A new study shows that some women with breast cancer fail to complete their radiation therapy, pointing to a need to help more women to see their treatment through to the end.

Researchers found that of 24,500 U.S. women diagnosed with breast cancer between 1992 and 2002, after surgery, radiation therapy was completed by 87 percent.

While that figure is “reassuring,” the researchers report in the journal Cancer, the 13 percent of patients who did not complete therapy still represents a fairly large number of women.

This is of concern because radiation treatment after breast cancer surgery lowers the chances of cancer recurrence, note Dr. Tomasz P. Srokowski of the University of Texas M.D. Anderson Cancer Center in Houston and colleagues.

The researchers based their findings on data from a government cancer- surveillance system. They focused on the records of 24,510 women 66 years of age or older who underwent surgery and radiation for early- to mid- stage breast cancer - cancer that had not spread to distant sites in the body.

In general, the study found, women who were treated with a mastectomy were less likely to complete radiation therapy than those who’d received less-extensive surgery. Black women were less likely to complete therapy than were white women - 16 percent did not have a full course of radiation, versus just over 12 percent of white women.

In the case of mastectomy patients, the researchers speculate that after such radical surgery, some women - as well as their doctors - may place less importance on follow-up radiation, compared with those who only have the tumor removed.

But the reason for the racial discrepancy is not clear, according to Srokowski’s team. Factors like income and education level did not appear to explain the difference.

Overall, women who did not complete radiation had a slightly higher risk of cancer recurrence over the next 5 years. However, the vast majority of both completers and non-completers - more than 95 percent in both cases - were recurrence-free during that time.

Still, the researchers say, more studies should look into why some women fail to complete their breast cancer treatment, and what should be done about it.

There was some evidence in the current study that the situation is improving, however. Women who had been diagnosed in more-recent years were more likely than others to complete post-surgery radiation.

This, according to Srokowski’s team, may reflect improvements in radiation therapy that have reduced side effects, as well as greater awareness of the potential benefits of post-surgery radiation.

SOURCE: Cancer, July 1, 2008.