Dear OncoLink "Ask The Experts,"
In December 2005, I completed 6 treatments of R-CHOP chemotherapy for non-Hodgkin's lymphoma. My "final" PET scan (skull to thigh) showed no evidence of residual active neoplasm - good news. I have recently read of the advisability of a brain scan in the management of essentially all cancers to detect early indications of brain metastasis. Did the skull-to-thigh PET scan which I got after completing chemotherapy include the brain? If not, is a brain scan recommended for patients like me?
Babis (Charalambos) Andreadis, MD, Assistant Professor in Medicine in the Division of Hematology/Oncology at the Abramson Cancer Center and an Associate Scholar in the Center for Clinical Epidemiology and Biostatistics at the University of Pennsylvania, responds:
Brain or central nervous system (CNS) involvement can occur with many different types of cancers. However, development of this complication in lymphomas is relatively rare. Information collected from several studies suggests that the average rate of CNS involvement in non-Hodgkin's lymphoma is only 5% over the course of the disease. Rates may be higher for a few subgroups of patients (more aggressive histologies such as diffuse large B-cell, Burkitt's, or lymphoblastic; bone marrow involvement; the presence of "B symptoms" such as night sweats, significant weight loss, itching; disease outside the lymph nodes; high blood LDH; and advanced age). These factors may predict for higher rates of CNS disease.
Screening for CNS involvement in the presence of neurological symptoms is definitely recommended. Screening for asymptomatic CNS disease is indicated for certain patients that have the high-risk factors listed above. However, even then, the yield from asymptomatic screening is low and the benefit obtained from this information is debatable. In other words, it is not clear that picking up CNS involvement early, in the absence of symptoms, has any benefit in terms of complications or survival.
Finally, the best screening modalities for CNS disease are a lumbar puncture (spinal tap) and brain MRI, when indicated. A PET scan, although very sensitive for certain kinds of lymphoma, has a limited track record in this setting. Alas, a "whole body" or "skull-to-thigh" PET scan only goes from the base of the skull to the thigh, and thus does not include the brain. A separate whole brain PET study has to be performed for the brain to be imaged, but would not likely be very helpful in lymphoma.