New suggestion for clinical downstaging of nasopharyngeal carcinoma in the era of intensity-modulated radiotherapy

Objective To propose a new suggestion for the clinical downstaging of nasopharyngeal carcinoma (NPC) in the era of intensity-modulated radiotherapy (IMRT) without changing the current T, N, and M staging system. Methods We reviewed the records of 536 NPC patients treated in Sun Yat-Sen University Cancer Center from January 2002 to December 2006.The Kaplan-Meier method was used to calculate the disease-specific survival (DSS) rate, and the log-rank test was used for survival difference analysis. The Cox regression model was used to calculate the hazard ratio (HR) of each subset. Results According to the 7th edition of UICC/AJCC staging system, the 5-year DSS rates of stage Ⅰ-Ⅲ patients (except T3N2M0) were all more than 85%(P>0.05), those of stage ⅣA and ⅣB patients were 71.8% and 46.2%, respectively (P=0.171), and that of stage ⅠVC patients was only 24.0%.In stage Ⅲ, the 5-year DSS rate of non-T3N2M0 patients (91.5%) was significantly higher than that of T3N2M0 patients (78.6%)(P=0.042), but there was no significant difference in DSS between T3N2M0 patients and stage ⅣA and ⅣB patients. Based on the above results, new stage Ⅰ included T1-3N0-1M0 and T1-2N2M0, new stage Ⅱ included T3N2M0, T4N0-2M0, and TxN3M0, and new stage Ⅲ included TxNxM1.The 5-year DSS rates of new stage Ⅰ, Ⅱ, and Ⅲ patients were 93.3%, 72.7%, and 24.0%, respectively (P=0.000). Compared with new stage Ⅰ patients, new stage Ⅱ and Ⅲ patients had HRs of 4.01 and 16.76, respectively, for 5-year DSS. Conclusions In the era of IMRT, the new clinical staging system (stages Ⅰ, Ⅱ, and Ⅲ) helps with prognostic evaluation and clinical treatment. Key words: Nasopharyngeal neoplasms/intensity modulated radiotherapy; Down-staging; New suggestion