Provider case volume and outcome in the evaluation and treatment of patients with mammogram-detected breast carcinoma.

Background: Practice volume may affect the outcome of patients with breast carcinoma. Defining factors that influence the relation of volume and outcome for the diagnosis and treatment of breast carcinoma is important, because breast carcinoma is common, and care is decentralized.

Methods: Community-wide diagnosis and treatment of mammogram-detected breast carcinoma was examined using claims data from a single insurer representing 25% of the regional population. Among 1001 mammogram-directed breast biopsies, the rate of breast carcinoma diagnosed by stereotactic core needle biopsy (SCNB) or excisional biopsy with needle localization (EBNL) and the rate at which breast-conserving surgery (BCS) was used were analyzed. Outcome and practice volume were examined for surgeons, radiologists, and medical centers.

Results: Two hundred twenty-four tumors were diagnosed by EBNL (604 diagnoses) and SCNB (397 tumors), for a 22.4% positive biopsy rate. The median number of procedures per physician was one. Positive biopsy rates for radiologists, surgeons, and medical centers did not correlate with practice volume. Positive biopsy rates for high-volume physician providers and medical centers ranged from 9% to 46%. The BCS rate was 45% and 64% for surgeons treating one or more than one claim, respectively. Tumor stage and surgeon case volume were the only independent predictors of BCS (P < 0.05).

Conclusions: There is wide variation in diagnosis and treatment outcomes for patients with mammogram-detected breast carcinoma. Overall, practice volume was correlated with the use of BCS but not with the rate of positive biopsy. A wide variation in the positive biopsy rate among high-volume providers and medical centers suggests that volume of practice is not a surrogate for quality in the diagnosis of breast carcinoma.