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
- 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
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
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:
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
Short & Long Term Side Effects of Chemotherapy
Cancer Clinical Trials