Change in maximum standardized uptake value on repeat positron emission tomography after chemoradiotherapy in patients with esophageal cancer identifies complete responders

Treatment Response to Neoadjuvant Therapy in Squamous Esophageal Cancer-Correlation Between Metabolic Response and Histopathology

PURPOSE

Esophageal cancer is among the leading causes of cancer-related mortality worldwide. Patients presenting with localized and loco-regionally advanced cancer without distant metastases have reasonable survival with multimodality management. Adequate and comprehensive staging is the backbone for proper selection of patients fit for curative treatment. Positron emission tomography (PET) in combination with contrast-enhanced computed tomography (CECT) is utilized as the standard staging modality. Multimodality treatment has been able to achieve evaluable tumor responses including pathological complete response (pCR). It is, therefore, necessary to understand whether the impact of neoadjuvant therapy can be evaluated on imaging, i.e., standardized uptake value (SUV) on PET scan done for response assessment and if this can be correlated with histopathological response and later, with survival. Squamous cell carcinoma (SCC) is more common globally and in the Indian subcontinent; hence, we chose this subgroup to evaluate our hypothesis.

METHODS

This is a single institution, retrospective study. Out of the 1967 patients who were treated between 2009 and 2019, 1369 (78.54%) patients had SCC. Out of these, 44 received NACTRT, whereas 1325 received NACT followed by curative surgery. The standardized uptake value (SUV) of 18-fluorodeoxyglucose was recorded during pre- and post-neoadjuvant treatment (NAT) using positron emission tomography (PET). The histopathology of the final resection specimen was evaluated using the Mandard tumor regression grade (TRG) criteria with response being graded from 0 to 5 as no residual tumor (NRT), scanty residual tumor (SRT), and residual tumor We attempted to find a cut-off value of the post neoadjuvant SUV of the primary tumor site which correlated with achievement of better histopathological response.

RESULTS

Out of 1325 patients of SCC esophagus who underwent surgery, 943 patients had available data of TRG, and it was categorized into the 0-2 category which had 325 patients (34.5%) and 3-5 category, 618 patients (65.5%). The SUV was taken only from the PET scans done at our institution, so as to achieve a more homogenous cohort, and this was available for 186 patients, 151 from the NACT group and 35 from the NACTRT group. The ROC method was used to find the cut-off for SUV (5.05) in the NACT cohort, which depicted significant difference in the outcome. Out of these, 93 patients who underwent NACT had SUV > 5.05 and 58 had SUV < 5.05. It was found that the subjective and objective histopathological scores correlated at a p value of < 0.0001. Specifically, the majority of cases with SRT tended to be in the 3-5 category of TRG, whereas cases with NRT are predominantly in the 0-2 category. In the ≥ 5.05 category of SUV, there were 76 cases with SRT. In the NACT cohort, the < 5.05 category of SUV, there are 26 cases with SRT and 32 cases with NRT. Among cases with SRT, 74.5% had SUV ≥ 5.05, while 25.5% had SUV < 5.05. Among cases with NRT, 34.7% had SUV ≥ 5.05, while 65.3% had SUV < 5.05 (p value 0.007). No significant association was found in the radio-pathological correlation in the NACTRT group.

CONCLUSION

Our study confirms the correlation of post neoadjuvant chemotherapy PET SUV with histopathological response, the cut-off of SUV being 5.05 in our cohort. This confirms the predictive value of FDG PET as demonstrated in other studies. Furthermore, its prognostic value with respect to survival has been verified in multiple other studies. With larger scale randomized studies, we may be able to identify the group of patients who have borderline operability anatomically as well as physiologically, where alternative treatment regimens may be indicated to improve outcomes.

18F-FDG-PET/CT Imaging for Gastrointestinal Malignancies

Gastrointestinal malignancies encompass a variety of primary tumor sites, each with different staging criteria and treatment approaches. In this review we discuss technical aspects of 18F-FDG-PET/CT scanning to optimize information from both the PET and computed tomography components. Specific applications for 18F-FDG-PET/CT are summarized for initial staging and follow-up of the major disease sites, including esophagus, stomach, hepatobiliary system, pancreas, colon, rectum, and anus.

Accuracy of Detecting Residual Disease After Neoadjuvant Chemoradiotherapy for Esophageal Cancer: A Systematic Review and Meta-analysis

OBJECTIVE

The aim of this study was to perform a meta-analysis on the accuracy of endoscopic biopsies, EUS, and 18F-FDG PET(-CT) for detecting residual disease after neoadjuvant chemoradiotherapy (nCRT) for esophageal cancer.

