Outcomes for Metastatic Colorectal Cancer Based on Microsatellite Instability: Results from the South Australian Metastatic Colorectal Cancer Registry

Variation in KRAS/NRAS/BRAF-Mutation Status by Age, Sex, and Race/Ethnicity Among a Large Cohort of Patients with Metastatic Colorectal Cancer (mCRC)

BACKGROUND

Racial/ethnic disparities in metastatic colorectal cancer (mCRC) survival are well documented as is the impact that tumor mutation of KRAS and BRAF has on prognosis. It has been suggested that frequency differences of KRAS- and BRAF-mutated tumors may partially explain this disparity. Demographic differences in mutation frequency are not well established nor whether mutation and microsatellite instability (MSI) differentially impact survival among groups.

METHODS

Using data for 11,117 patients diagnosed with de-novo mCRC from an electronic health record-derived database we estimated adjusted odds ratios (aOR) to characterize the association between demographics and MSI and KRAS/NRAS/BRAF-mutation status. Stratified Cox models were used to identify differences in overall survival (OS), adjusting for treatment and demographics.

RESULTS

Being female, compared to male, (aORKRAS:1.33 (1.23-1.44); aORBRAF:1.84 (1.56-2.16)), and non-Hispanic Black race (NHB), compared to non-Hispanic White (NHW) (aORKRAS:1.62 (1.42-1.85); aORBRAF: 0.55 (0.38-0.77)) were associated with KRAS- or BRAF-mutant tumors. MSI prevalence was similar across race/ethnicity but higher in women. BRAF-mutant tumors were associated with poorer prognosis overall, especially among non-white patients. Among patients who had KRAS/NRAS/BRAF-WT tumors we observed no difference in OS by race or MSI. Among patients with KRAS-mutant tumors, Hispanic patients had more favorable prognosis adjusted hazards ratio (aHR) = 0.76 (0.65-0.89)) than their NHW counterparts. Among those with BRAF-mutant tumors, NHB patients had poorer prognosis than NHW patients (aHR:1.78 (1.08-2.93)).

CONCLUSION

MSI and frequency of KRAS and BRAF mutations differed by demographics. Racial/ethnic disparities in OS differed by mutation. Future studies should explore biological and/or social determinants underlying these differences.

Colorectal cancer databases and registries in Australia: what data is available?

BACKGROUND

There are multiple data sources relating to colorectal cancer (CRC) nationwide. Prospective clinical cancer databases, population-based registries and linked administrative data are powerful tools in clinical outcomes research and provide real-world perspective on cancer treatments. This study aims to review the different Australian data sources for CRC from the perspective of conducting comparative research studies using a PICO (patient, intervention, comparison, outcome) framework.

METHODS

Data dictionaries from the different data sources were evaluated for the types of exposure and outcome variables contained to highlight their differing research utility.

RESULTS

State or territory-based cancer registries contain limited histology, cancer staging and treatment detail. They enable investigation of population-level patterns in overall survival (OS) of cancer patients with different demographics. Prospective clinical cancer databases contain more detail, especially surgical. Their strength is in auditing short-term surgical outcomes. They vary in the amount of data collected for other cancer treatments and completion of follow up data. Linked administrative databases have broad population coverage but less surgical detail. They provide population-level data on treatment patterns, short-term outcome measures and OS, as well as long-term surgical outcomes such as identifying patients who did not undergo stoma reversal. These databases cannot assess disease-free survival.

CONCLUSION

Of the various CRC data sources within Australia, linked administrative databases have the potential to provide the widest population coverage combined with the broadest range of exposures and outcomes, and arguably the most research utility.

