(ChemotherapyAdvisor) – Panitumumab monotherapy was generally well tolerated and had activity in patients previously treated for recurrent or metastatic squamous cell carcinoma of the head and neck, according to results of a multicenter, open-label, phase 2 study presented at the Multidisciplinary Head and Neck Cancer Symposium.

The PRISM study enrolled 52 patients, 79% with metastatic disease and 21% locoregional recurrent disease only. Median age was 61 years; 69% were men; and ECOG performance score was 0 (38%), 1 (60%), or 2 (2%), noted Danny Rischin, MBBS, of Peter MacCallum Cancer Centre, East Melbourne, Australia, and colleagues. Distribution of primary tumor sites was oral cavity (38%), oropharynx (35%), larynx (25%), and hypopharynx (2%).

Prior treatments included radiotherapy (92%), platinum-based chemotherapy (92%), taxane (65%), fluoropyrimidine (40%), and EGFR inhibitor therapy (10%). Discontinuation of first-line chemotherapy was due to disease progression in 94% of patients and intolerance in 6%.

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Panitumumab 9mg/kg was administered every three weeks until disease progression or intolerability. Primary endpoint was objective response rate; secondary endpoints included disease control rate, overall survival (OS), progression-free survival (PFS), and safety. RECIST confirmed partial response (PR) rate was 4% (2/51 patients); disease contorl rate was 39% (20/51 patients). Two patients had an unconfirmed PR and one patient had an unconfirmed complete response; these three responses were categorized as stable disease.

Median PFS was 1.4 months and median OS, 5.1 months. One patient was observed to have prolonged and continued disease stabilization after 25 cycles of therapy. The most common adverse events (AEs) were rash/dermatitis acneiform (69%), fatigue (33%), dry skin (21%), and hypomagnesemia (21%). Worst grade 3 AEs occurred in 18 patients (35%) and worst grade 4 in 4 (8%). Five patients died on study; one patient had angioedema that was deemed treatment-related.

The Multidisciplinary Head and Neck Cancer Symposium is sponsored by the American Head and Neck Society, the American Society of Clinical Oncology, the American Society for Radiation Oncology, and the Society of Nuclear Medicine.