Dose-Dense Chemotherapy Increases Breast Cancer Survival Rates

Chemotherapy has become one of the three standard types of treatment for breast cancer, along with surgery and radiation. Chemotherapy is used in one of two different ways: either as a neoadjuvant treatment, meaning it is administered before the surgical removal of a cancerous tumor, to help shrink it or as an adjuvant therapy, which means it is administered after surgery to kill any remaining cancer cells and help preclude future recurrence of the disease.

The White Blood Cell Problem
The standard chemotherapy treatment uses three drugs - doxorubicin (A), paclitaxel (T), and cyclophosphamide (C) - which are administered one by one in sequence. Because of the toxic effects of these chemicals on the body, it is not possible to administer them too quickly. One of the primary problems is the tendency they have to drive down the body’s white blood cell count. White blood cells are the soldiers of the immune system, the front-line warriors that allow the immune system to fight off invasion from bacteria, fungus or virus. In this case, the war metaphors really are appropriate, because these microscopic entities can do major damage to the body if they are able to infiltrate its defenses.

In order to give the body time to recover from their effects, these three chemicals were always administered to breast cancer patients at three-week intervals. However, it was long theorized that the negative effects of chemotherapy on cancer cells could be enhanced if the concentrations of these chemical cancer killers could be increased. But the problem of white blood cell reduction can become critical if chemotherapeutic concentrations are too high. When white blood cell counts fall too low, a condition called neutropenia can set in. When things get to this stage, the immune system is so compromised it can no longer fight off micro-invaders, and the body becomes extremely vulnerable to potentially life-threatening infections.

Dense Dose Therapy Provides an Answer
For some breast cancers, dense dose therapy has provided the answer to this conundrum. In dose dense therapy, concentrations of A,T and C are increased by shortening the time span between the sequential doses from three weeks to two weeks. In order to prevent the onset of neutropenia, patients are given an injection of one of two closely related drugs. Neopogen and Neulasta are made of a natural protein that acts as a growth factor, stimulating production of white blood cells in a way that usually prevents neutropenia from developing. Neulasta has been modified with an additive that makes it stay in the system longer than Neupogen. Because of this alteration, Neulasta can be administered in fewer doses than Neupogen, and its added potency has generally made it the drug of choice for dose dense therapy.

Dense dose therapy has been shown to modestly improve survival rates for breast cancer victims. Detailed information can be hard to come by, but one early study from 2002 found three year survival rates were 2% higher, and four year rates 7% higher, for dense dose therapy in comparison to A, T and C chemotherapy delivered in the usual three week intervals.