Oral Mucositis After Radiotherapy Compared With Chemotherapy

Radiotherapy-induced and chemotherapy-induced OM have similar complex mechanisms, which have been described as occurring in 5 steps: initiation, upregulation, signal amplification, ulceration/inflammation, and healing.6,12

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Both anticancer treatments initiate cellular damage to epithelial cells and generate reactive oxygen species, which also damage cells.6,12 The reactive oxygen species transmit signals that upregulate genes responsible for regulating pro-inflammatory cytokines, which leads to additional tissue injury and apoptosis. Upregulation of tumor necrosis factor-α, interleukin-1β, nuclear factor kappa B, and other transcription factors in mucosal cells activates pathways that amplify and accelerate mucosal tissue damage.6,12

Epithelial proliferation ceases, and the mucosal lining atrophies and breaks down, leading to ulceration and inflammation. Bacterial colonization of the ulcerated tissue stimulates macrophage production of additional pro-inflammatory cytokines. After therapy ends, the epithelium begins to heal spontaneously.6,12 The anticancer treatments also alter microflora in the oral cavity, which can affect the risk of OM during and after treatment.1,12

There are slight differences in the clinical course of OM induced by radiotherapy versus chemotherapy.1,11 With chemotherapy, mucositis onset is typically 4 to 7 days after the first dose and presents with erythema.13 Symptoms peak during the first 2 weeks of treatment and resolve within 2 to 4 weeks of chemotherapy cessation.1,6

Lesions generally arise on non-keratinized surfaces of the lateral and ventral tongue, buccal mucosa, mouth floor, and the soft palate.6,13 The onset of radiotherapy-induced OM is dose-dependent, but symptoms are often evident at the end of the first week (cumulative radiation dose, 10 Gy).11 Peak severity occurs with a cumulative radiation dose of 30 Gy. Lesions appear primarily on non-keratinized tissues within the field of radiation but can also appear on keratinized surfaces.13

They are typically irregular and may be covered by a white pseudomembrane.6,11,13 Oral mucositis usually subsides 2 to 6 weeks after completion of radiotherapy but may persist for months.1,11,13 Oral mucositis may have earlier onset, be more severe, and last longer in patients who are receiving chemotherapy concurrent with radiotherapy.13