Test can predict non-Hodgkin's lymphoma in people with HIV

The risk of non-Hodgkin’s lymphoma developing in people with HIV within two to five years can be predicted with a high degree of accuracy using an assay already used to monitor for the development of multiple myeloma, according to findings presented on Monday at the Sixteenth Conference on Retroviruses and Opportunistic Infections in Montreal, Canada.

Non-Hodgkin’s lymphoma is a relatively common cancer in people with HIV, and the most common type of lymphoma seen in people with HIV. It is a tumour that involves the uncontrolled multiplication of a type of white blood cells called lymphocytes. The vast majority of non-Hodgkin’s lymphomas are B-cell lymphomas, which are a result of uncontrolled proliferation of B-lymphocytes, the antibody-generating group of lymphocytes.

A range of cancers are related to B-cell proliferation, and a variety of markers of proliferation have been proposed as potential monitoring tools for predicting the development of these types of cancers.

Multiple myeloma, a cancer that emerges in the plasma cells of the bone marrow, is already routinely monitored using a free light chain assay. A light chain is a molecule that is normally bound to an immunoglobulin, or antibody, produced by B-cells. In the presence of myeloma, levels of unlinked, or free, light chain levels are elevated.

Researchers from the US National Cancer Institute and the Mayo Clinic in Rochester, New York, conducted a case-control study that matched 66 HIV-positive cases of non-Hodgkin’s lymphoma occurring between 1985 and 2004, each with four HIV-positive control cases selected on the basis of matching sex, race, age and CD4 count (225 total controls).

Levels of immunoglobulin (Ig) G, IgM and IgA levels were measured from stored plasma samples, together with levels of kappa and lambda free light chains, and their predictive value for the development of NHL was assessed.

Levels of kappa and lambda free light chains were found to strongly predict the development of NHL two to five years in advance, and levels of these molecules were elevated in all HIV-positive individuals compared with reference levels in the general population. The kappa/lamda free light chain ratio did not predict NHL, and nor did changes in free light chain levels over time.

Immunoglobulin levels did not predict the development of NHL.

However applicability of the findings may be limited by the lack of antiretroviral therapy; Eric Engels of the National Cancer Institute said that only 10% of those diagnosed with NHL had been taking antiretroviral drugs prior to the development of the tumour, and the median CD4 count at diagnosis was 74 cells/mm³. The median year of diagnosis was 1994.

Nevertheless, said Engels, the monitoring of free light chains could help to identify patients who need to start antiretroviral treatment early in order to reduce the risk of developing NHL, or to detect relapse of NHL after treatment.