Development and progression of colorectal cancer based on follow-up analysis

Performance of the Asia-Pacific Colorectal Screening score in stratifying the risk of advanced colorectal neoplasia: A meta-analysis and systematic review

BACKGROUND AND AIM

This study systematically reviewed and meta-analyzed the performance of the Asia-Pacific Colorectal Screening (APCS) score and its incorporation with the fecal immunochemical test (FIT) in stratifying the risk of advanced colorectal neoplasia (ACN).

METHODS

We systematically searched for relevant articles in 12 electronic databases and registers on October 20, 2021, and updated the search to September 1, 2023. Random-effect models were used to obtain the pooled performance statistics of the APCS score for ACN risk.

RESULTS

From the 101 records screened, 13 eligible studies in the Asia-Pacific region involving 69 762 subjects who had undergone colonoscopy were enrolled. The pooled prevalences of ACN in the average-risk (AR) tier (APCS 0-1), moderate-risk (MR) tier (APCS 2-3), and high-risk (HR) tier (APCS ≥ 4) groups were 0.9%, 3.1%, and 8.1%, respectively. Compared with the combined AR-MR group, the HR group was significantly associated with a higher ACN risk (pooled diagnostic odds ratio: 2.84, 95% confidence interval [CI]: 2.35-3.45, P < 0.001). The APCS score showed a sensitivity of 0.42 (95% CI: 0.40-0.44) and a specificity of 0.86 (95% CI: 0.85-0.86) for predicting the ACN risk, with a weighted area under the curve of 0.642 (95% CI: 0.610-0.657). The combination of the APCS score and FIT substantially improved ACN risk identification, demonstrating pooled diagnostic odds ratios of 4.02 (95% CI: 2.50-6.49) in the AR-MR groups and 5.44 (95% CI: 1.89-15.63) in the MR-HR groups.

CONCLUSIONS

The APCS score could effectively stratify the ACN risk in the Asia-Pacific population. Incorporating FIT further improves its performance in identifying high-risk subjects who should be prioritized for colonoscopy screenings.

Long-term outcomes after endoscopic submucosal dissection for colorectal epithelial neoplasms in patients with severe comorbidities

Background and Aim

Long-term outcomes after endoscopic submucosal dissection (ESD) for colorectal epithelial neoplasms (CENs) in patients with severe comorbidities have not been clarified; the current study aimed to examine these long-term outcomes and compared them with those in patients with non-severe comorbidities.

Methods

We included 231 patients with CENs who underwent ESD between April 2005 and March 2023. Patients with comorbidities were categorized according to the American Society of Anesthesiologists Physical Status (ASA-PS). We conducted a propensity score-matched analysis and compared long-term outcomes of the two groups after ESD for CENs.

Results

Of the 156 patients enrolled in the study, 43 and 113 had severe (ASA-PS III) and non-severe (ASA-PS I/II) comorbidities, respectively. The 1:1 propensity score analysis matched 36 patients with severe comorbidities to 36 patients with non-severe comorbidities. After matching, there was no difference in the procedural outcomes of ESD between both groups. Regarding long-term outcomes, the 5-year overall survival rates after matching in the ASA-PS I/II and III groups were 100% and 73.5%, respectively, and patients in the ASA-PS III group exhibited significantly shorter overall survival than those in the ASA-PS I/II group (hazard ratio 7.209; 95% confidence interval 1.592-32.646; P = 0.010). No colorectal cancer-related deaths were noted in either group.

Conclusion

Overall survival after ESD for CENs was shorter in patients with severe comorbidities than in those with non-severe comorbidities. Clinicians should carefully determine whether the benefits of CEN resection with ESD outweigh the procedural risks in patients with severe comorbidities.

Overexpression of VSNL1 Enhances Cell Proliferation in Colorectal Carcinogenesis

INTRODUCTION

We have previously reported that overexpression of visinin-like protein 1 (VSNL1) is frequently observed in advanced colorectal adenocarcinomas and correlates with poorer prognosis. In this study, we determined the levels of VSNL1 expression in the earlier stages of colorectal tumors including adenomas and adenocarcinomas, and attempted to clarify the functional significance of VSNL1 overexpression in colorectal carcinogenesis.

