Use of positron emission tomography scan response to guide treatment change for locally advanced gastric cancer: the Memorial Sloan Kettering Cancer Center experience

Perioperative versus total neoadjuvant chemotherapy in gastric cancer

Background

Perioperative chemotherapy is standard of care management for locally advanced gastric cancer (GC), but a substantial proportion of patients do not complete adjuvant therapy due to postoperative complications and prolonged recovery. Administration of all chemotherapy prior to surgery in the form of total neoadjuvant therapy (TNT) may optimize complete delivery of systemic therapy.

Methods

We performed a retrospective review of GC patients who had surgery at Memorial Sloan Kettering Cancer Center (MSKCC) from May 2014 to June 2020.

Results

One hundred and forty-nine patients were identified; 121 patients received perioperative chemotherapy and 28 patients received TNT. TNT was chosen if patients had interim radiographic and/or clinical response to treatment. Baseline characteristics were well-balanced between the two group except for chemotherapy regimen; more TNT patients received FLOT compared to the perioperative group (79% vs. 31%). There was no difference in the proportion of patients who completed all planned cycles, but TNT patients received a higher proportion of cycles containing all chemotherapy drugs (93% vs. 74%, P<0.001). Twenty-nine patients (24%) in the perioperative group did not receive intended adjuvant therapy. There was no significant difference in hospital length of stay or surgical morbidity. The overall distribution of pathologic stage was similar between the two groups. Fourteen percent of TNT patients and 5.8% of perioperative patients achieved a pathologic complete response (P=0.6). There was no significant difference in recurrence free survival (RFS) or overall survival (OS) between the TNT and perioperative groups [24-month OS rate 77% vs. 85%, HR 1.69 (95% CI: 0.80-3.56)].

Conclusions

Our study was limited by a small TNT sample size and biases inherent to a retrospective analysis. TNT appears to be feasible in a select population, without any increase in surgical morbidity.

Approach to Resectable Gastric Cancer: Evolving Paradigm of Neoadjuvant and Adjuvant Treatment

OPINION STATEMENT

Recent therapeutic advances have prolonged survival in patients with metastatic gastric cancer, though the prognosis for patients with locally advanced resectable gastric cancer remains poor. Long-term survival after resection of locally advanced gastric adenocarcinoma is dependent on early eradication of micrometastatic disease and optimal surgical resection. Preoperative therapy with a docetaxel-containing three-drug regimen has recently been shown to be superior to an anthracycline-containing three-drug regimen or two-drug therapy with a fluoropyrimidine and platinum. Chemoradiation is not essential and is reserved for patients with suboptimal resection. Emerging research strategies include introduction of pre- and postoperative checkpoint blockade and biomarker-directed therapy.

Variants and Pitfalls in PET/CT Imaging of Gastrointestinal Cancers

In the past two decades, PET/CT has become an essential modality in oncology increasingly used in the management of gastrointestinal (GI) cancers. Most PET/CT tracers used in clinical practice show some degree of GI uptake. This uptake is quite variable and knowledge of common patterns of biodistribution of various radiotracers is helpful in clinical practice. 18F-Fluoro-Deoxy-Glucose (FDG) is the most commonly used radiotracer and has quite a variable uptake within the bowel. 68Ga-Prostate specific membrane antigen (PSMA) shows intense uptake within the proximal small bowel loops. 11C-methyl-L-methionine (MET) shows high accumulation within the bowels, which makes it difficult to assess bowel or pelvic diseases. One must also be aware of technical artifacts causing difficulties in interpretations, such as high attenuation oral contrast material within the bowel lumen or misregistration artifact due to patient movements. It is imperative to know the common variants and benign diseases that can mimic malignant pathologies. Intense FDG uptake within the esophagus and stomach may be a normal variant or may be associated with benign conditions such as esophagitis, reflux disease, or gastritis. Metformin can cause diffuse intense uptake throughout the bowel loops. Intense physiologic uptake can also be seen within the anal canal. Segmental bowel uptake can be seen in inflammatory bowel disease, radiation, or medication induced enteritis/colitis or infection. Diagnosis of appendicitis or diverticular disease requires CT correlation, as normal appendix or diverticulum can show intense uptake. Certain malignant pathologies are known to have only low FDG uptake, such as early-stage esophageal adenocarcinoma, mucinous tumors, indolent lymphomas, and multicystic mesotheliomas. Response assessment, particularly in the neoadjuvant setting, can be limited by post-treatment inflammatory changes. Post-operative complications such as abscess or fistula formation can also show intense uptake and may obscure underlying malignant pathology. In the absence of clinical suspicion or rising tumor marker, the role of FDG PET/CT in routine surveillance of patients with GI malignancy is not clear.

