What happens to cancer cells after they die?

Cancer cells can die quietly and then be recycled, but sometimes they also promote the growth of nearby residual cancer cells.

Cancer treatments like chemotherapy kill tumor cells, usually by causing them to self-destruct, shrivel up, and die quietly, or sometimes by triggering a more violent form of cell death. But what happens to cancer cells after they die?

Normally, they are recycled like any other dead cell in the body. When cancer cells die, their outer membranes are often damaged. This occurs in the form of 'silent' cell death, or apoptosis, a pre-programmed process that eliminates unwanted or damaged cells.

Phagocytes, a type of immune cell, engulf and recycle dead cancer cells. (Photo: Design Cells).

When the molecular switch that triggers apoptosis is 'turned on ,' the dying cell shrinks and membrane fragments escape through bulges. This causes the cell's contents to leak out and attract phagocytes — immune cells that engulf the cell.

Phagocytes engulf dead cancer cells and break them down into smaller components such as sugars and nucleic acids . Through this process, dead cancer cells are recycled into something that other cells can reuse later. In apoptosis – the type of cell death that traditional cancer treatments target – cancer cell fragments are often recycled in this way rather than being excreted from the body, for example in urine.

Cancer treatments also sometimes cause other types of cell death, such as necroptosis —a type of 'explosive' cell death in which tumor cells swell and burst rather than shrink. Phagocytes also efficiently destroy these dying cells.

But cancer cells don't always go quietly. Research shows that when they release inflammatory debris, they can sometimes stimulate the growth of nearby cancer cells that remain. This phenomenon, called the Révész effect , helps explain why some cancers come back after treatment.

A 2023 study by a team of experts at the National Cancer Institute found that the control center, or nucleus, of dying cancer cells can sometimes swell and burst, spewing DNA and other molecules around. In mice, these molecules can accelerate metastasis — the spread of cancer cells beyond the original tumor.

Such studies help explain how tumor cell death contributes to cancer progression and recurrence. However, the research is still in its infancy and scientists do not fully understand the connection.

With more research in the future, they aim to better understand the biological mechanisms behind cancer, which could lead to more effective treatments. For example, a 2018 study suggested that a method to combat tumor growth caused by dead cancer cell fragments relies on resolvin — a molecule derived from omega-3s that can help reduce inflammation and cytokines, while also promoting the removal of cell debris.