The
information in this column is intended for informational
purposes only, and does not constitute medical advice or
recommendations by the author. Please consult with your
physician before making any lifestyle or medication changes, or if you
have any other concerns regarding your health.
RADIATION
TREATMENT OF
PROSTATE CANCER & RISK OF SECOND CANCERS
Exposure to high
doses of ionizing radiation, whether from a nuclear explosion or from
radiation
therapy for cancer, has long been known to increase the risk of cancer
formation. A
growing body of clinical data is helping to
further develop our understanding of secondary radiation-induced
cancers.
Much
of our
current understanding about radiation-induced cancer is based upon
long-term
observation of the Japanese survivors of the World War II atomic
bombings in Hiroshima
and Nagasaki. In particular, an
increased incidence of leukemia,
myeloma, and cancers of the thyroid, breast, lung, stomach, esophagus,
ovary
and bladder has been identified in atomic bomb survivors who were close
to
ground zero.
Following
the
catastrophic failure of the Chernobyl
nuclear
reactor in Ukraine,
in 1986, an excess of leukemia and thyroid cancer among workers who
were
involved in the clean-up of the reactor’s contaminated debris has
already been
documented.
More
recently,
several studies have reported upon the incidence of secondary cancers
in adults
who were treated with radiation therapy for lymphoma during childhood
and
adolescence. An
increased incidence of
cancers of the lung and the female breast has been confirmed among
patients who
previously underwent extended-field chest irradiation (also known as
mantle
radiation therapy) for Hodgkin’s Lymphoma, and these secondary cancers
typically occur 15 to 20 years following treatment.
Rare cancers of the bone and cartilage,
called sarcomas, have also been associated with prior radiation therapy
treatments. Now, a
new research study
suggests that certain forms of prostate cancer radiation therapy may
also be
linked to an increased risk of subsequent radiation-induced secondary
cancers.
Currently,
there
are several different treatment approaches available for prostate
cancer
therapy. Surgery
can be performed to
completely remove the prostate gland (prostatectomy) when the tumor is
still
confined to the prostate. Implants
of
radioactive seeds, placed within the prostate gland (brachytherapy),
can also
be used to destroy cancer within the prostate.
External beam irradiation is another form of radiation
therapy, but
unlike brachytherapy, external beam irradiation is delivered by a
machine that
concentrates radiation onto the prostate gland from a source external
to the
body. Although
great progress has been
made in fine-tuning the delivery of radiation to the prostate gland
with both
brachytherapy and external beam irradiation, there is, inevitably, some
“collateral damage” that occurs to the organs and tissues that surround
the
prostate, as it is impossible to confine 100 percent of the delivered
radiation
dose to the prostate gland alone.
A
new study, in
the Journal of Urology, evaluated
the
cancer treatment records of more than 240,000 men who had previously
been
treated for prostate cancer with prostatectomy, brachytherapy, external
beam
radiotherapy or a combination of brachytherapy and external beam
radiotherapy
between 1988 and 2003. The
data for this
study was collected from the massive Surveillance, Epidemiology and End
Results
(SEER) national cancer database, which is maintained by the National
Cancer
Institute. This
study was conducted by
researchers from Columbia
University
and the Mount
Sinai Medical
Center.
In
this study,
the authors compared the incidence of subsequent cases of cancers of
the
bladder and rectum occurring in these 243,082 men.
The men who underwent prostatectomy alone,
and who did not receive any radiation therapy, essentially served as
the
“control group” for this study.
An
almost
insignificant increase in the risk of bladder cancer was seen in the
men who
underwent brachytherapy alone. However,
there was a more pronounced and statistically significant increase in
the risk
of both bladder cancer and rectal cancer observed among the men
who received either external beam radiotherapy alone or combined
brachytherapy
and external beam radiotherapy. Compared
to the men who underwent prostatectomy alone, external beam irradiation
was associated
with an 88 percent increase in the relative
risk of developing bladder cancer,
and a 26 percent increase in the relative
risk of developing rectal cancer.
Among those men who received both
brachytherapy and external beam
radiotherapy, the relative risk of
developing bladder cancer was 85 percent higher than what was observed
in the
men who underwent prostatectomy alone, while the relative
risk of developing rectal cancer was 21 percent
higher. (It should
be noted that “relative risk” is a
measure of the
difference in risk between two patient treatment populations, and is
not the
same as the “absolute risk” of developing a particular disease.)
In
this
retrospective study, which involves a relatively short duration of
clinical
follow-up, external beam irradiation for prostate cancer (either
administered
alone or in combination with brachytherapy) was associated with a
significant
increase in the risk of developing subsequent cancers of the bladder
and
rectum.
