Jan 20, 2005 - 2:21 am
Chemotherapy Sensitivity and Resistance Assays
When a patient has an infection, doctors often send a sample of infected blood or tissue to a lab where they can grow the bacteria and see which antibiotics are most effective (called Bacterial Culture and Sensitivity Testing). Chemosensitivity testing is an attempt to do something similar for cancer; fresh samples of the patient's tumor from surgery or a biopsy are grown in test tubes and tested with various drugs. Drugs that are most effective in killing the cultured cells are recommended for treatment. It is highly desirable to know what drugs are effective against your particular cancer cells before highly-toxic agents are systemically administered to your body.
One approach to individualizing patient therapy is chemosensitivity testing. Chemosensitivity assay is a laboratory test that determines how effective specific chemotherapy agents are against an individual patient's cancer cells. Often, results are obtained before the patient begins treatment. This kind of testing can assist in individualizing cancer therapy by providing information about the likely response of an individual patient's tumor to proposed therapy. Chemosensitivity testing may have utility at the time of initial therapy, and in instances of severe drug hypersensitivity, failed therapy, recurrent disease, and metastatic disease, by providing assistance in selecting optimal chemotherapy regimens.
All available chemosensitivity assays are able to report drug 'resistance' information. Resistance implies that when a patient's cancer cells are exposed to a particular chemotherapy agent in the laboratory, the cancer cells will continue to live and grow. Some chemosensitivity assays also are able to report drug 'sensitivity' information. Sensitivity implies that when a patient's cancer cells are treated with a particular chemotherapy agent in the laboratory, that agent will kill the cancer cells or inhibit their proliferation.
The goal of all chemosensitivity tests is to determine the response of a patient's cancer cells to proposed chemotherapy agents. Knowing which chemotherapy agents the patient's cancer cells are resistant to is important. Then, these options can be eliminated, thereby avoiding the toxicity of ineffective agents. In addition, some chemosensitivity assays predict tumor cell sensitivity, or which agent would be most effective. Choosing the most effective agent can help patients to avoid the physical, emotional, and financial costs of failed therapy and experience an increased quality of life.
Fresh samples of the patient's tumor from surgery or a biopsy are grown in test tubes and tested with various drugs. Drugs that are most effective in killing the cultured cells are recommended for treatment. Chemosensitivity testing does have predictive value, especially in predicting what 'won't' work. Patients who have been through several chemotherapy regimens and are running out of options might want to consider chemosensitivity testing. It might help you find the best option or save you from fruitless additional treatment. Today, chemosensitivity testing has progressed to the point where it is 85% - 90% effective.
Chemosensitivity testing might help you find the best option, or save you from fruitless additional treatment. Another situation where chemosensitivity testing might make particularly good sense is in rare cancers where there may not be enough experience or previous ideas of which drugs might be most effective.
Finally, there has been a veritable deluge of new approvals of cytotoxic drugs in recent years as the tortuous FDA process has been speeded and liberalized. In many cases a new drug has been approved on the basis of a single very very narrow indication. But these drugs may have many useful applications - and it's going to take years to find out. Chemosensitivity testing offers a way of seeing if any of these new drugs might apply to your specific cancer.
Cell Culture Drug Resistance Testing (Chemotherapy Sensitivity and Resistance Assays) refers to laboratory testing of a patient's own cancer cells with drugs that may be used to treat the patient's cancer. A group of lab tests known as human tumor assay systems (HTAS) can aid oncologists in deciding which chemotherapies work best in battling an individual patient's form of cancer. The assay is a lab test performed on a biopsy specimen containing living cancer cells. It's used to determine the sensitivity or resistance of malignant cells to individual chemotherapy agents. Depending on how well the tumor cells respond to each chemotherapy agent, they are rated as sensitive, resistant or intermediate to chemotherapy. The concept is that you are better off using a chemotherapy drug that your tumor reacts to strongly than one your tumor resists.
There have been over 40 publications in peer-reviewed medical literature showing correlations between cell-death assay test results and the results of clinical chemotherapy in more than 2,000 patients. In every single study, patients treated with drugs active in the assays had a higher response rate than the entire group of patients as a whole. In every single study, patients treated with drugs inactive in the assays had lower response rates than the entire group of patients. In every single study, patients treated with active drugs were much more likely to respond than patients treated with inactive drugs, with assay-active drugs being 7 to 9 times more likely to work than assay-inactive drugs. A large number of peer-review publications also reported that patients treated with assay-tested 'active' drugs enjoyed significantly longer survival of cancer than patients with assay-tested 'negative' drugs.
How May a Patient Arrange to Have Their Tumor or Leukemia Tested?
Both fluid and solid tumor specimens may be sent out via Federal Express or another overnight courier service for testing at one of more than a dozen labs around the country. Note that the choice of a lab is not a geographical consideration, but a technical consideration. All of the labs are experienced and capable of providing very useful information. However, the labs vary considerably with regard to technologies, approach to testing, what they try to achieve with the testing, and cost. By investing a little time on the phone speaking with the lab directors, you should have enough knowledge to present the concept to the patient's own physician. At that point, the best thing is to ask the physician, as a courtesy to the patient, to speak on the phone with the director of the laboratory in which you are interested, so that everyone (patient, physician, and laboratory director) understand what is being considered, what is the rationale, and what are the data which support what is being considered.
The fact that some doctors don't agree isn't stopping many cancer patients from taking this matter into their own hands, and sending their live path specimens off to one of the above private labs for assay-testing to be done. There has been much discussion about whether assay (in vitro) tests are of any use, as the in vivo response to a drug may very well be different in the body than in the petri dish. But, they said the same for Bacterial Culture and Sensitivity Testing. Doctors cannot remember a time when they didn't have this technology. It is a 'gold' standard. So will Chemosensitivity Testing.
Source: Human Tumor Assay Journal