Background: The mainstay of treatment of nasopharyngeal carcinoma (NPC) is radiotherapy (RT) with or without concurrent chemotherapy (CRT). The standard of care of NPC has undergone significant changes in HK since last decade: these included adopting the 7 th edition the AJCC/UICC staging system, employing MRI as standard radiological staging of loco-regional disease, adding concurrent cisplatin chemotherapy to radiation in patients with loco-regional advanced disease, and using IMRT as standard radiotherapy treatment. Methods: Eligible patients were identified from the Hong Kong Cancer Registry data base. All clinical data were retrieved throught the Electronic Patient Record System which is used in all public hospitals for clinical patient management. Data entry codes were pre-specified according to study protocol. Data was then retrieved by oncologist working in individual centers. The final electronic clinical data was then verified and analyzed by the principal investigator and the study statistican. Results: A total of 3328 patients were recruited. The median follow-up time was 80.2 months. The 8-year actuarial overall survival (OS), local failure-free survival (LFFS), regional failure-free survival (RFFS), distant failure-free survival (DFFS) and progression-free suruvial (PFS) for whole group was 68.5%, 85.8%, 91.5%, 81.5% and 62.6% respectively. Male gender, older age, advanced T and N stage were adverse prognostic factors for OS, DFFS and PFS, whereas use of chemotherapy in form of concurrent chemo-irradiation (CRT), neoadjuvant þ CRT, or CRT þ adjuvant chemotherapy were favorable prognostic factors for OS and PFS. The local control was adversely affected by advanced T stage. N stage remained as the single adverse prognostic factor for regional control. Seventy percent of the patients were free of symptomatic late complications. Distant metastasis was the commonest site of failure. Conclusions: IMRT is an effective treatment of NPC with excellent overall locoregional control. Distant metastasis is the major site of failure. Concurrent chemotherapy with cisplatin has an established role in NPC patients treated by IMRT. Serious symptomatic late complications related to IMRT are uncommon. Legal entity responsible for the study: KH Au Funding: None Disclosure: All authors have declared no conflicts of interest.
and site-specific analyses. Future modifications of the nodal staging system should be based on the lymph node status, with consideration given to a separate system for oropharyngeal cancers. Patients with more than 5 positive nodes have significantly worse survival in all subsites and should be considered for alternative treatment regimens.Purpose/Objective(s): We investigated for dosimetric predictors of hypothyroidism after radical intensity modulated radiation therapy (IMRT) for nonmetastatic nasopharyngeal carcinoma (NPC). Materials/Methods: Patients with nonmetastatic NPC treated with radical IMRT from 2008 to 2013 were reviewed. They were regularly monitored clinically with serum thyroid function tests before and after IMRT. Univariable and multivariable analyses were performed for demographic and dosimetric predictors of biochemical and clinical hypothyroidism. Results: A total of 149 patients fulfilled eligibility criteria. After a median follow-up duration of 3.1 years (range, 1.3-8.2 years), 33 patients (22.1%) and 21 patients (14.1%) developed biochemical and clinical hypothyroidism, respectively. Eight patients (24.2%) who had biochemical hypothyroidism developed clinical hypothyroidism later. Univariable and multivariable analyses revealed that volume of the thyroid (PZ.002, multivariable), VS60 (the absolute thyroid volume spared from 60 Gy or less) (P<.001, multivariable), and VS45 (P<.001, multivariable) of the thyroid were significant predictive factors of biochemical hypothyroidism. The freedom from biochemical hypothyroidism was longer for those whose VS6010 mL (mean 90.9 months vs 62.6 months; P<.001) and VS455 mL (mean 91.9 months vs 65.2 months; PZ.001). Similarly, multivariable analyses revealed that VS60 (PZ.001) and VS45 (PZ.003) were significant predictors of clinical hypothyroidism. The freedom from clinical hypothyroidism was longer for those whose VS6010 mL (91.5 months vs 73.3 months, PZ.002) and VS455 mL (91.5 months vs 75.9 months, PZ.007). Receiver-operating characteristics (ROC) analyses revealed that the areaunder-the-curve (AUC) value for VS60 was significantly higher than that for VS45 for both biochemical (0.751 vs 0.660; PZ.009) and clinical hypothyroidism (0.718 vs 0.607; PZ.007), respectively. Conclusion: VS60 and VS45 of the thyroid significantly predicted post-IMRT hypothyroidism and should be considered important priorities of dose constraints during IMRT optimisation for NPC.
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