So superficial.

Top Line: Even with IMRT, xerostomia remains a notable side effect of head and neck radiation.

The Study: That’s because even IMRT can’t change the fact that level II cervical lymph nodes closely abut the parotid gland. When treating locally advanced head and neck cancer, it is often almost impossible to both cover the target volume and meaningfully spare the parotid. This randomized phase 2 trial investigated whether sparing of the superficial lobe of the parotid, rather than the whole gland, reduced xerostomia in patients receiving chemoradiation for nasopharyngeal carcinoma. In both arms, the whole parotid (deep and superficial lobes) was contoured and the optimization objective was V36Gy <40%. The superficial and deep lobes are separated by the posterior mandibular vein, which can also be approximated by a line from the stylomastoid foramen (superior) or anterior border of the sternocleidomastoid (inferior) and the mandible. In the experimental arm, the objective for the superficial lobe was tighter at V26Gy <30%. At 12 months, the rate of xerostomia was significantly lower with superficial lobe sparing (83.4% v 95%). In particular, grade 3 xerostomia dropped from 12.5% to 0%. There were no differences in disease or survival outcomes between arms.

TBL: When planning challenging head and neck cases with disease near the parotids, sparing the superficial parotid lobe is a practical way to reduce xerostomia while maintaining target volume coverage. | Huang, Radiother Oncol 2022