostatectomy

Researchers from Belgium have reported that adjuvant high-dose (74Gy) intensity modulated radiotherapy (IMRT) is associated with a 93% biochemical relapse-free survival in men with high-risk prostate cancer undergoing radical prostatectomy. The details of this study will appear in the October 2009 issue of European Urology.[1]

Controversy exists over optimal treatment choices in patients with locally advanced prostate cancer (T3). Patients with T3 prostate cancer have extra-capsular extension, positive margins, and/or seminal vesicle involvement. Identifying specific variables that are associated with either an improved or poor prognosis may help define individualized treatment regimens that will provide optimal long-term outcomes in this group of patients. Clinical studies are underway to address these issues. Patients with pT3 prostate cancer have many options available to them, with trials attempting to provide answers in terms of long-term outcomes coupled with side effects. Previous studies have suggested that adjuvant radiotherapy is of benefit in decreasing local and distant recurrences after prostatectomy for T3 prostate cancer. However, researchers affiliated with the European Organisation for Research and Treatment of Cancer have reported that men with early prostate cancer who have negative margins following surgery may not benefit from adjuvant radiation following surgery.

IMRT is a relatively new way of delivering radiation that theoretically delivers more radiation to cancers while delivering less radiation to normal tissues than conventional three-dimensional conformal radiation (3D-CRT). IMRT developed through improvements and a decrease in the cost of server-type computers; the development of multileaf collimators with multiple tungsten shields, which allowed the delivery of radiation through multiple ports (often referred to as “beamlets”); and the development of software that combined computerized tomography or other imaging of the cancer with control of the radiation delivered. The equipment allows for intensity modulation of the radiation beam during treatment. This is accomplished by the computer telling the machine to shield or not shield various ports with the tungsten shields.

The current study evaluated high-dose IMRT in 104 men with high-risk prostate cancer (capsule perforation, seminal vesicle invasion, and/or positive surgical margins). These authors reported that adjuvant conventional radiotherapy in their institution was associated with a 25% recurrence rate in men with these adverse characteristics. Acute and late toxicities did not exceed grade 3 following IMRT. The incidence of urethral stricture was 6%. The three- and five-year biochemical relapse-free survival was 93% for this group of patients.

Comments: These data suggest that the dose of radiation delivered to the prostate can be significantly increased with IMRT and that this increased dose decreases recurrences of prostate cancer. However, these results should be confirmed in a randomized trial that includes salvage radiotherapy.

Reference: