Fox Chase Cancer Center Study Finds Higher Radiation Doses Improve Cure Rates for Men With Prostate Cancer
PHILADELPHIA (November 3, 1999) -- Differences in pretreatment risk factors among men with prostate cancer help determine who needs higher doses of radiation therapy, according to a new Fox Chase Cancer Center study.
Fox Chase radiation oncology chairman Gerald E. Hanks, M.D., internationally recognized as an expert in the treatment of prostate cancer, directed the clinical trial. Results will be presented today at the American Society for Therapeutic Radiology and Oncology (ASTRO) conference in San Antonio, Texas.
The five-year study included a total of 862 men classified by low, intermediate or high levels of prostate-specific antigen (PSA) found in their blood at the time of their prostate cancer diagnosis. The three groups had PSA levels of less than 10, 10 to 20 and greater than 20, respectively.
All men in the study were treated with the technique called conformal radiation therapy, which uses three-dimensional treatment planning to customize an external radiation beam to the shape and size of the man's prostate. Compared to conventional radiation therapy with large square beams, conformal radiation permits higher, potentially more curative radiation doses because it spares nearby normal tissue and produces fewer side effects.
"We continue to define the subsets of patients who benefit from increasing radiation doses and to determine what specific dose is best for each patient," said Hanks.
The study divided each PSA group into two subgroups, one with a "favorable" and one with an "unfavorable" prognosis based on the characteristics of their tumors. The researchers classified these two risk groups by the extent, or stage, of the cancer and by what is known as the Gleason score, determined by a microscopic assessment of how aggressive the cancer cells are.
The favorable subgroup in each of the three PSA categories had cancer at the earliest stages as well as a Gleason score of 2 to 6 and no invasion of the adjacent nerve fibers (called perineural invasion). In these subgroups, totaling 506 men, the stage of cancer was defined as either a non-palpable tumor (stage T1) or a tumor involving only one of the two prostate lobes (stage T2A).
Unfavorable subgroups had cancer involving both prostate lobes (stage T2B) or extending outside one or both sides of the gland (stages T31 or T3B). These three subgroups, which included 356 men, also had Gleason scores ranging from 7 to 10 and/or perineural invasion.
The researchers determined the how each of the resulting six subgroups of patients responded to higher than standard doses of radiation, measured in units of absorbed radiation energy called Gy. The most favorable group achieved a cure rate of 90+ percent at 72 to 73 Gy while all other groups required 75 to 80 Gy to achieve maximum cure rates.
With high doses (greater than 76 Gy), more than 80 percent of patients in favorable and unfavorable subgroups with PSA levels less than 20 were cured of their cancer.
"Future research will require testing of doses in excess of 80 Gy and transferring the technology that allows high doses to all radiation facilities," Hanks said.
Fox Chase Cancer Center is one of 36 National Cancer Institute-designated comprehensive cancer centers in the nation. The Center's activities include basic and clinical research, prevention, detection and treatment of cancer and community outreach programs.
Note to Editor: The study will be presented by Dr. Hanks at the ASTRO annual conference in San Antonio, Texas, on Nov. 3, 1999. For more information about the ASTRO conference, call Keri Sperry at 703-295-6775.
Fox Chase Cancer Center, part of Temple University Health System, is one of the leading cancer research and treatment centers in the United States. Founded in 1904 in Philadelphia as one of the nation’s first cancer hospitals, Fox Chase also was among the first institutions to receive the National Cancer Institute’s prestigious comprehensive cancer center designation in 1974. Fox Chase researchers have won the highest awards in their fields, including two Nobel Prizes. Fox Chase physicians are routinely recognized in national rankings, and the Center’s nursing program has achieved Magnet status for excellence three consecutive times. Fox Chase conducts a broad array of nationally competitive basic, translational, and clinical research and oversees programs in cancer prevention, detection, survivorship, and community outreach. For more information, call 1-888-FOX-CHASE (1-888-369-2427).