Oral Mucositis (OM) consists in the painful inflammation and ulceration of the mucous membranes lining the digestive tract, lasting between 7 and 98 days; and starts as an acute inflammation of oral mucosa, tongue, and pharynx after RT exposure. Gel X spray is a product based on zinc gluconate. It could be helpful to achieve the prevention of Oral Mucositis and, in case of OM manifestation, the reduction of oral pain symptoms and to accelerate the healing process of oral mucositis ulcerations. The aim of this study is to demonstrate the efficacy of the treatment with Gel X to reduce the incidence of oral mucositis, in comparison with Sodium Bicarbonate.