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.

Prospective evaluation of metabolic intratumoral heterogeneity in patients with advanced gastric cancer receiving palliative chemotherapy

Although metabolic intratumoral heterogeneity (ITH) gives important value on treatment responses and prognoses, its association with treatment outcomes have not been reported in gastric cancer (GC). We aimed to evaluate temporal changes in metabolic ITH and the associations with treatment responses, progression-free survival (PFS), and overall survival (OS) in advanced GC patients. Eighty-five patients with unresectable, locally advanced, or metastatic GC were prospectively enrolled before the first-line palliative chemotherapy and underwent [¹⁸F]FDG PET at baseline (TP1) and the first response follow-up evaluation (TP2). Standardized uptake values (SUVs), volumetric parameters, and textural features were evaluated in primary gastric tumor at TP1 and TP2. Of 85 patients, 44 had partial response, 33 had stable disease, and 8 progressed. From TP1 to TP2, metabolic ITH was significantly reduced (P < 0.01), and the degree of the decrease was greater in responders than in non-responders (P < 0.01). Using multiple Cox regression analyses, a low SUV_max at TP2, a high kurtosis at TP2 and larger decreases in the coefficient of variance were associated with better PFS. A low SUV_max at TP2, larger decreases in the metabolic tumor volume and larger decreased in the energy were associated with better OS. Age older than 60 years and responders also showed better OS. An early reduction in metabolic ITH is useful to predict treatment outcomes in advanced GC patients.

Limited Usefulness of 18F-FDG PET/CT in Predicting Tumor Regression After Preoperative Chemotherapy for Noncardia Gastric Cancer: The Italian Research Group for Gastric Cancer (GIRCG) Experience

BACKGROUND

The present study aimed to better define the usefulness of F-FDG PET/CT in predicting pathological tumor response (PTR) and survival in patients with noncardia gastric cancer treated with preoperative chemotherapy.

METHODS

Seventy-one patients were recruited in 6 Italian centers. The SUV of F-FDG PET/CT was measured at baseline and after treatment, and the difference (dSUV) was computed. The association between PET indexes and PTR, assessed by the Becker score, was evaluated by nonparametric regression. The discriminant power of PET indexes with respect to the absence of PTR (Becker 2/3) was studied by receiver operating characteristic (ROC) curve and synthesized by the area under the curve (ROC-AUC).

RESULTS

dSUV allowed to partially discriminate between absence/presence of PTR, when expressed as either absolute value (ROC-AUC, 0.73; 95% confidence interval, 0.59-0.87) or percentage (ROC-AUC, 0.74; 95% confidence interval, 0.59-0.89). However, only extreme values of percent dSUV were really informative. All 7 patients whose F-FDG uptake had increased despite preoperative treatment showed no tumor regression at pathologic examination. Seven of the 10 patients whose metabolic response had been 70% or greater had complete or nearly complete pathologic tumor regression (Becker score 1a or 1b). The metabolic response of the remaining 54 patients, which ranged between 0% and 70%, did not permit to reliably forecast pathologic tumor regression. Survival significantly decreased with increasing Becker score but was unaffected by metabolic response.

