This article focuses on the role of PET/computed tomography in evaluating and managing gastric cancer and colorectal cancer. The authors start with describing the common aspects of imaging with 2-deoxy-2-18F-d-glucose, followed by tumor-specific discussions of gastric and colorectal malignancies. Finally, the authors provide a brief overview of non-FDG tracers including their potential clinical applications, and describe future directions in imaging these malignancies.

Approximately 25% of those who are diagnosed with colorectal cancer will develop colorectal liver metastases (CRLM) as their illness advances. Despite major improvements in both diagnostic and treatment methods, the prognosis for patients with CRLM is still poor, with low survival rates. Accurate employment of imaging methods is critical in identifying the most effective treatment approach for CRLM. Different imaging modalities are used to evaluate CRLM, including positron emission tomography (PET)/computed tomography (CT). Among the PET radiotracers, fluoro-18-deoxyglucose (18F-FDG), a glucose analog, is commonly used as the primary radiotracer in assessment of CRLM. As the importance of 18F-FDG-PET/CT continues to grow in assessment of CRLM, developing a comprehensive understanding of this subject becomes imperative for healthcare professionals from diverse disciplines. The primary aim of this article is to offer a simplified and comprehensive explanation of PET/CT in the evaluation of CRLM, with a deliberate effort to minimize the use of technical nuclear medicine terminology. This approach intends to provide various healthcare professionals and researchers with a thorough understanding of the subject matter.

Morphologic response (MR) is a novel chemotherapeutic efficacy predictor of solid tumors, especially those treated with anti-vascular endothelial growth factor antibodies. Nevertheless, the importance of systemic chemotherapy MR for colorectal liver metastases (CLM) remains unclear. We aimed to evaluate the usefulness of MR as a factor associated with the therapeutic effects of chemotherapy plus bevacizumab for initially unresectable CLM cases.

We retrospectively evaluated the associations between MR and/or Response Evaluation Criteria in Solid Tumors (RECIST), progression-free survival (PFS), and overall survival (OS) in patients who received first-line capecitabine, oxaliplatin, and bevacizumab treatment for initially unresectable CLM using multivariate analysis. Patients who showed a complete or partial response based on the RECIST, or an optimal response based on MR, were defined as "responders."

Ninety-two patients were examined, including 31 (33%) patients who responded optimally. PFS and OS estimates were comparable in MR responders and non-responders (13.6 vs. 11.6 months, p = 0.47; 26.6 vs. 24.6 months, p = 0.21, respectively). RECIST responders showed better PFS and OS than non-responders (14.8 vs. 8.6 months, p < 0.01; 30.7 vs. 17.8 months, p < 0.01, respectively). The median PFS and OS estimates of MR and RECIST responders were better than those of single responders or non-responders (p < 0.01). Histological type and RECIST response were independently associated with PFS and OS.

MR predicts neither PFS nor OS; nevertheless, it may be useful when combined with the RECIST. The Ethics Committee of The Cancer Institute Hospital of JFCR approved this study in 2017 (No. 2017-GA-1123): retrospectively registered.

One of the most common cancers worldwide, colorectal cancer (CRC) has been associated with significant morbidity and mortality and therefore represents an enormous burden to the health care system. Recent advances in CRC treatments have provided patients with primary and metastatic CRC a better long-term prognosis. The presence of synchronous or metachronous metastasis has been associated, however, with worse survival. The most common site of metastatic disease is the liver. A variety of treatment modalities aimed at targeting colorectal liver metastases (CRLM) has been demonstrated to improve the prognosis of these patients. Loco-regional approaches such as surgical resection and tumor ablation (operative and percutaneous) can provide patients with a chance at long-term disease control and even cure in select populations. Patient selection is important in defining the most suitable treatment option for CRLM in order to provide the best possible survival benefit while avoiding unnecessary interventions and adverse events. Medical imaging plays a crucial role in evaluating the characteristics of CRLMs and disease resectability. Size of tumors, proximity to adjacent anatomical structures, and volume of the unaffected liver are among the most important imaging parameters to determine the suitability of patients for surgical management or other appropriate treatment approaches. We herein provide a comprehensive overview of current-state-of-the-art imaging in the management of CRLM, including staging, treatment planning, response and survival assessment, and post-treatment surveillance. Computed tomography (CT) scan and magnetic resonance imaging (MRI) are two most commonly used techniques, which can be used solely or in combination with functional imaging modalities such as positron emission tomography (PET) and diffusion weighted imaging (DWI). Providing up-to-date evidence on advantages and disadvantages of imaging modalities and tumor assessment criteria, the current review offers a practice guide to assist providers in choosing the most suitable imaging approach for patients with CRLM.

