An interim analysis of acute treatment adverse events and patient reported quality of life for functional imaging guided salivary gland sparing radiation therapy using diffusion-weighted magnetic resonance imaging

Background and purpose Evolving evidence suggests that regional sparing of the parotid gland during radiation therapy could reduce radiation-induced xerostomia in head and neck cancer. This interim analysis investigates the functional relationship between the diffusion-weighted magnetic resonance imaging (DW-MRI) derived parotid gland biological at-risk volume (BRV) dose and acute adverse events, including patient-reported quality of life (QoL). Materials and methods Twenty-four head and neck cancer patients underwent MRI-simulation to delineate parotid gland BRVs using DW-MRI derived apparent diffusion coefficient measurements. Dose was optimised, sparing the parotid gland BRV. Clinician-reported acute adverse events (xerostomia, dysphagia, oral pain) were recorded and patient-reported QoL were assessed using University of Washington QoL Questionnaire v4.1 with Radiation Therapy Oncology Group modification. Adverse events were quantified using area under the curve and time to side effect peaks were calculated and analysed. Results A moderate positive correlation trend was observed between contralateral BRV mean dose and xerostomia area under the curve, although this did not reach statistical significance (r = 0.34 , p = 0.13). There was a strong relationship between the contralateral BRV sector and days to peak dysphagia ( r = 0.56, p = 0.005 ). Low-and high-dose grouped analysis revealed a trend toward significance for time to peak xerostomia ( p = 0.059 ). There were no significant associations with the ipsilateral parotid gland BRVs. Conclusion Findings suggest a potential functional-dose relationship between the contralateral BRV mean dose and acute xerostomia. Ongoing follow-up will determine whether the suggestive trends observed in the acute phase strengthen with long-term recovery time.