Ineffectiveness of 18F-Fluorodeoxyglucose Positron Emission Tomography in the Evaluation of Tumor Response After Completion of Neoadjuvant Chemoradiation in Esophageal Cancer

The application of functional imaging techniques to personalise chemoradiotherapy in upper gastrointestinal malignancies

Functional imaging gives information about physiological heterogeneity in tumours. The utility of functional imaging tests in providing predictive and prognostic information after chemoradiotherapy for both oesophageal cancer and pancreatic cancer will be reviewed. The benefit of incorporating functional imaging into radiotherapy planning is also evaluated. In cancers of the upper gastrointestinal tract, the vast majority of functional imaging studies have used (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET). Few studies in locally advanced pancreatic cancer have investigated the utility of functional imaging in risk-stratifying patients or aiding target volume definition. Certain themes from the oesophageal data emerge, including the need for a multiparametric assessment of functional images and the added value of response assessment rather than relying on single time point measures. The sensitivity and specificity of FDG-PET to predict treatment response and survival are not currently high enough to inform treatment decisions. This suggests that a multimodal, multiparametric approach may be required. FDG-PET improves target volume definition in oesophageal cancer by improving the accuracy of tumour length definition and by improving the nodal staging of patients. The ideal functional imaging test would accurately identify patients who are unlikely to achieve a pathological complete response after chemoradiotherapy and would aid the delineation of a biological target volume that could be used for treatment intensification. The current limitations of published studies prevent integrating imaging-derived parameters into decision making on an individual patient basis. These limitations should inform future trial design in oesophageal and pancreatic cancers.

Current management of esophageal cancer

Management of esophageal cancer has evolved since the two last decades. Esophagectomy remains the primary treatment for early stage esophageal cancer although its specific role in superficial cancers is still under debate since the development of endoscopic mucosal treatment. To date, there is strong evidence to consider that locally advanced cancers should be recommended for a multimodal treatment with a neoadjuvant chemotherapy or a combined chemoradiotherapy (CRT) followed by surgery. For locally advanced squamous cell carcinoma or for a part of adenocarcinoma, some centers have proposed treating with definitive CRT to avoid related-mortality of surgery. In case of persistent or recurrent disease, a salvage esophagectomy remains a possible option but this procedure is associated with higher levels of perioperative morbidity and mortality. Despite the debate over what constitutes the best surgical approach (transthoracic versus transhiatal), the current question is if a minimally procedure could reduce the periopertive morbidity and mortality without jeopardizing the oncological results of surgery. Since the last decade, minimally invasive esophagectomy (MIE) or hybrid operations are being done in up to 30% of procedures internationally. There are some consistent data that MIE could decrease the incidence of the respiratory complications and decrease the length of hospital-stay. Nowadays, oncologic outcomes appear equivalent between open and minimally invasive procedures but numerous phase III trials are ongoing.

[Importance of PET in surgery of esophageal cancer]

Perioperative or preoperative radiochemotherapy (RCTx) is nowadays standard for locally advanced esophageal cancer in Europe, as randomized studies have shown a significant survival benefit for patients with multimodal treatment. As responders and nonresponders have a significantly different prognosis, a response-based tailored preoperative treatment would be of utmost interest. An established method is a metabolic response evaluation by 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). The level of metabolic response is known to be dependent on the localization, tumor entity and type of preoperative treatment. Association of FDG-PET with later response and prognosis was shown for absolute standardized uptake values (SUV) or a decrease of SUV levels before and after therapy but there are also contradictory findings in the literature and no prospective validation. However, neither time points nor cut-off for metabolic response evaluation have been defined so far. The most interesting approach seems to be early response monitoring during preoperative chemotherapy, which has shown promising results in prospective single center trials (MUNICON I/II) during chemotherapy of adenocarcinoma of the esophagogastric junction (AEG), but needs to be validated in prospective multicenter trails.

Does timing of surgical procedure after neoadjuvant chemoradiation affect outcomes in esophageal cancer?

BACKGROUND

To date, for esophageal cancer (EC), the optimal timing of surgical procedures after neoadjuvant chemoradiation (nCRT) is not well defined. Data in rectal cancer suggest that a prolonged interval between treatment and operation may improve tumoral pathologic response, R0 resection rate, and survival. The aims of this study were to evaluate whether delaying operation after nCRT in EC increases pathologic response and has an impact on oncologic outcome or postoperative course.

METHODS

A total of 257 consecutive EC patients (n=161 squamous cell carcinomas and n=96 adenocarcinomas) undergoing nCRT followed by operation between 1997 and 2011 were retrospectively analyzed by the use of prospectively collected data. The patients were divided into two groups according to the median delay between nCRT and operation (<7 weeks, n=122; ≥7 weeks, n=135). The impact of surgical delay on outcomes was studied through univariable and multivariable analyses.

RESULTS

The groups were comparable regarding patient and tumor characteristics (p≥0.074). The ypT0 and R0 resection rates were similar between the two groups, as were postoperative course, median survivals, and incidence and patterns of recurrence (p≥0.332). Multivariable analysis failed to identify any impact of the surgical delay on the endpoints. Subgroup analysis according to the histologic type found similar results.

CONCLUSIONS

After nCRT for EC, delaying operation does not affect the ypT0 rate, postoperative course, or oncologic outcome and cannot therefore be justified by these aims.

Response to chemotherapy in gastric adenocarcinoma with diffusion-weighted MRI and (18) F-FDG-PET/CT: correlation of apparent diffusion coefficient and partial volume corrected standardized uptake value with histological tumor regression grade

PURPOSE

To assess whether changes in diffusion-weighted MRI (DW-MRI) and (18) F-fluoro-2-deoxyglucose positron emission tomography/computed tomography ((18) F-FDG PET/CT), correlate with treatment response to neoadjuvant therapy (NT), as expressed by tumor regression grade (TRG), from locally advanced gastric adenocarcinoma (GA).

MATERIALS AND METHODS

Seventeen patients underwent both DW-MRI and (18) F-FDG-PET/CT scans before and after the end of NT. Apparent diffusion coefficient (ADC) and mean standardized uptake value (SUV) corrected for partial volume effect (PVC-SUVBW-mean ) were evaluated and compared with histopathological TRG.

RESULTS

Pre- and post-NT and percentage changes for ADC and PVC-SUVBW-mean were assessed. Post-NT ADC and ΔADC showed a significant inverse correlation with TRG (r = -0.71; P = 0.0011 and r = -0.78; P = 0.00020, respectively) and significant differences in their mean values were found between responders (TRG 1-2-3) and nonresponders (TRG 4-5) (P = 0.0009; P = 0.000082, respectively). No correlations with TRG were found for pre-NT ADC and for all PVC-SUVBW-mean values as well as between ΔADC and Δ PVC-SUVBW-mean .

CONCLUSION

DW-MRI seems more accurate than (18) F-FDG-PET/CT and ADC modifications may represent a reproducible tool to assess tumor response for GA.