Interim Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography to Predict Pathologic Response to Preoperative Chemoradiotherapy and Prognosis in Patients With Locally Advanced Rectal Cancer

Case report: Efficacy of immunotherapy as conversion therapy in dMMR/MSI-H colorectal cancer: a case series and review of the literature

Immunotherapy has demonstrated a role in the therapeutic landscape of a small subset of patients with colorectal carcinoma (CRC) that harbor a microsatellite instability (MSI-H) status due to a deficient DNA mismatch repair (dMMR) system. The remarkable responses to immune checkpoint inhibitors (ICIs) are now being tested in the neoadjuvant setting in localized CRC, where the dMMR/MSI-H status can be found in up to 15% of patients, with remarkable results obtained in NICHE2 and 3 trials, among others. This case series aims to report our experience at a tertiary center and provide a comprehensive analysis of the possible questions and challenges to overcome if ICIs were established as standard of care in a neoadjuvant setting, as well as the potential role they may have as conversion therapy not only in locoregional advanced CRC but also in oligometastatic disease.

MRI VS. FDG-PET for diagnosis of response to neoadjuvant therapy in patients with locally advanced rectal cancer

Aim

In this study, we aimed to compare the diagnostic values of MRI and FDG-PET for the prediction of the response to neoadjuvant chemoradiotherapy (NACT) of patients with locally advanced Rectal cancer (RC).

Methods

Electronic databases, including PubMed, Embase, and the Cochrane library, were systematically searched through December 2021 for studies that investigated the diagnostic value of MRI and FDG-PET in the prediction of the response of patients with locally advanced RC to NACT. The quality of the included studies was assessed using QUADAS. The pooled sensitivity, specificity, positive and negative likelihood ratio (PLR and NLR), and the area under the ROC (AUC) of MRI and FDG-PET were calculated using a bivariate generalized linear mixed model, random-effects model, and hierarchical regression.

Results

A total number of 74 studies with recruited 4,105 locally advanced RC patients were included in this analysis. The pooled sensitivity, specificity, PLR, NLR, and AUC for MRI were 0.83 (95% CI: 0.77-0.88), 0.85 (95% CI: 0.79-0.89), 5.50 (95% CI: 4.11-7.35), 0.20 (95% CI: 0.14-0.27), and 0.91 (95% CI: 0.88-0.93), respectively. The summary sensitivity, specificity, PLR, NLR and AUC for FDG-PET were 0.81 (95% CI: 0.77-0.85), 0.75 (95% CI: 0.70-0.80), 3.29 (95% CI: 2.64-4.10), 0.25 (95% CI: 0.20-0.31), and 0.85 (95% CI: 0.82-0.88), respectively. Moreover, there were no significant differences between MRI and FDG-PET in sensitivity (P = 0.565), and NLR (P = 0.268), while the specificity (P = 0.006), PLR (P = 0.006), and AUC (P = 0.003) of MRI was higher than FDG-PET.

Conclusions

MRI might superior than FGD-PET for the prediction of the response of patients with locally advanced RC to NACT.

Predicting Factors of Complete Pathological Response in Locally Advanced Rectal Cancer

Background: Current treatment of choice for locally advanced rectal cancer is neoadjuvant chemoradiotherapy (neo-CRT) followed by surgical resection and adjuvant chemotherapy. Some patients may experience complete pathological response (cPR) after the neoadjuvant treatment. However, the predicting factors are still debated. Methods: In this registry-based retrospective cohort study, 258 patients with locally advanced rectal cancer were included. Patients were categorized into two groups with or without cPR. Logistic regression analysis was recruited to investigate the odds ratio for all independent variables, and those with significant results were included in multivariate regression analysis. Results: Achievement of cPR was 21.3%. The odds ratio of cPR was significantly lower when the tumor distance from the anal verge was>10 centimeters (OR=0.24, P=0.040). Also, the odds of cPR with N1 involvement in comparison with N0 involvement decreased for 0.41 (P=0.043). It was also true for patients with N2 involvement in comparison with N0 involvement (OR=0.31, P=0.031). Higher odds ratio of cPR was observed in patients who underwent surgery in>12 weeks after neo-CRT (OR=2.9, P=0.022). Furthermore, the odds of cPR decreased for 0.9 with increasing in carcinoembryonic antigen (CEA) level (P=0.044). Conclusion: Patients with rectal cancer in clinical stage II or lower, without the involvement of the lymphatic system at diagnosis, and with tumors located in the lower parts of the rectum, with lower levels of CEA, and longer duration between neo-CRT and surgery were more likely to achieve cPR after neo-CRT. With the current knowledge, the "wait and watch policy" is still debated and needs to be defined more precisely by upcoming studies.

