Room: AAPM ePoster Library
Purpose: Determine if prospectively minimizing the dose to parotid ducts improves patient xerostomia for those treated with de-intensified chemoradiation for oropharynx cancer.
Methods: We conducted a prospective clinical trial assessing MRI sialography guided parotid ductal sparing (PDS) in patients with oropharynx cancer in an effort to mediate patient radiation induced xerostomia. Fifteen patients received de-intensified chemoradiotherapy and PDS and had 6 months of follow-up. We used a previous cohort of 173 patients treated with de-intensified chemoradiotherapy that submitted patient reported outcome (PRO) surveys at 3 and 6 months post-treatment. These patients formed our comparison cohort. We compared PRO xerostomia severity between those receiving PDS and those that underwent conventional parotid sparing. In addition, to determine the impact of the parotid ductal dose on patient xerostomia at 6 months (none/mild vs. moderate-to-very severe), we compared nested logistic models containing parotid mean dose and contralateral submandibular mean dose with and without mean parotid ductal dose using an ANOVA test.
Results: At 3 months post-treatment, 2/12 (17%) of PDS patients reported severe-to-very severe toxicity compared to 82/173 (47%) in our comparison cohort (p = 0.01). At 6 months post-treatment, 6/15 (40%) of PDS patients reported moderate-to-very severe toxicity compared to 115/173 (66%) in our comparison cohort (p = 0.04). Comparing logistic models for moderate-to-very severe xerostomia at 6 months post-treatment found that adding mean dose of the parotid ducts to mean parotid dose and mean contralateral submandibular dose significantly improved model fit (p = 0.03).
Conclusion: Our results suggest that patients undergoing prospective PDS have improved PRO xerostomia at 3 and 6 months post treatment. In addition, parotid ducts may be more important for predicting xerostomia than the mean parotid dose or mean contralateral submandibular dose; supporting the hypothesis that parotid glands are not purely parallel structures.
Not Applicable / None Entered.
TH- External Beam- Photons: functional imaging treatment planning