Fluorodeoxyglucose positron emission tomography (FDG-PET) imaging has been suggested as a useful modality in staging, assessing response to treatment, and detecting disease recurrence in primary cutaneous T-cell lymphoma (CTCL).1 Indices of FDG uptake include conventional measurements such as maximum standardized uptake value (SUVmax) mean SUV (SUVmean) and global measurements such as global metabolic volume (GMV) and global lesion glycolysis (GLG). Some investigators support conventional metrics,2,3 while others have demonstrated greater value in global tumor measurements.4
Herein we present the cases of 2 patients with CTCL who had PET scans performed at baseline and follow-up in addition to the usual clinical and laboratory assessments. The FDG-PET images were analyzed by ROVER software (ABX Advanced Biochemical Compounds GmbH), which is capable of measuring whole body disease burden by GMV and GLG. This software also measures SUVmax and SUVmean.
The first patient was a woman in her 40s with gamma/delta T-cell lymphoma. Histopathologic analysis demonstrated infiltration of subcutaneous fat by neoplastic cytotoxic T cells with apoptosis, necrosis, and angioinvasion. There was a moderately dense, predominantly lymphocytic, inflammatory infiltrate in relation to the superficial and deep vascular plexus, with interstitial and periadnexal involvement as well. There was also an increase in interstitial mucin.
She had received 6 cycles of R-CHOP therapy (rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone) before this study. Her lactate dehydrogenase level (LDH) was 962 U/L (normal, 140-280 U/L) at initial evaluation. After 3 months of treatment with bexarotene and hyper-CVAD (cyclophosphamide, vincristine, doxorubicin, and dexamethasone), her LDH increased to 5856 U/L. The FDG-PET scan showed more extensive lesions after 3 months than at baseline despite treatment (Figure 1). Measuring FDG uptake activity in the tumors demonstrated that GMV (131.3 cm3 at baseline to 342.7 cm3 at follow-up) and GLG (161.2 to 429.8 g) increased significantly, which was expected considering tumor extension and LDH level elevation at the follow-up visit. In contrast, SUVmean (1.2 to 1.3 g/mL) had a minimal increase and SUVmax showed significant reduction (5.7 to 3.7 g/mL).
A, Baseline image shows FDG uptake in cutaneous tumors (red arrowheads) and lymph nodes (blue arrowheads) (mean standardized uptake value [SUVmean], 1.2 g/mL; maximum SUV [SUVmax], 5.7 g/mL; global metabolic volume [GMV], 131.3 cm3; global lesion glycolysis [GLG], 161.2 g). B, In the follow-up scan, there is more extensive skin (red arrowheads) and lymph node (blue arrowheads) involvement (SUVmean, 1.3 g/mL; SUVmax, 3.7 g/mL; GMV, 342.7 cm3; GLG, 429.8 g).
The second patient was a man in his 60s with mycosis fungoides, which is the most common type of CTCL. Histopathologic analysis demonstrated epidermotropic atypical lymphocytes. The patient underwent treatment with narrowband UV-B phototherapy but did not respond well. The PET scan showed significant tumor reduction after 3 months of treatment with romidepsin and irradiation (Figure 2). Serum LDH level correspondingly decreased (261 U/L to 144 U/L). Based on the FDG uptake measurement, GLG showed significant decrease (from 834.7 g at baseline to 265.7 g at follow-up) as did GMV (from 111.1 to 14.7 cm3), which were in line with decreased LDH levels and tumor extension, but SUVmean (7.5 to 18 g/mL) and SUVmax (19.3 to 35.3 g/mL) indicated elevated tumor activity.
A, Baseline image shows cutaneous lesions (red arrowheads) in the legs and scalp and also lymph node involvement (blue arrowheads) of neck, mediastinum and axillae (mean standardized uptake value [SUVmean], 7.5 g/mL; maximum SUV [SUVmax], 19.3 g/mL; global metabolic volume [GMV], 111.1 cm3; global lesion glycolysis [GLG], 834.7 g). B, In the follow-up scan, lesions are limited to the leg skin (red arrowheads) (SUVmean, 18.0 g/mL; SUVmax: 19.3 g/mL; GMV, 14.7 cm3; GLG, 265.7 g).
The utility of global assessment for evaluation of primary tumors and response to treatment has not been well studied. Herein we demonstrate greater accuracy of global quantitative FDG-PET indices such as GLG and GMV in reflecting extension of malignant tumors and changes in blood LDH. Conventional metrics including SUVmax and SUVmean are useful regional indices that may be effective in showing tumor behavior and aggressiveness in a single location, but they may not be informative in describing degree of tumor extension and global tumor activity. Moreover, these indices may be affected by tumor heterogeneity, which is a common phenomenon in malignant solid tumors.5 Since cutaneous lymphomas can be unpredictable in their progression, the analysis approach provided by the methodology described herein allows assessment of global activity regardless of focal clinical involvement. Therefore, we believe that by adopting this methodology, we will be able to determine the extent of disease and response to treatment soon after treatment and be able to detect recurrence in a timely and effective manner.
Corresponding Author: Abass Alavi, MD, MD (Hon), PhD (Hon), DSc (Hon), Department of Radiology, Hospital of the University of Pennsylvania, 3400 Spruce St, Philadelphia, PA 19104 (firstname.lastname@example.org).
Published Online: September 30, 2015. doi:10.1001/jamadermatol.2015.2706.
Conflict of Interest Disclosures: None reported.
Additional Information: Drs Fardin and Gholami are joint first authors of this article.
Fardin S, Gholami S, Samimi S, Rook AH, Alavi A. Global Quantitative Techniques for Positron Emission Tomographic Assessment of Disease Activity in Cutaneous T-Cell Lymphoma and Response to Treatment. JAMA Dermatol. 2016;152(1):103-105. doi:10.1001/jamadermatol.2015.2706