Review
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Oncol. Feb 24, 2020; 11(2): 53-73
Published online Feb 24, 2020. doi: 10.5306/wjco.v11.i2.53
Objective response rate assessment in oncology: Current situation and future expectations
Nuri Faruk Aykan, Tahsin Özatlı
Nuri Faruk Aykan, Tahsin Özatlı, Department of Medical Oncology, Istinye University Medical School, Bahcesehir Liv Hospital, Istanbul 34510, Turkey
Author contributions: Aykan NF and Özatlı T performed the literature search; and Aykan NF wrote the manuscript.
Conflict-of-interest statement: No potential conflicts of interest and no financial support are associated with this manuscript.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Nuri Faruk Aykan, MD, Professor, Department of Medical Oncology, Istinye University Medical School, Bahcesehir Liv Hospital, Atatürk Bulvarı, No. 6, Istanbul 34510, Turkey. nfaruk@mac.com
Received: May 5, 2019
Peer-review started: May 8, 2019
First decision: October 23, 2019
Revised: November 5, 2019
Accepted: November 28, 2019
Article in press: November 28, 2019
Published online: February 24, 2020
Abstract

The tumor objective response rate (ORR) is an important parameter to demonstrate the efficacy of a treatment in oncology. The ORR is valuable for clinical decision making in routine practice and a significant end-point for reporting the results of clinical trials. World Health Organization and Response Evaluation Criteria in Solid Tumors (RECIST) are anatomic response criteria developed mainly for cytotoxic chemotherapy. These criteria are based on the visual assessment of tumor size in morphological images provided by computed tomography (CT) or magnetic resonance imaging. Anatomic response criteria may not be optimal for biologic agents, some disease sites, and some regional therapies. Consequently, modifications of RECIST, Choi criteria and Morphologic response criteria were developed based on the concept of the evaluation of viable tumors. Despite its limitations, RECIST v1.1 is validated in prospective studies, is widely accepted by regulatory agencies and has recently shown good performance for targeted cancer agents. Finally, some alternatives of RECIST were developed as immune-specific response criteria for checkpoint inhibitors. Immune RECIST criteria are based essentially on defining true progressive disease after a confirmatory imaging. Some graphical methods may be useful to show longitudinal change in the tumor burden over time. Tumor tissue is a tridimensional heterogenous mass, and tumor shrinkage is not always symmetrical; thus, metabolic response assessments using positron emission tomography (PET) or PET/CT may reflect the viability of cancer cells or functional changes evolving after anticancer treatments. The metabolic response can show the benefit of a treatment earlier than anatomic shrinkage, possibly preventing delays in drug approval. Computer-assisted automated volumetric assessments, quantitative multimodality imaging in radiology, new tracers in nuclear medicine and finally artificial intelligence have great potential in future evaluations.

Keywords: Objective response rate, Tumor shrinkage, World Health Organization criteria, Response Evaluation Criteria in Solid Tumors, Immune Response Evaluation Criteria in Solid Tumors criteria, Early tumor shrinkage, Depth of response, Waterfall plot, Spider plot, Swimmer plot

Core tips: The tumor objective response rate is an important parameter in oncology. World Health Organization and Response Evaluation Criteria in Solid Tumors (RECIST) are anatomic response criteria developed mainly for cytotoxic chemotherapy. These criteria may not be optimal for biologic agents, some disease sites, and some regional therapies. Some alternatives of RECIST were developed, but RECIST v1.1 is validated in prospective studies, is widely accepted by regulatory agencies and has recently shown good performance for targeted cancer agents. The newest alternatives of RECIST are immune-specific response criteria for checkpoint inhibitors. Metabolic response assessments using positron emission tomography (PET) or PET/computed tomography may reflect the viability of cancer cells or functional changes that occur after anticancer treatments.