Doctors have suspected that radiation therapy
helps prevent patients from dying of prostate cancer, but they had
little scientific evidence to support that theory. Now, Richard
Valicenti, MD, assistant professor of radiation oncology at Jefferson
Medical College of Thomas Jefferson University in Philadelphia and
his colleagues have confirmed that radiation therapy helps patients
with localized prostate cancer live longer. Dr. Valicenti presented
these findings at the 1999 meeting of the American Society of
Clinical Oncology (ASCO).
The researchers retrospectively examined the results of radiation
therapy in 1,560 prostate cancer patients. The patients were among
those treated in four separate trials conducted by the Radiation
Therapy Oncology Group between 1975 and 1995. The average follow-up
was 8 years, with some patients monitored for as long as 12 years.
Patients With Worst Prognosis Benefit Most From Higher Radiation Doses
After dividing the men into four categories according to their
likelihood of having more serious disease, Dr. Valicenti and
colleagues found that those with the worst prognosis benefited the
most from higher doses of radiation. After the investigators
statistically adjusted their data for disease severity and patient
age, they found that patients who received higher-than-usual
radiation doses were 32% less likely to die of prostate cancer.
I think these results will change how we evaluate the use of
higher radiation doses and new radiation treatment systems for
prostate cancer, said Dr. Valicenti.
Dr. Valicenti and his coworkers at Jefferson, Wayne State University
in Detroit, the University of Southern California, McAuley Health
Center in Ann Arbor, Michigan, and Einstein Medical Center in
Philadelphia evaluated the Gleason scores and radiation doses of
patients in four separate studies. They found that overall, patients
with the highest Gleason scores (between 8 and 10, on a scale of 2 to
10), who should have had the worst prognoses but who received higher
radiation doses, had better local control of their cancer and were
more likely to be disease-free and alive longer.
Radiation therapy provides an overall survival benefit for
clinically localized prostate cancer for those with a Gleason score
between 8 and 10, said Dr. Valicenti. Those less than 8
didnt experience an observable advantage with follow-up to 12 years.
We were happy to see improvement of local control with higher
radiation doses, he said. This would suggest in part that
the disease-free survival advantage is attributed to improved tumor control.
The work was funded, in part, by the National Cancer Institute.