Chemosensitivity Testing

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.

Listing of 'Reputable' Labs USA:

These labs will provide you and your physician with in depth information and research on the testing they provide.

Analytical Biosystems, Inc., Providence, Rhode Island. Ken Blackman, PhD. Solid Tumors Only. 1-800-262-6520

Anticancer, Inc., San Diego, CA. Robert Hoffman, PhD. Solid Tumors Only. 1-619-654-2555

Impath, Inc., New York, NY. David Kern, MD Solid Tumors and Hematologics. 1-800-447-8881

Oncotech, Inc., Irvine, CA. John Fruehauf, MD. Solid Tumors and Hematologics. 1-714-474-9262 / FAX 1-714-474-8147

Sylvester Cancer Institute, Miami, FL. Bernd-Uwe Sevin, MD. Solid Tumors Only. (especially GYN). 1-305-547-6875

Human Tumor Cloning Laboratory, San Antonio, TX. Daniel D. Von Hoff, MD. Solid Tumors Only. 1-210-677-3827

Oncovation LLC, New York, N.Y. Howard Bruckner, M.D. Solid Tumors Only. 1-212-514-2422

Rational Therapeutics Institute, Long Beach, CA. Robert A. Nagourney, MD Solid Tumors and Hematologics. 1-562-989-6455

DiaTech Oncology, Brentwood, TN. Vladimir D. Kravtsov, MD, PhD Medical Director 1-615-294-9033

Weisenthal Cancer Group, Huntington Beach, CA. Larry M. Weisenthal, MD, PhD. Solid Tumors and Hematologics. 1-714-894-0011 / FAX 1-714-893-3659

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 that I listed above 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.

Some Resistance

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.

Currently, physicians select an empirically-selected drug and must wait about six months to see whether it is effective on a particular patient. For many cancer, especially after a relapse or when a particular treatment is ineffective, more than one standard treatment exists.

What are the data which prove that an empiric, "one-size-fits-all" treatment identified by the clinical trials paradigm of randomized trials to identify the single best treatment to give to the "average" patient is clearly the most promising treatment to receive?

All available assay tests 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 assay tests are also able to report drug "sensitivity" (synergy) 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.There are a family of assays based on the concept of total cell kill, or cell death occurring in the entire popluation of tumor cells.

A fresh specimen is obtained from a viable neoplasm. The specimen is most oftern a surgical specimen from a viable solid tumor. Less often, it is a malignant effusion, bone marrow, or peripheral blood specimen containing "tumor" cells. These cells are isolated and then cultured in the continuous presence or absence of drugs, most often for 3 to 7 days. At the end of the culture period, a measurement is made of cell injury, which correlates directly with cell death. There is evidence that the majority of available anticancer drugs may work through a mechanism of causing sufficient damage to trigger so-called programmed cell death or apoptosis.

Some patients may not have easily-accessible tumors (needle biopsies do not gather enough specimen), making it difficult to harvest a large enough sample (200mg or 10mm in size). The tests are most reliable before a tumor has been exposed to chemotherapy. However, after a patient fails a previous chemotherapy treatment, the test still can be done once a patient waits at least four weeks.

There are four endpoint measurements of cell death that have been applied:

1. DISC assay. The delayed loss of cell membrane integrity.

2. MTT assay. The loss of mitochondrial Krebs cycle activity.

3. ATP assay. The loss of cellular ATP.

4. Caspase 3/7 assay. Directly measures key apoptosis expression markers.

(EDR assay is a cell-proliferation endpoint used to identify "inactive" drugs. It is not optimal to identify "active" drugs)

The DISC assay is the only assay that involves direct visualization of the cancer cells at endpoint. This allows for accurate assessment of drug activity, discriminates tumor from non-tumor cells, and provides a permanent archival record. Originators of the MTT and ATP assays modeled assay conditions on the DISC assay. The use of complementary tests improves accuracy and provides quality control. Also, certain drugs cannot be tested reliably in all assay systems. Use of different tests with different mechanisms helps to overcome this.

These four endpoints can and do, in most cases, produce valid and reliable measurements of cell death, which correlate very well with each other on direct comparisons of the different methods. This is not surprising any more than should the fact that auscultating heart sounds, observing spontaneous breathing, palpating a carotid pulse, measuring core body temperture, and recording an electroencelphalogram or electrocardiogram are all good and reliable methods of determing patient death.

Different investigators have favored different cell death endpoints, depending on the laboratory and clinical situation. What is important is that each of the cell death endpoints do give essentially the same results (except in the case of isolated drugs like taxanes and 5FU). So, it is entirely reasonable and proper to consider as a whole the clinical validation data which has been published over the last 15 years, using the above four endpoints.

Cell death assays are not intended to be scale models of chemotherapy in the patient, anymore than the barometric pressure is a scale model of the weather. But it's always more likely to rain when the barometer is falling than when it is rising, and chemotherapy is more likely to work in the patient when it kills the patient's cancer cells in the laboratory. It is no different than any other medical test in this regard.

