Care During Chemotherapy and Beyond

Chemotherapy Resistance

What Is Chemotherapy Resistance?

Chemotherapy resistance occurs when cancers that have been responding to a therapy suddenly begin to grow.  In other words, the cancer cells are resisting the effects of the chemotherapy. You may hear statements like the "cancer chemotherapy failed."  When this occurs, the drugs will need to be changed.

There are several possible reasons for chemotherapy resistance:

  • Some of the cells that are not killed by the chemotherapy mutate (change) and become resistant to the drug.  Once they multiply, there may be more resistant cells than cells that are sensitive to the chemotherapy.
  • Gene amplification.  A cancer cell may produce hundreds of copies of a particular gene.  This gene triggers an overproduction of protein that renders the anticancer drug ineffective.
  • Cancer cells may pump the drug out of the cell as fast as it is going in using a molecule called p-glycoprotein.
  • Cancer cells may stop taking in the drugs because the protein that transports the drug across the cell wall stops working.
  • The cancer cells may learn how to repair the DNA breaks caused by some anti-cancer drugs.
  • Cancer cells may develop a mechanism that inactivates the drug.

Research is underway to investigate ways of reducing or preventing chemotherapy resistance.

The development of drug resistance is one reason that drugs are often given in combination.  It is thought that this may reduce the incidence of developing resistance to any one drug.  Often, if a cancer becomes resistant to one drug or group of drugs, it is more likely that the cancer may be resistant to other drugs.  This is why it is very important to select the best possible treatment protocol FIRST.  In other words, when treating cancer, one should use the best weapon when there is the smallest possibility of chemotherapy resistance.

More Chemotherapy Information:

Chemotherapy Terms Chemotherapy Protocols - How Chemotherapy Works How Chemotherapy Is Given How Doctors Decide Which Chemotherapy Drugs To Give How Long Chemotherapy Is Given How To Tell If Chemotherapy Is Working Cancer Cells & Chemotherapy Types of Chemotherapy Targeted Therapy The Immune System About Immunotherapy Hormone Therapy Chemoporotective Agents Chemotherapy Resistance Short & Long Term Side Effects of Chemotherapy Nadir Cancer Clinical Trials is designed to provide the latest information about chemotherapy to patients and their families, caregivers and friends. For information about the 4th Angel Mentoring Program visit