FDG PET/CT is a valuable imaging study in the management of HIV-infected patients, according to a review published in the August issue of American Journal of Roentgenology.
There were approximately 30 million people living with HIV infection in 2007. More than 2.7 million individuals became newly infected with HIV, and approximately two million AIDS-related deaths occur annually.
Jessica M. Davison, MD, of Boston University School of Medicine, and colleagues sought to assess 18F-FDG normal variant uptake and the role of FDG PET/CT in malignancies in HIV-infected patients, central nervous system (CNS) manifestations of HIV, fever of unknown origin in HIV patients, response to highly active antiretroviral therapy and complications.
Whole-body FDG PET images of HIV-positive patients have shown a clear association between the pattern of lymphoid tissue activation and HIV progression, according to the authors. During acute disease, FDG uptake increases in the head and neck. In mid-stages, hypermetabolism in cervical, axillary and inguinal lymph nodes is observed. Significant FDG accumulation in the colon along with mesenteric and ileocecal lymph nodes occurs during late disease.
Disorders associated with impaired cellular immunity, such as HIV infection, predispose individuals to the development of neoplasms. In HIV-infected patients, the particular type of neoplasms as well as average time to development of these cancers is similar to that observed in solid organ transplant recipients on chronic immunosuppressive therapy as well as in patients with deficiencies of cell-mediated immunity. Also, the researchers added that most cancers associated with HIV infection are driven by oncogenic viruses, such as Epstein-Barr virus, Kaposi sarcoma–associated herpesvirus and human papillomavirus.
As for cancer, one of the most common AIDS-related lymphomas, Burkitt lymphoma, is an aggressive disease best treated with short-duration high-intensity chemotherapy regimens.
Davison and colleagues wrote that “failure to achieve complete remission is a poor prognostic sign associated with relapse and death. Accordingly, accurate staging and close follow-up are essential in AIDS-related Burkitt lymphoma. FDG PET/CT has emerged as one of the main imaging modalities for staging, restaging, predicting prognosis and therapeutic surveillance for patients with Burkitt lymphoma, largely replacing CT or 67Ga scanning as the modality of choice.”
However, the authors also acknowledged the complications in imaging HIV patients with FDG PET. For example, in these individuals, AIDS-related B-cell lymphoma has a propensity to involve unexpected sites. When compared with sporadic variants, AIDS-related B-cell lymphoma has a higher prevalence of bone marrow, CSF and lymph node involvement and a lower prevalence of abdominal involvement. Also, patients with bone marrow and CSF involvement may not have a distinctive local pattern of FDG uptake.
Based on this evidence, the authors concluded that FDG PET has proven useful in the diagnosis, staging and detection of metastasis and in post-treatment monitoring of several AIDS-defining malignancies. “The efficacy of this imaging modality has important implications in treatment planning for HIV-positive patients, particularly in AIDS-Burkitt lymphoma in which a negative PET scan can lead to discontinuation of a chemotherapy regimen that is especially difficult for those with low CD4 counts,” Davison and colleagues wrote. “It also has the ability to make the important distinction between malignancy and infection in the evaluation of CNS lesions.”