P Han¹*, P Lakshminarayanan² , W Jiang³ , I Shpitser⁴ , X Hui⁵ , S Lee⁶ , Z Cheng⁷ , Y Guo⁸ , R Taylor⁹ , S Siddiqui¹⁰ , M Bowers¹¹ , K Sheikh¹² , J Lee¹³ , H Quon¹⁴ , T McNutt¹⁵ , (1) Johns Hopkins University, Baltimore, MD, (2) Johns Hopkins University, Baltimore, MD,(3) Johns Hopkins University, Baltimore, MD, (4) Johns Hopkins University, Baltimore, MD, (5) The University of Chicago, Chicago, IL, (6) Johns Hopkins University, Baltimore, MD, (7) Johns Hopkins University, Baltimore, MD, (8) Johns Hopkins University, Baltimore, MD, (9) Johns Hopkins University, Baltimore, MD, (10) Johns Hopkins University, Baltimore, MD, (11) Johns Hopkins University, Baltimore, MD, (12) Johns Hopkins University, Baltimore, MD, (13) Johns Hopkins University, Baltimore, MD, (14) Johns Hopkins University, Baltimore, MD, (15) Johns Hopkins University, Severna Park, MD

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  P Han

(Wednesday, 8/1/2018) 10:15 AM - 12:15 PM

Room: Davidson Ballroom A

Purpose: CTCAE-graded xerostomia is systematically captured in our clinic demonstrating maximum severity within 3 mos of RT (injury) with the severity decreasing thereafter (recovery). We sought to characterize the spatial dosimetry to the salivary glands and the oral cavity for xerostomia injury and recovery controlling for clinical variables.

Methods: HNC patients with CTCAE-graded xerostomia < 2 before RT and with xerostomia grade available for at least 18 mos of follow-up were evaluated. 62 spatial zones from ipsilateral/contralateral parotid glands (iPG, cPG), submandibular glands (SMG), and oral cavity (OC) for each patient were geometrically created. For PG and SMG, the zones include the contoured glands, a shell produced by a 3 mm expansion, and the combined gland and shell (Figure 1). DVH features (D10-D90) for each zone as well as clinical parameters were used to predict xerostomia injury (CTCAE grade ≥ 2 at 3-6 mos) and recovery (grade decrease to < 2) after 18 mos of follow-up. Three ridge logistic regressions with leave-one-out cross-validation (LOOCV) were developed with DVH features extracted from 1) contoured glands only, 2) shells only, and 3) contoured glands + shells to predict injury and recovery of xerostomia separately.

Results: 217 HNC patients were identified with 146 developing moderate to severe xerostomia within 18 mos of follow-up. The dose to the medial inferior portion of both PGs was associated with injury while the superior portion of the iPG was associated with recovery (Figure 2). The 3 models yielded similar feature importance and good cross-validated AUCs (above 0.79).

Conclusion: We demonstrated that different spatial-dose patterns exist for xerostomia injury vs. recovery highlighting the strength of this analytic technique along with the importance of assessing xerostomia during follow-up. These observations if validated provide insights into new strategies for RT deintensification.

Funding Support, Disclosures, and Conflict of Interest: Todd R McNutt: research agreement with Philips and funding from Radiation Oncology Institute Junghoon Lee: Toshiba, Canon research grant and JHU Radiation Oncology Discovery award

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