Responses With Immunotherapy Versus Chemotherapy

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Although researchers originally thought that cell-based therapies that engage T-cells would take a long time to exert an antitumor effect compared with antibodies, that may not be the case, says Madhav Dhodapkar, MD. Immunotherapies are producing rapid effects in solid tumors. One important distinction between immunologic approaches and non-immunologic approaches, explains Dhodapkar, is that immune memory allows an effect to persist over time.

In individuals with large tumor burden, clinicians may see a rapid reduction in disease that can occur with either chemotherapy or immunotherapy. Although this rapid effect is desirable, adds Ivan Marques Borrello, MD, the persistent effects are also very important.

When it comes to response, different rules may apply to immunotherapy compared with chemotherapy, states Dhodapkar. For example, pseudoprogression may occur with immunologic responses, which makes tumors appear bigger while they are actually responding to therapy. The immune RECIST criteria, used to help judge clinical response to therapy, has been modified to take pseudoprogression into account, adds Borrello.

Responses to immunotherapy can differ from chemotherapy at the durable response level, leading to challenges in clinical trial designs and endpoint selection, notes Dhodapkar. It may be more meaningful to show progression-free survival (PFS) at a defined follow-up than standard PFS, for example.