AbstractBackgroundAdditional evaluations, including second opinions, before breast cancer surgery may improve care, but may cause detrimental treatment delays that could allow disease progression.AimsWe investigate the timing of surgical delays that are associated with survival benefits conferred by preoperative encounters versus the timing that are associated with potential harm.Methods and resultsWe investigated survival outcomes of SEER Medicare patients with stage 1–3 breast cancer using propensity score‐based weighting. We examined interactions between the number of preoperative evaluation components and time from biopsy to definitive surgery. Components include new patient visits, unique surgeons, medical oncologists, or radiation oncologists consulted, established patient encounters, biopsies, and imaging studies. We identified 116 050 cases of whom 99% were female and had an average age of 75.0 (SD= 6.2). We found that new patient visits have a protective association with respect to breast cancer mortality if they occur quickly after diagnosis with breast cancer mortality subdistribution Hazard Ratios [sHRs] = 0.87 (95% Confidence Interval [CI] 0.76–1.00) for 2, 0.71 (CI 0.55–0.92) for 3, and 0.63 (CI 0.37–1.07) for 4+ visits at minimal delay. New patient visits predict worsened mortality compared with no visits if the surgical delay is greater than 33 days (CI 14–53) for 2, 33 days (CI 17–49) for 3, and 44 days (CI 12–75) for 4+. Medical oncologist visits predict worse outcomes if the surgical delay is greater than 29 days (CI 20–39) for 1 and 38 days (CI 12–65) for 2+ visits. Similarly, surgeon encounters switch from a positive to a negative association if the surgical delay exceeds 29 days (CI 17–41) for 1 visit, but the positive estimate persists over time for 3+ surgeon visits.ConclusionPreoperative visits that cause substantial delays may be associated with increased mortality in older patients with breast cancer.