Determining breast cancer axillary surgery within the surveillance epidemiology and end results-Medicare database

Use of sentinel lymph node biopsy (SLNB) is under-reported by cancer registries' "Scope of Regional Lymph Node Surgery" variable. In 2011, the Surveillance Epidemiology and End Results (SEER) Program recommended against its use to determine extent of axillary surgery, leaving a gap in the utilization of claims data for breast cancer research. The objective was to develop an algorithm using SEER registry and claims data to classify extent of axillary surgery for breast cancer.

We analyzed data for 24,534 breast cancer patients. CPT codes and number of examined lymph nodes classified the extent of axillary surgery. The final algorithm was validated by comparing the algorithm derived extent of axillary surgery to direct chart review for 100 breast cancer patients treated at our breast center.

Using the algorithm, 13% had no axillary surgery, 56% SLNB and 31% axillary lymph node dissection (ALND). SLNB was performed in 77% of node negative patients and ALND in 72% of node positive. In our validation study, concordance between algorithm and direct chart review was 97%.

Given recognized inaccuracies in cancer registries' "Scope of Regional Lymph Node Surgery" variable, these findings have high utility for health services researchers studying breast cancer treatment.