Many cancer treat strategies include the administration of chemotherapy drugs -- toxic chemicals that halt cancer growth and promote tumor shrinkage. Chemotherapy drugs target cellular pathways required for cell division, stopping cancer growth and leading to cancer cell death. Although chemotherapy drugs often prove effective in managing or treating cancer growth, a patient's response to chemotherapy depends on a number of factors.
Prior Health
A major factor that influences a patient's response to chemotherapy is the patient's overall health before treatment. Chemotherapy drugs, while effective in targeting cancer, also harm a number of healthy tissues in the body. Patients with low levels of health before chemotherapy treatment may prove more vulnerable to the harmful side effects of chemotherapy. According to CancerHelp UK, patients undergoing chemotherapy often experience a drop in blood cell counts due to bone marrow damage. Low levels of red blood cells can leave a patient vulnerable to anemia, and low levels of white blood cells leave a patient open to infection. In some cases, conditions such as anemia can act as limiting factors in chemotherapy, and extreme low blood counts may require a delay in cancer treatment, decreasing the efficacy of chemotherapy in treating the cancer.
Severity of the Cancer
Earlier-stage cancers often contain cells with fewer genetic mutations than later-stage cancers, as cancer cells develop new mutations with each round of cell division. As a result, small numbers of cancer cells may gain genetic mutations that provide chemotherapy drug resistance as the cancer progresses, leading to a decrease in the patient's response to chemotherapy as the cancer progresses. Doctors take into account the stage and progression of a tumor when determining a cancer treatment strategy, to try increase the change of a positive response to chemotherapy. Patients with advanced cancer may receive chemotherapy consisting of two or more drugs in an effort to kill a wide range of cancer cells and promote the remission of severe cancer.
Previous Drug Resistance
A patient's response to a course of chemotherapy often depends on previous cancer treatment and drug resistance. According to ChemoCare.com, cancer cells may grow resistant to chemotherapy drugs through acquired genetic mutations that may either inactivate the drug within the cancer cell, prevent the drug from entering the cell or move the drug out of the cancer cell before the cell becomes damaged. As a result, a patient's response to chemotherapy depends on drug treatments received in the past and the types of drug the cancer has grown resistant to. HealthCommunities.com indicates that doctors often prescribe second-line cancer treatments to patients with a history of cancer drug resistance, such as administering the drug Hexalen to treat ovarian cancer after other chemotherapy drugs have failed. By taking into account a patient's prior treatment history, doctors can increase the chance the cancer will respond to future chemotherapy.
