Maximum Standard Uptake Value of Pre‐Therapeutic ¹⁸F‐Fluorodeoxyglucose Positron Emission Tomography Predicts Outcomes in Indolent Adult T‐Cell Leukemia/Lymphoma Patients With Cutaneous Involvement

The prognostic utility of 18F‐fluorodeoxyglucose positron emission tomography (FDG‐PET) in adult T‐cell leukemia/lymphoma (ATLL) remains unclear, particularly in patients with indolent subtypes and cutaneous involvement. This study aimed to evaluate the usefulness of FDG‐PET in predicting clinical outcomes in patients with indolent ATLL presenting with skin lesions. We retrospectively reviewed indolent ATLL with cutaneous involvement who underwent 18 F‐fluorodeoxyglucose positron emission tomography at our institute for initial disease staging between April 2007 and March 2022. The data obtained were compared with the findings of cutaneous involvement in ATLL. The effect of maximum standardized uptake value on progression‐free survival was analyzed using the Kaplan–Meier method. Patients were divided into groups based on whether their maximum standardized uptake value was above or below the overall mean maximum standardized uptake value (2.18), and progression‐free survival was compared between the groups. Forty‐three patients with indolent ATLL were included. We divided the cutaneous involvement of ATLL into six subtypes according to a previously reported classification of eruption types: patch, plaque, multipapular, nodulotumoral, erythrodermic, and purpuric. A total of 18 of 43 patients (41.9%) had 18 F‐fluorodeoxyglucose‐positive cutaneous lesions. However, 25 patients showed no 18 F‐fluorodeoxyglucose uptake in cutaneous lesions. There was a significant difference in the mean maximum standardized uptake value between the nodulotumoral and multipapular ( p = 0.036), nodulotumoral and patch ( p = 0.036). There was a statistically significant difference in progression‐free survival between the maximum standardized uptake value ≥ 2.18 and < 2.18 groups ( p = 0.020). These findings indicate that the maximum standardized uptake value in cutaneous lesions could determine the prognostic association of ATLL with cutaneous lesions. Careful follow‐up is required for patients with a higher maximum standardized uptake value for cutaneous lesions.