Part 4/11:
Better scans detect tiny, slow-growing tumors in people who feel perfectly healthy.
Some of these individuals, previously classified as healthy, are now diagnosed with early-stage cancer.
Removing these people from the "healthy" group increases its average lifespan (since these individuals were destined to die sooner).
Simultaneously, moving these relatively healthier cancer patients into the cancer group increases the average survival time within that group, giving the illusion of progress.