April 21 (HealthDay News) -- In women aged 80 and older, regular mammograms reduce the risk of being diagnosed with late-stage breast cancer, but only about 20 percent of U.S. women in this age group have regular screenings, a new study shows.

The study is published online April 21 in the Journal of Clinical Oncology.

Women aged 80 and older account for an estimated 17 percent of breast cancer cases in the United States.

"This study suggests that mammography benefits may have no age limit and that women should consider being screened on a regular basis, even into their 80s and possibly 90s, depending on their current health status," study author Dr. Brian D. Badgwell, a surgical oncology fellow at the University of Texas M.D. Anderson Cancer Center, said in a prepared statement.

"Mammography has been shown to be an excellent means of detecting breast cancer early, when it is more likely to be cured. We found that when breast cancer was diagnosed, it was more likely to be found at an early stage when a woman had at least three mammograms in the five-year period before diagnosis," Badgwell said.

Doctors and older female patients should discuss the benefits of mammography, he recommended.

For this study, Badgwell and colleagues analyzed five years (1996 to 2002) of mammography use among 12,358 women aged 80 and older before they were diagnosed with breast cancer. The data came from the Surveillance, Epidemiology, and End Results (SEER) national cancer registry.

Women who didn't have a mammography during this time were labeled nonusers (49 percent), those who had one to two mammograms were irregulars users (29 percent), and those who had three or more mammograms were regular users (22 percent).

The researchers found that 68 percent of regular users were diagnosed with stage I (early) breast cancer, compared with 56 percent of irregular users and 33 percent of nonusers. Only 32 percent of regular users were diagnosed with stage II-IV cancers, compared with 44 percent of irregular users and 67 percent of nonusers.

SOURCE: American Society of Clinical Oncology, news release, April 21, 2008