Objective: To identify time trends and factors associated with breast-conserving surgery (BCS) and delivery of postoperative radiation therapy among women with stage I or II breast cancer.
Design: Survey.
Setting: Population-based cancer registry in the Seattle-Puget Sound (Wash) region.
Participants: The study included 8095 women diagnosed with stage I or II breast cancer (American Joint Committee on Cancer staging criteria) from 1983 through 1989.
Main outcome measures: Breast-conserving surgery with or without radiation therapy vs mastectomy, and, among women with BCS, a comparison of radiation therapy vs no therapy.
Results: In 1985 when results from a US randomized clinical trial of BCS were published, the frequency of BCS peaked (46.3% of stage I; 30.1% of stage II) followed by a return to levels before 1985 for women with stage II breast cancer and a more moderate decline for stage I breast cancer. The likelihood of BCS decreased with increasing age (P less than .001), with stage II disease, and with residence outside the region's major urban center, and it increased with education (P less than .001) or median income (P less than .001) by census tract. The proportion of women who received radiation therapy after BCS decreased with age (P less than .001), was lower for women with stage II than stage I disease, and was lowest in counties without radiation therapy facilities.
Conclusions: Despite scientific evidence of the equivalent efficacy of BCS with radiation therapy and mastectomy, BCS is not performed on the majority of women with stage I or II breast cancer as recommended by the National Institutes of Health, and factors are associated with its use that differ from selection criteria outlined by the National Institutes of Health.