Background: A second medical oncology opinion (SMO) may facilitate chemotherapy decision-making. However, little is known about the interplay between SMOs, treatment decision-making and chemotherapy use. Methods: We surveyed women newly diagnosed with early-stage invasive breast cancer and treated in 2013-2014 (response rate 70%), accrued approximately 3 months after surgery through 2 population-based SEER registries (Georgia and Los Angeles), about their experiences with medical oncologists, decision-making, and chemotherapy use. We evaluated demographic, clinical and decisional factors associated with SMO using logistic regression, and evaluated the association between SMO and chemotherapy, adjusting for clinical indication for chemotherapy, results of the 21-gene recurrence score assay, and estimated propensity for SMO given patient and tumor-specific characteristics. Results: Among 1182 insured patients who consulted any medical oncologist, 8.7% had SMO and 2.4% received chemotherapy from the SMO provider. On multivariable analysis, predictors of SMO use were younger age (odds ratio, OR 0.97 per year, 95% confidence interval, CI 0.94-0.99), education (college vs. high school graduate, OR 1.88, CI 1.06-3.33), an intermediate 21-gene recurrence score (OR 2.21, CI 1.18-4.16) and a variant of uncertain significance on BRCA1/2 gene testing (OR 5.61, CI 1.22-25.72). Satisfaction with chemotherapy decision-making was high and did not differ between patients who did vs. did not receive SMO (85.3% quite or totally satisfied vs. 86%, p-value 0.85). On multivariable analysis, chemotherapy use did not differ between SMO recipients vs. non-recipients (p-value 0.25). Conclusions: SMO use was low among early-stage breast cancer patients, and was not followed by more or less receipt of chemotherapy. High decision satisfaction regardless of SMO use suggests little unmet demand. Along with younger age and more education, the factor that predicted SMO use was uncertain results of genomic testing. Studies of precision medicine should track patients’ demand for SMO, which may rise with the dissemination of increasingly complex genomic tests. Funding: P01-CA-163233