METHODS

Levels of VSNL expression in colorectal tumor tissues were analyzed using immunohistochemistry. The effects of VSNL1 downregulation and overexpression on cell proliferation, resistance to apoptosis, and invasiveness were determined using two VSNL1-overexpressing colorectal cancer cell lines, CW-2 and HCT-116 and VSNL1 inducibly expressing SNU-C5, respectively. Gene expression signatures in VSNL1-downregulated CW-2 and HCT-116 were identified using transcriptome and gene set enrichment analyses.

RESULTS

VSNL1 expression was restricted to only a few crypt cells in the non-tumorous epithelium, whereas it became enhanced in adenomas and adenocarcinomas with the progression of tumorigenesis. Downregulation of VSNL1 in CW-2 and HCT-116 cells suppressed their proliferation through induction of apoptosis. Conversely, overexpression of VSNL1 in SNU-C5 cells enhanced resistance to anoikis. Transcriptome and gene set enrichment analyses revealed that downregulation of VSNL1 altered the expression level of the apoptosis-related gene set in CW-2 and HCT-116 cells.

CONCLUSION

VSNL1 plays a role in both the development and progression of colorectal tumors by enhancing cell viability.

Establishment of a large-scale patient-derived high-risk colorectal adenoma organoid biobank for high-throughput and high-content drug screening

BACKGROUND

Colorectal adenoma (CA), especially high-risk CA (HRCA), is a precancerous lesion with high prevalence and recurrence rate and accounts for about 90% incidence of sporadic colorectal cancer cases worldwide. Currently, recurrent CA can only be treated with repeated invasive polypectomies, while safe and promising pharmaceutical invention strategies are still missing due to the lack of reliable in vitro model for CA-related drug screening.

METHODS

We have established a large-scale patient-derived high-risk colorectal adenoma organoid (HRCA-PDO) biobank containing 37 PDO lines derived from 33 patients and then conducted a series of high-throughput and high-content HRCA drug screening.

RESULTS

We established the primary culture system with the non-WNT3a medium which highly improved the purity while maintained the viability of HRCA-PDOs. We also proved that the HRCA-PDOs replicated the histological features, cellular diversity, genetic mutations, and molecular characteristics of the primary adenomas. Especially, we identified the dysregulated stem genes including LGR5, c-Myc, and OLFM4 as the markers of adenoma, which are well preserved in HRCA-PDOs. Based on the HRCA-PDO biobank, a customized 139 compound library was applied for drug screening. Four drugs including metformin, BMS754807, panobinostat and AT9283 were screened out as potential hits with generally consistent inhibitory efficacy on HRCA-PDOs. As a representative, metformin was discovered to hinder HRCA-PDO growth in vitro and in vivo by restricting the stemness maintenance.

CONCLUSIONS

This study established a promising HRCA-PDO biobank and conducted the first high-throughput and high-content HRCA drug screening in order to shed light on the prevention of colorectal cancer.

Intraprocedure Artificial Intelligence Alert System for Colonoscopy Examination

Colonoscopy is a valuable tool for preventing and reducing the incidence and mortality of colorectal cancer. Although several computer-aided colorectal polyp detection and diagnosis systems have been proposed for clinical application, many remain susceptible to interference problems, including low image clarity, unevenness, and low accuracy for the analysis of dynamic images; these drawbacks affect the robustness and practicality of these systems. This study proposed an intraprocedure alert system for colonoscopy examination developed on the basis of deep learning. The proposed system features blurred image detection, foreign body detection, and polyp detection modules facilitated by convolutional neural networks. The training and validation datasets included high-quality images and low-quality images, including blurred images and those containing folds, fecal matter, and opaque water. For the detection of blurred images and images containing folds, fecal matter, and opaque water, the accuracy rate was 96.2%. Furthermore, the study results indicated a per-polyp detection accuracy of 100% when the system was applied to video images. The recall rates for high-quality image frames and polyp image frames were 95.7% and 92%, respectively. The overall alert accuracy rate and the false-positive rate of low quality for video images obtained through per-frame analysis were 95.3% and 0.18%, respectively. The proposed system can be used to alert colonoscopists to the need to slow their procedural speed or to perform flush or lumen inflation in cases where the colonoscope is being moved too rapidly, where fecal residue is present in the intestinal tract, or where the colon has been inadequately distended.

