Interest and Prognosis Value of Fluorine-18-Fluoro-2-Deoxy-D-Glucose Positron Emission Tomography ([¹⁸F] FDG-PET/CT) in Aggressive T-Cell Lymphomas

Background: The interest and prognosis value of [¹⁸F] FDG-PET/CT in aggessive T-cell lymphoma entities remains controversial. In particular, the value of a negative [¹⁸F] FDG-PET/CT after completion of treatment is unknown. To adress these issues, we conducted a multicentric retrospective study. The aims of this study were to compare [¹⁸F] FDG-PET/CT to computed tomography (CT-scan) at initial staging and evaluate the prognosis value of [¹⁸F] FDG-PET/CT performed after completion of therapy. In addition, we investigated the prognosis value of an intermediate [¹⁸F] FDG-PET/CT performed after 3 or 4 cycles of CHOP-like regimen. Of note, the intermediate [¹⁸F] FDG-PET/CT result did not modify the initial scheduled strategy.

Patient characteristics: Forty eight patients were enrolled. All patients had an histologically proven aggressive T-cell lymphoma. Histopathological subtypes were anaplastic large cell lymphoma ALK+ (ALCL) (n=8), ALCL ALK- (n=11), peripheral T-cell lymphoma NOS (n=15), angio-immunoblastic T-cell lymphoma (AITL) (n=11) or other (n=3). Twenty eight patients were male. Median age at diagnosis was 53 years (range 19–77). According to clinical examination, biological evaluation and CT-scan assessment at diagnosis, thirty five patients had a stage III/IV disease and 19 patients presented with an aa IPI index < 2. Frontline treatment consisted of CHOP-like regimen only in 29 cases or followed by autologous stem cell transplantation (SCT) in 10 cases or allogeneic SCT in 9 cases.

Results:. Initial [¹⁸F] FDG-PET showed abnormal FDG uptake in all patients. At diagnosis, stage of the disease (n=34) using [¹⁸F] FDG-PET/CT was upgraded in 7 cases translating into an increase in the aaIPI in 3 cases. Twenty-five patients were evaluated by [¹⁸F] FDG-PET at the end of their therapy with a median follow-up of 19 months. The PFS estimate was significantly better for negative [¹⁸F] FDG-PET/CT patients (n= 12) versus positive [¹⁸F] FDG-PET/CT patients (n=13): 57% versus 22%, respectively (p = 0.01). This result was identical when the population was restricted to non ALCL Alk + patients (n=40): 46% versus 24% (p = 0.03). Moreover, the negativity of an intermediate [¹⁸F] FDG-PET/CT was associated with a more favorable outcome: the PFS estimate for negative (n= 18) versus positive [¹⁸F] FDG-PET/CT patients (n= 19) was 62% versus 26%, (p= 0.01). This result remained relevant when ALCL ALK+ patients were excluded from the analysis: 55% versus 24% (p = 0.03).

Conclusion: This study confirms that [¹⁸F] FDG-PET/CT is a sensitive method and is complementary to CT-scan at initial staging in aggressive T-cell lymphomas. In addition, our results may suggest that both intermediate and final assesment using [¹⁸F] FDG-PET/CT might be predictive of patient’s outcome. Netherless, approximatively half of the patients who reached CR with a negative [¹⁸F] FDG-PET/CT experienced relapse outlining the severity of these disease.