(18)F-FDG PET in Patients with Primary Systemic Anaplastic Large Cell Lymphoma: Differential Features According to Expression of Anaplastic Lymphoma Kinase.

Abstract

Primary systemic anaplastic large cell lymphoma (ALCL) is divided into two entities according to the expression of anaplastic lymphoma kinase (ALK). We investigated (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) findings in primary systemic ALCL according to ALK expression. Thirty-seven patients who had baseline PET before CHOP (cyclophosphamide, doxorubicin, vincristine and prednisolone)-based chemotherapy were enrolled. Among them, patients who underwent interim and/or post-therapy PET were further investigated for the treatment response and survival analysis. Baseline PET was analyzed visually and semi-quantitatively using peakSUV, and interim and post-therapy PETs were visually analyzed. All cases were (18)F-FDG-avid on baseline PET. The peakSUV of ALK-positive ALCL (n = 16, 18.7 ± 10.5) was higher than that of ALK-negative ALCL (n = 21, 10.0 ± 4.9) (P = 0.006). In ALK-negative ALCL, complete response (CR) rate in negative-interim PET was higher than positive-interim PET (100% vs 37.5%, P = 0.02); however, there was no such difference in ALK-positive ALCL (100% vs 75%, P = 0.19). The 3-year progression-free survival (PFS) was not significantly different between ALK-positive and ALK-negative ALCL (72.7% vs 47.6%, P = 0.34). In ALK-negative ALCL, negative interim and post-therapy PET patients had better 3-year PFS than positive interim (83.3% vs 25.0%, P = 0.06) and post-therapy PET patients (70.0% vs 20.0%, P = 0.04). In contrast, ALK-positive ALCL had no such differences between PFS and PET results. On baseline PET, all cases showed (18)F-FDG-avidity, and ALK expression was related to higher (18)F-FDG uptake. ALK-positive patients tend to have better PFS than ALK-negative patients. Negative-interim PET was a good indicator of CR, and interim or post-therapy PET was helpful for predicting the prognosis only in the ALK-negative group.