Which tumor marker is used to determine whether treatment with a targeted therapy is appropriate for non-Hodgkin lymphoma?

In the context of non-Hodgkin lymphoma (NHL) treatment, the CD20 marker is particularly significant. CD20 is a surface protein found on B-cells, and its expression is a critical factor in informing therapeutic decisions for certain types of NHL, especially B-cell lymphomas. Targeted therapies such as rituximab, a monoclonal antibody that targets CD20, have shown considerable effectiveness in treating patients with CD20-positive B-cell malignancies. Thus, the presence of the CD20 marker is utilized to determine the appropriateness of these targeted treatments.

The other markers and mutations listed play important roles in other types of cancers or treatment decisions but are not used for the specific purpose of guiding therapy in non-Hodgkin lymphoma. For example, ALK gene rearrangements are primarily associated with anaplastic large cell lymphoma, BRAF mutation V600E is related to melanoma and certain other malignancies, and EGFR mutation analysis is typically used in the context of non-small cell lung cancer. Therefore, while these markers have their clinical relevance, they do not pertain to the determination of targeted therapy options for non-Hodgkin lymphoma like CD20 does.