Patterns of local extension and nodal involvement from 1300 nasopharyngeal carcinoma patients: An imaging-based predictor of distant metastases.

Abstract

e17516 Background: Distant metastasis is a main determinant of prognosis in patients with nasopharyngeal carcinoma(NPC). We explored the patterns of disease spread in NPC patients and identified the pattern correlates with distant metastases. Methods: The imaging documents of 1300 consecutive newly diagnosed nasopharyngeal carcinoma between 2012 and 2016 were reviewed. According to the incidence rates of tumor invasion, the anatomic sites were classified into high-risk group (≥50%), medium-risk group (≥10%~ < 50%) and low-risk group ( < 10%). The location of lymph nodes was determined by 2013 updated guidelines for neck node levels. Additionally, we developed a novel classification based on tumor spreading patterns, as shown in Table. Moreover, we validated the prognostic accuracy of the classification in a validation cohort from a different institution, 241 non-metastatic NPC patients were retrospectively enrolled. Kaplan-Meier method and log-rank test were used to analyze all time-to-event data. Results: The incidence rates of tumor invasion were 0.2% ~91.2%, 95.2% cases across the midline. If anatomic sites in high-risk group or median-risk group were involved, the incidence rates in adjacent medium-risk sites or low-risk group were increased. On the contrary, the incidence rates were decreased when the adjacent high-risk sites or median-risk group were not involved. 85.9% cases had involved lymph nodes. Only 3.9% had skip metastases. The incidence rates of nodal involvement were increased when adjacent upper nodal level was involved. In validation cohort, distant metastases were present in 32/241 NPC patients (13.3%) and 3-year distant metastasis-free survival(DMFS) in local, superior, inferior, and mixed type were 95.0%, 91.3%, 89.0%, and 78.7%, respectively. Cumulative survival curves for former three patterns were relatively similar and were clearly separated from mixed type. DMFS was significantly lower for patients with mixed type pattern than for those with other patterns(P = 0.018). Conclusions: Local disease in NPC patients spreads stepwise from proximal sites to more distal sites. The frequency of metastases in the jugular lymph node chains decreased in the cranio-caudal direction. Based on the patterns of tumor extension, an imaging-based predictor of distant metastases was developed and may be used as a prognostic marker for selecting patients to further systemic treatments. [Table: see text]