Guidelines for Clinical Target Volume Definition for Perineural Spread of Major Salivary Gland Cancers

Postoperative radiotherapy is the standard of care for resected major salivary cancers that are at risk of locoregional recurrence. Of the various histological subtypes, perineural invasion is most common in adenoidcystic carcinomas of the three major salivary glands – parotid, submandibular and sublingual. The clinical target volume (CTV) for these cases must include the relevant cranial nerve pathways at risk. A contouring atlas was devised for delineation of the CTV of the nerves supplying the major salivary glands. Using standard anatomy texts and e-anatomy sources the nerves supplying the major salivary glands were identified. Subsequently the pathways of the nerves were drawn on an archived patient's planning computed tomography scan. The innervation of the major salivary glands has been identified and studied. Both bone and soft tissue CTVs have been delineated. A full set of images and CTVs of all the relevant transverse computed tomography slices has been archived, a number of which are printed in this article. Variation in CTV delineation is a recognised problem in a variety of anatomic sites. Guidelines and atlases can standardise practice and may improve the safety and efficacy of therapy. An atlas has been generated to guide clinicians in delineating the CTVs for perineural spread in major salivary gland cancers. •The major series which examined the use of postoperative radiotherapy for major salivary gland cancers and for adenoidcystic cancers in particular are mostly historical and used 2-dimensional radiation therapy. These older technologies did not mandate a sophisticated 3-dimensional approach to target volume definition. With the advent of 3-dimensional conformal radiotherapy and intensity modulated radiation therapy (IMRT) a more precise 3-dimensional approach to target volume definition is required.•If a decision is made to include pathways of potential perineural spread, then the clinical target volume (or CTV) for these cases must include the relevant cranial nerve pathways at risk. Contouring atlases standardize CTV definition in other organs and are now routinely used in clinical practice as a way of standardising care. Given the complex anatomy of the cranial nerves it would be very useful to have an atlas delineating pathways of perineural spread. The aim of this project was to devise a contouring atlas for delineation of the CTV of the nerves supplying the major salivary glands.•The clinical target volumes incorporating potenti