CONCLUSIONS

The present study suggests that F-FDG PET/CT has limited usefulness in predicting cancer regression. The lack of metabolic response in serial measurements indicates the probable ineffectiveness of preoperative treatment.

The Utility of PET/Computed Tomography for Radiation Oncology Planning, Surveillance, and Prognosis Prediction of Gastrointestinal Tumors

At present, the strongest evidence for the use of PET/computed tomography (CT) in gastrointestinal (GI) malignancies is to rule out distant metastatic disease at diagnosis, radiation treatment planning for anal malignancies, and disease recurrence monitoring in colorectal and anal malignancies. Use of PET/CT for GI malignancies continues to evolve over time, with new studies evaluating prognostic abilities of PET/CT and with increasing sensitivity and spatial resolution of more modern PET/CT scanners. The authors encourage future applications and prospective evaluation of the use of PET/CT in the staging, prognostication, and recurrence prediction for GI malignancies.

Comparing PET/MRI with PET/CT for Pretreatment Staging of Gastric Cancer

18F-FDG PET/MRI has been applied to the diagnosis and preoperative staging in various tumor types; however, reports using PET/MRI in gastric cancer are rare because of motion artifacts. We investigated the value of PET/MRI for preoperative staging compared with PET/CT in gastric cancer (GC). Thirty patients with confirmed GC underwent PET/CT and PET/MRI. TNM staging for each patient was determined from the PET/MRI and PET/CT images. The diagnostic performance of PET/MRI and PET/CT was calculated compared with the pathologic TNM stage. The two methods were compared using statistical analyses. The accuracy for T staging between PET/MRI and PET/CT was 76.9% vs. 57.7%, respectively. In T₁ and T_4a staging, the sensitivity and specificity for PET/MRI vs. PET/CT was 1.0 vs. 0.6 and 1.0 vs. 0.8, respectively. The area under the curve (AUC) for PET/MRI vs. PET/CT was 1.00 vs. 0.78 in the T₁ stage, 0.73 vs. 0.66 in the T₂ stage, 0.72 vs. 0.57 in the T₃ stage, and 0.86 vs. 0.83 in the T₄ stage. The accuracy for N staging of PET/MRI vs. PET/CT was 53.9% vs. 34.0%, and that for N₀ vs. N₊ was 85.0% vs. 77.0%. The sensitivity for PET/MRI in N3 staging was 0.67 and 0 for PET/CT. There was a statistically significant difference in the AUC for N₁ staging (PET/MRI vs. PET/CT, 0.63 vs. 0.53, p = 0.03). SUVmax/ADC positively correlated with tumor volume and Ki-67. PET/MRI performs more accurately in TNM staging compared with PET/CT and is optimal for accurate N staging. SUVmax/ADC has positive correlations with tumor volume and Ki-67.

Prognostic Value of Nodal Response After Preoperative Treatment of Gastric Adenocarcinoma

Background: Pathologically positive lymph nodes (ypN+) after preoperative chemotherapy are associated with poor survival in patients with gastric cancer. Little is known about the association between response to preoperative therapy and the benefit of postoperative therapy. Methods: This retrospective cohort study of the National Cancer Database included patients with clinically node-positive (cN+) gastric cancer treated with preoperative therapy followed by surgery (2006-2014). Preoperative treatment modality was categorized as the inclusion of radiation therapy (RT) or chemotherapy alone. Pretreatment clinical and pathologic stages were used to determine pathologic treatment response rates. The association between overall risk of death and preoperative treatment, disease response, and adjuvant therapy use was evaluated using multivariable Cox regression. Results: Preoperative RT was used in 53.6% of 1,976 patients with cN+ gastric cancer, (74.3% cardia and 10.1% noncardia). The nodal response rate was 38.9% and was higher with RT than with chemotherapy alone (cardia, 46.0% vs 29.1%; P<.001; noncardia, 43.8% vs 31.9%; P=.06). Preoperative RT was associated with an approximate 2-fold increase in the odds of pathologic response compared with chemotherapy. Overall, use of adjuvant therapy was not associated with a decreased risk of death. A primary tumor response with residual nodal disease was not associated with survival (hazard ratio [HR], 1.03; 95% CI, 0.66-1.60). However, a nodal response with residual primary disease was significantly associated with survival (HR, 0.54; 95% CI, 0.44-0.65). Conclusions: More than one-third of node-positive gastric cancers showed pathologic nodal response with preoperative treatment. RT is associated with a higher response than chemotherapy. Patients with ypN+ disease have worse survival, regardless of whether they receive postoperative therapy. Future gastric cancer trials should evaluate the role of preoperative RT and individualize postoperative therapy use.

