Emergence of sentinel node biopsy in breast cancer as standard-of-care in academic comprehensive cancer centers

Background: Ongoing clinical trials are addressing the accuracy and safety of sentinel node biopsy (SNB) in the treatment of breast cancer; however, SNB is already increasingly being used in clinical practice. This study examined the extent and time trends of the use of SNB in stage I and II breast cancer patients. Methods: Clinical data were collected from stage I and II (tumor size less than or equal to5.0 cm) breast cancer patients (n = 3003) who were treated at five comprehensive cancer centers between July 1, 1997, and December 31, 2000. Axillary surgery was classified as SNB alone, SNB + axillary node dissection (AND), AND alone, or none. Patterns of use of axillary surgery were summarized as the percentage of patients receiving each surgery type. The statistical significance of time trends for the use of SNB alone was analyzed by logistic regression models. All statistical tests were two-sided. Results: Overall, SNB alone was used in 13% of patients, SNB + AND in 22%, AND alone in 59%, and no axillary surgery in 6%. Use of SNB alone was statistically significantly associated with breast-conserving surgery of both smaller (less than or equal to2 cm) and larger tumors (2-5 cm) (P<.001 for both associations). For stage I cancer patients treated with breast-conserving surgery (n = 1763), use of SNB increased statistically significantly over the study period, from 8% in 1997 to 9%, 14%, 15%, 22%, 42%, and 58% for the next six consecutive 6-month time intervals, respectively. After controlling for center, age, and comorbidity, the odds ratio for the use of SNB alone was 2.30 (95% confidence interval = 1.88 to 2.82) for each 6-month interval (P<.001). Conclusions: Widespread use of SNB outside the clinical trial setting suggests that oncologists at cancer centers in our study have accepted SNB as standard-of-care for the treatment of breast cancer. This acceptance, if it occurs in other cancer centers and community practice, may affect accrual and generalizability of ongoing clinical trials of SNB.