Oral mucositis: the hidden side of cancer therapy

Abstract

Inflammation response of epithelial mucosa to chemo- radiotherapy cytotoxic effects leads to mucositis, a painful side effect of antineoplastic treatments. About 40% of the patients treated with chemotherapy develop mucositis; this percentage rises to about 90% for head and neck cancer patients (HNC) treated with both chemo- and radiotherapy. 19% of the latter will be hospitalized and will experience a delay in antineoplastic treatment for high-grade mucositis management, resulting in a reduction of the quality of life, a worse prognosis and an increase in patient management costs. Currently, several interventions and prevention guidelines are available, but their effectiveness is uncertain. This review comprehensively describes mucositis, debating the impact of standard chemo-radiotherapy and targeted therapy on mucositis development and pointing out the limits and the benefits of current mucositis treatment strategies and assessment guidelines. Moreover, the review critically examines the feasibility of the existing biomarkers to predict patient risk of developing oral mucositis and their role in early diagnosis. Despite the expression levels of some proteins involved in the inflammation response, such as TNF-α or IL-1β, partially correlate with mucositis process, their presence does not exclude others mucositis-independent inflammation events. This strongly suggests the need to discover biomarkers that specifically feature mucositis process development. Non-coding RNAs might hold this potential.

Keywords: Biomarker; Cytokine; HNC; Non-coding RNA; Oral mucositis; Quality of life.

Fig. 1

Mucositis pathobiology: (a) normal tissue; (b) initiation phase and primary injury response. Radio and chemotherapy-induced damages lead to an increase in DNA double strand brakes and ROS production with a consequent induction of cell apoptosis and DAMPS release. DAMPs and ROS signaling promote the NF-κB-mediated transcription of cytokines; (c) amplification of the injury signal. The effectors produced during the previous phase lead to an amplification of the injury signal. The released TNF-α initiates the activation of MAPK that sustains NF-κB activity. During this stage, the primary damage signaling is amplified through positive-feedback loop mechanisms. (d) ulceration. Breaks in the submucosa allows to microorganisms to invade this tissue district leading to mononuclear-infiltrating cells-mediated inflammation response; (e) tissue re-epithelialization. Stimuli from the submucosa extracellular matrix and mesenchyme promote the healing process

Fig. 2

Representative images of mucositis induced by target therapies. (a-b) patchy ulcerations (aphtous ulcerations) induced by cetuximab, (c) erythema of the mucosa induced by temsirolimus and (d) ulcerations bleeding with minor trauma induced by everolimus