The clinical significance of discordant radiological and pathological response to preoperative chemotherapy of colorectal liver metastases (CLM) is unknown.

From 2011 to 2016, all eligible patients undergoing resection for CLM after preoperative chemotherapy were included at two centres. Patients were categorized according to radiologic response using RECIST as Rad-responders (complete/partial response) or Rad-non responders (stable disease) and according to Blazer et al. pathologic response grade as Path-responders (complete/major response) or Path-non responders (minor response). Survival outcome was analysed according to radiologic and pathologic response.

Among 413 patients undergoing resection of CLM, 119 fulfilled the inclusion criteria. Among these, 52 (44%) had discordant radiologic and pathologic response including 27 Rad-non responders/path responders and 25 Rad-responders/Path-non responders. Rad-non responders/path responders and Rad-responders/Path-non responders had similar characteristics except for the proportion receiving more than 6 cycles of preoperative chemotherapy (7/27 vs 16/25; P = 0.017). Median disease-free survival was not different in patients with or without discordant radiologic and pathologic responses (P = 0.195) but the type of discordance had an impact on oncologic outcome as median disease-free survival was 13.9 months (95% CI 5.7-22.2 months) in Rad-non responders/Path responders and 8.6 (6.2 - 10.9 months) in Rad-responders/Path-non responders (P = 0.034). Univariate and multivariate analysis showed that major pathologic response was associated with improved disease-free survival (OR 0.583, 95% CI 0.36-0.95, P = 0.031).

A discordant radiologic and pathologic response is common after preoperative chemotherapy for CLM. In these patients, pathologic response drives oncologic outcome.

Colorectal cancer (CRC) represents one of the leading causes of tumor-related deaths worldwide. Among the various tools at physicians' disposal for the diagnostic management of the disease, tomographic imaging (e.g., CT, MRI, and hybrid PET imaging) is considered essential. The qualitative and subjective evaluation of tomographic images is the main approach used to obtain valuable clinical information, although this strategy suffers from both intrinsic and operator-dependent limitations. More recently, advanced imaging techniques have been developed with the aim of overcoming these issues. Such techniques, such as diffusion-weighted MRI and perfusion imaging, were designed for the "in vivo" evaluation of specific biological tissue features in order to describe them in terms of quantitative parameters, which could answer questions difficult to address with conventional imaging alone (e.g., questions related to tissue characterization and prognosis). Furthermore, it has been observed that a large amount of numerical and statistical information is buried inside tomographic images, resulting in their invisibility during conventional assessment. This information can be extracted and represented in terms of quantitative parameters through different processes (e.g., texture analysis). Numerous researchers have focused their work on the significance of these quantitative imaging parameters for the management of CRC patients. In this review, we aimed to focus on evidence reported in the academic literature regarding the application of parametric imaging to the diagnosis, staging and prognosis of CRC while discussing future perspectives and present limitations. While the transition from purely anatomical to quantitative tomographic imaging appears achievable for CRC diagnostics, some essential milestones, such as scanning and analysis standardization and the definition of robust cut-off values, must be achieved before quantitative tomographic imaging can be incorporated into daily clinical practice.