Head and neck cancer (HNC) and its treatments are among the most impactful conditions affecting oral health, daily functioning and health-related quality of life. The overall aim of this thesis was to explore oral status and oral mucositis in relation to health-related quality of life and patient-related factors in patients with head and neck cancer during and shortly after oncological treatment. This thesis is based on four prospective multicentre cohort studies following patient from their diagnosis until three months after curative treatment.

Paper I explored changes in health-related quality of life (HR-QoL) and the impact of oral mucositis (OM). HR-QoL declined progressively and was worst week 4 to 6 when patients reported symptoms such as pain, dry mouth, fatigue,appetite-loss and problems with swallowing, senses (taste and smell). Significantly impaired role and social functioning was also reported at these timepoints. Patients with severe OM reported significantly worse HR-QoL compared to those with no/mild OM. Three months after completing treatment problems with dry mouth, sticky saliva, taste and smell, appetite loss, and continued need for nutritional support persisted.

Paper II explored differences in HR-QoL between men and women, and the importance of salivary secretion rates for HR-QoL. Men and women showed similar patterns regarding HR-QoL during treatment. Men reported more problems with pain and sexuality, a higher use of painkillers and need for nutritional support during treatment, while women reported more problems with weight loss and dry mouth. Three months post treatment, women reported more problems and symptoms than men with the highest scores noted for dry mouth, weight loss and sticky saliva. Patients with hyposalivation reported significantly more problems especially with dry mouth, sticky saliva, and social eating compared with those with no hyposalivation.

Paper III explored self-perceived oral health and general self-efficacy in relation to dental plaque, gingival inflammation, and oral mucositis. The majority had low levels of plaque and gingival inflammation at all timepoints, and oral mucositis occurred in 82% of patients. Almost half of the patients perceived their oral health as good at baseline with a significant decrease week 6 of treatment. Toothbrushing twice a day was reported by 95% of patients, and daily interdental cleaning by 51%. The majority had high self-efficacy at all timepoints. No statistically significant differences between self-perceived oral health and clinical variables were found.

Paper IV explored clinical aspects and patient-reported symptoms in patients undergoing treatment for tonsillar carcinoma. Oral mucositis was initiated week 2 and peaked at week 5. The soft palate, hard palate, lateral tongue and buccal mucosa were the sites most affected by OM. Taste alterations, difficulty eating hard food, problems with sticky saliva, and dry mouth were the most prominent patient-reported symptoms during treatment. Significant positive correlations were observed between OM and difficulties eating soft and hard food week 4 and 5 during treatment. Opioid use peaked at weeks 5–6 (59–65%), and enteral nutrition was required by 39% at week 6. One month after completed treatment, 36% still required enteral nutrition, especially those who had received chemoradiotherapy (CRT). Three months post-treatment, dry mouth and taste alterations remained the most common complaints.

This thesis concludes that OM and especially severe OM have a substantial impact on symptoms, daily functioning and HR-QoL during and shortly after HNC treatment. Although some symptoms improved three months post-treatment, persistent problems such as dry mouth, taste changes and difficulties with social eating remained especially in those with hyposalivation. There might be differences in symptom patterns between men and women, which could be important for dental and health care personal to be aware of. High self-efficacy and good oral-health related behaviours may mitigate some effects why these aspects could be important to take into consideration before cancer treatment. Despite good oral hygiene in most patients, OM and in most cases severe OM could not be avoided. In summary, there is a need to improve the multidisciplinary supportive care, particularly oral care and nutritional support throughout the treatment trajectory and to monitor patients also after completed cancer treatment.