18 F-Fluorodeoxyglucose positron emission tomography can be used to determine the indication for endoscopic resection of superficial esophageal cancer

¹⁸F‐Fluorodeoxyglucose positron emission tomography (FDG‐PET) is a useful imaging modality that reflects the tumor activity. However, FDG‐PET is mainly used for advanced cancer, not superficial cancer. In this study, we investigated the relationship between the superficial tumor depth of esophageal cancer and the FDG uptake to determine the indications for endoscopic resection (ER). From 2009 to 2017, 444 patients with esophageal cancer underwent esophagectomy or endoscopic submucosal dissection (ESD), and 195 patients were pathologically diagnosed with superficial cancer. Among them, 146 patients were examined by FDG‐PET before esophagectomy or ESD. In these 146 patients, the relationship between the pathological tumor depth and FDG uptake was analyzed. The mean maximum standardized uptake value in pT1a‐EP/LPM tumors was 1.362 ± 0.890, that in pT1a‐MM/pT1b‐SM1 tumors was 2.453 ± 1.872, and that in pT1b‐SM2/SM3 tumors was 4.265 ± 3.233 (P < .0001). Among 51 pT1a‐EP/LPM tumors, 10 (19.6%) showed positive detection of FDG. For pT1a‐MM/pT1b‐SM1 and pT1b‐SM2/SM3 tumors, the detection rate was 52.9% (18/34) and 82.0% (50/61), respectively. The detection rate of pT1a‐EP/LPM was significantly lower than in the other two groups (P < .0001). Among 10 FDG‐PET‐positive lesions, only 1 had no apparent reason for PET positivity; however, 9 of 10 had a suitable reason for detectability by PET and inadequacy for ER. Negative detection of superficial esophageal squamous cell carcinoma by FDG‐PET is useful to determine the indication for ER when the tumor depth cannot be diagnosed even after performing magnifying endoscopy with narrow band imaging and endoscopic ultrasonography. When FDG uptake is recognized, a therapeutic modality other than ER should be considered.

[18F]Fluorodeoxyglucose PET/CT and prediction of histopathological response to neoadjuvant chemotherapy for adenocarcinoma of the oesophagus and oesophagogastric junction

Background

The aim of this prospective study was to assess whether [18F]fluorodeoxyglucose PET can be used to predict histopathological response early in the course of neoadjuvant chemotherapy in patients with adenocarcinoma of the oesophagus and oesophagogastric junction.

Methods

Following the PET response criteria in solid tumours (PERCIST 1.0) as a standardized method for semiquantitative assessment of metabolic response, FDG-PET/CT was performed before (PET1) and after (PET2) initiation of the first cycle of chemotherapy. The relative changes in the peak standardized uptake value (ΔSUL) and total lesion glycolysis (ΔTLG) between PET1 and PET2 were correlated with histopathological response, defined as less than 50 per cent viable tumour cells in the resection specimen. A receiver operating characteristic (ROC) curve analysis was used to identify the optimal cut-off value with the highest accuracy of histopathological response prediction.

Results

PET2 was performed a median of 16 (range 12–22) days after the start of chemotherapy. Some 27 of 90 patients who underwent surgery had a histopathological response. There was no association between the median ΔSUL or median ΔTLG and the histopathological response. A post hoc analysis in 47 patients with PET2 performed 16 days or less after the start of chemotherapy showed that ΔTLG, but not ΔSUL, was associated with the histopathological response (P = 0·009). The optimal cut-off value of ΔTLG was 66 per cent or more.

