Radiologic Measurements of Tumor Response to Treatment: Practical Approaches and Limitations

Abstract

Objective response assessment is important to describe the treatment effect of anticancer drugs. Standardization by using a "common language" is also important for comparison of results from different trials. In contrast to clinical results, which can be subjective, diagnostic imaging provides a greater opportunity for objectivity and standardization. It was generally accepted that a decrease in tumor size correlated with treatment effect; as a result, imaging was adopted for lesion measurement in the World Health Organization (WHO) criteria in 1979. However, because of some limitations of the WHO criteria, the Response Evaluation Criteria in Solid Tumors (RECIST) were introduced in 2000. In RECIST, imaging was recognized as indispensable for response evaluation of solid tumors. Nevertheless, the widespread use of multidetector computed tomography and other imaging innovations have made RECIST outdated, with a concomitant need for modifications. Meanwhile, newer anticancer agents with targeted mechanisms of action have demonstrated an inherent limitation and unsuitability of anatomic tumor evaluation that assesses only lesion size. In addition, the effect of these new drugs changes the paradigm according to which tumor response or response rate is measured. Complete and partial responses cannot be the end points in all clinical trials; in some cases, disease control or progression-free survival may be the more relevant end point.

Comparison of diffusion‐weighted MRI and MR volumetry in the evaluation of early treatment outcomes after preoperative chemoradiotherapy for locally advanced rectal cancer

“…The patients with tumoral downstaging were classified as the responder group. Second, according to the modified Response Evaluation Criteria in Solid Tumors (mRECIST) and World Health Organization (WHO) criteria for imaging-based treatment response evaluation, a partial response (PR) was defined as a 65% decrease in lesion volume (10,17). Therefore, patients with a late tumor volume reduction rate of >65% were classified as responders.…”

Radiological Evaluation of the Therapeutic Response of Malignant Diseases: Status Quo, Innovative Developments and Requirements for Radiology

“…If several lesions are present, then their products are added up. These criteria have disadvantages: the type of imaging modality is not specified, there is no minimum definition of the lesions, and there is no specification of the minimum and maximum number of lesions to be determined [10] ( • " Fig. 1).…”

The ALARA concept in pediatric oncology

“…The Response Evaluation Criteria in Solid Tumors (RECIST) are used in most adult protocols and in many pediatric protocols. As has been noted by many investigators, the most common non-CNS pediatric solid tumors (neuroblastoma, Wilms tumor, and lymphoma) are not well-suited to RECIST measurement criteria [21,22]. Pediatric bone tumors, including Ewing sarcoma and osteosarcoma, are not readily measurable by traditional RECIST criteria and there is no generally acceptable standard for measuring bone tumor size.…”