Two cases of stereotactic radiosurgical boost as an initial treatment for young nasopharyngeal cancer patients.

Case 1: A 14-year-old boy with nasopharyngeal cancer (T4N0M0) was treated with stereotactic radiosurgery (SRS) as a boost therapy after conventional radiotherapy. Persistent residual tumor visible with MR remained after conventional radiotherapy comprising 59.6 Gy in total. We therefore performed SRS to add a further irradiation dose while causing minimal damage to adjacent normal tissue. SRS was performed using multiple non-coplanar arcs delivered to the residual tumor, which was defined to add 2 mm margins to the residual tumor. This was 30 cc as defined by CT and MR images. Twenty Gy were administered to the periphery of the planning target volume (PTV), corresponding to the 80% isodose line. No recurrences or late complications have been observed 4 years and 6 months after the SRS. Case 2: A 27-year-old man with nasopharyngeal cancer (T1N0M0) was treated with SRS as a boost therapy following conventional radiotherapy with 55 Gy. The SRS was performed using multiple non-coplanar arcs delivered to the PTV, which was 10 cc as defined by CT and MR images as in case 1. Sixteen Gy were administered to the periphery of the residual tumor, corresponding to the 80% isodose line. The tumor was not visible on follow-up MR images and no complications have been observed 4 years and 2 months after the SRS.