Negative Impact of COVID-19 Associated Health System Shutdown on Patients Diagnosed With Colorectal Cancer: A Retrospective Study From a Large Tertiary Center in Ontario, Canada

Background

In March 2020, a directive to halt all elective and non-urgent procedures was issued in Ontario, Canada because of COVID-19. The directive caused a temporary slowdown of screening programs including surveillance colonoscopies for colorectal cancer (CRC). Our goal was to determine if there was a difference in patient and tumour characteristics between CRC patients treated surgically prior to the COVID-19 directive compared to CRC patients treated after the slowdown.

Methods

CRC resections collected within the Champlain catchment area of eastern Ontario in the 6 months prior to COVID-19 (August 1, 2019-January 31, 2020) were compared to CRC resections collected in the 6 months post-COVID-19 slowdown (August 1, 2020-January 31, 2021). Clinical (e.g., gender, patient age, tumour site, and clinical presentation) and pathological (tumour size, tumour stage, nodal stage, and lymphovascular invasion) features were evaluated using chi-square tests, T-tests, and Mann-Whitney tests where appropriate.

Results

Three hundred and thirty-eight CRC specimens were identified (173 pre-COVID-19, 165 post-COVID-19 slowdown). CRC patients treated surgically post-COVID-19 slowdown had larger tumours (44 mm vs. 35 mm; P = 0.0048) and were more likely to have presented emergently (24% vs. 10%; P < 0.001). Although there was a trend towards higher tumour stage, nodal stage, and clinical stage, these differences did not reach statistical significance. Other demographic and pathologic variables including patient gender, age, and tumour site were similar between the two cohorts.

Interpretation

The COVID-19 slowdown resulted in a shift in the severity of disease experienced by CRC patients in Ontario. Pandemic planning in the future should consider the long-term consequences to cancer diagnosis and management.

COVID-19 Impact on Diagnosis and Staging of Colorectal Cancer: A Single Tertiary Canadian Oncology Center Experience

Background: Public health measures have imposed drastic reductions in cancer screening programs at the beginning of the COVID-19 pandemic, with an unknown impact on the diagnosis and staging of colorectal cancer (CRC). Methods: Newly diagnosed CRC cases at the Centre Hospitalier de l’Université de Montréal (CHUM) were divided into two groups according to the timeline: pre-pandemic (1 January 2018–12 March 2020), and pandemic (13 March 2020–30 June 2021) periods. Colonoscopy, surgery, and staging at diagnosis during the pandemic period were compared to the pre-pandemic period. Results: 254 CRC diagnoses were made during the pre-pandemic period in comparison to 125 during the pandemic period. Mean diagnosis rates were lower in the pandemic period (7.8 vs. 9.8 diagnoses/month, p = 0.048). Colonoscopy deadlines were less respected in the pandemic period (51.7% vs. 38.3%, p = 0.049). The rate of elective surgery did not differ (2.9 vs. 3.5 surgeries/month, p = 0.39) and mean delays were similar (58.6 vs. 60.4 days, p = 0.77). Stages at diagnosis did not differ (p = 0.17). Most of the delayed colonoscopies led to a stage 0 or I CRC (p = 0.2). Conclusion: In our center, the COVID-19 pandemic resulted in a decreased rate of CRC diagnosis and increased endoscopic delays without affecting the rate of advanced stage disease. Delays to surgery were quite similar once the CRC diagnosis was established.

The diagnostic accuracy of the faecal immunohistochemical test in identifying significant bowel disease in a symptomatic population

AIM

Provisional research on the faecal immunohistochemical test (FIT) for symptomatic colorectal patients has shown a high negative predictive value but has lacked long-term patient follow-up, raising the possibility of missed diagnoses of colorectal cancer (CRC). The aim of this work is to describe the long-term diagnostic accuracy of the FIT for CRC and significant bowel disease (SBD) in a symptomatic population in NHS Lanarkshire.

METHOD

From October 2016 to February 2019, all primary care referrals of symptomatic colorectal patients in NHS Lanarkshire were asked to provide a FIT. The baseline demographics, investigations and diagnoses for each patient were prospectively completed until February 2021. A FIT result of ≥10 μg haemoglobin (Hb)/g faeces was considered to be positive.

