The use of stereotactic radiotherapy boost to improve local control in patients with locally advanced nasopharyngeal carcinoma (NPC)

Abstract

6056 Background: To determine the long term outcomes and delayed side effects in patients receiving stereotactic radiotherapy (SRT) as a boost following external beam radiotherapy (EBRT) for locally advanced NPC. Methods: 82 NPC patients received a STR boost after EBRT at our institution between 9/1992 and 5/2006. Nine patients had T1, 31 had T2, 12 had T3, and 30 had T4 tumors (1997 AJCC staging). Sixteen patients had stage II, 20 had stage III, and 46 had stage IV neoplasms. Most patients received 66 Gy of EBRT followed by a single fraction STR boost of 7–15 Gy, delivered 2–6 weeks after EBRT. 70 patients also received cisplatin-based chemotherapy delivered concurrently with and adjuvant to EBRT. Results: At median follow-up of 40.7 months for living patients (range: 6.5 –144.2 months), there was only 1 local failure in a patient with a T4 tumor. At five years, the freedom from local relapse rate was 98%, freedom from nodal relapse was 83%, freedom from distant metastasis was 68%, freedom from any relapse was 67% and overall survival was 69%. Late toxicity included unresolved V2 or V3 numbness in 2, radiation-related retinopathy in 1, carotid aneurysm in 1, and radiographic temporal lobe necrosis in 9 patients, of which 2 were symptomatic with seizures. All but one patient with temporal lobe necrosis had intracranial tumor extension at diagnosis. Conclusions: STR boost after EBRT resulted in excellent local control. However, the incidence of temporal lobe necrosis approached 11% in these patients and higher in patients with intracranial extension. Improved target delineation and dose homogeneity of radiation delivery for both EBRT and STR is important to avoid long-term complications. No significant financial relationships to disclose.