A 58-year-old woman with multiple basal cell carcinomas on her trunk and extremities (consistent with Gorlin syndrome) is not a surgical candidate due to comorbidities. Which systemic agent is the drug of choice for advanced or metastatic basal cell carcinoma in this setting?

Explanation

## Systemic Treatment of Advanced Basal Cell Carcinoma **Key Point:** Vismodegib is the FDA-approved and gold-standard systemic agent for locally advanced, metastatic, or multiple basal cell carcinomas, particularly in Gorlin syndrome (nevoid basal cell carcinoma syndrome). ### Vismodegib: Mechanism and Pharmacology Vismodegib is a **hedgehog pathway inhibitor** that: 1. Blocks smoothened (SMO) protein in the hedgehog signaling cascade 2. Inhibits proliferation of basal cell carcinoma cells (which depend on aberrant hedgehog signaling) 3. Induces cell cycle arrest and apoptosis **High-Yield:** ~90% of sporadic BCCs and nearly 100% of Gorlin syndrome BCCs have mutations in the hedgehog pathway (PTCH1 or SMO mutations), making this pathway essential for BCC pathogenesis. ### Clinical Efficacy | Parameter | Data | |-----------|------| | **Objective response rate (locally advanced/metastatic)** | 60–80% | | **Complete response rate** | 10–20% | | **Time to response** | 3–6 months | | **Median duration of response** | 7–10 months | | **Indication** | Locally advanced, metastatic, or multiple BCCs (Gorlin) | ### Dosing and Administration - **Dose:** 150 mg once daily orally - **Duration:** Continue until disease progression or intolerable toxicity - **Monitoring:** Regular clinical assessment; baseline and periodic imaging for metastatic disease ### Adverse Effects **Common (>30%):** - Muscle cramps and myalgia - Dysgeusia (taste disturbance) - Alopecia - Weight loss **Serious:** - Teratogenicity (absolute contraindication in pregnancy) - Premature fusion of epiphyses in growing children (use with caution) **Clinical Pearl:** Muscle cramps are often the dose-limiting toxicity but may improve with continued use or dose reduction. Patients must use strict contraception (Category X in pregnancy). ### Comparison with Other Systemic Agents | Agent | Role in BCC | Rationale | |-------|-------------|----------| | **Vismodegib** | First-line systemic agent | Targets hedgehog pathway; high response rates | | **Methotrexate** | Not standard | Non-specific; used in cutaneous lymphomas, not BCC | | **Interferon-α** | Obsolete | Weak activity; replaced by vismodegib | | **Doxorubicin** | Palliative only | Chemotherapy for metastatic disease; poor outcomes | **Warning:** Methotrexate, interferon-α, and doxorubicin are NOT indicated for BCC and represent older, less effective approaches.