High-dose Radiation Decreases Prostate Cancer

Failure after treatment with conventional radiation therapy is typical, with a resulting increase in prostate-specific antigen (PSA) levels, secondary treatment, and eventually, clinical recurrence. Increasing the delivered radiation dose may increase the likelihood of local tumor management but in addition bears a risk of greater adverse effects unless the amount of healthy tissue treated along with the tumor can be reduced.

In the 1990s a number of computed tomography- (CT)-based methods became available to deliver radiation more precisely and thereby allow the delivery of higher doses. These techniques are jointly known as three-dimensional conformal therapy and include the use of conformal photon beams, intensity-modulated photon beams, and proton beams.

Anthony L. Zietman, M.D., and coworkers from Massachusetts General Hospital (MGH) and Harvard Medical School (both based in Boston, MA, USA), performed a study to determine whether tumor control could be improved in patients with prostate cancer, including those with low-risk disease, by using higher radiation doses.

The study included 393 patients with stage T1b through T2b prostate cancer and PSA levels less than 15 ng/ml, randomized between January 1996 and December 1999. The median value for PSA levels was 6.3 ng/ml, and the median follow-up time was 5.5 years. Patients received either external beam radiation to a total dose of either 70.2 Gy (radiation dose unit; conventional dose) or 79.2 Gy (high dose). This was delivered using a combination of conformal photon and proton beams.

The scientists discovered that the extent of men who did not have biochemical failure (increasing PSA level) at five years were 61.4% for conventional-dose and 80.4% for high-dose therapy, a 49% decrease in the risk of failure. The benefit of high-dose therapy was seen in both the low-risk and the higher-risk subgroups (risk reduction, 51% and 44%, respectively).


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