Current Therapeutic Strategies in BRAF-Mutant Metastatic Colorectal Cancer

Around 8–12% of patients with advanced colon rectal cancer (CRC) present with BRAF alterations, in particular V600E mutation, which is associated with right-side, poorly differentiated and mucinous type tumors. The presence of BRAF mutation (BRAF-mt) has been identified as a hallmark of poor prognosis and treatment optimization in this patient subgroup is an important goal. Currently, the standard of care is an aggressive strategy involving triplet chemotherapy and anti-VEGF agents, but new therapeutic approaches are emerging. Very promising results have been obtained with targeted therapy combinations, such as anti-BRAF agents plus anti-EGFR agents. Furthermore, around 60% of BRAF-mt patients show a strong association with high microsatellite instability (MSI-H) and immune checkpoint inhibitors could represent the new standard of care for this subgroup. The focus of this review is to summarize current strategies for BRAF-mt CRC treatment and highlight new therapeutic options.

Assessment of the Circulating Tumor Cells and Microsatellite Instability in Colorectal Cancer Patients: Prognostic and Diagnostic Value

Background

Microsatellite instability (MSI) and circulating tumor cells (CTCs) play important roles in the diagnosis, prognosis and management of colorectal cancer (CRC) patients.

Methods

CTCs and MSI were assessed in the blood and representative tumor tissues of 100 CRC patients by flow cytometry (FCM) and PCR amplification. The data were correlated to relevant clinicopathological features of the patients, progression-free survival (PFS) and overall survival (OS) rates.

Results

MSI-high was detected in 44 (44.0%) patients, MSI-low in 37 (37%), and microsatellite stable (MSS) in 19 (19.0%) patients (P=0.007). The baseline CTCs count (<4 cells/7mL blood) was reported in 39% of the patients, and CTCs ≥4 cells/7mL blood in 61% of the patients (P=0.028). Improved PFS and OS rates were associated significantly with MSI-high (P<0.001), decreased CTC levels during the course of treatment (P<0.001) and post-treatment CTCs (P=0.008). There was no significant association between MSI-high and PFS or OS in early-stage patients (P=0.187 and P=0.187; respectively); however, it was associated significantly with better PFS and OS in late-stage patients (P<0.001). Multivariate analysis showed that only a change in serial CTC levels is considered an independent prognostic factor for OS (P<0.012). Post-treatment CTCs level, serial CTCs level changes during the course of treatment, lymph nodes and distant metastasis were independent prognostic factors for PFS (P<0.001, P= 0.047, P=0.001 and P<0.001; respectively).

Conclusion

MSI and CTCs could be used as accurate, reliable and sensitive diagnostic and prognostic biomarkers for CRC patients’ survival rates and outcomes.

A review of the sensitivity of metastatic colorectal cancer patients with deficient mismatch repair to standard-of-care chemotherapy and monoclonal antibodies, with recommendations for future research

In 5% of metastatic colorectal cancer (mCRC) patients, tumours display a deficient mismatch repair (dMMR) system. Immunotherapy is beneficial in dMMR mCRC patients and has recently been approved by the Food and Drug Administration for patients with unresectable or metastatic dMMR CRC. Although dMMR and proficient MMR (pMMR) CRC tumours are biologically distinct, they are commonly treated with the same chemotherapy and monoclonal antibodies. This includes dMMR mCRC patients who did not respond to immunotherapy (20-30%). However, it is unclear if these treatments are equally beneficial in dMMR mCRC. Of note, dMMR mCRC patients have a worse prognosis compared to pMMR, which may in part be caused by a lower response to treatment. To avoid unnecessary exposure to ineffective treatments and their associated toxicity, it is important to identify which systemic treatments are most beneficial in dMMR mCRC patients, thus improving their outcome. Indeed, future treatment strategies are likely to involve combinations of immunotherapy, chemotherapy and monoclonal antibodies. In this evidence-based review, we summarize clinical trials reporting treatment efficacy of different types of chemotherapy and monoclonal antibodies in dMMR mCRC patients. We also review the biological rationale behind a potential differential benefit of chemotherapy with or without monoclonal antibodies in dMMR mCRC patients. A barrier in the interpretation of preclinical results is the choice of model systems. They largely comprise traditional models, including cell lines and xenografts, rather than more representative models, such as patient-derived organoids. We provide concrete recommendations for clinical investigators and fundamental researchers to accelerate research regarding which systemic therapy is most effective in dMMR mCRC patients.

