Targeting genomic instability in cancer.

Genomic instability is a defining feature of cancer, which arises when the cellular systems that maintain DNA integrity falter, enabling the accumulation of genetic and epigenetic alterations that drive malignant transformation. It is both the architect of cancer's evolution and its Achilles' heel. Targeting genomic instability has reshaped oncology: first through systemic chemotherapy and external beam radiation and then with poly(ADP-ribose) polymerase (PARP) inhibitors in homologous recombination repair-deficient tumors and other DNA damage response targets. Recently, tumor-targeted DNA-damaging platforms, namely antibody-drug conjugates (ADCs) and radiopharmaceuticals, have emerged alongside modern precision medicine strategies to optimize patient selection, develop rational combinations, and widen the therapeutic index.