FDG PET evaluation of residual masses and regrowth of abdominal lymph node metastases from colon cancer compared with CT during chemotherapy

What is the most accurate whole-body imaging modality for assessment of local and distant recurrent disease in colorectal cancer? A meta-analysis : imaging for recurrent colorectal cancer

PURPOSE

The objective of this study was to compare the diagnostic performance of positron emission tomography (PET), PET/CT, CT and MRI as whole-body imaging modalities for the detection of local and/or distant recurrent disease in colorectal cancer (CRC) patients who have a (high) suspicion of recurrent disease, based on clinical findings or rise in carcinoembryonic antigen (CEA).

METHODS

A meta-analysis was undertaken. PubMed and Embase were searched for studies on the accuracy of whole-body imaging for patients with suspected local and/or distant recurrence of their CRC. Additionally, studies had to have included at least 20 patients with CRC and 2 × 2 contingency tables had to be provided or derivable. Articles evaluating only local recurrence or liver metastasis were excluded. Summary receiver-operating characteristic (ROC) curves were constructed from the data on sensitivity and specificity of individual studies and pooled estimates of diagnostic odds ratios (DORs) and areas under the ROC curve (AUCs) were calculated. To test for heterogeneity the Cochran Q test was used.

RESULTS

Fourteen observational studies were included which evaluated PET, PET/CT, CT and/or MRI. Study results were available in 12 studies for PET, in 5 studies for CT, in 5 studies for PET/CT and in 1 study for MRI. AUCs for PET, PET/CT and CT were 0.94 (0.90-0.97), 0.94 (0.87-0.98) and 0.83 (0.72-0.90), respectively. In patient based analyses PET/CT had a higher diagnostic performance than PET with an AUC of 0.95 (0.89-0.97) for PET/CT vs 0.92 (0.86-0.96) for PET.

CONCLUSION

Both whole-body PET and PET/CT are very accurate for the detection of local and/or distant recurrent disease in CRC patients with a (high) suspicion of recurrent disease. CT has the lowest diagnostic performance. This difference is probably mainly due to the lower accuracy of CT for detection of extrahepatic metastases (including local recurrence). For clinical practice PET/CT might be the modality of choice when evaluating patients with a (high) suspicion of recurrent disease, because of its best performance in patient based analyses and confident prediction of disease status.

Early response evaluation and prediction in neoadjuvant-treated patients with esophageal cancer

Since the introduction of multimodal therapy regimens, the prognosis of esophageal cancer has improved. There is undoubtedly true for patients with surgically resected tumors in the case of a response to neoadjuvant chemotherapy or chemoradiation. Important conclusions can be drawn from this regarding the indication for perioperative therapies, the radicality of surgery, or the surgical indications. Thus, most of the current research in this field is aimed at the early identification of this subset of patients, at the beginning of, or even before, neoadjuvant treatment. Conventional staging tools have failed to predict responses to neoadjuvant therapy. However, molecular imaging methods, e.g. positron emission tomography (PET)-scans, have shown promising results in the early selection of responders and non-responders during the course of neoadjuvant therapy, allowing physicians to alter the treatment plan accordingly. Even more desirable is the identification of potential responders before the start of neoadjuvant therapy. Preliminary molecular data on biopsy specimens demonstrate the possibility of early response prediction in these patients. We present the current knowledge on response evaluation and prediction in esophageal cancer and draw conclusions for future clinical practice and studies in this review.

Predicting the response of localised oesophageal cancer to neo-adjuvant chemoradiation

BACKGROUND

A complete pathological response to neo-adjuvant chemo-radiation for oesophageal cancer is associated with favourable survival. However, such a benefit is seen in the minority. If one could identify, at diagnosis, those patients who were unlikely to respond unnecessary toxicity could be avoided and alternative treatment can be considered. The aim of this review was to highlight predictive markers currently assessed and evaluate their clinical utility.

METHODS

A systematic search of Pubmed and Google Scholar was performed using the following keywords; "neo-adjuvant", "oesophageal", "trimodality", "chemotherapy", "radiotherapy", "chemoradiation" and "predict". The original manuscripts were sourced for further articles of relevance.

RESULTS

Conventional indices including tumour stage and grade seem unable to predict histological response. Immuno-histochemical markers have been extensively studied, but none has made its way into routine clinical practice. Global gene expression from fresh pre-treatment tissue using cDNA microarray has only recently been assessed, but shows considerable promise. Molecular imaging using FDG-PET seems to be able to predict response after neo-adjuvant chemoradiation has finished, but there is a paucity of data when such imaging is performed earlier.

CONCLUSION

Currently there are no clinically useful predictors of response based on standard pathological assessment and immunohistochemistry. Genomics, proteomics and molecular imaging may hold promise.

Effects of substituting a OH group by a F atom in D-glucose. Ab initio and DFT analysis

High-level ab initio and DFT methods up to MP2/6-311++G//B3LYP/6-31G and B3LYP/6-311++G//B3LYP/6-31G levels have been used to assess the relative energies of 17 different structures of D-glucose and 13 different structures of 4-deoxy-4-fluoro-D-glucose. The structures were confirmed to correspond to minima on the potential energy surface at the RHF/6-31G level. Solvation Model 5.4/AM1 was used to calculate the effects of aqueous solution. The substitution of a OH group by a F atom does not much change the shape and electrostatic potential around corresponding conformers, but in the gas phase it destabilizes the cooperative network of intramolecular hydrogen bonds. This destabilization mostly affects structures with a chain of intramolecular hydrogen bonds oriented counterclockwise, as fluorine is unable to donate a hydrogen bond and therefore causes a gap in the chain. In contrast, for clockwise-oriented networks of hydrogen bonds, the fluorine can act as an acceptor at the end of a chain of cooperative hydrogen bonds. A slightly higher energy of anomeric and exo-anomeric stabilization is another effect of substituting the fourth hydroxyl group by a fluorine atom in D-glucose, observed both in the gas phase and in aqueous solution. For this reason, the alpha anomers contribute more to the equilibrium population of structures of 4-deoxy-4-fluoro-D-glucose than D-glucose. In aqueous solution, both D-glucose and its 4-deoxy-4-fluoro analogue are present as a mixture of mainly three corresponding structures. This indicates that 4-deoxy-4-fluoro-D-glucose is a good substitute for D-glucose in terms of its biochemical and biological activity. Moreover, this suggests that, for molecules with limited conformational freedom, the substitution of a OH group by a F atom is very likely to lead to a potential new drug. In contrast, it had already been shown that, for conformationally labile aliphatic compounds, replacement of a hydroxyl by a fluorine increases conformational diversity, so the fluorine-containing aliphatic molecules were not likely to be an example of a successful drug design. On the other hand, this work shows that, among molecules with limited conformational freedom, such as cyclic compounds, one is very likely to find targets for a successful rational drug design.