UCSF

Background

Cetuximab combined with radiation therapy (RT) is an evidence-based treatment for locally advanced head and neck squamous cell carcinoma (HNSCC); however, locoregional failure remains the primary cause of cancer-related death in this disease. Intratumoral injection of epidermal growth factor receptor (EGFR)-antisense plasmid DNA (EGFR-AS) is safe and has been associated with promising lesional responses in patients who have recurrent/metastatic HNSCC. For the current study, the authors investigated the antitumor effects of cetuximab and EGFR-AS in preclinical HNSCC models and reported their phase 1 experience adding intratumoral EGFR-AS to cetuximab RT.

Methods

Antitumor mechanisms were investigated in cell line and xenograft models. Phase 1 trial eligibility required stage IVA through IVC HNSCC and a measurable lesion accessible for repeat injections. Patients received standard cetuximab was for 9 weeks. EGFR-AS was injected weekly until they achieved a lesional complete response. RT was delivered by conventional fractionation for 7 weeks, starting at week 3. Research biopsies were obtained at baseline and week 2.

Results

When added to cetuximab, EGFR-AS decreased cell viability and xenograft growth compared with EGFR-sense control, partially mediated by reduced EGFR expression. Six patients were enrolled in the phase 1 cohort. No grade 2 or greater EGFR-AS-related adverse events occurred. The best lesional response was a complete response (4 patients), and 1 patient each had a partial response and disease progression. EGFR expression decreased in 4 patients who had available paired specimens.

Conclusions

In preclinical models, dual EGFR inhibition with cetuximab and EGFR-AS enhanced antitumor effects. In a phase 1 cohort, intratumoral EGFR-AS injections, cetuximab, and RT were well tolerated. A phase 2 trial is needed to conduct an extended evaluation of safety and to establish efficacy.