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(HealthDay News) — For patients with nasopharyngeal carcinoma (NPC), a minimal axial diameter (MAD) threshold of 6 mm for retropharyngeal lymph node (RLN) predicts survival, according to a study published online Sept. 27 in the American Journal of Roentgenology.
Yuliang Zhu, Ph.D., from Zhongshan City People’s Hospital in China, and colleagues investigated the optimal size thresholds for determining the presence of metastatic RLNs on magnetic resonance imaging (MRI) in a retrospective study involving 1,752 patients with NPC treated by intensity-modulated radiotherapy from January 2010 to March 2014. A total of 438 patients underwent MRI three to four months after treatment.
The researchers found that an optimal threshold of 6 mm was detected on receiver operating curve and restricted cubic spline analyses. MAD ≥6 mm independently predicted progression-free survival (PFS) in all patients, patients with N0 to N1 disease, and those who underwent posttreatment MRI in multivariable analyses (hazard ratios, 1.35, 1.80, and 1.68, respectively). Five-year PFS was worse for MAD ≥6 mm than for MAD ≥5 to <6 mm in patients with N1 disease without cervical lymph node involvement (77.2 versus 89.7 percent). For patients with stage I and stage II disease defined using a 6-mm — but not using a 5-mm — threshold, overall survival was significantly different. The rate of five-year PFS was associated with postradiation therapy MAD ≥6 mm, but not ≥5 mm (hazard ratio, 1.68).
“Given the absence of a defined size threshold in the American Joint Committee on Cancer 8th edition staging manual, we propose that future updates to the manual incorporate this threshold for N-category and tumor-stage determination,” the authors write.
