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Older Women Who Receive Pelvic Radiation at Risk for
Pelvic Fracture
Nov. 22, 2005 - Older women who received radiation
therapy for cervical, rectal or anal cancer have a substantially
increased risk for pelvic fractures, including hip fractures, which lead
to death for women almost as often as breast cancer.
Pelvic fractures, including hip fractures, are
common in older people and are a major source of illness and death,
particularly in women, according to background information in the
article published in the November 23/30 issue of JAMA..
The lifetime risk of a hip fracture after 50 years
of age for white women is estimated at 17 percent. Within the first year
after a hip fracture, 10 percent to 20 percent more women die than
expected for age.
The number of deaths due to hip fractures is
comparable with the number of deaths due to pancreatic cancer and is
only slightly lower than the number of deaths due to breast cancer.
It is well recognized that therapeutic radiation
can result in bone damage and may increase fracture risks. However, the
risks have not been well studied. Because of the high baseline incidence
of fractures in older people and the significant illness and death
associated with fractures, even a small increase in the fracture rate
would be an important finding.
Nancy Baxter, M.D., Ph.D., of the University of
Minnesota, Minneapolis, and colleagues conducted a study to determine if
women who undergo pelvic irradiation for pelvic malignancies (anal,
cervical, or rectal cancers) have a higher rate of pelvic fracture than
women with pelvic malignancies who do not undergo irradiation.
The researchers used Surveillance, Epidemiology,
and End Results (SEER) cancer registry data linked to Medicare claims
data. A total of 6,428 women aged 65 years and older diagnosed with
pelvic malignancies from 1986 through 1999 were included.
The researchers found that the cumulative incidence
of pelvic fractures was greater in the group that received radiation
than in the nonirradiated group for all 3 types of cancer diagnoses.
Within the first 5 years of the study period, the
incidence of pelvic fractures was:
● for women with anal cancer, 14.0 percent in the
irradiated group vs. 7.5 percent in the nonirradiated group;
● for women with cervical cancer, 8.2 percent in
the irradiated group vs. 5.9 percent in the nonirradiated group; and
● for women with rectal cancer, 11.2 percent in
the irradiated group vs. 8.7 percent in the nonirradiated group.
The incidence of arm or spine fractures was similar
in both groups.
The observed hazard ratio for radiation therapy in
women with anal cancer was 3.16.
This value can be interpreted as a 3-fold increase
in pelvic fracture risk for women with anal cancer who underwent
radiation therapy (vs. women who did not) at any given time.
The observed hazard ratio for radiation therapy in
women with cervical cancer was 1.66; in women with rectal cancer, 1.65.
These values indicate a lesser effect, but are still consistent with a
substantial increase in fracture risk, the researchers write.
Given the high baseline rate of fractures in women
aged 65 years or older, the hazard ratio of 1.65 that we found in our
study may represent an increased lifetime incidence of fractures from
the baseline rate of 17 percent to 27 percent a substantial and
clinically significant absolute increase.
The high risk of pelvic fracture after radiation
therapy for anal cancer may reflect the radiation therapy technique used
to treat this disease. In the treatment of anal cancer, it is usually
appropriate to treat the inguinal (pertaining to the groin) nodes
because of the risk of disease at this site. Because of the location of
these nodes with respect to the femoral head and neck, it has been
difficult to treat these nodes well without concomitant irradiation of
the femur, and thus the femoral heads are exposed to a relatively high
irradiation dose in the treatment of anal cancer patients, the authors
write.
The researchers add that it is important to note
that the study population (older, predominantly white women) was already
at high risk for pelvic fractures. Therefore, our results cannot be
generalized to other populations (e.g., men, younger age groups). The
risk of pelvic fractures after irradiation in other populations should
be the focus of future studies.
In conclusion, older women undergoing irradiation
therapy for anal, cervical, or rectal cancer should be counseled with
respect to fracture risks from irradiation. Potentially, these women
could be targeted for preventive strategies, such as bone mineral
densitometry screening, medical regimens aimed at preventing
osteoporosis, and fall prevention. Such strategies should be evaluated
in prospective studies. In addition, changes in irradiation techniques
for high-risk individuals to minimize the irradiation dose received by
bone should be investigated.
Editors Note: This research was supported by a
Veterans of Foreign Wars Surgical Oncology research grant and by the
University of Minnesota Comprehensive Cancer Center. Dr. Baxter is
supported by a University of Minnesota Cancer Center Clinical Scholars
Award and by an American Society of Clinical Oncology Career Development
Award.
Editorial: Postradiotherapy Pelvic Fractures -
Cause for Concern or Opportunity for Future Research?
In an accompanying editorial, William Small, Jr.,
M.D., of Northwestern University, Chicago, and Lisa Kachnic, M.D., of
Boston University Medical Center, Boston, comment of the findings by
Baxter and colleagues.
How should clinicians use the knowledge of an
increased risk of pelvic fractures associated with radiotherapy? This
potential morbidity should be discussed with the patient at the time of
radiation oncology consultation and factored into informed decision
making and informed consent regarding the use of radiotherapy. More
important, patients who have received prior pelvic radiation must
receive long-term follow-up examinations, and must be carefully assessed
when pelvic pain appears.
The authors add that besides improved targeting of
radiotherapy, there may warrant consideration of agents that reduce
toxicity or improve the osseous (of bone-like consistency or structure)
environment after radiotherapy.
In conclusion, Baxter et al have provided
compelling evidence for a significant increase in pelvic fracture risk
with the use of pelvic radiotherapy as a component of definitive cancer
management. The morbidity associated with pelvic fractures and the
widespread use of pelvic radiotherapy make research into reducing such
osseous effects a high priority, the authors conclude.
Editors Note: Dr. Small is on the speakers bureau
for MedImmune, the company that manufactures amifostine.
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