Survival of patients with deficient mismatch repair metastatic colorectal cancer in the pre-immunotherapy era

Background

Metastatic colorectal cancer patients with deficient mismatch repair (dMMR mCRC) benefit from immunotherapy. Interpretation of the single-arm immunotherapy trials is complicated by insignificant survival data during systemic non-immunotherapy. We present survival data on a large, comprehensive cohort of dMMR mCRC patients, treated with or without systemic non-immunotherapy.

Methods

Two hundred and eighty-one dMMR mCRC patients (n = 54 from three prospective Phase 3 CAIRO trials; n = 227 from the Netherlands Cancer Registry). Overall survival was analysed from diagnosis of mCRC (OS), from initiation of first-line (OS1) and second-line (OS2) systemic treatment. Cox regression analysis examined prognostic factors. As comparison for OS 2746 MMR proficient mCRC patients were identified.

Results

Of 281 dMMR patients, 62% received first-line and 26% second-line treatment. Median OS was 16.0 months (13.8–19.6) with antitumour therapy and 2.5 months (1.8–3.5) in untreated patients. OS1 was 12.8 months (10.7–15.2) and OS2 6.2 months (5.4–8.9) in treated dMMR patients. Treated dMMR patients had a 7.6-month shorter median OS than pMMR patients.

Conclusion

Available data from immunotherapy trials lack a control arm with standard systemic treatment. Given the poor outcome compared to the immunotherapy results, our data strongly suggest a survival benefit of immunotherapy in dMMR mCRC patients.

The heterogeneous clinical and pathological landscapes of metastatic Braf-mutated colorectal cancer

Colorectal cancer (CRC) is a complex and molecularly heterogeneous disease representing one of the most frequent causes of cancer-related death worldwide. About 8–15% of CRCs harbor a mutation in BRAF gene, a proto-oncogene involved in cell proliferation, differentiation and survival through the MAPK signaling cascade. The acquisition of BRAF mutation is an early event in the “serrated” CRC carcinogenetic pathway and is associated with specific and aggressive clinico-pathological and molecular features. Despite that the presence of BRAF mutation is a well-recognized negative prognostic biomarker in metastatic CRC (mCRC), a great heterogeneity in survival outcome characterizes these patients, due to the complex, and still not completely fully elucidated, interactions between the clinical, genetic and epigenetic landscape of BRAF mutations. Because of the great aggressiveness of BRAF-mutated mCRCs, only 60% of patients can receive a second-line chemotherapy; so intensive combined and tailored first-line approach could be a potentially effective strategy, but to minimize the selective pressure of resistant clones and to reduce side effects, a better stratification of patients bearing BRAF mutations is needed.

Over expression of METRN predicts poor clinical prognosis in colorectal cancer

BACKGROUND

The role of meteorin (METRN) in colorectal cancer has not been reported previously. We aimed to explore the relationship between METRN and colorectal cancer (CRC) prognosis.

METHODS

Data were retrieved from the Gene Expression Omnibus database. Gene expression values were log2 transformed and normalized by quantile normalization. Missing values were imputed with the R impute package. Differentially expressed genes were analyzed using the R limma package. METRN expression was compared between normal and CRC tissues and among different stages and subtypes of CRC. We assessed the relationship between METRN and KRAS/BRAF mutations in CRC. Five-year overall (OS), disease-free (DFS), and disease-specific survival (DSS) rates were determined by Kaplan-Meier analysis and analyzed by log-rank test.

RESULTS

METRN was expressed at a higher level in CRC (p = .0011) than in normal tissues, especially in advanced stages (p = .0343). METRN expression levels were higher in the MSI (dMMR) subtype (p < .001) and usually with BRAF mutations (p < .0001). METRN overexpression was associated with poor prognosis and low OS (p = .01014), DFS (p = .0146), and DSS (p < .0001) rates.

CONCLUSION

METRN overexpression is a predictive factor for poor prognosis in patients with CRC.