A comparative review of the potential role of adenovirus and Herpes Simplex Virus in the treatment of advanced squamous cell carcinoma of the head and neck

The unsatisfactory outcome of patients who receive intensive multimodality treatment for advanced squamous cell carcinoma of the head and neck (SCCHN) has motivated investigators to seek novel treatments to improve survival. Advances in molecular biology has led to the development of cancer gene therapy (CGT) and revived interest in viral vectors as a mechanism. SCCHN is an ideal model for CGT as disease remains locoregional and is amenable to injection of viruses. Adenovirus and Herpes Simplex Virus Type-1 (HSV) are the most studied Oncolytic Viruses (OVs). Both viruses have been shown to select and replicate in tumour cells and demonstrate anti-tumour effect in laboratory studies and clinical trials. Toxicity from OVs is minor and manageable. Different adenoviral mutants have been investigated with mixed responses. One vector, H101, has now been licensed after showing significant tumour regression in conjunction with chemotherapy. HSV has a larger capacity to carry genetic material and with the addition of the granulocyte-macrophage colony-stimulating factor, has the potential to stimulate an immune response systemically and at the site of disease. OVs are limited by the distribution of virus beyond injection site and by pre-existing or rapidly established immune response. Phase III studies are required.