Chemotherapy and radiation boost growth of genetically altered healthy cells, study finds

A recent study published in *Nature Medicine* reports that conventional cancer therapies such as chemotherapy and radiation can unintentionally favor the expansion of normal cells that carry specific genetic alterations. The research, led by scientists at the University of Cambridge, examined tissue samples from patients who had undergone treatment for solid tumors and identified a higher frequency of clonal expansions in cells harboring mutations in DNA‑repair genes, notably TP53 and ATM, compared with untreated controls.

Using single‑cell sequencing and lineage tracing in both human biopsies and mouse models, the investigators showed that the DNA damage inflicted by these therapies creates a selective environment in which pre‑existing mutant cells gain a growth advantage. The study found that these cells proliferate more rapidly after treatment, potentially seeding the development of secondary malignancies or contributing to therapy‑related complications. The authors suggest that monitoring for such clonal expansions could become an important component of post‑treatment surveillance.

The findings underscore the need for strategies that mitigate the unintended promotion of mutant cell populations during cancer therapy. While the primary goal of chemotherapy and radiation remains to eradicate malignant cells, the research highlights a paradoxical effect that could influence long‑term patient outcomes and informs future efforts to design treatments that spare healthy tissue while minimizing the risk of secondary cancers.