A 52-year-old Indian woman presents with a 3-month history of progressive dyspnea, chest pain, and palpitations. Chest X-ray reveals a large mediastinal mass. CT chest shows a 10 cm anterior mediastinal mass with heterogeneous enhancement. Core needle biopsy confirms classical Hodgkin lymphoma (cHL), stage IIIB. Baseline PET-CT shows FDG-avid disease in the mediastinum and supraclavicular nodes. She is started on ABVD chemotherapy. After 2 cycles, repeat PET-CT shows minimal response with persistent FDG uptake (SUV max 8.5). Given the primary refractory disease, which targeted agent is most appropriate to add to her regimen?

Explanation

## Clinical Context: Primary Refractory Hodgkin Lymphoma **Key Point:** Brentuximab vedotin (anti-CD30 monoclonal antibody conjugated to monomethyl auristatin E, a microtubule-disrupting agent) is the standard targeted therapy for ABVD-refractory or primary refractory classical Hodgkin lymphoma. ## Mechanism of Action Brentuximab vedotin works via: 1. CD30 antigen recognition on Hodgkin/Reed-Sternberg cells (highly expressed in cHL) 2. Internalization and trafficking to lysosomes 3. Release of MMAE (monomethyl auristatin E), which binds β-tubulin and causes mitotic arrest 4. Induction of apoptosis in CD30+ malignant cells ## Evidence & Clinical Use **High-Yield:** In the HD21 trial and subsequent real-world data, brentuximab vedotin demonstrated: - Objective response rate (ORR) of 75% in primary refractory cHL - Significantly improved 4-year progression-free survival when added to ABVD upfront in high-risk patients - FDA approval for relapsed/refractory cHL and primary refractory disease **Clinical Pearl:** Brentuximab vedotin is now incorporated into first-line therapy for high-risk cHL (e.g., bulky mediastinal disease, advanced stage) and is the standard salvage agent for ABVD-resistant disease. ## Dosing & Toxicity | Parameter | Detail | |-----------|--------| | Dose | 1.8 mg/kg IV q3 weeks | | Half-life | ~4–6 days | | DLT | Peripheral neuropathy (dose-limiting), neutropenia, infusion reactions | | Monitoring | Baseline & periodic neuropathy assessment (FACT/GOG-Ntx scale) | **Warning:** Cumulative peripheral neuropathy is the main dose-limiting toxicity; monitor sensory/motor function at each cycle. ## Why This Patient Needs Brentuximab Vedotin - Primary refractory disease (minimal response after 2 ABVD cycles) is a strong indication - CD30 is universally expressed in classical Hodgkin lymphoma - Brentuximab vedotin has level 1 evidence for this exact scenario - Allows bridging to stem cell transplantation if needed [cite:Harrison 21e Ch 104]