Role of 18F-FDG PET/CT in assessing treatment response of metastatic colorectal carcinoma: metabolic (EORTC) versus morphologic (RECIST 1.1) criteria

Document Type : Original Paper, PET/CT

Authors

1 Lecturer of nuclear medicine, department of clinical oncology and nuclear medicine, faculty of medicine, Assiut university

2 Department of Clinical Oncology and Nuclear Medicine, Faculty of Medicine, Assiut University

3 Department of Medical Oncology, South Egypt Cancer Institute, Assiut University

4 Department of Clinical Oncology and Nuclear Medicine, Faculty of Medicine, Cairo University

Abstract

ABSTRACT


Background: Colorectal cancer (CRC) is the third most common diagnosed cancer globally. Response Evaluation Criteria in Solid Tumors (RECIST) are the morphologic criteria extensively used to measure tumor response. However, they based on the size changes.18F-FDG PET/CT is increasingly used to track tumor responses, which allows response evaluation irrespective of anatomical alterations. The FDG PET-based Research and Treatment of Cancer (EORTC) criteria are used to assess metabolic response to the anti-cancer therapy. We compared both criteria in the current work.
Patients and methods: A total of 35 metastatic CRC (mCRC) patients were recruited in this prospective study. Twenty-seven patients received chemo plus target therapy, whereas eight received only chemotherapy. Baseline and post-therapy FDG PET/CT scans were conducted. PET/CT-derived parameters; SUVmax, TLG, and MTV were measured in each scan. The values of SUVmax of the target lesions (up to five lesions) were summed in both studies, and the assessment of the treatment response by EORTC and RECIST 1.1 criteria was carried out. The percent changes in the SUVmax, TLG, and MTV of the hottest lesions between the baseline and follow-up scans were calculated. Also, the value of the PET/CT metrics in predicting disease control was determined.
Results: We found a poor agreement rate (48.6%) between EORTC and RECIST1.1 in response evaluation, a κ-coefficient = 0.053, while a significant good agreement (κ-coefficient = 0.719, p < 0.01) between both criteria was observed when the patients were divided into disease control and non-control groups. The %Δ SUVmax remained a significant independent predictor of disease control (p= 0.029).
Conclusions: FDG PET/CT-based metabolic criteria are more accurate in assessing treatment response in patients with mCRC than CT-based morphologic criteria. The ΔSUVmax is the most significant predictor of disease control.

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