CT versus FDG‐PET/CT response evaluation in patients with metastatic colorectal cancer treated with irinotecan and cetuximab

Abstract

We compared morphologic computed tomography (CT)-based to metabolic fluoro-deoxy-glucose (FDG) positron emission tomography (PET)/CT-based response evaluation in patients with metastatic colorectal cancer and correlated the findings with survival and KRAS status. From 2006 to 2009, patients were included in a phase II trial and treated with cetuximab and irinotecan every second week. They underwent FDG-PET/CT examination at baseline and after every fourth treatment cycle. Response evaluation was performed prospectively according to Response Evaluation Criteria in Solid Tumors (RECIST 1.0) and retrospectively according to Positron Emission Tomography Response Criteria in Solid Tumors (PERCIST). Best overall responses were registered. Sixty-one patients were eligible for response evaluation. Partial response (PR) rate was 18%, stable disease (SD) rate 64%, and progressive disease (PD) rate 18%. Partial metabolic response (PMR) rate was 56%, stable metabolic disease rate 33%, and progressive metabolic disease (PMD) rate 11%. Response agreement was poor, κ-coefficient 0.19. Hazard ratio for overall survival for responders (PR/PMR) versus nonresponders (PD/PMD) was higher for CT- than for FDG-PET/CT evaluation. Within patients with KRAS mutations, none had PR but 44% had PMR. In conclusion, morphologic and metabolic response agreement was poor primarily because a large part of the patients shifted from SD with CT evaluation to PMR when evaluated with FDG-PET/CT. Furthermore, a larger fraction of the patients with KRAS mutations had a metabolic treatment response.

Evaluating tumor response with FDG PET: updates on PERCIST, comparison with EORTC criteria and clues to future developments

“…So far, however, there only relatively few and mostly small studies comparing RECIST and PERCIST (References: [17] [42] [43] [44] [45] [46] [47] [48] [20] [49] [50] [51] [21] [52] [53] [24] [23] [25] [54] [26] [55] [56]). A meta-analysis published in 2016 identified 6 studies including 268 patients [57].…”

Utility of FDG-PET/CT in Patients with Advanced Renal Cell Carcinoma with Osseous Metastases: Comparison with CT and 99mTc-MDP Bone Scan in a Prospective Clinical Trial

“…Several studies have previously reported the ability of FDG-PET/CT to predict outcomes in patients undergoing treatment for mRCC [12][13][14][23][24][25][26][27][28][29], but the methodologies between these studies were variable limiting overall conclusions. Our study used PERCIST which provides greater detail on lesion analysis and may be less ambiguous [18] than other PET based criteria [30,31].…”

Interactive Communication Between PET Specialists and Oncologists

“…The most common evaluation of a certain therapy to cancer is based on the initial diagnosis of TNM stage, which may reveal the current status and might predict the therapeutic outcome [27]. However, the morphologic and metabolic responses of cancer cells to a specific treatment are incongruent.…”

“…However, the morphologic and metabolic responses of cancer cells to a specific treatment are incongruent. For example, cetuximab and other targeted therapies inhibit cancer cell growth by inhibiting the proliferation, angiogenesis, and metastatic spread and by promoting apoptosis [28][29][30], which should be cytostatic rather than cytotoxic [27]. However, in many cases, especially in the early-phase post-therapy, the change of cellular or biochemical function may be significant, but a measurable reduction in tumor size may not occur.…”