Acute and late toxicities following postoperative intensity-modulated radiotherapy simultaneously integrated boost (IMRT-SIB) in oral cavity cancer — a retrospective analysis

Introduction. Head and neck squamous cell carcinoma (SCCHN) is a major health concern in Asia, accounting for 57.5% of global cases. In India, SCCHN represents 30% of all cancers, largely due to widespread tobacco use. Tobacco contains over 5,000 chemicals, including carcinogens such as polycyclic aromatic hydrocarbons (PAHs) and nitrosamines. Surgery remains the mainstay for oral cavity tumors, with adjuvant radiotherapy, with or without chemotherapy, advised for patients with high-risk features. Radiation therapy can cause acute and late toxicities including mucositis, skin changes, xerostomia, weight loss, odynophagia, and dysphagia. Higher radiation doses increase toxicity risk in critical structures like the floor of the mouth and salivary glands. Intensity-modulated radiotherapy (IMRT) enables sparing of organs at risk, reducing toxicities while maintaining tumor control. Material and methods. This IRB-approved retrospective study (2023–2024) enrolled 59 postoperative SCCHN patients. Twenty received adjuvant radiotherapy alone. All underwent IMRT with simultaneous integrated boost (IMRT-SIB), delivering 60–66 Gy (2–2.2 Gy/fraction) to high-risk planning target volume (HR-PTV) and 54 Gy (1.8 Gy/fraction) to low-risk PTV (LR-PTV) over 30 fractions in 6–6.5 weeks. Toxicities were assessed using CTCAE v5.0. Results. All patients received IMRT-SIB; 62.7% had concurrent chemotherapy. Grade 1–2 skin reactions occurred in >90%, and grade 2 mucositis in 40.8%, with no grade ≥ 3 toxicities. At six months, xerostomia was seen in 49.3% (mostly grade 1), dysphagia in 27.2%, and hoarseness in 23.8%, all improving over time. Median radiotherapy duration was 45 days; most completed treatment on schedule. Late toxicities were mild and manageable. Conclusions. Toxicities following radiotherapy in SCCHN are multifactorial. Although dysphagia may persist beyond a year, IMRT facilitates parotid sparing, reducing long-term xerostomia and improving quality of life.