KEY POINTS
- This retrospective paired planning study included 17 patients with contralateral node-negative oropharyngeal squamous-cell carcinoma who underwent surgical transfer of the contralateral submandibular gland into the submental space before definitive proton therapy.
- All patients received bilateral-neck intensity-modulated proton therapy to 66–70 Gy in 30–35 fractions, with at least 54 Gy delivered to ipsilateral and contralateral neck levels II–IV. Ten patients (59%) had tonsillar and seven base-of-tongue primaries; 10 of 17 tumors crossed the midline.
- Each patient's diagnostic CT was used to reconstruct the gland's original position. Identical beam geometry was then optimized around either the pre-transfer or actual post-transfer gland position, allowing a within-patient estimate of the dosimetric effect of surgery.
- Mean contralateral submandibular dose fell from 32.92 Gy before transfer to 20.22 Gy after transfer, a median reduction of 12.02 Gy (95% CI 9.46–14.59; p<0.001).
- Transfer significantly increased the proportion of plans meeting the strictest tested mean-dose constraint of ≤26 Gy (p=0.004); improvements were also seen for the ≤35- and ≤39-Gy thresholds.
- Benefit remained visible even with challenging target anatomy. Among the 10 tumors crossing midline, mean contralateral gland dose fell from 34.20 to 22.04 Gy (p=0.007), and achievement of the ≤26-Gy constraint improved from 20% to 70%. Among seven lateralized tumors, dose fell from 30.38 to 20.10 Gy (p=0.018).
- Target coverage, ipsilateral submandibular dose and other evaluated organ-at-risk doses did not significantly worsen. However, the study measured planned dose only: no objective salivary-flow measurements or patient-reported xerostomia outcomes were available to establish whether the approximately 12-Gy reduction translates into clinically meaningful benefit.
CLINICAL TAKEAWAY
A surgical technique from the 2D/3D era may still have a role even with modern proton therapy. Moving the gland physically away from bilateral neck targets produced a large additional dosimetric gain beyond IMPT alone, particularly when targets crossed midline. Whether that justifies an operation requires prospective evidence showing better salivary function and quality of life.