SUMMARY OF BACKGROUND DATA

After nCRT, one-third of patients have a pathologically complete response in the resection specimen. Before an active surveillance strategy could be offered to these patients, clinically complete responders should be accurately identified.

METHODS

Embase, Medline, Cochrane, and Web-of-Science were searched until February 2018 for studies on accuracy of endoscopic biopsies, EUS, or PET(-CT) for detecting locoregional residual disease after nCRT for squamous cell- or adenocarcinoma. Pooled sensitivities and specificities were calculated using random-effect meta-analyses.

RESULTS

Forty-four studies were included for meta-analyses. For detecting residual disease at the primary tumor site, 12 studies evaluated endoscopic biopsies, 11 qualitative EUS, 14 qualitative PET, 8 quantitative PET using maximum standardized uptake value (SUVmax), and 7 quantitative PET using percentage reduction of SUVmax (%ΔSUVmax). Pooled sensitivities and specificities were 33% and 95% for endoscopic biopsies, 96% and 8% for qualitative EUS, 74% and 52% for qualitative PET, 69% and 72% for PET-SUVmax, and 73% and 63% for PET-%ΔSUVmax. For detecting residual nodal disease, 11 studies evaluated qualitative EUS with a pooled sensitivity and specificity of 68% and 57%, respectively. In subgroup analyses, sensitivity of PET-%ΔSUVmax and EUS for nodal disease was higher in squamous cell carcinoma than adenocarcinoma.

CONCLUSIONS

Current literature suggests insufficient accuracy of endoscopic biopsies, EUS, and 18F-FDG PET(-CT) as single modalities for detecting residual disease after nCRT for esophageal cancer.

Using positron-emission tomography-computed tomography for predicting radiotherapy-induced tumor regression in carcinoma esophagus in an Indian population

Carcinoma esophagus is a common malignancy of the Indian subcontinent. The role of positron-emission tomography–computed tomography (PET-CT) in the assessment of response to radiotherapy has been widely studied and accepted. However, its precise use as a predictive tool for actual histopathological response to radiotherapy needs further evaluation, especially in an Indian population. The aim of this study was to identify a quantum of metabolic response on PET-CT that can also predict for a good pathological response. Forty-four patients of carcinoma esophagus treated with neoadjuvant chemoradiotherapy followed by surgery were included in the study. All patients underwent a PET-CT before starting treatment as well as at 4–6 weeks after completion of radiotherapy. The percentage change in pre and posttreatment maximum standardized uptake value (SUV_max) value (ΔSUV%) of the primary tumor was correlated against histopathological tumor regression grade (TRG) as per the Mandard's system. Seventy-five percent of the patients with a significant metabolic response, i.e., a ΔSUV% of 60% or more, also had a good pathological response to treatment. Thus, by considering a ΔSUV% of 60%, we could predict for a good pathological response (TRG of 1 or 2) to chemoradiotherapy in our patient set with a sensitivity of 95.45% and a specificity of 72.72%.

18F FDG-PET/CT evaluation of histological response after neoadjuvant treatment in patients with cancer of the esophagus or gastroesophageal junction

BACKGROUND

In most parts of the world, curatively intended treatment for esophageal cancer includes neoadjuvant therapy, either with chemoradiotherapy or chemotherapy alone, followed by esophagectomy. Currently 18F-FDG positron emission tomography/computed tomography (PET/CT) is used for preoperative disease staging, but is not well established in the evaluation of neoadjuvant treatment.

PURPOSE

To evaluate changes in PET parameters in relation to the histological primary tumor response in the surgical specimen in patients randomized to neoadjuvant chemoradiotherapy or chemotherapy.

MATERIAL AND METHODS

Patients were randomized between either neoadjuvant chemotherapy or chemoradiotherapy followed by esophagectomy.18F-FDG PET/CT exams were conducted at baseline and following neoadjuvant treatment. Standardized uptake ratio (SUR) values were measured in the primary tumor and compared as regards histological responders and non-responders as well as different treatment arms.

RESULTS

Seventy-nine patients were enrolled and 51 were available for analysis. A significant rate of SUR reduction was observed ( P = 0.02) in the primary tumor in histological responders compared to non-responders. Changes in SUR were significantly greater in responders following chemoradiotherapy ( P = 0.02), but not following chemotherapy alone ( P = 0.49). There was no statistically significant difference in SUR in patients with a complete histological response compared to those with a subtotal response.