RESULTS

A total of 5250 patients were identified (median age 62 years; 46% male; median follow-up 31 months) with 65.1% (3418) being FIT negative. The SBD rate was 6.2% and the CRC rate was 2.9% (151). The SBD rate was significantly higher in the FIT-positive group (13.8% vs. 2.2%; p < 0.001) and 32.9% of patients with FIT ≥ 400 μg Hb/g had SBD. The sensitivity of FIT ≥ 10 μg Hb/g for CRC was 87.4% and for SBD it was 76.9%. Specificity was 66.6% and 66.7%, and the negative-predictive value was 99.4% and 97.7%, respectively. Sensitivity for CRC could theoretically be increased to 94.8% if FIT-negative patients were to undergo flexible sigmoidoscopy.

CONCLUSION

A FIT-only referral pathway for symptomatic colorectal patients will miss over 12% of cancers and over 23% of SBD. Theoretically, combining FIT-negative patients with flexible sigmoidoscopy increases the sensitivity for CRC. The FIT offers a mechanism for prioritizing patient access to investigations, particularly in resource-limited areas; however, further work to identify FIT-negative patients diagnosed with CRC is required.

Aspirin, ibuprofen, and reduced risk of advanced colorectal adenoma incidence and recurrence and colorectal cancer in the PLCO Cancer Screening Trial

BACKGROUND

Studying the differential impact of aspirin and other nonsteroidal anti-inflammatory drugs across the stages of colorectal neoplasia from early adenoma to cancer is critical for understanding the benefits of these widely used drugs.

METHODS

With 13 years of follow-up, the authors prospectively evaluated the association between aspirin and ibuprofen use and incident distal adenoma (1221 cases), recurrent adenoma (862 cases), and incident colorectal cancer (CRC; 2826 cases) among men and women in the population-based Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. With multivariable-adjusted models, odds ratio (ORs) and 95% confidence intervals (CIs) for adenoma incidence and recurrence and hazard ratios (HRs) and 95% CIs for incident CRC were determined.

RESULTS

The authors observed a significantly reduced risk of incident adenoma with ibuprofen use (≥30 vs <4 pills per month: OR, 0.76 [95% CI, 0.60-0.95]; Ptrend = .04), particularly advanced adenoma (OR, 0.48 [95% CI, 0.28-0.83]; Ptrend = .005). Among those with a previous adenoma detected through screening, aspirin use was associated with a decreased risk of advanced recurrent adenoma (≥30 vs <4 pills per month: OR, 0.56 [95% CI, 0.36-0.87]; Ptrend = 0.006). Both aspirin (HR, 0.88 [95% CI, 0.81-0.96]; Ptrend <.0001) and ibuprofen use (HR, 0.81 [95% CI, 0.70-0.93); Ptrend = 0.003) ≥30 versus <4 pills per month were significantly associated with reduced CRC risk.

CONCLUSIONS

In this large prospective study with long-term follow-up, a beneficial role for not only aspirin, but also ibuprofen, in preventing advanced adenoma and curbing progression to recurrence and cancer among older adults was observed.

The Role of Imaging in Health Screening: Overview, Rationale of Screening, and Screening Economics

Imaging screening examinations are growing in their indications and volume to identify conditions at an early, treatable stage. The Radiology Research Alliance's 'Role of Imaging in Health Screening' Task Force provides a review of imaging-based screening rationale, economics, and describes established guidelines by various organizations. Various imaging modalities can be employed in screening, and are often chosen based on the specific pathology and patient characteristics. Prevalent disease processes with identifiable progression patterns that benefit from early potentially curative interventions are ideal for screening. Two such examples include colonic precancerous polyp progression to adenocarcinoma in colon cancer formation and atypical ductal hyperplasia progression to ductal carcinoma in situ and invasive ductal carcinoma in breast cancer. Economic factors in imaging-based screening are reviewed, including in the context of value-based reimbursements. Global differences in screening are outlined, along with the role of various organizational guidelines, including the American Cancer Society, the US Preventive Services Task Force, and the American College of Radiology.

Clinicopathologic features and prognosis of synchronous and metachronous multiple primary colorectal cancer

PURPOSE

Multiple primary colorectal cancers (MPCCs) are different from solitary colorectal cancers in many aspects, which are not well studied. The aim of this study was to clarify the clinicopathological features and prognosis of MPCCs.

