Topical Diclofenac for Prevention of Radiation-induced Dermatitis

Radiation induced dermatitis (RID) is one of the most commonly reported adverse events of Head and neck tumor, breast cancer radiation therapy (RT). Radiation therapy toxicity is exhibited within hours to weeks of exposure and persisting throughout the course of treatment. Radiation induced dermatitis is a result of generation of reactive oxygen species (ROSs), which in return induces epidermal and dermal inflammatory responses. Radiation causes structural tissue damage, which trigger production of pro-inflammatory mediators; as NF-κB, COX-2, and cytokines such as IL-6, TNF-a, and IFN- γ. Subsequently erythema, ulceration, and edema are developed，then followed by thinning of the epidermis, dry desquamation. If damage is more severe, moist desquamation occur. It can be deduced that inflammatory response plays a significant role in the radiotherapy induced dermatitis. There are many agents that are used in the management of RID in the clinical settings, however, up till now there is none supported by the guidelines. Radiation induced dermatitis occurrence, not only could it impair the patient's quality of life but it could also affect the RT course of treatment, which could negatively influence the cancer treatment. Therefore more effort is needed to find a method of prevention of RID, resulting from Head and neck tumor,breast cancer RT. Diclofenac sodium gel, a COX-2 inhibitor and nonsteroidal anti-inflammatory drug (non-NSAID), is widely used to treat inflammatory conditions, and studies show that topical diclofenac has no safety concerns. It has been used for more than 20 years in patients with osteoarthritis without any significant adverse effects. The combination of diclofenac sodium as a COX-2 inhibitor and ionising radiation not only enhances the effect of radiation on tumour cells, but also improves radiation therapy for patients. Studies have shown that diclofenac sodium gel, through COX-2, can be used to prevent the development of capecitabine-induced hand-foot syndrome (HFS). RID upregulates COX-2 due to inflammatory stimulation, and COX-2 indirectly produces reactive oxygen species (ROS). The investigators conclude that diclofenac gel can reduce ROS by locally inhibiting COX-2 enzyme, thus preventing radiation dermatitis and reducing skin damage. Therefore, the investigators plan to conduct a study on the use of diclofenac sodium gel in radiation dermatitis to investigate the incidence of RID grade 2 and above at different time points after radiotherapy in patients with head and neck tumours, and whether it can reduce the incidence and severity of RID-related symptoms.