BACKGROUNDGamma Knife radiosurgery (GKRS; Elekta AB) remains a well-established treatment modality for vestibular schwannomas. Despite highly effective tumor control, further research is needed toward optimizing long-term functional outcomes. Whereas dose-rate effects may impact post-treatment toxicities given tissue dose-response relationships, potential effects remain largely unexplored.OBJECTIVETo evaluate treatment outcomes and potential dose-rate effects following definitive GKRS for vestibular schwannomas.METHODSWe retrospectively reviewed 419 patients treated at our institution between 1998 and 2015, characterizing baseline demographics, pretreatment symptoms, and GKRS parameters. The cohort was divided into 2 dose-rate groups based on the median value (2.675 Gy/min). Outcomes included clinical tumor control, radiographic progression-free survival, serviceable hearing preservation, hearing loss, and facial nerve dysfunction (FND). Prognostic factors were assessed using Cox regression.RESULTSThe study cohort included 227 patients with available follow-up. Following GKRS 2-yr and 4-yr clinical tumor control rates were 98% (95% CI: 95.6%-100%) and 96% (95% CI: 91.4%-99.6%), respectively. Among 177 patients with available radiographic follow-up, 2-yr and 4-yr radiographic progression-free survival rates were 97% (95% CI: 94.0%-100.0%) and 88% (95% CI: 81.2%-95.0%). The serviceable hearing preservation rate was 72.2% among patients with baseline Gardner-Robertson class I/II hearing and post-treatment audiological evaluations. Most patients experienced effective relief from prior headaches (94.7%), tinnitus (83.7%), balance issues (62.7%), FND (90.0%), and trigeminal nerve dysfunction (79.2%), but not hearing loss (1.0%). Whereas GKRS provided effective tumor control independently of dose rate, GKRS patients exposed to lower dose rates experienced significantly better freedom from post-treatment hearing loss and FND (P = .044).CONCLUSIONWhereas GKRS provides excellent tumor control and effective symptomatic relief for vestibular schwannomas, dose-rate effects may impact post-treatment functional outcomes. Further research remains warranted.

Background We report treatment outcomes for a large non-endemic cohort of patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy (IMRT) and chemotherapy. Methods We identified 177 consecutive patients with newly diagnosed, non-metastatic nasopharyngeal cancer treated with definitive IMRT between 1998 and 2011. Endpoints included local, regional, distant control, and overall survival. Results Median follow-up was 52 months. The 3-/5-year actuarial rates of local control, regional control, distant control, and overall survival were 92%/83%, 93%/91%, 86%/83%, and 87%/74%, respectively. The median time to local recurrence was 30 months; the annual hazard of local recurrence did not diminish until the 6th year of follow-up. Conclusion s. Overall, we observed excellent rates of disease control and survival consistent with initially reported results from our institution. Attaining locoregional control in patients with extensive primary tumors remains a significant clinical challenge. With mature follow-up we observed that more than half of observed local relapses occurred after 2 years, a pattern distinct from that of carcinomas arising from other head and neck sites. These findings raise the possibility that patients with NPC may benefit from close follow-up during post-treatment years 3–5.

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