Background Vismodegib has been used for the treatment of locally advanced basal cell carcinoma (laBCC) and metastatic BCC (mBCC) since 2011. Most efficacy and safety data are provided by clinical... Show moreBackground Vismodegib has been used for the treatment of locally advanced basal cell carcinoma (laBCC) and metastatic BCC (mBCC) since 2011. Most efficacy and safety data are provided by clinical trials. This study evaluates the effectiveness of vismodegib for the treatment of laBCC, mBCC and basal cell nevus syndrome (BCNS) patients, and the tumour characteristics associated with a higher probability of achieving a complete response in the Netherlands. Methods A retrospective cohort study that included all patients >= 18 years with histologically proven basal cell carcinoma that received >= 1 dose of vismodegib between July 2011 and September 2019 in the Netherlands. Results In total, 48 laBCC, 11 mBCC and 19 BCNS patients were included. Median progression-free survival was 10.3 months (95% confidence interval (CI), 7.5-22.6) for laBCC, 11.7 (95% CI, 5.2-17.5) for mBCC and 19.1 (95% CI, 7.4-20.2) for BCNS. Larger laBCCs were associated with a lower probability of complete response (hazard ratio (HR) 0.77 per increase in cm, p = 0.02). Of all BCNS patients, 63% received >= 2 treatment sequences with vismodegib; all achieved partial responses. Conclusions Half of the aBCC patients progress within 1 year after the start of vismodegib treatment. More research is needed to investigate other treatment strategies after vismodegib progression and to evaluate long-term effects of repetitive vismodegib treatment. Show less