Combined effect of bevacizumab with erlotinib and irradiation in head and neck cancer. A preclinical study on an orthotopic model Free

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Clinical benefit has been demonstrated in patients with head and neck tumors receiving an anti-epidermal growth factor receptor (EGFR) agent in combination with radiotherapy. Recent preclinical and clinical studies suggest beneficial effects from combining antiangiogenic drugs with radiotherapy.

To investigate the effect of combining these approaches, we evaluated in vivo the anti-tumor efficacy of the anti-angiogenic compound bevacizumab, a highly specific monoclonal antibody directed against the vascular endothelial growth factor (VEGF), erlotinib, an EGFR tyrosine kinase inhibitor, and irradiation given alone and in combination. Investigations were performed using a VEGF-secreting human head and neck tumor cell line, CAL33, with a high EGFR content, injected as orthotopic xenografts into the mouth floor of nude mice. Three days after tumor cell injection, bevacizumab (5 mg/kg 5 days /week, i.p.), erlotinib (100 mg/kg 5 days/week, orally) and irradiation ([Rt] 6 Gy, 3 days/week), were administered alone and in combination for 10 days (ten animals per treatment group). At that time, animals were sacrificed and weighed tumor dimensions and weights were measured and bilateral node chain dissection performed. Tumor mass, number of inflammatory nodes either invaded or not, and tumor cell proliferation (Ki67 with immunohistochemistry) were examined and the results were compared between the different treatment groups using the Mann and Whitney non parametric statistic test. The interactions between combined treatments were measured by calculating the combination ratio (CR); CR = FTv A x FTv B / FTv (A+B), where FTvx is the fractional tumor volume for the agent x.

As compared with the control, concomitant administration of drugs produced a marked and significant synergistic (p< 0.05 , CR = 2) decrease in tumor mass ; the addition of irradiation almost completely abolished tumor growth (p< 0.001, CR = 2.3). The drug association significantly reduced the number of invaded nodes (p = 0.03) and the triple combination significantly reduced the total node number as compared with controls (p = 0.001). The Rt-induced proliferation, reflected by Ki67 labeling (p<0.01),was reduced to control level with the triple combination (p< 0.001). The efficacy of such new combination of bevacizumab-erlotinib and Rt may be of clinical importance in the management of head and neck cancer .