Summary: A new study shows that older women who get radiation therapy for anal, cervical, or rectal cancer increase their risk of breaking a hip later. Women of all races are affected. The findings by researchers at the University of Minnesota Comprehensive Cancer Center appear in the Journal of the American Medical Association.

Why it's important: In 2005, around 10,000 women were diagnosed with cervical cancer, 17,000 with rectal cancer and 2,000 with anal cancer. The standard treatment for these cancers often includes radiation to the pelvis. Doctors and patients need to know if this treatment increases the risk of breaking a bone in the pelvis because this type of injury is disabling and can even be deadly. Fractures, particularly of the pelvis, hip, and sacrum bones, interfere with walking and force people to spend much of their time recovering in bed, which can lead to bed sores, dangerous blood clots, and other complications. One study found that 1% of all deaths in people 50 and older were related to a hip fracture.

What's already known: Doctors have long known that radiation therapy damages bones. Bone is a living tissue that depends on living cells to maintain it, and radiation kills some of those cells. Past studies of the effects of a 1-week course of radiation in patients with rectal cancer found more pelvic fractures in both men and women. But no studies had been done of people after they were given lower doses of radiation over 5-6 weeks, which is the typical treatment schedule in the United States.

How this study was done: Women who were over 65 years old and diagnosed with anal, rectal, or cervical cancer were identified through SEER (Surveillance, Epidemiology and End Results), the US national cancer registry. Because SEER routinely collects data on treatment, the researchers could identify those who received radiation therapy. Their later medical history was then examined in the Medicare database. Medicare pays a portion of the medical costs for almost all US citizens over age 65. By examining Medicare records, the researchers could determine which of these women had developed a fracture of a pelvic bone.

What was found: Through the SEER registry, researchers found 6,428 women who had been diagnosed with anal, rectal, or cervical cancer. Their average age at diagnosis was about 76. Of these women, 2,855 received radiation therapy and were found to have a higher rate of pelvic bone fractures -- fractures of the pelvis or sacrum or hip. The average time from treatment to fracture was around 4 years. Women who were treated with radiation for anal cancer had 3 times the rate of fractures as women with the same diagnosis who didn't get radiation. Women irradiated for cervical or rectal cancer had a 65% increase in the rate of their fractures.

In the general population, African-American women have a lower rate of osteoporosis and fractures than do women of other races. But when looking at this group of cancer patients, researchers found that it made no difference whether the women were African-American or not. All races had a higher rate of fracture after radiation therapy.

The bottom line: Pelvic fractures are a major long-term complication of pelvic radiation therapy -- at least in older women. Although men weren't studied, earlier reports following short-term radiation found they, too, suffered a higher rate of pelvic fractures. This study serves as a wake-up call for doctors treating these patients. Since the radiation is often life-saving and less onerous than surgery in some cases, eliminating it is not an option. Instead, doctors must keep a close watch on these patients' bone density and consider drug treatment to prevent osteoporosis, the researchers say. Patients who have had pelvic radiation need to know their pelvic bone density and, if it is below normal, how to take steps to protect themselves from falls.

Citation: "Risk of Pelvic Fractures in Older Women Following Pelvic Irradiation." Published in the Nov. 23/30, 2005, Journal of the American Medical Association (Vol. 294, No. 20: 2587-2593). First author: Nancy Baxter, MD, PhD, University of Minnesota Comprehensive Cancer Center.