New Prostate Cancer Survival Rates Underscore Importance of PSA Nadir 0.2 ng/ml
Study by Atlanta Physicians Challenges Radiation Oncologists
To Set Standard Definition for Disease Freedom
ATLANTA, Oct. 10 /PRNewswire/ -- A new study completed by Atlanta radiation oncologists and just released in the September issue of The Journal of Urology substantiates the effectiveness of simultaneous radiation for men with early stage prostate cancer. The study, conducted by Atlanta-based Radiotherapy Clinics of Georgia (RCOG), documented that all men with early stage prostate cancer who were treated with modern, simultaneous radiation (transperineal implantation followed by external beam radiation) demonstrated an overall 88% five- and seven-year disease-free survival(1). Of equal importance, the cure rates were calculated with an undetectable PSA (prostate specific antigen) of 0.2 ng/ml. According to Dr. Frank Critz, Medical Director of RCOG, how cure rates are calculated is just as important as the results because there is no standard definition of PSA cure of prostate cancer. To illustrate this point, Dr. Critz notes Dr. Frank Vicini's medical research paper published in The Journal of Urology(2) as an excellent example of manipulating cure rates. Dr. Vicini treated a large number of men with linear accelerator irradiation alone. He then calculated five-year cure rates in this same group of men but used different post-treatment PSA nadir levels to define freedom from prostate cancer. (PSA nadir means the lowest PSA measured after treatment.) The men had pre-treatment PSAs ranging from 4.1-10.0 ng/ml. The five-year cure rate was 74% when calculated with PSA nadir of 4.0 ng/ml. It dropped to 54% when calculations were made with PSA nadir 1.5 ng/ml, and dropped even further to 45% when calculated with PSA nadir 1.0 ng/ml. "Had Dr. Vicini used PSA nadir 0.2 ng/ml, the cure rate would have been significantly lower," explains Dr. Critz. "In other words, if an investigator of radiation wants to make his cure rate better, all he has to do is calculate his results with a high PSA nadir number. We found that unless men achieved at least PSA nadir 0.2 ng/ml after irradiation, they would not be cured of prostate cancer." Dr. Critz' demand that PSA 0.2 ng/ml be the standard definition for disease freedom from prostate cancer, whether treated by surgery or irradiation, has created a national controversy in the radiation community. Virtually all radiation oncologists calculate cure rates with the ASTRO Committee definition of disease freedom. The ASTRO Committee definition is based on a rising PSA after treatment and not on PSA nadir. Dr. Critz and the doctors from RCOG argue against this definition because it produces inaccurate, inflated cure rates. "Defining disease freedom as PSA nadir 0.2 ng/ml for radiation treatment is the same definition used after radical prostatectomy," states Dr. Critz. "What upsets the radiological community is that PSA cutpoint 0.2 ng/ml produces significantly lower cure rates from the ASTRO Committee definition of disease freedom commonly used by radiation investigators." The study referenced in the recently published article, conducted from August 1992 through November 1996, followed 689 men ranging from 45 to 88 years of age (median age of 66) with clinical stage T1-T2, N0, Nx prostate cancer. These patients were treated with modern, ultrasound guided transperineal 125-I iodine seed implantation followed by three-weeks of external beam irradiation. Treatment failure was defined as PSA nadir greater than 0.2 ng/ml or a subsequent PSA increase above this level. Follow-up was performed every six months starting from the date of implantation. Median follow-up was four years. Compared with other published cure rates after irradiation, simultaneous irradiation has the highest documented cure rate for radiotherapy of prostate cancer in the United States. With disease freedom calculated using PSA nadir 0.2 ng/ml, the overall cure rate of 88% is superior to the next highest published cure rate of 55%. The Challenge "The physicians at RCOG strongly suggest a universal, standard PSA definition of disease freedom for prostate cancer be used for all clinical research, surgery or irradiation, and recommend this definition be PSA cutpoint 0.2 ng/ml," says Dr. Critz. "We challenge all radiation oncology investigators to calculate their results with PSA cutpoint 0.2 ng/ml. Only by calculating with the same definition can treatment results be compared fairly. This will allow patients to equitably compare prostate cancer treatments across all modalities and choose the option -- and the physician -- that is right for them." RCOG prioritizes extensive physician training as opposed to two-day seed implant courses; and its research findings have been published extensively in scientific, peer-reviewed medical journals. (1) Results of pretreatment PSA groups 4.0 ng/ml or less were 94%; 4.1 to 10.0 were 93%; 10.1 to 20.0 were 75%; and greater than 20.0 were 69%. (2) The Journal of Urology 158:319-325,1997
SOURCE Radiotherapy Clinics of Georgia
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