Radiation-induced xerostomia (dry mouth) is one of the most common and severe side effects for patients receiving radiation therapy for head and neck cancer. New approaches are needed to reduce this side effect and improve patients' quality of life after treatment. This is a Phase II, single-center, double-masked, parallel-arm, randomized controlled trial. It compares MRI-guided parotid ductal sparing to the standard approach of mean parotid gland sparing, focusing on patient-reported dry mouth outcomes in individuals receiving definitive radiotherapy for oropharyngeal cancer.

Radiation-induced dry mouth (xerostomia) is the most commonly reported long-term side effect in patients receiving radiation therapy (RT) for head and neck cancer. It occurs when saliva production decreases and the saliva becomes thicker. Patients with xerostomia often have trouble chewing, swallowing, and speaking, and are more likely to develop tooth decay. These problems can significantly lower a patient's quality of life-and the impact tends to get worse over time. The most common way to reduce radiation-related dry mouth is by limiting the average radiation dose to the parotid glands (which produce saliva). However, this is often not possible because of the patient's anatomy, and many patients still report moderate to severe symptoms long after treatment. To reduce side effects, some studies have tested giving a lower radiation dose (60Gy instead of the usual 70Gy) in patients with low-risk, HPV-associated tumors. While this has helped improve overall symptoms, xerostomia still remains the most severe and persistent problem reported by patients. New strategies are needed to better protect patients from radiation-related dry mouth and help maintain their quality of life after treatment. Recent research shows that the parotid gland does not respond evenly to radiation; certain areas, especially large salivary ducts where stem/progenitor cells live, may be key for recovery after damage. If these ducts can be located during treatment planning, the radiation dose to them could be reduced. A pilot study showed that using MRI sialography to identify the parotid ducts and plan radiation therapy around them is both possible and promising. Patients who received this type of duct-sparing RT had fewer moderate-to-severe dry mouth symptoms compared to patients treated with standard RT (46% vs. 71% at 6 months, and 36% vs. 50% at 12 months post-treatment). A larger, randomized study is still needed to confirm whether reducing radiation dose to the parotid ducts can meaningfully lower the risk of xerostomia and improve recovery after radiation treatment.