Predicting pathological response to chemoradiotherapy for rectal cancer: a systematic review

Introduction: Pathological complete response (pCR) rates of approximately 20% following neoadjuvant long-course chemoradiotherapy for rectal cancer have given rise to non-operative or watch-and-wait (W&W) management. To improve outcomes there has been significant research into predictors of response. The goal is to optimize selection for W&W, avoid chemoradiotherapy in those who won't benefit and improve treatment to maximize the clinical complete response (cCR) rate and the number of patients who can be considered for W&W.Areas covered: A systematic review of articles published 2008-2018 and indexed in PubMed, Embase or Medline was performed to identify predictors of pathological response (including pCR and recognized tumor regression grades) to fluoropyrimidine-based chemoradiotherapy in patients who underwent total mesorectal excision for rectal cancer. Evidence for clinical, biomarker and radiological predictors is discussed as well as potential future directions.Expert opinion: Our current ability to predict the response to chemoradiotherapy for rectal cancer is very limited. cCR of 40% has been achieved with total neoadjuvant therapy. If neoadjuvant treatment for rectal cancer continues to improve it is possible that the treatment for rectal cancer may eventually parallel that of anal squamous cell carcinoma, with surgery reserved for the minority of patients who don't respond to chemoradiotherapy.

Clinical application and research advancement of positron emission tomography/computed tomography in colorectal cancer

Colorectal cancer is one of the most common malignant tumors of the digestive system. Early diagnosis and accurate staging and restaging of tumors are the preconditions for standardized treatment of colorectal cancer, which is conducive to the selection of treatment options and the evaluation of prognosis, as well as the improvement of patients' quality of life. With the popularization of fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT), its value in the diagnosis, staging and restaging, treatment decision-making, and efficacy and prognosis assessment of colorectal cancer is becoming increasingly important. This review briefly introduces the application and advancement of PET/CT in the diagnosis and treatment of colorectal cancer, in the hope that clinicians can have a more comprehensive understanding of the significance of PET/CT in the diagnosis and treatment of colorectal cancer.

Is interim 18F-fluoride PET/CT a predictor of outcomes after radium-223 therapy?

Objective

To determine whether an interim ¹⁸F-fluoride positron-emission tomography/computed tomography (PET/CT) study performed after the third cycle of radium-223 dichloride (²²³RaCl₂) therapy is able to identify patients that will not respond to treatment.

Materials and Methods

We retrospectively reviewed 34 histologically confirmed cases of hormone-refractory prostate cancer with bone metastasis in patients submitted to ²²³RaCl₂ therapy. All of the patients underwent baseline and interim ¹⁸F-fluoride PET/CT studies. The interim study was performed immediately prior to the fourth cycle of ²²³RaCl₂. The skeletal tumor burden-expressed as the total lesion fluoride uptake above a maximum standardized uptake value of 10 (TLF₁₀)-was calculated for the baseline and the interim studies. The percent change in TLF₁₀ between the baseline and interim studies (%TFL₁₀) was calculated as follows: %TFL₁₀ = interim TLF₁₀ - baseline TLF₁₀ / baseline TLF₁₀. End points were overall survival, progression-free survival, and skeletal-related events.

Results

The mean age of the patients was 72.4 ± 10.2 years (range, 43.3-88.8 years). The %TLF₁₀ was not able to predict overall survival (p = 0.6320; hazard ratio [HR] = 0.753; 95% confidence interval [CI]: 0.236-2.401), progression-free survival (p = 0.5908; HR = 1.248; 95% CI: 0.557-2.797) nor time to a bone event (p = 0.5114; HR = 1.588; 95% CI: 0.399-6.312).

