Maximun Standard Uptake Value At the Biopsy Site During ¹⁸f-Fluorodeoxyglucose Positron Emission Tomography Does Not Predict the Proliferation Potential of Tumor Cells in Extranodal Natural Killer/T-Cell Lymphoma, Nasal Type

Extranodal natural killer (NK)/T cell lymphoma, nasal type (ENKL) is a distinct subtype of non-Hodgkin lymphoma. ENKL is extremely rare in the United States of America and in Europe, but is rather common in East Asia. The overall prognosis is usually poor when compared to that of B cell lymphoma. Ki-67 is a nuclear antigen expressed by dividing cells. Thus, the Ki-67 proliferation index ((MIB-1) labeling index) indicates the proliferation potential of tumor cells. In recent studies (Ann Oncol. 2007; 18: 1382–1387, J Clin Oncol. 2006; 24: 2472–2479, Anticancer Res. 2008; 28: 1113–1118), a high MIB-1 labeling index was associated with poor prognosis in non-Hodgkin lymphoma, T-cell lymphoma, and localized ENKL. We recently reported that the maximum standard uptake value (SUVmax) of the biopsy site during ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) reflects tumor aggressiveness in the cases of non-Hodgkin lymphoma (Leuk Lymph. 2010; 51: 279–283). The positive rate of FDG-PET was reported to be 100% in ENKLs (Ann Oncol. 2007; 18: 1685–1690). In this study, we studied the biopsy sites of patients with untreated ENKL to clarify the correlation between SUVmax at the biopsy site and the proliferation potential of tumor cells.

Between 1998 and 2011, 22 patients were newly diagnosed with ENKL at Yokohama City University Hospital and Kanagawa Cancer Center. In 17 cases, the tumors were staged by positron emission tomography (PET) or PET/computed tomography (CT) and were simultaneously biopsied. Variations in SUVmax among institutions and the underestimations derived from small tumors, which are limitations of PET performed in multicenter studies, were adjusted using a phantom study. The difference in accuracy of SUVmax between 2 institutions was less than 2%. One patient was excluded because the biopsy site was not scanned by PET or PET/CT. The biopsy specimens were reviewed by 2 hematopathologists (S. S. and K. T.) in accordance with the World Health Organization (WHO) classification, and the proliferation potential of lymphoma cells was evaluated by measuring the MIB-1 labeling index. One patient was excluded because the diagnosis made by central review was not compatible with ENKL. Two patients were excluded because the biopsy specimens were very small and the MIB-1 labeling index could not be evaluated. Consequently, we studied 15 extranodal biopsy specimens from 13 patients with untreated ENKL, for whom complete data were available. The patients included 10 males and 3 females with a median age of 52 years (range, 18–82 years).

For the 15 ENKL specimens included, the biopsy site was the nasal cavity in 7 cases, the pharynx in 4, and the skin in 4, respectively. The measured MIB-1 labeling index ranged from 0.44% to 77.44%. The MIB-1 labeling index for 7 patients was more than 60% and for 2 patients was less than 20%. The SUVmax at the biopsy sites ranged from 2.1 to 20.8. The SUVmax at the biopsy site was not correlated with the MIB-1 labeling index (r = −0.33, P = 0.22). The SUVmax was also not correlated with the MIB-1 labeling index/tumor cell proportion in the biopsy specimens (r = 0.18, P = 0.52).

The SUVmax during FDG-PET does not predict the proliferation potential of ENKLs.

No relevant conflicts of interest to declare.