Diagnostic Accuracy of Surveillance of FDG-PET/CT in Detection of Early Relapse in Malignant Lymphoma.

Introduction: Integrated PET/CT has been shown to be more accurate for lesion localization and characterization in lymphoma than PET and CT alone. Addition of CECT to PET/CT changed management of lymphoma in only about 10% of patients, while FDG/PET resulted in a management change in almost 50 % of HL patients compared with CECT alone. The majority of patients with high-grade non-Hodgkin’s lymphomas (NHL) are cured with combination treatments. However, acute and long-term toxicities impair survival. Patients with poor-risk, progressive, or relapsed disease; the goal is to improve survival with a strategy using more intensive therapy. Hence, the focus of management has now shifted towards reducing the treatment toxicity and long-term side effects while maintaining favorable outcomes especially in low-risk patients. The successful application of this tailored approach is dependent on an accurate and non-invasive diagnostic test that would reflect the true extent of disease as well as its viability early during the course of treatment. Metabolic parameters in malignant lymphoma: An imaging task force was created to update the relevance of existing imaging for staging, assessing bulk, and bone marrow involvement (BMI); the role of interim PET; standardization of PET reporting; and role for quantitative evaluation using PET and CT. A clinical task force assessed the current relevance of Ann Arbor and how best to incorporate PET/CT into staging lymphoma, the relevance of B symptoms and bone marrow biopsy (BMB), as well as to create recommendations relevant to both FDG-avid and non-avid lymphomas. The revised IWG response criteria (rIWG) incorporated FDG PET to accurately assess end-therapy persistent masses in both NHL and HL. PET/CT in surveillance assessment: Surveillance CT or PET-CT scans are widely used because of the impression that treatment at relapse is more likely to be effective when the disease is in a preclinical stage with a small tumor burden: the earlier the detection of disease the higher the treatment efficacy. The authors concluded that the routine use of surveillance PET in HL patients entering complete remission after first-line treatment should be reserved for high-risk patients. Current guidelines warrant that, once the first clinical remission is obtained, surveillance should be grounded on frequent physical examination and routine blood tests. By contrast, a significant proportion of these patients undergo follow-up CT radiological studies and fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT, especially in the first 2 years after therapy. FDG-PET/CT follow up exams may be associated with false positive results. These confounding findings add up to the already significant FDG-PET/CT expense, which in turn is significantly more resource-consuming when compared to clinical and biochemical evaluation. CONCLUSION: PET/CT imaging for surveillance in malignant lymphoma may be useful in special subtypes of both Hodgkin and non-Hodgkin lymphoma.