The purpose of this study is to evaluate if the addition of valproic acid to standard platinum-based chemoradiation as definitive treatment of locally advanced Head and Neck squamous cell carcinoma can improve treatment outcomes, such as response rate.

Valproic acid is a known histone deacetylase inhibitor. In addition to activating apoptosis pathways, cell differentiation and downregulating expression of growth factors, it also promotes radiosensitization.

Most patients with Head and Neck squamous cell carcinoma are diagnosed with locally advanced disease, in which long term disease control is still a challenge. The incorporation of epigenetic regulation into standard treatment could improve results of definitive platinum-based chemoradiation in such patients.

Inclusion Criteria:

• Unresectable Oropharyngeal or oral cavity squamous cell carcinoma
• Candidate for definitive chemoradiation
• No previous treatment
• Measurable disease according to RECIST v 1.1
• Previous neoplasia, other than Head and Neck, with more than five years without evidence of disease; basocellular carcinoma of the skin and in situ cervical dysplasia if resected
• Age under 60 years
• ECOG performance status 0-2
• Ability of understanding and giving informed consent
• Adequate renal and hepatic function
• Adequate bone marrow function
• Normal serum magnesium
• Absence of QTc prolongation
• Life expectancy of over 12 weeks

Exclusion Criteria:

• Pregnancy
• Distant metastasis
• Hypersensibility to valproic acid or other antiepileptic drugs
• Valproic acid chronic use
• Severe neurologic impairment
• Uncontrolled comorbidity
• Hypoalbuminemia
• Known history of hepatitis B, C or HIV