Redefining Classification System For Metastatic Cancer: Molecular vs. Organ Origin

Context

The scientists have proposed a classification system for metastatic cancers, placing the molecular characteristics of the cancer over the tissue of origin.

Classification of Cancer Origin

• Traditional Approaches to Treating Cancer: It targets the organs in which the tumor is present. This practice formed the basis of classifying cancers after the organ in which they originate, like breast cancer, lung cancer, prostate cancer, liver cancer, etc.
  • However, most deaths due to cancer are the result of the disease metastasising beyond the organ of origin.

Need for Change in Metastatic Cancer Classification

• Mutations Not Limited to Single Organ:  All cancers from the same organ don’t always share the same mutations, and these mutations aren’t limited to cancers of a single organ.
  • This requires cancers to be classified based on their molecular and genetic Characteristics rather than the organ in which they originate.
• Treatment Delays due to Clinical Trials: Oncologists spend a lot of time testing new drugs in clinical trials sequentially, leading to “delay in treatment access”.

Significance of the Proposed Metastatic Cancer Classification

• Streamlining Clinical Trials: This will reduce the time needed to run clinical trials. Instead of testing the drug in each disease defined by the organ of origin, only a few randomised trials would be required.
  • A trial for a drug targeting a particular genetic mutation will cover all cancer types with those mutations. This will reduce the time required for the trials.
• Helping patients understand the rationale behind their therapy:  The two people may have same cancer but not the same therapy because the biological mechanisms underlying their tumors are different. 
  • Thus, naming cancers with biological mechanisms would decrease such heterogeneity and will also help the patient better to understand the rationale for his/her therapy.

The Challenge with the Proposed Cancer Classification System

• Without trials that encompass a substantial number of patients representing each type of cancer-based on molecular signatures, there is a risk of generalizing the results across all cancers.

Way Forward

• Approval of Drugs Based on Molecular Target: The regulatory agencies, scientific groups, and insurance companies will need to clarify when a drug should be approved based on its molecular target. 
• Analysing Molecular Profiles: Institutions need to establish teams focusing on analysing patients’ molecular profiles irrespective of the cancer type. 
• Training to Medical Students: Medical students must be trained to understand the molecular basis of cancers instead of memorising the characteristics of primary tumours.

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