Not all patients will have the same response to the same chemotherapy. Special laboratories can test tumor samples from individual patients to see which chemotherapy drugs have the best likelihood of killing tumor cells and optimizing survival. The results provide medical and surgical oncologists with patient-specific tumor information that may provide additional insight when determing the appropriate course of treatment for a patient.

Assay-testing focuses on the unique characteristics of a particular cancer. The test results help the physician to determine which anti-cancer drugs are "likely" to be effective against a particular cancer. The assay test also helps the physician to determine which anti-cancer drugs are "unlikely" to affect a cancerous tumor, which can help to avoid toxic and possibly ineffective therapy.

The tests have a specifity (for drug resistance) of 0.92 and a sensitivity (for drug resistance) of 0.71, which means that a treatment regimen "not" resistant in the assays is 7-9 fold more likely to work than is a treatment regimen which "is" resistant in the assays. A preponderance of evidence would indicate that it would be worthwhile to consider the assay results in drug selection.

The traditional criteria ever used to evaluate laboratory tests has been the predictive 'accuracy' of the test.

None of the available laboratory tests used in the selection of treatments for cancer patients have ever been tested for 'efficacy'. This includes estrogen receptor, progesterone receptor, Her2/neu, immunohistochemical staining for tumor classification, bacterial culture and sensitivity testing, CT, MRI and FDG Pet Scans to measure tumor response to treatment.

There is no literature establishing clinical 'efficacy' of these laboratory tests, because the costs of such clinical trials are prohibitive, granting agency support is non-existent, and no other analogous tests have been or will likely ever be subjected to such an unreasonably high bar criterion for clinical use.

The only data supporting any of them relate to test 'accuracy', and there is a total lack of information regarding test 'efficacy'. (randomized trials with outcome measurements for diagnostic tests)

Also, no one is seriously proposing that any of the molecular tests now available (Oncotype DX, EGFR amplification/mutation) should have to be proven 'efficacious', as opposed to merely 'accurate', before they are used in clinical decisions regarding treatment selection.

The American Society of Clinical Oncology (ASCO) reviews of cell culture assay tests for establishing clinical 'efficacy' specifically excluded all studies reporting the predictive 'accuracy' of the tests. In other words, they excluded reports that only reported correlations between assay results and clinical outcomes.

Instead, ASCO reviews included old, previously-reviewed studies comparing outcomes of patients who had treatment based on assay results versus patients with empirically chosen therapy. The criteria of laboratory assay 'efficacy', as opposed to laboratory assay 'accuracy' sound reasonable, but it is unprecendented with regard to any other laboratory test ever evaluated.

Cell culture assay tests have been well proven to have predictive 'accuracy' with that of estrogen receptor, progesterone receptor, Her2/neu and the newer molecular tests. In light of the precious little in the way of guidance from clinical trials with respect to best empiric therapy (where the only thing that has been proven to correlate with treatment decisions is reimbursement to the prescribing oncologist) and the importance of basing cancer treatment at least in part on patient preferences, it is entirely reasonable to support judicious application of laboratory tests which have been well characterized with respect to test 'accuracy'. These are diagnostic tests and should be held to that criteria, and not to that of therapy.

These laboratory tests are a tool for the oncologist. The oncologist should take advantage of all the tools available to him/her to treat a patient. And since studies show that only 25-30% of patients do respond to chemotherapy that is available to them, there should be due consideration to looking at the advantage of human tissue assay tests to the resistance that has been found to chemotherapy drugs.

Cell culture drug resistance testing is for preventing use of known anti-cancer drugs that are not likely effective in the specific tumor. Cell culture drug sensitivity testing tries to determine specific drug and dose effectiveness. The distinction between sensitivity and resistance is more semantic than substantive.

In virtually all forms of cancer, clinical trials have failed to identify best drug regimens for use in all individuals with a given form of cancer.

Oncologists have been documented to use reimbursement (payment to the oncologist) as the most important criterion for selecting between the large array of otherwise equally acceptable regimens. (Jacobson, M.,O'Malley, A.J., Earle, C.C., et al. Health Affairs 25(2):437-443, 2006) & (Patterns of Care: 2005,Vol 2,Issue 1)

The established criterion on which to judge all laboratory tests used to help in the selection of cancer treatment is test 'accuracy' and not test 'efficacy'.

Cell culture assay tests with cell-death endpoints have been exceedingly and reproducibly well established to be usefully 'accurate' in correlation with and predicting for clinical outcomes, including tumor response and patient survival.

There should an expansion of Medicare and private insurance reimbursement to promote even greater utilization and development of laboratory-based mechanisms, like cell culture assays, for improving the match between tumors and an ever-increasing number of partially effective and very expensive drug therapies.