9024 Background: Vismodegib (VISMO) is the first Hh pathway inhibitor approved for use in adults with advanced BCC (aBCC) that is inappropriate for surgery or radiotherapy. While most VISMO-related adverse events (AEs) are mild to moderate, the presence of multiple chronic AEs may lead to treatment interruption or discontinuation. Treatment breaks are allowed in the STEVIE study (NCT01367665) for the management of toxicity, among other reasons. Herein we present an exploratory analysis assessing the safety and efficacy profile in patients (pts) with treatment breaks on study. Methods: STEVIE is an ongoing study focusing on safety of VISMO in pts with aBCC. Pts receive VISMO 150 mg once daily until progressive disease, unacceptable toxicity, or withdrawal. The primary objective is safety; efficacy is a secondary end point. Tumor response assessments are performed using RECIST 1.1 as assessed by the investigator. Exploratory analyses were performed using data from a planned interim analysis (data cutoff Nov 6, 2013). Results: 499 pts were included in the safety population and analyzed according to number of treatment breaks received. The median duration of treatment was 223.5, 299.0, 399.0, and 454.0 days in pts with 0, 1, 2, or ≥ 3 treatment breaks, respectively. Median dose intensity was 97%, 89%, 86%, and 81%, respectively. Median treatment break duration was 22 days (SD 13.92). Safety and efficacy results are presented in the Table. Patients with more treatment-emergent AEs (TEAEs) including those experiencing more grade ≥ 3 TEAEs had more treatment breaks. These were AEs known to be commonly associated with VISMO use. The most common grade ≥ 3 TEAE was muscle spasm. Conclusions: Increased number of treatment breaks was associated with longer median duration of VISMO treatment and did not appear to compromise efficacy. Clinical trial information: NCT01367665.