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Sparing Submandibular Gland Following Gland Transfer in Head and Neck Cancer Patients: Effect of Day-To-Day Setup Uncertainty

V Moiseenko1*, T Atwood2, C Coffey3, P Hua4, M Cornell5, P Sanghvi6, (1) UC San Diego, La Jolla, CA, (2) University of California San Diego, La Jolla, CA, (3) University Of California, San Diego, ,,(4) University Of California, San Diego, ,,(5) UC San Diego, San Diego, CA, (6) University Of California, San Diego,

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Xerostomia is a common toxicity observed in head-and-neck (HN) cancer patients following radiotherapy (RT). Submandibular gland transfer is an attractive option to spare salivary function in patients with unilateral disease. Sparing depends on the gland stability through the course of RT.


Methods: HN patients with unilateral disease are eligible for a submandibular gland transfer trial. For each gland transfer patient a matched control is enrolled. Fourteen patients have been enrolled to trial thus far. Salivary flow is assessed prior to RT, at 3, 6, and 12 months after RT, also questionnaires are used to evaluate QOL. Patients were treated with daily CBCT on the Halcyon linear accelerator. CBCTs, one for each week, were imported in MiM for contouring, co-registration with the planning CT, and quantification of positional and dosimetric stability of the gland. Center of mass (COM) coordinates were calculated in three directions from the isocenter and mean dose was calculated by overlaying the dose from the original plan.


Results: Mean dose to spared submandibular gland was 15.4±3.4 Gy. Transferred gland position was stable through the treatment for most patients. Mean COM deviations were 1.5±2.5mm, 4.5±2.8mm and 4.7±1.3 mm in lateral, ant/post and sup/inf directions. A subset of patients showed COM deviations ~1 cm attributable to head tilt/lower jaw position. Because the transferred gland is close to high dose gradient, this caused mean dose increase by approximately 15 Gy.


Conclusion: Position of the transferred submandibular gland was stable through the treatment for most patients, allowing for a significant dosimetric sparing of the gland. For a subset of patients image guidance with emphasis on head tilt is required to maintain transferred gland sparing. Because of significant change in mean dose for this subset of patients, salivary flow measurements have to be connected to dose as delivered.

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Funding Support, Disclosures, and Conflict of Interest: Supported by a UCSD Head & Neck Cancer Center Pilot Project Grant

Keywords

NTCP, Cone-beam CT, Dose Response

Taxonomy

Not Applicable / None Entered.

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