Parotid gland shrinkage during IMRT predicts the time to XXXX resolution.

@entity1 @entity2133 @entity16091
PURPOSE: To assess the impact of mid-treatment parotid gland shrinkage on long term @entity2133 during IMRT for oropharyngeal SCC. METHODS AND MATERIALS: All @entity1 treated with IMRT at a single Institution from November 2007 to June 2010 and undergoing weekly CT scans were selected. Parotid glands were contoured retrospectively on the mid treatment CT scan. For each parotid gland, the percent change relative to the planning volume was calculated and combined as weighted average. @entity1 were considered to be xerostomic if developed GR2+ dry mouth according to CTCAE v3.0. Predictors of the time to @entity2133 resolution or downgrade to 1 were investigated at both uni- and multivariate analysis. RESULTS: 85 @entity1 were selected. With a median follow up of 35.8 months (range: 2.4-62.6 months), the actuarial rate of @entity2133 is 26.2% (SD: 5.3%) and 15.9% (SD: 5.3%) at 2 and 3 yrs, respectively. At multivariate analysis, mid-treatment shrink along with weighted average mean parotid dose at planning and body mass index are independent predictors of the time to @entity2133 resolution. @entity1 were pooled in 4 groups based on median values of both mid-treatment shrink (cut-off: 19.6%) and mean WA parotid @entity16091 (cut-off: 35.7 Gy). @entity1 with a higher than median parotid dose at planning and who showed poor shrinkage at mid treatment are the ones with the outcome significantly worse (3-yr rate of @entity2133         50%) than the other three subgroups (3-yr rate of @entity2133         10%). CONCLUSION: For a given planned dose, @entity1 whose parotids significantly shrink during IMRT are less likely to be long-term supplemental fluids dependent.
