WEDNESDAY, July 6 (HealthDay News) -- An estimated 20 percent of breast cancer patients in the United States who receive radiation after they undergo breast-conserving surgery may not have their radiation treatments recorded in a federal database, a new study suggests.

The Surveillance Epidemiology and End Results (SEER) registry is maintained by the U.S. National Cancer Institute and is used by researchers to examine patterns of cancer treatment, including racial or regional disparities.

In this study, a University of Michigan Comprehensive Cancer Center team compared SEER data with treatment reports from breast cancer patients in Detroit and Los Angeles. Of the 1,292 patients in both cities who said they received radiation therapy, 273 (just over 20 percent) were not coded that way in the SEER database.

When the researchers looked at the cities separately, they found that radiation treatment was not correctly noted in the SEER database for 11 percent of patients in Detroit and about one-third of patients in Los Angeles.

The study was published online June 29 in the journal Cancer.

Previous studies based on SEER data have suggested that a number of patients aren't receiving recommended radiation therapy after breast-conserving surgery, leading to efforts to increase radiation treatment in this group of patients.

If SEER data is not accurate, researchers don't know if resources to improve cancer care are being used appropriately, noted lead study author Dr. Reshma Jagsi, an associate professor of radiation oncology at the University of Michigan Medical School.

"With increased interest in comparative effectiveness research, more and more researchers are using registry databases like SEER. If the quality of the data in some of these databases has limitations, these must be understood to avoid potentially misleading conclusions that affect both clinical decision-making and policy," Jagsi said in a university news release.

More information

The U.S. National Cancer Institute has more about breast cancer.