CONCLUSION

Our results are similar to those of previous studies and show that changes in the rate of SUR can be used reliably to differentiate histological responders from non-responders after neoadjuvant treatment with either chemoradiotherapy or chemotherapy. Limitations of current PET technology are likely to restrict the possibility of accurately ruling out limited residual disease.

PET/Computed Tomography Scanning and Precision Medicine: Esophageal Cancer

Esophageal cancer commonly has a poor prognosis, which requires an accurate diagnosis and early treatment to improve outcome. Other modalities for staging, such as endoscopic ultrasound imaging and computed tomography (CT) scans, have a role in diagnosis and staging. However, PET with fluorine-18 fluoro-2-deoxy-d-glucose/CT (FDG PET/CT) scanning allows for improved detection of distant metastatic disease and can help to prevent unnecessary interventions that would increase morbidity. FDG PET/CT scanning is valuable in the neoadjuvant chemotherapy assessment and predicting survival outcomes subsequent to surgery. FDG PET/CT scanning detects recurrent disease and metastases in follow-up.

The predictive value of 18F-FDG PET for pathological response of primary tumor in patients with esophageal cancer during or after neoadjuvant chemoradiotherapy: a meta-analysis

OBJECTIVE

We want to review the value of 18-fluoro-deoxy-glucose positron emission tomography for response prediction of primary tumor in patients with esophageal cancer during or after neoadjuvant chemoradiotherapy.

METHODS

Studies were searched in Pubmed, Embase and Cochrane Library with specific search strategy. The published articles were included according to the criteria established in advance. The included studies were divided into two groups according to the time of the repeat positron emission tomography: during (Group A) or after neoadjuvant chemoradiotherapy (Group B). The studies that performed the repeat positron emission tomography after neoadjuvant chemoradiotherapy were graded Quality Assessment of Diagnostic Accuracy Studies. The pooled sensitivity, specificity and diagnostic odds ratio were obtained for both groups on the basis of no-existing of threshold effect.

RESULTS

Fifteen studies were included in the present study. The threshold effect did not exist in both groups. The pooled sensitivity, specificity and diagnostic odds ratio were 85%, 59%, 6.82 with 95% confidence interval 76-91%, 48-69%, 2.25-20.72 in Group A. The equivalent values were 67%, 69%, 6.34 with 95% confidence interval 60-73%, 63-74%, 2.08-19.34 in Group B. The pooled sensitivity was 90% in four studies that enrolled patients with esophageal squamous cell carcinoma merely in Group B.

CONCLUSIONS

According to the present data, positron emission tomography should not be used routinely to guide treatment strategy in esophageal cancer patients. We speculated that positron emission tomography could be used as a tool to predict treatment response after neoadjuvant chemoradiotherapy in patients with esophageal squamous cell carcinoma.

Utility of 18F-FDG PET for Predicting Histopathologic Response in Esophageal Carcinoma following Chemoradiation

INTRODUCTION

For patients with esophageal cancer undergoing neoadjuvant chemoradiation (CRT) followed by surgical resection, complete histopathologic response (pCR) is associated with favorable overall survival (OS). The aim of this study was to evaluate the correlation between ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG PET) response to neoadjuvant CRT and pCR.

METHODS

Maximum standardized uptake values and standardized uptake ratios (SURs) were measured before and after CRT. SUR was normalized to liver uptake and mediastinal blood pool uptake. FDG PET complete response was defined as metabolic activity normalization to hepatic and blood pool activity. The correlation between FDG PET parameters and pCR was examined through logistic regression analyses.

RESULTS

In total, 193 patients were monitored for a median of 3.6 years after initiation of CRT. Most tumors were adenocarcinoma (85%) and stage T3 (75%). Complete FDG PET response and pCR occurred in 27% and 34% of patients, respectively. Histologic findings, chemotherapy type, tumor stage, and radiation dose were not significantly associated with complete radiographic response. The rates of pCR in patients with and without radiographic complete response were 42% and 31% (p = 0.17), respectively. No predictive correlation was found between pCR and change in maximum standardized uptake value (p = 0.25), in SUR normalized to blood pool uptake (p = 0.20), or in SUR normalized to liver uptake (p = 0.15). The 5-year OS rate was 46% for patients with a complete FDG PET response versus 44% without a complete response (p = 0.78). The 5-year OS rate of patients who achieved pCR was 49% versus 43% for patients with residual tumor (p = 0.04).

CONCLUSION

For patients with esophageal cancer who received neoadjuvant chemoradiation, pretreatment and posttreatment FDG PET parameters did not correlate with pCR or OS.

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.

