SURGEON VOLUME OF EARLY STAGE BREAST CANCER CASES. A. Nattinger 1 , R. Hoffmann 1 , R. Sparapani 1 ; 1 Medical College of Wisconsin, Milwaukee, WI PURPOSE: The percentage of U.S. women with early stage breast cancer who receive initial treatment in accordance with national guidelines has been declining. We are interested in whether physician volume of cases is related to processes or outcomes of care, and therefore determined for a population-based cohort the distribution of cases cared for by each surgeon operating on one or more cohort patients. METHODS: We used data from a population-based SEER-Medicare linked data base to study women aged 65 or older, who were diagnosed with a stage I or II breast cancer in 1993 ± 95, and underwent either breast-conserving surgery (BCS) or mastectomy. We determined the operating surgeons from the Medicare part B claims, and eliminated surgeons with an office zip code outside the SEER states. RESULTS: Over the three study years, 15,574 women were operated on by 3,265 different physicians. The median number of cases performed per physician per year was 1.0 with 1st/3rd quartiles of 0.0/4.0. Over three years, 35.3% of physician-years were zero-case years. We We developed a conceptual model for assessing the validity of existing guidelines using literature searches and expert guidance. Two physicians with expertise in literature retrieval and evaluation conducted limited literature searches for new evidence that could affect the validity of the guideline statements. We also searched for practice guidelines that had been published after the release of the AHCPR guidelines. Guideline statements were sent to original guideline panel members and other content experts, who were asked to evaluate the current validity of each statement and include evidence to support their assessment. The evidence collected was then used to determine the validity of the guidelines, which were classified as``still valid'' or``needs updating.'' Finally, we conducted a``survival analysis'' to estimate the rate at which guidelines become outdated using a Kaplan ± Meier survival curve and the Weibull parametric model. RESULTS: We reviewed 17 guidelines and surveyed 170 experts, 121 (71%) of whom returned their surveys. Our literature searches identified 6,994 titles, which were all reviewed.