Purpose: Although the optimum treatment of primary central nervous system lymphoma (PCNSL) remains a challenge, there is increasing interest in methotrexate-based chemotherapy as an effective strategy. Here, we report evidence supporting the utility of methionine PET/CT for evaluating PCNSL disease extent and response to high-dose methotrexate therapy.
Patients and Methods: Four patients newly diagnosed with diffuse large B-cell PCNSL underwent methionine PET/CT and MRI of the brain at baseline and again after completion of high-dose methotrexate combination chemotherapy. Three patients also received pretreatment FDG PET/CT, and the intervals between MRI and both PET/CTs were within 3 weeks. The results of methionine PET/CT were compared with MRI and clinical findings.
Results: Pretreatment methionine PET/CT demonstrated clear demarcation of PCNSL tumors with high contrast in 3 patients and only faint uptake in the remaining patient, which also showed low FDG uptake. In 1 patient, methionine PET/CT displayed more tumor lesions than FDG PET/CT did. After high-dose methotrexate chemotherapy, methionine images displayed complete disappearance of abnormal uptake in all 4 patients. In 3 of the patients, posttreatment MRI and clinical follow-up corroborated findings of complete remission. In the remaining patient, MRI showed nonenhancing T2 hyperintensities in the periventricular white matter, for which the significance was inconclusive.
Conclusions: Methionine PET/CT may provide clinically useful information complementary to MRI for monitoring the response to systemic chemotherapy in patients with PCNSL.
From the *Department of Nuclear Medicine, CHA Bundang Medical Center, CHA University; and Departments of †Nuclear Medicine, and ‡Hemato-oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Received for publication April 2, 2011; and revision accepted July 10, 2011.
Conflicts of interest and sources of funding: This work was supported by the Sungkyunkwan University Research Foundation (S-2009-0826-000).
Reprints: Kyung-Han Lee, MD, PhD, Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, #50 Ilwon-dong, Gangnam-gu, Seoul 135-710, Korea. E-mail: firstname.lastname@example.org.