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Chemosensitivity Testing

gdpawel's picture
Posts: 538
Joined: May 2001

There are few more imprecise and drastic measures than chemotherapy as a treatment for cancer. The process involves poisoning a patient's system with toxic chemicals in an effort to kill malignant cancer cells. As one who has personnally seen a loved one suffer, I can attest to its destructive and debilitating side effects. Patients generally need steroid pre-treatment and many have a severe reduction in white blood cells.

There has been no real progess in the treatment of most common forms of cncer. Recent NCI data showed that U.S. cancer mortality rates have increased and age-adjusted cancer mortality rates in response to treatment have not imporved in several decades, despite the introduction of many new drugs. There is a mind-set of cancer culture that pushes tens of thousands of physicians and scientists toward the goal of finding the tiniest improvements in treatment rather than genuine breakthroughs, that rewards academic achievement and publication over all else.

Investigators rely on models that are grossly deficient at predicting success. Hundreds of cancer drugs are pushed into the pipeline and many are approved by the FDA, even though their proven activity has little to do with curing cancer. Hundreds of clinical trials of one-size-fits-all therapy in tens of thousands of patients having results that have trivial hypotheses and produce no progress.

Proof of efficacy of a cancer treatment such as chemotherapy requires a randomized trial in which it has been shown that the group treated with chemotherapy experienced significantly increased survival when compared to that of an untreated group. This has never been done. Most claims for the efficacy of a chemotherapeutic agent comes from trials showing shrinkage of tumors or from comparison of survival rates of unmatched groups over time. Unless tumor shrinkage is accompanied by evidence of increased survival, the treatment cannot be claimed to be effective.

Additionally, in clinical trials, many patients are excluded because they could not complete the rather arduous treatment. So randomized comparisons are of healthier treated patients against all the controls, rendering a lot a trials flawed.

Studies of Assay-Directed Chemotherapy in Ovarian Cancer

Kurbacher and colleagues (Kurbacher, CM, et al. Anticancer Drugs 9:51-57, '98) treated 25 previously treated patients with ovarian cancer with assay-directed chemotherapy and compared outcomes with 30 non-randomized but clinically well-matched controls. In the control group, there was a response rate of 37%, in the assay-directed group, there was a response rate of 64%. Assay-directed therapy also produced a greater benefit with respect to both response rate and progression-free survival in the subgroup of patients with platinum-resistant disease. A current multi-institutional, international trial is currently in progress to further determine whether assay-directed therapy is superior to empiric therapy.

Loizzi and colleagues (Loizzi, V, et al. Am J Obstet Gynecol. 2003 Nov;189(5):1301-7) treated 50 ovarian cancer patients in their first recurrence following platinum-based therapy with assay-directed therapy and compared clinical outcomes with 50 additional non-radnomized but well-matched patients who received chemotherapy without assay information. In the group with initial platinum-sensitive disease, response rates were 65% for assay-directed chemotherapy versus 35% for empiric chemotherapy. However, in the platinum-resistant group, there was no improvement for assay-directed therapy. Response rates were 21% versus 16% (not significant).

Weisenthal and colleagues (Weisenthal, et al.) recently completed an analysis of the overall survival of 549 ovarian cancer patients with tumors submitted to their laboratory for testing between January, 1993 and January, 2001. Kaplan-Meier survival curve analysis showed median survivals of 44 months for first-line chemotherapy of previously untreated patients and 41 months for second-line chemotherapy of patients meeting the clinical definition of initially platinum-sensitive disease.

In addition, recently performed analysis of long-term survival of ovarian cancer patients who had tumor biopsy specimens referred to their laboratory for cell culture drug resistance testing (CCDRT or chemosensitivity testing), with the data analyzed as a function of whether or not the attempted chemosensitivity testing was evaluable or in-evaluable. Approximately 95% of specimens submitted for testing yielded an evaluable result, while approximately 5% were in-evaluable for reasons relating to poor viability of the specimen, insufficient yield of tumor cells in the specimen.

This data represented the survival of patients for whom tumor biopsy specimens were submitted to the laboratory for cell culture drug resistance testing (chemosensitivity testing). There was no information regarding what forms of chemotherapy was actually administered to these patients. The Kurbacher study and Weisenthal series employed assays using cell death endpoints, while the Loizzi study employed a cell proliferation endpoint.

It is important to note what has been known for more than 40 years, that ovarian and other forms of cancer represent heterogenous diseases where the tumors of different patients have different responses to chemotherapy, and where important treatment advances will require individualizing treatment based on testing the individual properties of each patient's cancer. This is far superior to empiric analaysis which which results in a one-size-fits-all treatment paradigm. Cell culture drug resistance testing improves patient survival in chemotherapy for ovarian cancer.

Cell Culture Drug Resistance Testing Predicts for Patient Survival in Ovarian Cancer

Konecny, et al. (Gynecol Oncology 77:258-73,'00) tested the tumors of 38 previously untreated FIGO stage III patients who received treatment (independent of assay results) with one of serveral platinum-based regimens. Drugs were tested as combinations: cicplatin + cyclophosphamide, cisplatin + Taxol, etc. Twenty nine assay-sensitive patients had a significantly longer progression-free survival (median 28.5 vs 12.6 months, P=0.033) and overall survival (median 46 vs 18 months, P=0.03), compared with nine patients classified as assay-resistant. The ATP endpoint was used in this study.

