Genomic instability is a hallmark of cancer, leading to mutations that drive tumor growth and resistance to therapy. The DNA damage that occurs in cancer cells disrupts normal cellular processes, resulting in the accumulation of mutations over time. These mutations can affect tumor suppressor genes, oncogenes, and DNA repair mechanisms, contributing to cancer progression and metastasis. Understanding genomic instability has paved the way for targeted therapies aimed at exploiting these weaknesses in cancer cells. Advances in sequencing technologies and bioinformatics now allow researchers to identify genetic alterations that could predict treatment responses, ultimately leading to more personalized and effective cancer therapies.