Conclusion

The skeletal tumor burden on an interim ¹⁸F-fluoride PET/CT, performed after three cycles of ²²³RaCl₂, is not able to predict overall survival, progression-free survival, or time to bone event, and should not be performed to monitor response at this time.

Prognostic factors in breast cancer patients evaluated by positron-emission tomography/computed tomography before neoadjuvant chemotherapy

Neoadjuvant chemotherapy (NAC) is a significant modality in breast cancer therapy. We sought to characterize prognostic factors in patients scheduled for NAC who had a pretreatment positron-emission tomography paired with diagnostic quality contrast-enhanced computed tomography (CT) (positron-emission tomography/CT [PET/CT]). A total of 118 breast cancer patients were analyzed through chart review who underwent pretreatment PET/CT imaging and received NAC from 2008 to 2014. We collected information on molecular markers, PET/CT, pathologic complete response (pCR), survival, and disease status. Pretreatment standard uptake value (SUV) max of the primary breast tumor showed no relationship to pCR; however, there was a statistically significant relationship with relapse-free survival (RFS) using univariate cox regression (P = 0.03, odds ratio (OR) = 1.06 [1.01-1.12]) with comparable findings observed with overall survival (OS). Multivariate analysis revealed SUV max to be significantly correlated with shortened OS (P = 0.022, OR = 1.08 [1.01-1.16]), with a similar trend reported for RFS. By pathological subtype, this correlation was the strongest within hormone receptor (HR+)/human epidermal growth factor receptor 2 (HER2-) tumors. In addition, Kaplan-Meier estimates demonstrated a significant difference between the RFS of triple-negative tumors and HER2 positive tumors (P = 0.001). Interestingly, within this cohort, multivariate Cox regression analysis showed HER2 positivity to be associated with favorable outcome (P = 0.04, HR = 0.22 [0.05-0.94]). These findings demonstrate a significant association between SUV max of HR+/HER2-- tumors and relapse-free and OS. Furthermore, highlighted here is the favorable survival in the once classically aggressive HER2+ breast cancer subgroup.

Junior E, Machado AM, Mamede M. Individualized threshold for tumor segmentation in 18F-FDG PET/CT imaging: The key for response evaluation of neoadjuvant chemoradiation therapy in patients with rectal cancer?

Summary Introduction: The standard treatment for locally advanced rectal cancer (RC) consists of neoadjuvant chemoradiation followed by radical surgery. Regardless the extensive use of SUVmax in 18F-FDG PET tumor uptake as representation of tumor glycolytic consumption, there is a trend to apply metabolic volume instead. Thus, the aim of the present study was to evaluate a noninvasive method for tumor segmentation using the 18F-FDG PET imaging in order to predict response to neoadjuvant chemoradiation therapy in patients with rectal cancer. Method: The sample consisted of stage II and III rectal cancer patients undergoing 18F-FDG PET/CT examination before and eight weeks after neoadjuvant therapy. An individualized tumor segmentation methodology was applied to generate tumor volumes (SUV2SD) and compare with standard SUVmax and fixed threshold (SUV40%, SUV50% and SUV60%) pre- and post-therapy. Therapeutic response was assessed in the resected specimens using Dworak's protocol recommendations. Several variables were generated and compared with the histopathological results. Results: Seventeen (17) patients were included and analyzed. Significant differences were observed between responders (Dworak 3 and 4) and non-responders for SUVmax-2 (p<0.01), SUV2SD-2 (p<0.05), SUV40%-2 (p<0.05), SUV50%-2 (p<0.05) and SUV60%-2 (p<0.05). ROC analyses showed significant areas under the curve (p<0.01) for the proposed methodology with sensitivity and specificity varying from 60% to 83% and 73% to 82%, respectively. Conclusion: The present study confirmed the predictive power of the variables using a noninvasive individualized methodology for tumor segmentation based on 18F-FDG PET/CT imaging for response evaluation in patients with rectal cancer after neoadjuvant chemoradiation therapy.