METHODS

The data of 64 patients with MPCCs out of 2300 patients with colorectal cancers (CRCs) from January 2009 to December 2017 were retrospectively analyzed. Stratified analysis was conducted based on subtypes and microsatellite status.

RESULTS

The overall incidence of MPCC was 2.8% and the median follow-up duration was 51.5 (range 1-120) months. Metachronous CRCs (MCRCs) are more likely to appear in the right colon (p < 0.05). However, no significant differences regarding age, sex, BMI, tumor size, smoking/drinking history, TNM stage, family history of cancer, and 5-year survival rate were observed between synchronous CRC (SCRC) and MCRC. Advanced TNM stage (III) and the presence of polyps were found to be independent poor prognostic factors for MPCCs. The prevalence of mismatch repair deficiency (dMMR) in MPCCs was 28.1%. Deficient MMR is more likely to appear in younger, lighter MPCC patients with polyps (p < 0.05). Of four mismatch repair proteins, MLH-1, MSH-2, MSH-6, and PMS-2 were negative in nine, nine, five, and nine patients, respectively. The 5-year survival rate did not differ significantly between MMR-proficient (pMMR) and dMMR groups (p = 0.752).

CONCLUSIONS

Synchronous CRC (SCRC) and MCRC might represent similar disease entities with different courses. Deficient MMR is more likely to appear in younger, lighter MPCC patients with polyps and it is an essential indicator for screening Lynch syndrome.

Personalized Indicator Thrombocytosis Shows Connection to Staging and Indicates Shorter Survival in Colorectal Cancer Patients with or without Type 2 Diabetes

Background: Pre- and postoperative thrombocytosis was reported to have significant effect on patient survival. However, the definition of thrombocytosis throughout the literature is not unified. Methods: A retrospective longitudinal observational study has been conducted with the inclusion of 150 colorectal cancer (CRC) patients and 100 control subjects. A new measure of platelet changes at an individual level, named personalized indicator thrombocytosis (PIT) was defined, including 4 anemia adjusted variants. Results: In concordance with the literature, PIT values of control subjects showed a slow decrease in platelet counts, while PIT values of CRC patients were significantly higher (p < 0.0001). More advanced staging (p < 0.0001) and both local (p ≤ 0.0094) and distant (p ≤ 0.0440) metastasis are associated with higher PIT values. Higher PIT values suggested shorter survival times (p < 0.0001). Compared to conventional, a PIT-based definition resulted in approximately 3-times more patients with thrombocytosis. 28% and 77% of the deceased patients had conventional- and PIT-based thrombocytosis, respectively. Conclusions: Compared to conventional thrombocytosis, as an individual metric, PIT values may indicate the condition of patients more precisely. Possible future applications of PIT may include its usage in therapy decision and early cancer detection; therefore, further investigations are recommended.

Early Detection and Recurrence of Colorectal Adenomas by Combination of Eight Cancer-Associated Biomarkers in Plasma

INTRODUCTION

Plasma levels of eight combined proteins have shown value as biomarkers for detection of colorectal cancer (CRC). However, their value in identifying colorectal adenoma needs further evaluation. The aim was to evaluate the eight proteins (AFP, CA19-9, CEA, CyFra21-1, Ferritin, Galectin-3, hs-CRP and TIMP-1) in detection of high-risk adenoma (HRA) and in prediction of recurrence of adenoma. Furthermore, the discrimination between HRA and low-risk adenoma (LRA) or CRC lesions was evaluated.

METHODS

The study included 4698 individuals undergoing diagnostic colonoscopy. Automated ELISA platforms were used in the determination of protein levels in samples collected just before colonoscopy.

RESULTS

Univariably, five proteins (AFP, CEA, CyFra21-1, hs-CRP and TIMP-1), respectively, significantly discriminated individuals with HRA from individuals with non-malignant findings. Multivariably, the combination of CEA and hs-CRP improved performance; AUC= 0.63 (sensitivity=0.19 at specificity=0.90). CyFra21-1, Ferritin and TIMP-1 demonstrated significant discrimination between individuals with HRA and LRA in univariable analyses, respectively. Performance was improved in multivariable analysis; AUC=0.61 (sensitivity=0.13 at specificity=0.90). Discrimination between individuals with colorectal adenomas and healthy individuals was significant for CA19-9, CEA, hs-CRP and TIMP-1, respectively, in univariable analyses. Multivariable analysis improved performance; AUC=0.63 (sensitivity=0.17 at specificity=0.90). All proteins except AFP demonstrated significant discrimination between individuals with HRA and CRC. Combination of CEA, CyFra21-1, Ferritin, hs-CRP and TIMP-1 in multivariable analysis improved discrimination; AUC=0.78 (sensitivity=0.34 at specificity=0.90). Association between plasma levels of any of the eight proteins and recurrence of colorectal adenomas after endoscopic removal could not be demonstrated.

