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

Oct 10, 2000, 01:00 ET from Radiotherapy Clinics of Georgia

    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
     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