[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.

Complete metabolic response is not uniformly predictive of complete pathologic response after induction therapy for esophageal cancer

BACKGROUND

Positron emission tomography scanning is used to assess response to induction therapy after treatment of esophageal cancer. A decrease in standardized uptake value has been correlated with response to therapy, with a standardized uptake value of zero often assumed to indicate complete absence of disease. We hypothesize that a significant number of patients may have residual esophageal cancer despite complete metabolic response (CMR).

METHODS

A prospective database was reviewed for esophageal cancer patients receiving induction therapy followed by esophagectomy on whom both preinduction and postinduction positron emission tomography scans were obtained. Patients with a postinduction SUV of 0 (or "no uptake") were categorized as complete metabolic responders. Survival was calculated by the Kaplan-Meier statistic.

RESULTS

Among 120 patients, 32 (27%) had postinduction CMR after chemotherapy (21 of 81, 26%) or chemoradiation (11 of 39, 28%). At surgery, 19 patients (59%) with CMR had residual disease, including 12 (38%) with nodal metastases. Even among patients with a negative postinduction biopsy, 4 of 10 (40%) had residual disease. Final pathologic stages of patients with CMR were yp0 (complete pathologic response) in 13 (41%), ypI in 4 (12%), ypII in 9 (28%), and ypIII in 6 (19%). Three-year survival was 83% in the CMR group versus 41% in the remainder of the cohort (p = 0.02).

CONCLUSIONS

A CMR on postinduction positron emission tomography scan predicts but should not be assumed to be synonymous with complete pathologic response in esophageal cancer patients. The presence of residual disease should be strongly considered despite CMR and negative biopsy in patients receiving induction therapy.

Opportunities and pitfalls of cancer imaging in clinical trials

Cancer treatment strategies have changed considerably over the past two decades, with increasing emphasis on cancer-specific biological therapies. This situation has led to the incorporation of biomarkers, including those obtained by medical imaging, into trial designs to better understand mechanisms of action and, hopefully, to provide early evidence of treatment efficacy at a molecular or physiological level. Unlike blood tests and tissue samples, an imaging biomarker allows assessment of treatment in the whole tumor, in all tumors in the body, and at multiple time points. This situation has increased the complexity of clinical trials, as each imaging modality has issues related to cost, ease of use, patient compatibility, data analysis, and interpretation. This article reviews strengths and limitations of the current imaging methods available in clinical cancer trials, including MRI, CT, PET, and ultrasonography. The information gained by each test, and the difficulties in acquiring the data and interpreting it are also discussed in order to help researchers plan imaging in clinical trials and interpret data from such studies.

Prediction of tumor response to neoadjuvant therapy in patients with esophageal cancer with use of 18F FDG PET: a systematic review

PURPOSE

To systematically review the accuracy of fluorine 18 ((18)F) fluorodeoxyglucose (FDG) positron emission tomography (PET) in the prediction of tumor response to neoadjuvant therapy in patients with esophageal cancer.

MATERIALS AND METHODS

The MEDLINE and EMBASE databases were systematically searched for relevant studies. Methodologic quality of the included studies was assessed. Sensitivities and specificities of (18)F FDG PET in individual studies were calculated and underwent meta-analysis with a random effects model. A summary receiver operating characteristic curve (sROC) was constructed with the Moses-Shapiro-Littenberg method. A chi(2) test was performed to test for heterogeneity (defined as P < .10). Potential sources for heterogeneity were explored by assessing whether certain covariates significantly (P < .05) influenced the relative diagnostic odds ratio.

RESULTS

Twenty reports, comprising a total of 849 patients with esophageal cancer, were included. Overall, the studies were of moderate methodologic quality. Sensitivity and specificity of (18)F FDG PET ranged from 33% to 100% and from 30% to 100%, respectively, with pooled estimates of 67% (95% confidence interval: 62%, 72%) and 68% (95% confidence interval: 64%, 73%), respectively. The area under the sROC curve was 0.7815. There was significant heterogeneity in both the sensitivity and specificity of the included studies (P < .0001). Spearman rho between the logit of sensitivity and the logit of 1-specificity was 0.086 (P = .719), which suggested that there was no threshold effect. Studies performed outside of the United States and studies of higher methodologic quality yielded significantly higher overall accuracy.

CONCLUSION

On the basis of current evidence, (18)F FDG PET should not yet be used in routine clinical practice to guide neoadjuvant therapy decisions in patients with esophageal cancer.

SUPPLEMENTAL MATERIAL

http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.09091324/-/DC1.