The best possible treatment - individualized for each patient


An American Society of Clinical Oncology (ASCO) publication reports independent confirmation of the same findings in breast cancer that Dr. Weisenthal observed in our lab and reported formally to ASCO four years ago.   Dr. Weisenthal’s clients began benefitting from this information long before it was uncovered through traditional chemotherapy trial and error methods.  Such early treatment discoveries have occurred many times, in many cancers, and with many chemotherapy drugs and drug combinations through personalized cytometric profiling.   Click here to see a letter published in the ASCO Post.


“To whom it may concern:

I am a board certified medical oncologist in private practice in New York City.

I have been using chemosensitivity and chemoresistance assays for more than 25 years.

[Note: “chemosensitivity” and “chemoresistance” testing are other terms used to describe cytometric profiling.]

Nearly 95% of my patients have their treatments determined by chemosensitivity and chemoresistance testing.

For nearly 2 decades I was Chief of Medical Oncology and Cancer Research at St. Vincent's Hospital and Medical Center of Manhattan. I have been selected by the Castle Conley Guide to Best Doctors in America, Better Living Magazine and by the Consumers Research Council of America as one of America's top oncologists.

I can take little credit for those awards as I feel my reputation as having outstanding oncologic outcomes should be credited to the work of Dr. Larry Weisenthal who makes me look good. I have had patients who came from the most prestigious cancer centers in America on hospice care who had their disease eradicated by using the drugs suggested by Dr. Weisenthal’s chemosensitivity and chemoresistance testing.

The value of this testing is acute in the initial and subsequent management of many cancers. Physicians wishing information about patients whose otherwise incurable disease was eradicated by Dr. Weisenthal's work through me or any patients whose survival was enhanced by his work, please do not hesitate to phone my office.

- William R. Grace M.D.”





Telephone (212) 675·6826

Fax (212) 366·1697

[Dr. Grace is a brilliant and compassionate physician who achieves remarkable successes for his patients.  We admire his modesty and thank him for his unsolicited words of endorsement.  We are honored that Dr. Grace has used our personalized cytometric profiling services for many years in his skillful treatment of cancer.]

For additional endorsements and case studies please click here.




Increasingly, cancer physicians are turning away from the one-size-fits-all approach to chemotherapy drug selection.  It has become apparent to physicians and researchers worldwide that better results can be achieved if cancer treatments are personalized, based upon specific biologic factors.  These factors occur at the cellular level and are unique to each patient. 

The two main approaches to what is called “personalized medicine” are cytometric profiling (performed by Weisenthal Cancer Group and, in other forms, by a very small number of other labs scattered throughout the world) and gene, or “molecular,” testing (available in some form from hundreds of large and small labs located virtually everywhere).  Important differences in the two main approaches relate to precisely which biologic factors are tested, what technologies are used, and how expertly the technologies are applied.  It is highly probable that even your physician is not fully-aware of the differences which exist and how these differences dramatically affect the accuracy and usefulness of the information provided by the different tests. 


Gene testing (also called molecular testing or target profiling) attempts to link expression of certain genes within the nucleus of a cancer cell to a theoretical potential for drug activity.  In gene testing no chemotherapy drugs are actually tested and  other biological mechanisms of the cancer cell are ignored.

This is the opposite of Whole Cell Cytometric Profiling, in which tens of thousands of whole, living cancer cells obtained from each patient are separately exposed to many different candidate chemotherapy drugs so that the true cell killing ability of each drug can be observed and measured. 

Many companies offer commercial gene testing, services.  These services are also marketed as molecular testing or, as one company calls it, target profiling.  The names are different but it all means the same thing.  In our experience, and in the published opinions of many medical experts, the usefulness of these tests has been greatly exaggerated.  Not surprisingly, gene testing is widely misunderstood, even by cancer physicians. 

  1. First, the gene tests marketed today apply only to a very small number of drugs and only to a limited array of cancer types.  Gene testing has a narrow goal: to rule-out one or two of the drugs typically used for a particular cancer type.  Gene tests are not designed to reach out and identify active drugs within a broader range of potentially active agents.

  2. Even more importantly, in gene tests, patients’ cancer cells are never exposed to even a single chemotherapy drug.  Instead, gene tests rely upon a handful of gene patterns (only a few of these have been discovered to date) which are thought to suggest a potential for drug susceptibility - a theoretical predisposition.  No actual anti-cancer drug activity is ever demonstrated by the tests.  Gene tests do not tell us if the targeted genes truly are relevant, independent of other biological factors, or even if the targeted genes are active. 

  3. Even more basically, gene testing fails to account for some resistance mechanisms present in living cancer cells which can prevent chemotherapy drugs from ever entering the cancer cell.  Likewise, it does not account for different mechanisms which can inactivate an anti-cancer drug before it goes to work.  Nor does it account for the thousands - perhaps millions - of known and unknown chemical interactions occurring within a cancer cell, or for the very important cell-to-cell drug resistance signaling which is known to occur among living cancer cells.  All of these factors profoundly affect the susceptibility of cancer cells to chemotherapy drugs - and all are completely ignored by gene testing. 

  4. In addition, testing for activity among different drugs in the same class is not possible in gene testing.  This is
    important because different drugs within the same class of drugs often exert vastly different anti-tumor effects. 

  5. Neither can gene testing predict for activity of drug combinations. Since most chemotherapy today is administered in combination, this is a serious drawback. 

  6. Equally disadvantageous is the inability of gene testing to reliably predict for anti-tumor activity in the important new class of anti-vascular drugs, which work by cutting off the blood supply to tumor cells.

