Novel Approach for Clinical Validation of the cobas KRAS Mutation Test in Advanced Colorectal Cancer

Criteria for assessing evidence for biomarker-targeted therapies in rare cancers-an extrapolation framework

Background

Advances in targeted therapy development and tumor sequencing technology are reclassifying cancers into smaller biomarker-defined diseases. Randomized controlled trials (RCTs) are often impractical in rare diseases, leading to calls for single-arm studies to be sufficient to inform clinical practice based on a strong biological rationale. However, without RCTs, favorable outcomes are often attributed to therapy but may be due to a more indolent disease course or other biases. When the clinical benefit of targeted therapy in a common cancer is established in RCTs, this benefit may extend to rarer cancers sharing the same biomarker. However, careful consideration of the appropriateness of extending the existing trial evidence beyond specific cancer types is required. A framework for extrapolating evidence for biomarker-targeted therapies to rare cancers is needed to support transparent decision-making.

Objectives

To construct a framework outlining the breadth of criteria essential for extrapolating evidence for a biomarker-targeted therapy generated from RCTs in common cancers to different rare cancers sharing the same biomarker.

Design

A series of questions articulating essential criteria for extrapolation.

Methods

The framework was developed from the core topics for extrapolation identified from a previous scoping review of methodological guidance. Principles for extrapolation outlined in guidance documents from the European Medicines Agency, the US Food and Drug Administration, and Australia's Medical Services Advisory Committee were incorporated.

Results

We propose a framework for assessing key assumptions of similarity of the disease and treatment outcomes between the common and rare cancer for five essential components: prognosis of the biomarker-defined cancer, biomarker test analytical validity, biomarker actionability, treatment efficacy, and safety. Knowledge gaps identified can be used to prioritize future studies.

Conclusion

This framework will allow systematic assessment, standardize regulatory, reimbursement and clinical decision-making, and facilitate transparent discussions between key stakeholders in drug assessment for rare biomarker-defined cancers.

Cancer Incidence Relation to Heavy Metals in Soils of Kyzylorda Region of Kazakhstan

OBJECTIVE

The purpose of this study was to investigate the relationship of soil pollution factors such as heavy metal ions with the incidence of cancer in the Kyzylorda region of Kazakhstan.

METHODS

Concentrations of heavy metal ions in the soils of different sites of Kyzylorda region, Kazakhstan, were sampled and correlated with incidence of cancer in 2021.

RESULTS

Chromium content in the soil exceeded maximum permissible concentration (MPC) in the samples for all sites except Kazaly and Shieli, and the highest excess of 2.8 MPC was found in Terenozek. Content of copper, lead, and cobalt ions was also increased and varied in the range 1.9-15.4, 1.2-4, and 1.2-2.44 MPC, respectively. In addition, lung cancer incidence was statistically significantly correlated with soil concentration to MPC ratio of copper, cobalt, and lead; colorectal cancer was correlated with soil concentration of chromium. Cases of invasive cancer and mutations were recorded Terenozek and Kyzylorda areas.

CONCLUSION

The higher the soil concentration correlate with higher cancer incidence in Kyzylorda region, Kazakhstan.

The current understanding on the impact of KRAS on colorectal cancer

KRAS (kirsten rat sarcoma viral oncogene) is a member of the RAS family. KRAS mutations are one of most dominant mutations in colorectal cancer (CRC). The impact of KRAS mutations on the prognosis and survival of CRC patients drives many research studies to explore potential therapeutics or target therapy for the KRAS mutant CRC. This review summarizes the current understanding of the pathological consequences of the KRAS mutations in the development of CRC; and the impact of the mutations on the response and the sensitivity to the current front-line chemotherapy. The current therapeutic strategies for treating KRAS mutant CRC, the difficulties and challenges will also be discussed.

KRAS Mutation Test in Korean Patients with Colorectal Carcinomas: A Methodological Comparison between Sanger Sequencing and a Real-Time PCR-Based Assay

Background

Mutations in the KRAS gene have been identified in approximately 50% of colorectal cancers (CRCs). KRAS mutations are well established biomarkers in anti–epidermal growth factor receptor therapy. Therefore, assessment of KRAS mutations is needed in CRC patients to ensure appropriate treatment.

Methods

We compared the analytical performance of the cobas test to Sanger sequencing in 264 CRC cases. In addition, discordant specimens were evaluated by 454 pyrosequencing.

Results

KRAS mutations for codons 12/13 were detected in 43.2% of cases (114/264) by Sanger sequencing. Of 257 evaluable specimens for comparison, KRAS mutations were detected in 112 cases (43.6%) by Sanger sequencing and 118 cases (45.9%) by the cobas test. Concordance between the cobas test and Sanger sequencing for each lot was 93.8% positive percent agreement (PPA) and 91.0% negative percent agreement (NPA) for codons 12/13. Results from the cobas test and Sanger sequencing were discordant for 20 cases (7.8%). Twenty discrepant cases were subsequently subjected to 454 pyrosequencing. After comprehensive analysis of the results from combined Sanger sequencing–454 pyrosequencing and the cobas test, PPA was 97.5% and NPA was 100%.

Conclusions

The cobas test is an accurate and sensitive test for detecting KRAS-activating mutations and has analytical power equivalent to Sanger sequencing. Prescreening using the cobas test with subsequent application of Sanger sequencing is the best strategy for routine detection of KRAS mutations in CRC.