Of all the diseases affecting humankind, cancer is one of the most difficult to treat and cure. One of the main reasons for this difficulty relates to the fact that cancer is not a single disease but consists of hundreds of different types. Furthermore, cancers exhibit considerable genetic complexity with more than 400 different genes implicated in their development. In addition, cancers display major inter- and intratumor heterogeneity. Despite these complexities, several successes have been achieved in recent years. Most of these successes relate to the specific targeting of driver genes involved in cancer development. These successes include imatinib for the treatment of chronic myeloid leukemia, anti-HER2 therapies (trastuzumab, pertuzumab, and lapatinib) to treat breast cancer, anti-EGFR tyrosine kinase inhibitors (gefitinib and erlotinib) to treat non-small cell lung cancer, and anti-BRAF agents (vemurafenib and dabrafenib) to treat melanoma. Although the war on cancer has not yet been won, neither has it been lost. With continued basic and clinical research, cancer is being transformed into a chronic disease in which patients have increased survival rates and better quality of life.