Information on radiation treatment in patients with breast cancer: The advantages of the linked medicare and SEER data

Several studies have found underutilization of radiotherapy in patients with breast cancer; but there are concerns about the completeness of various databases on radiotherapy. We used the linked Medicare-SEER (Surveillance, Epidemiology and End Results) database to compare information on receipt of radiotherapy after diagnosis of breast cancer. More than 18% of women identified by Medicare data as receiving radiotherapy were not so identified by SEER, and 7% of those identified as receiving radiotherapy by SEER were not identified by Medicare. Risk of discordance on radiotherapy information between the two data sets was especially high in women receiving breast-conserving surgery. The combined SEER-Medicare database gives a more complete picture on the use of radiotherapy. The previously reported geographic variations in the use of radiotherapy for breast cancer may be due in part to underreporting of radiotherapy in some areas. J CLIN EPIDEMIOL 52;5:463-470, 1999. (C) 1999 Elsevier Science Inc.