Conceptualizing overdiagnosis in cancer screening.

Area of Science:

• Oncology
• Medical Screening
• Public Health

Background:

• Cancer screening aims to detect early-stage cancers for improved survival.
• Overdiagnosis, detecting cancers that would not be life-threatening, is an unintended consequence of screening.
• The concept of overdiagnosis is often misunderstood by patients and clinicians.

Purpose of the Study:

• To propose a novel classification system to clarify the concept of overdiagnosis in cancer screening.
• To differentiate between types of overdiagnosed cancers based on their potential clinical impact.

Main Methods:

• Introduction of the "tumor-patient" classification dichotomy.
• Defining "tumor" overdiagnosis: cancers that regress or stagnate without causing harm.
• Defining "patient" overdiagnosis: cancers with limited clinical relevance due to competing causes of death.

Main Results:

• Cancer screening likely leads to both "tumor" and "patient" overdiagnosis.
• The ratio of these overdiagnosis types varies significantly by organ, screening method, and patient factors.
• The classification provides a framework for understanding the nuances of overdiagnosis.

Conclusions:

• The "tumor-patient" classification aids in explaining and accepting the concept of overdiagnosis.
• Understanding overdiagnosis is crucial for informed decision-making in cancer screening.
• Further research is needed to explore the varying ratios of overdiagnosis across different contexts.