Salivary gland cancers are uncommon cancers and make up 3-5% of all head and neck malignancies. These tumors can arise not only in major salivary glands, including parotid, submandibular, and sublingual glands, but also in small salivary glands distributed throughout the upper aerodigestive tracts. The treatment modalities for salivary gland cancers include surgery, radiotherapy, and chemotherapy. With the advance of radiotherapy technologies in recent years, modern techniques including three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), RapidArc volumetric modulated arc therapy (VMAT), and image-guided radiotherapy (IGRT) enable precise radiation beam delivery to the target volumes and avoid unnecessary normal organ radiation exposure, and the side effects are remarkably reduced.

Proton therapy, either passive scattering or intensity-modulated proton therapy (IMPT), is especially beneficial for salivary gland cancer treatment because of the physical advantages of the proton beam. With these novel proton therapy techniques, precise radiation dose delivery tailored to the complex shapes of head and neck structures can be achieved, and the treatment-related toxicity can be effectively abated. In addition, with the application of pencil beam scanning technology and multi-field optimization, IMPT provides the flexibility to apply simultaneous integrated boost (SIB) to enhance tumor control.

Article author: Dr. Chen-Enn Shieh

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