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We investigated the incidence of temporal lobe injury (TLI) in 132 nasopharyngeal carcinoma (NPC) patients who had undergone intensity-modulated radiotherapy (IMRT) in our hospital between March 2005 and November 2009; and identified significant dosimetric predictors of TLI development. Contrast-enhanced lesions or cysts in the temporal lobes, as detected by magnetic resonance imaging (MRI), were regarded as radiation-induced TLIs. We used the least absolute shrinkage and selection operator (LASSO) method to select Dmax (the maximum point dose) and the D1cc (the top dose delivered to a 1-mL volume) from 15 dose-volume-histogram-associated and four clinically relevant candidate factors; the Dmax and the D1cc were the most significant predictors of TLI development. We drew dose-response curves for Dmax and D1cc. The tolerance dose (TD) for the 5% and 50% probabilities of TLI development were 69.0 ± 1.6 and 82.1 ± 2.4 Gy for Dmax and 62.8 ± 2.2 and 80.9 ± 3.4 Gy for D1cc, respectively. The incidence of TLI in NPC patients after IMRT was higher than expected because the therapeutic window is narrow. High-quality longitudinal studies are needed to gain further insight into the complex spatiotemporal effects of non-uniform irradiation on TLI development in NPC patients.

Background and Purpose: To investigate the American Joint Commission on Cancer (AJCC) sixth edition staging system of nasopharyngeal carcinoma (NPC) by Magnetic Resonance Imaging (MRI)., Patients and Methods: One hundred and fifty-nine non-disseminated biopsy-proven NPC patients were studied with MRI before treatment. Retrieval of MRI information enabled us to restage all patients accurately according to the sixth edition of the AJCC staging system. Splitting the respective T and N stages by the significant defining factors identified, the cancer death hazard ratios were modeled by the Cox model in SPSS 10.0 for windows (SPSS Inc, Chicago, IL)., Results: Single site of skull base abnormality (HR = 3.91, 95% CI: 0.74-20.56) has a superior result to others involved in T3 (HR = 5.83, 95% CI: 1.24-27.29). Involvement of either anterior or posterior cranial nerves solely (HR = 6.02, 95% CI: 1.55-35.60) was not found to be as a poor prognostic indicator as others involved in T4 (HR = 7.81, 95% CI: 1.81-33.63). Less than or equal to 3 cm of N1 (HR = 4.01, 95% CI: 0.48-33.83) and N2 (HR = 4.72, 95% CI: 0.62-35.78) have a better result than >3 cm of N1 (HR = 8.09, 95% CI: 0.95-68.97) and N2 (HR = 10.58, 95% CI: 1.32-84.62), respectively., Conclusions: Perhaps, it is better to down-stage single site of skull base abnormality from T3 to T2, and involvement of either anterior or posterior cranial nerves solely from T4 to T3, meanwhile, < or =3 cm of N2 down-stage to N1, >3 cm of N1 up-stage to N2.