Lymphoma

INTRODUCTION
Lymphoma is generally divided into two groups: Hodgkin’s disease (HD) and an inhomogeneous group of conditions called non-Hodgkin’s lymphoma (NHL). HD tends to involve a single nodal group and spread in a fixed pattern along the lymphatic chain. NHL is a multifocal disease which often presents late with disseminated spread. Lymphoma tends to be both chemosensitive and radiosensitive. Localized disease can be effectively treated with radiotherapy, but disseminated spread requires systemic chemotherapy. The prognosis of a patient with lymphoma is related to the disease stage at presentation. Accurate, effective staging is required to guide the appropriate therapeutic pathway. The Ann Arbor classification is commonly used for the staging of lymphomas. Originally developed for Hodgkin’s disease, this staging scheme was later expanded to include non-Hodgkin’s lymphoma.Over the last 10 to 15 years, PET scanning has emerged as a powerful imaging modality in the assessment of patients with both Hodgkin’s and non-Hodgkin’s lymphoma. PET/CT is not only used to identify sites of residual disease after therapy but is a useful tool in staging, restaging, identifying potential biopsy sites and quantifying the response to therapy. Since a PET/CT scan can be used to image the whole body it gives an accurate anatomical distribution of the disease burden within the patient, allowing the appropriate therapeutic pathway to be chosen.
Stage I
Involvement of a single lymph node region (I) or of a single extralymphatic organ or site (IE)
Stage II
Involvement of two or more lymph node regions on the same side of the diaphragm (II) or localized involvement of extra-lymphatic organ or site and of one or more lymph node regions on the same side of the diaphragm (IIE).
Stage III
Involvement of lymph node regions on both sides of the diaphragm (III) which may also be accompanied by localized involvement of extralymphatic organ or site (IIIE) or by involvement of the spleen (IIIS) or both (IIISE)
Stage IV
Diffuse or disseminated involvement of one or more extralymphatic organs or tissues with or without associated lymph node enlargement Source: Lister TA, Crowther D, Sutcliffe SB, et al. Report of a committee convened to discuss the evaluation and staging of patients with Hodgkin’s disease. J Clin Oncol 1989;7:1630–1636.
The Role of PET/CT in Lymphoma
• Assess response to therapy/residual disease
• Identify recurrent disease
• Initial diagnosis and staging
• Identify suitable sites for biopsy and possibly
• Disease surveillance
• Radiotherapy planning
Figure 3.1 is an example of a patient with known non-Hodgkin’s lymphoma within right sided neck nodes. After the PET/CT scan this patient was upstaged from stage I to stage IV disease. Active disease was found in the neck, mediastinum and abdomen as indicated by the arrows. Normal uptake and excretion is seen in the brain and urinary system respectively.