Since
most
studies of radiation-induced secondary cancers have shown an average
biological
lag time of 15 to 20 years between radiation therapy and the diagnosis
of
secondary malignancies, the findings of this study may actually
underestimate
the long-term risks of secondary bladder and rectal cancers in men who
have
previously received external beam radiotherapy as treatment for their
prostate
cancers. At the
same time, however,
recent and continuing improvements in the accuracy of radiation therapy
delivery have significantly reduced the “innocent bystander” effect,
whereby
clinically significant doses of radiation are absorbed by the organs
that
surround the prostate gland (namely, the bladder and the rectum). As a final note, all
retrospective studies
that are based upon prospectively collected data, such as this study,
are
subject to potential biases, including the “completeness” of the
clinical data
that is present within large databases such as the SEER database. However, based upon a
large body of clinical
literature on this topic, the findings of this particular study are not
at all
surprising, or unexpected.
All
patients who
are planning to undergo therapy for prostate cancer should first talk
with
their oncologists about the unique risks and benefits associated with
each
potential treatment option before choosing the best and most
appropriate form
of therapy.
SEXUAL
CONTENT ON TV
& TEEN PREGNANCY RISK
Although
the
effects of violent and sexual content on television, or on video games,
on
adolescents and young adults is the subject of considerable debate,
there are
multiple recent studies that appear to substantiate the concerns of
many
parents who wrestle with these issues.
For example, several clinical research studies have
recently found that
children who frequently play video games with violent themes are more
likely to
engage in aggressive or antisocial behavior at school and at home.
In
view of the
enormous impact of teen pregnancy on individuals, families and society,
many
parents and family advocates have viewed with alarm the increasingly
unfiltered
sexual content present in both movies and television shows. A new Rand Corporation
study, just published
in the journal Pediatrics, has
concluded that there may well be a significant link between exposure to
television shows with sexual content or themes, on the one hand, and
the
likelihood of pregnancy prior to age 20.
This study was funded by the National Institute of Child
Health and
Human Development, which is part of the National Institute of Health
(NIH).
In
this study,
data from prospective surveys of teens were analyzed over a 3-year
period. A total of
1,762 adolescents between the ages
of 12 and 17 anonymously completed surveys regarding their sexual
experiences
and their television viewing habits, and the same group of teens then
completed
the same survey one year later. The
incidence of teen pregnancy in this group of adolescents was monitored
for a
period of 3 years.
Sexual
content in
television shows measured by the surveys included: (1)
sexually-oriented
behaviors such as kissing, intimate touching, and implied or depicted
intercourse; and (2) discussions about sexual plans or desires, or
about sexual
behavior that had already occurred, or “expert advice” about
sexually-related
topics.
The
results of
this study demonstrated a linear association between heavy exposure to
sexual
content on television and the initiation of intercourse and other
sexual behaviors
during adolescence. The
teens who
anonymously admitted to watching the greatest number of sexually-themed
television shows were 2 times as likely to initiate sexual intercourse
within
the following year as were the teens who watched the least
amount of sexual content on TV. In
terms of age-related sexual behavior, 12
year-olds who watched the greatest number of television shows with
sexual
themes engaged in sexual activities at a level comparable to 14- and
15-year-old teens who watched the least
number of shows with sexual content.
An
especially interesting finding of this study was that television shows
that featured
only discussions about sexual
activities were still associated with an increased likelihood of
engaging in
intercourse, and in teenage pregnancies, among adolescents viewing such
shows.
Other
adolescent
behaviors linked with the early initiation of intercourse included:
older age,
hanging out with older friends, achieving lower grades at school,
sensation-seeking behaviors, and rule-breaking behaviors (e.g.,
skipping
classes).
On
the other
hand, behaviors most associated with a lower
likelihood of intercourse during adolescence included: having parents
who
monitored their teens’ behavior, having more educated parents, having
parents
who disapproved of teenage sexual activity, and living with both
parents (please
note that the greatest deterrents to adolescents engaging in
intercourse, based
upon the results of this prospective clinical study, involved
parent-related
factors…).
In
this study, an
early age at initiation of sexual activity (including intercourse), and
the
incidence of teen pregnancy, were found to strongly correlate with the
extent
to which television shows with sexual content (including mere
discussions about
sexual activities and behaviors) were viewed by teens.
Conversely, minimizing viewing exposures to
such television programming, and being supervised by two parents who
disapproved of adolescent sexual behavior, was associated with the
lowest rates
of teen sexual activity and teen pregnancy.
Many
parents will
respond to the findings of this research study with something along the
lines
of, “No, duh….” However,
this is the
first prospectively conducted research study to confirm what many of us
parents
have long believed. My
advice is to stay
connected with your teens, and stay involved with their lives, even
when they
demand that you do otherwise.
Disclaimer:
As always, my advice to readers is to seek the advice of your physician
before making any significant changes in
medications, diet, or level of physical activity.