DISCUSSION

The protein panel shows a promising potential in detection of colorectal adenomas in general, but specifically of HRA. However, improvements are needed for the panel to be valuable as a screening test. Finally, plasma levels of the eight proteins were not predictive of recurrence of colorectal adenomas.

Patients with Non-Hodgkin's Lymphoma Are at Risk of Adenomatous Colon Polyps

BACKGROUND

Patients with non-Hodgkin's lymphoma (NHL) are frequently referred for colonoscopy to evaluate gastrointestinal symptoms during their treatment course. Here, we described the rate of colonic adenomas in patients with NHL.

METHODS

This was a retrospective study of patients with NHL who underwent colonoscopy after being diagnosed with NHL between January 2000 and December 2017.

RESULTS

Of the 17,938 patients who had been diagnosed with NHL in the study period, 2176 met the inclusion criteria. The mean age at the time of colonoscopy was 61 years. Most patients were male (61%). Overall, 1273 polyps were detected in 811 patients (37%). Sessile serrated adenomas were detected in 102 (5%) patients. The overall ADR was 12% in patients younger than 40 years of age (n = 103), 26% in patients aged 40-50 (n = 251), 34% in patients aged 51-60 (n = 630), and 43% in patients older than 60 (n = 1212). Most polyps were located in the right colon (63%), and 101 (8%) were larger than 1 cm. Villous adenomatous features were present in 1% of polyps, while high-grade dysplasia was detected in 22%. Invasive adenocarcinoma was identified in 4%. The median interval from lymphoma diagnosis to adenoma detection was 1.4 years (interquartile range 0.5-3.8 years). A repeat colonoscopy was performed in 343 patients. The overall ADR on repeat colonoscopy was 30%. Cox regression analysis revealed that age (hazards ratio 1.04; 95% confidence interval 1.03-1.05; P < 0.001) and male sex (hazards ratio 1.35; 95% confidence interval 1.13-1.60; P = 0.001) were independent factors associated with worse overall survival. By contrast, screening colonoscopy was associated with longer survival duration (hazards ratio 0.48; 95% confidence interval 0.36-0.63; P < 0.001).

CONCLUSION

The ADR in NHL patients aged 40-50 years was equivalent to that reported in the literature in non-cancer patients aged 50-70 years. Early screening colonoscopy may be warranted in NHL patients younger than 50 years. Screening colonoscopy significantly improved the overall survival of patients with NHL.

Molecular markers for colorectal cancer screening

Colorectal cancer (CRC), although a significant cause of morbidity and mortality worldwide, has seen a declining incidence and mortality in countries with programmatic screening. Faecal occult blood testing and endoscopic approaches are the predominant screening methods currently. The discovery of the adenoma-carcinoma sequence and a greater understanding of the genetic and epigenetic changes that drive the formation of CRC have contributed to innovative research to identify molecular markers for highly accurate, non-invasive screening tests for CRC. DNA, proteins, messenger RNA and micro-RNA have all been evaluated. The observation of tumour cell exfoliation into the mucocellular layer of the colonic epithelium and proven stability of DNA in a harsh stool environment make stool DNA a particularly promising marker. The development of a clinically useful stool DNA test has required numerous technical advances, including optimisation in DNA stabilisation, the development of assays with high analytical sensitivity, and the identification of specific and broadly informative molecular markers. A multitarget stool DNA test, which combines mutant and methylated DNA markers and a faecal immunochemical test, recently performed favourably in a large cross-sectional validation study and has been approved by the US Food and Drug Administration for the screening of asymptomatic, average-risk individuals. The ultimate way in which molecular marker screening assays will be used in clinical practice will require additional studies to determine optimal screening intervals, factors affecting compliance, management of false-positive results, and the use of these assays in high-risk populations, as well as other considerations.