How Can We Tell if Chemotherapy is Working?

With the exception of adjuvant chemotherapy, in which there is no apparent cancer present, the effectiveness of chemotherapy on cancer cells is measured in terms of "response."  The techniques to monitor responses can be similar to the tests used to diagnose cancer. 

• A lump or tumor involving some lymph nodes can be felt and measured externally by physical examination
• Some internal cancer tumors will show up on an x-ray or CT scan and can be measured with a ruler
• Blood tests, including those that measure organ function can be performed.
• A tumor marker test can be done for certain cancers

Regardless of the test used - whether blood test, cell count, or tumor marker test, it is repeated at specific intervals so that the results can be compared to earlier tests of the same type.

How Is Response Defined?

Response to cancer treatment is defined several ways:

• Complete response - all of the cancer or tumor disappears; there is no evidence of disease.  A tumor marker (if applicable) may fall within the normal range.
• Partial response - the cancer has shrunk by a percentage but disease remains.  A tumor marker (if applicable) may have fallen but evidence of disease remains.
• Stable disease - the cancer has neither grown nor shrunk; the amount of disease has not changed.  A tumor marker (if applicable) has not changed significantly.
• Disease progression - the cancer has grown; there is more disease now than before treatment.  A tumor marker test (if applicable) shows that a tumor marker has risen.

When Is Response Measured?

For a newly diagnosed person who has been prescribed chemotherapy for cancer, the number of treatments is set.  For example, an oncologist will prescribe a specific number of chemotherapy cycles based on the treatment protocol.  Responses may be measured during the chemotherapy, but the number of cycles does not generally change unless the cancer grows.  If the cancer grows, the chemotherapy will likely be stopped or changed to different drugs.

For a person who has had a recurrence or has advanced disease, a specific number of cycles may not be prescribed.  Rather, 2-3 cycles are given and then response is evaluated.  If the disease is stable or shrinking, additional chemotherapy may be given as long as responses are maintained, provided the toxicity of the chemotherapy is tolerable.  In general, a minimum of 2-3 cycles of chemotherapy is required in order to measure response.  One cycle of chemotherapy may not be adequate to evaluate its effectiveness.

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

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