All modern cancer therapies are limited by the development of drug resistance. Chemotherapy is one of the principal modes of treatment for cancer, but the effectiveness of chemotherapy is limited by drug resistance. Chemotherapy resistance occurs when cancers that have been responding to a therapy suddenly begin to grow. Malignant tumors usually consist of mixed populations of malignant cells, some of which are drug-sensitive while others are drug-resistant. Chemotherapy kills drug-sensitive cells, but leaves behind a higher proportion of drug-resistant cells. Before personalized medicine, most patients with a specific type and stage of cancer received the same treatment. In cancer, personalized medicine uses specific information about a person’s tumor to help diagnose, plan treatment, find out how well treatment is working, or make a prognosis. Although personalized medicine is a new and exciting approach to cancer treatment, doctors still don't know everything about the genetic changes that occur in a cancerous cell. Cancer is a heterogeneous disease. Different regions of a tumor often have different molecular features at the genetic and protein levels, and this intratumoral molecular heterogeneity is thought to cause drug resistance and treatment failure in cancer. There is considerable genetic diversity between different tumors of the same type, and even within a tumor. There are many thousands of cancer sub-types. In fact each individual cancer is genetically unique - which supports the approach known as personalized medicine. The Father of Oncology says that primary tumors always develop at body sites of excessive iron deposits. Such deposits can be inherited or acquired. Cancer is a disease of iron-overloaded cells. Cancer occurs when cellular iron overload chaotically affects cellular molecules and organelles (DNA, chromosomes, mitochondria, lysosomes, peroxisomes, etc). Unfortunately, iron/cancer information-1905-2015 is largely ignored. Genetic instability is a characteristic of all cancers because cellular iron overload chaotically affects DNA and chromosomes in cancerous cells. Personalized surgery (ceramic blades), personalized direct intratumoral injections of iron-deficiency agents (ceramic needles) and personalized clinical iron-deficiency methods (special diets, blood donations, etc.) can successfully neutralize tumors, metastases and micrometastases in hospitalized patients.