Conclusion

FDG-PET/CT after the first cycle of chemotherapy does not predict histopathological response in patients with adenocarcinoma of the oesophagus and oesophagogastric junction.

Endoscopic Ultrasound as a Pretreatment Clinical Staging Tool for Gastric Cancer: Association with Pathology and Outcome

BACKGROUND

Endoscopic ultrasound (EUS) is a guideline-recommended diagnostic test to estimate pretreatment clinical stage in gastric cancer. The impact of EUS to discriminate long-term outcomes has not been established.

OBJECTIVES

The objectives of our study were to (1) evaluate the association between EUS and pathologic stage; (2) evaluate the ability of EUS to predict disease-specific survival (DSS); and (3) determine how neoadjuvant chemotherapy (NCT) affects these relationships.

METHODS

A prospective gastric cancer database at a tertiary care cancer center identified 734 patients who underwent curative intent resection. Patients were separated into EUS low-risk (T1-2, N0) and EUS high-risk (T3-4 Nany, or Tany N+) groups. Agreement statistics and 5-year DSS were estimated stratified by NCT.

RESULTS

Between 1987 and 2015, 68% (502/734) of patients were not treated with NCT. Among these patients, percentage agreement between EUS and pathology was moderate (individual T stage: 52%; N stage: 70%; risk group: 73%). EUS accurately estimated pathologic risk group in 73% (365/502) of patients, whereas it overestimated pathologic risk group in 19% (93/502) of patients and underestimated risk in 8% (41/502) of patients. EUS in non-NCT staging was able to discriminate DSS for T stage (hazard ratio [HR] 5.07, p < 0.05), N stage (HR 3.58, p < 0.05), and risk group (HR 6.35, p < 0.05). Among patients treated with NCT, EUS was unable to discriminate DSS for T stage (HR 0.94, p > 0.05), N stage (HR 1.46, p > 0.05) and risk group (HR 0.50, p > 0.05).

CONCLUSIONS

Pretreatment clinical staging based on EUS alone could lead to over- or under treatment in 27% of patients and can discriminate DSS in NCT-naive patients. EUS should be used in the context of other validated clinical risk tools.

Serial imaging using [18F]Fluorodeoxyglucose positron emission tomography and histopathologic assessment in predicting survival in a population of surgically resectable distal oesophageal and gastric adenocarcinoma following neoadjuvant therapy

Background and objectives

We retrospectively evaluated the value of PET/CT in predicting survival and histopathological tumour-response in patients with distal oesophageal and gastric adenocarcinoma following neoadjuvant treatment.

Methods

Twenty-one patients with resectable distal oesophageal adenocarcinoma and 14 with gastric adenocarcinoma between January 2002 and December 2011, who had undergone serial PET before and after neoadjuvant therapy followed by surgery, were enrolled. Maximum standard uptake value (SUVmax) and metabolic tumour volume were measured and correlated with tumour regression grade and survival.

Results

Histopathological tumour response (PR) is a stronger predictor of overall and disease-free survival compared to metabolic response. ∆%SUVmax ≥70% was the only PET metric that predicted PR (82.4% sensitivity, 61.5% specificity, p = 0.047). Histopathological non-responders had a higher risk of death (HR 8.461, p = 0.001) and recurrence (HR 6.385, p = 0.002) and similarly in metabolic non-responders for death (HR 2.956, p = 0.063) and recurrence (HR 3.614, p = 0.028). Ordinalised ∆%SUVmax showed a predictive trend for OS and DFS, but failed to achieve statistical significance.

Conclusions

PR was a stronger predictor of survival than metabolic response. ∆%SUVmax ≥70% was the best biomarker on PET that predicted PR and survival in oesophageal and gastric adenocarcinoma. Ordinalisation of ∆%SUVmax was not helpful in predicting primary outcomes.