  7. Of all available methods purporting to “personalize” chemotherapy treatments, gene testing (aka molecular targeting) is the least direct testing method - farthest removed from the testing of actual chemotherapy drugs in the cancer patient.  To better understand what that means, please click here.  

Here is what New York Times Science and Medicine Writer, Gina Kolata, wrote in her 2011 article entitled, “How Bright Promise In Cancer Testing Fell Apart:” 

“The episode is a stark illustration of serious problems in a field in which the medical community has placed great hope: using patterns from large groups of genes or other molecules to improve the detection and treatment of cancer. Companies have been formed and products have been introduced that claim to use genetics in this way, but assertions have turned out to be unfounded. While researchers agree there is great promise in this science, it has yet to yield many reliable methods for diagnosing cancer or identifying the best treatment.  Instead, as patients and their doctors try to make critical decisions about serious illnesses, they may be getting worthless information that is based on bad science. (Link to full article.)


In contrast, cytometric profiling, as performed by the Weisenthal Cancer Group, accurately and indisputably measures the cancer cell killing ability of each drug as it occurs in real-time the the presence of each patient’s own, living cancer cells. 

  1. In cytometric profiling each patient’s cancer cells actually are exposed to the broadest possible range of candidate chemotherapy drugs, including the new “targeted” agents, accurately identifying both effective and ineffective drugs. 

  2. In addition, cytometric profiling clearly identifies widely varying patterns of susceptibility occurring within each patients’s cancer cells to different anti-cancer drugs within the same class of drugs.  Oncologists often see differences in patient response to different drugs which are thought to work via the same general mechanism.  In contrast, gene testing looks only at the mechanism and not at the drug or at the cell in the presence of the drug and so it cannot detect specific differences in drug activity. 

  3. Unlike gene testing, cytometric profiling measures the combined effect of all cellular gene and protein interactions occurring within the cancer cell.   Millions of these are known to occur but most are not yet identified or fully-understood.  However, it is still possible to account for these known and unknown chemical interactions by observing the behavior of the entire cancer cell when actually exposed to different chemotherapy drugs (as opposed to relying on the presence of only a few presumed markers in cells that are never exposed to drugs, as in gene testing). 

  4. Cytometric profiling also has the proven ability to identify synergy which frequently occurs in rationally-selected drug combinations.  Drugs which are only moderately active as single agents sometimes become extremely effective when combined with certain other agents.  Cytometric profiling can pinpoint these drug combinations - gene testing cannot. 

  5. Finally, Dr. Weisenthal and the Weisenthal Cancer Group apply the only technology capable of assessing the effectiveness of new anti-vascular agents (such as Avastin© and others) in mixed-cell micro-clusters.  No gene test can do this.  This critically-important anti-vascular drug profiling technology was originated by Larry Weisenthal, M.D., Ph.D. and is exclusive to Weisenthal Cancer Group.  (To read more about it, click here.) 


In the only head-to-head study of gene testing (molecular profiling) versus cytometric profiling to date, cytometric profiling was found to be highly relevant - 90% concordance with treatment outcome - while gene testing was found to be considerably less relevant (0%, 25%, or 75%, depending upon which genes were studied).  This rigorous, independently-conducted study was published in a peer-reviewed medical journal.  For more information about this study and its findings - and about gene testing versus personalized cytometric profiling, please click here.


In over 100 separate, published clinical studies, personalized cancer cytometrics, using cell death-based assays, accurately and reproducibly measured drug-induced cell death and correlated with individual patient chemotherapy response and survival.  Overall, the studies found that drugs which successfully killed patients’ tumor cells in prospectively reported cytometric profiling tests were 7.5 times more likely to improve clinical response rates and prolong the lives of cancer patients than drugs identified in advance by the tests as ineffective for those patients. 


Thousands of patients around the world have benefitted from personalized therapy selection provided by Dr. Weisenthal, an NCI-trained medical oncologist and extensively-published cytometric profiling pioneer.  Dr. Weisenthal is widely-acknowledged as the
leading expert in this field.  He personally leads his team in each patient’s cytometric profiling study - from beginning to end.  His methods are rigorous and the extent of his analysis far exceeds that which occurs at other labs.  Specimen processing, disaggregation, and concentration, drug panel selection, drug concentrations, cell incubation environments, cell exposure times, assay take-down and slide preparation, data analysis, and assay reporting are all performed precisely and with uncompromising attention to detail.  Each patient receives the benefit of parallel testing in 3 to 5 separate cytometric profiling technologies for greater test accuracy.  All laboratory results are benchmarked though statistical analysis involving the most specifically-detailed cytometric profiling database in existence.  Dr. Weisenthal personally examines and interprets each microscope slide, analyzes and calculates all test data, and recommends the personalized treatment plan which offers each patient the highest probability for success.  Typically, he devotes over eight hours to each patient’s cytometric profiling analysis. 

In a new era of personalized medicine, cytometric profiling is a superior approach.  Nobody performs it more comprehensively, more personally, and with greater experience and expertise than Dr. Weisenthal.   


To learn more, please phone our laboratory for a friendly, no-obligation discussion with Connie Rueff, M.T., Laboratory Manager.  All callers are accorded patience, compassion, and complete confidentiality.  (714) 596-2100.               


This website is sponsored and administered solely by the Weisenthal Cancer Group, which provides a laboratory testing method called Personalized Cancer Cytometric Profiling.  Weisenthal Cancer Group accepts no financial support from any drug company, medical equipment manufacturer, insurance carrier, professional organization, or hospital group.  We do not administer treatments nor do we derive any benefit, financial or otherwise, from recommending any specific treatment.  Our treatment recommendations are free from outside influence, obligation, or institutional bias. 

Larry Weisenthal, M.D., Ph.D.