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The CancerWeb Report, What's New In Cancer
Prostate Cancer: November 1995
Last modified on:
Tuesday, April 20, 1999 12:03:10
Copyright © 1994-2008, Information Ventures, Inc.
p53 protein -
As discussed in earlier CANCERWEB articles, distinguishing which
prostate cancers will progress is an important issue in a disease
which does not progress to a life-threatening form in most men,
but which can be extremely aggressive in a smaller percentage of
them. The November, 1995 issue of Clinical Cancer Research had an
article from the Walter Reed Army Medical Center in Washington,
describing a study in which the protein product of the p53 gene
was stained with a dye. The product of the normal gene which is
a suppressor of tumor growth, is so short lived that it does not
stain sufficiently to be seen, but the abnormal gene in tumors is
long-lived and retains the stain. In this study, increased p53
protein stain was associated with disease progression, a higher
stage disease, and increased PSA, and was an independent
predictor of shorter disease-free survival.
Radiation Therapy - The use of radiation therapy to treat prostate cancer, especially
in younger men, has declined over the past decade, possibly
because of a widespread conviction that the beneficial effects of
radiation are short-lived. According to this line of reasoning,
radiation should be reserved for older patients with shorter
potential life spans in whom there would be less time for disease
to recur. Three studies, carried out at Fox Chase Cancer Center,
at Stanford University Medical Center, and at the University of
Michigan, presented at the meeting of the American Society for
Therapeutic Radiology and Oncology in Miami Beach, found this
"just ain't so." Two of these studies reported that radiation
treatment of men aged 60 or younger with early prostate cancer
gave results equivalent to those obtained in older men, during
follow-up for 5 (Fox Chase) or 18 (Stanford) years. The Michigan
study used the newer technique of 3-dimensional (3-D) conformal
radiation therapy, in which beams are focussed from various
angles with great precision, based on computerized 3-D models, to
deliver a higher dose to all parts of the prostate while sparing
normal tissue to a greater extent. This study reported 87% 5-
year disease-free survival based on PSA measurements in 707
patients aged 65 or less who had early-stage disease. In the
unfavorable group whose PSA was above 20, disease-free survival
was only 22%.
Side-effects of radiation therapy - Side-effects of radiation therapy for prostate cancer was the
focus of attention for two presentations at the October, 1995 meeting
of the American Society for Therapeutic Radiology and Oncology in
Miami Beach. The Memorial Sloan-Kettering Cancer Center, also
used 3-D conformal radiation in a study of 300 patients that
focused on impotence. Of those patients who were fully potent
before radiation, 84% remained potent afterwards, but those who
had some potency problem before therapy were seven times more
likely to become impotent. A history of heart attacks affected
potency, since only 54% remained potent after radiation therapy
compared with 70% of those who did not have heart attacks, and
heart attacks without radiotherapy gave anywhere from 16 to 40%
chance of becoming impotent. Another study from the University
of Chicago also addressed the issue of impotence, comparing
external beam radiation therapy with nerve-sparing surgery.
Those aged 50 to 69 had rates of impotence only slightly lower
than those having surgery, but in the 70 to 79 age group, rates
of impotence were over four times lower than for the surgical
patients. Overall, impotence was no more frequent among prostate
cancer patients treated with radiation than in the normal male
population, who become impotent from a variety of other causes
and diseases.
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