Imaging modalities, including computed tomography, magnetic resonance imaging, and positron emission tomography, are often essential in evaluating the response to treatment and deciding whether to continue or suspend cancer therapy, yet immunotherapies present potential challenges to the assessment of treatment response when using conventional response criteria. Immune-modifying agents require more time than conventional treatments to induce an antitumor response, and tumor volume may even increase during the early phases of treatment. The criteria for evaluating tumor responses have evolved over time from a relatively simple assessment of tumor size using computed tomography, to more recent response criteria with detailed recommendations regarding the number and size of lesions to evaluate, the incorporation of magnetic resonance imaging and other imaging modalities, and the specific outcomes that should be measured in patients who are receiving immune-based therapies. The use of immune-related response criteria for patients with cancer has been shown to identify a substantial number of patients who are responding to immune-based treatments but who would have been considered to have failed treatment using conventional response criteria that were developed primarily for patients receiving chemotherapy drugs. This article will describe how immune-based treatment strategies may improve clinical outcomes in patients with cancer, as well as why conventional imaging criteria may be less effective for detecting treatment responses in patients receiving immune-based therapies. Potential benefits and limitations of different imaging modalities in evaluating the effects of immunotherapy in patients with cancer will also be discussed.
After reading this article, the participant should be able to:
- Describe potential mechanisms by which immune-based treatment strategies may improve clinical outcomes in patients with cancer.
- List 4 commonly used systems to assess radiologic evidence of treatment response in patients receiving cancer treatment, and describe how they differ in terms of target lesion selection, lesion size measurement, and definitions of progressive disease.
- Explain why conventional imaging criteria may be less effective for detecting treatment responses in patients receiving immune-based therapies.
- Summarize potential benefits and limitations of different imaging modalities to visualize the effects of immunotherapy in patients with cancer.
Categories: CT, MRI