Taylor, et al. (Eur J Gynaecol Oncol 22:278-82,'01) tested the tumors of 93 previously untreated FIGO stage III and IV patients who received treatment (independent of assay results) with either a platinum-based regimen (71 patients) or with a single agent alkylator (22 patients). Drugs were tested as single agents, with the tumor classified as sensitive, if at least one drug used in subsequent treatment was active in cell culture drug resistance testing and as resistant, if all drugs were inactive in cell culture drug resistance testing. Fifty-one assay-sensitive patients had a median survival of 23 months, while fourty-two assay-resistant patients had a median survival of 19 months. The three year survival of the sensitive group was 36% compared to 16% in the resistant group, while five year survivals for the sensitive group were 24% versus 12% for the resistant group (P=0.033). The MTT endpoint was used in this study.

Holloway, et al. (Gynecol Oncology 87:8-16,'02) tested the tumors of 79 previously untreated patients with optimally debulked stage III/IIc disease (63 cases) and suboptimally debulked stage III or stage IV disease (16 cases). Patients were treated with platinum/taxol if cell culture drug resistance testing did not show resistance to Taxol or else cyclophosphamide/platinum, cyclophosphamide/doxorubicin/platinum or platinum alone if cell culture drug resistance testing showed resistance to Taxol. Median progression-free survival was 6 months in 17 cases with platinum resistance in the assay, compared to 24 months for 62 cases exhibiting sensitivity to platinum. Median overall survial for the resistant group was 24 months, but was not reached in the sensitive group. Estimated 5 year survival was 19% in the resistant group, compared to 68% in the sensitive group. The tritiated thymidine endpoint was used in this study.

Nagourney, et al. (Gynecol Oncology 88:35-39,'02) tested the tumors of 17 previously treated ovarian cancer patients with the combination of gemcitabine + cisplatin. Assay results were cut at the median IC50 value for the drug combination. Patients with sensitive tumors had an 85% progression-free survival probability at 6 months, compared to approximately 28% for assay-resistant tumors, and Kaplan-Meier progression-free survival curves were superior in the assay-sensitive group (P2=0.012). Overall survival was also superior in the assay-sensitive group (P2=0.05). The DISC assay endpoint (delayed loss of cell membrane integrity) was used in this study.

Weisenthal, et al correlated the results of cell culture drug resistance testing to both cisplatin and carboplatin with long-term, overall patient survival in ovarian cancer. Specimens from previously treated patients were significantly more resistant to platinums than were specimens from untreated patients, and this difference was most pronounced in the case of poorly-differentiated tumors. Well-differentiated tumors had significantly greater platinum resistance than poorly-differentiated tumors. In untreated patients, resistance to cisplatin and (separately) to carboplatin correlated significantly with long-term survival, as reported prospectively. This relationship was strongest in the case of poorly-differentiated tumors. There was also a significant relationship between platinum resistance and patient survival in previously treated patients who relapsed greater than 6 months following the most recent chemotherapy with the primary, platinum-based regimen.

Posts: 650
Joined: Mar 2003

I have seen your postings on different boards, and know that your wife suffered considerably with her cancer (and subsequent illnesses), and I am truly sorry for your loss.

Your information is appreciated, but is a bit overwhelming for a lay person. It has been suggested on this board in the past that there are ways of testing for drug resistance; can you tell us how that might be accomplished prior to the start of chemotherapy, and how much time it might take?

Also, do you consider it important for lower stages of OVCA? What about second-line treatment; should women ask for resistance testing?

I do agree that we are being treated with standards that don't seem to be changing; after I had surgery I was asked if I had a place that I wanted to have chemo in my home town, and was told it didn't really matter where I had it, because it's the same everywhere. Is there a way to get resistance testing fresh out of surgery? I had no idea that I had ovarian cancer until after my hysterectomy, although I had ultrasound and a cat scan prior to it.

My original dx was uterine cancer, so there was no question about a hysterectomy, but I had no reason to investigate chemo for ovarian. Given that most women are not doctors, nor have advocates with medical training, if you can give us the tools to work with (if they're available), we could start to ask these questions - before any treatment.

gdpawel's picture
Posts: 538
Joined: May 2001

Without information provided by chemo sensitivity and resistance assay testing, oncologists have the freedom to choose between a multiple of different drug regimens, all of which have approximately the same probability of working. Some of these regimens are highly profitable to oncologists. Other regimens are much less profitable.

Assay-testing takes away a lot of this freedom to choose and narrows the selection to those drugs that have the highest probability to be successful but may have lower profitability for the oncologist. This cuts into the oncologist's bottom line, though it benefits the patient. Many of these less profitable regimens are oral-dose.

The new targeted, relatively non-toxic oral-dose anti-cancer drugs are based on a variety of biological mechanisms that essentially stop cancer from spreading. Targeted cancer therapies use drugs that block the growth and spread of cancer. They interfere with specific molecules involved in the process by which normal cells become cancer cells and tumor growth. By focusing on molecular and cellular changes that are specific to cancer, targeted cancer therapies are indispensable new feature of quality cancer care and will replace, enhance or even make more effective therapies that are largely based on intravenous administration (infusion therapy).

Compared to infusional therapy, oral-dose anti-cancer drugs can make receiving cancer treatment more convenient for patients by allowing flexibility in taking medication without disrupting work or other activities. They can often result in less time spent in office-based oncology practices because of the absence of intravenous administration and its related side-effects.

Targeted cancer therapies will give doctors a better way to tailor cancer treatment. Treatments may be individualized based on the unique set of molecular targets produced by the patient's tumor, and these important treatment advances will require individualizing treatment based on testing the individual properties of each patient's cancer. Chemo sensitivity and resistance assay testing can improve patient survival in chemotherapy for cancer.

The American Society of Clincial Oncology fought long and hard to retain the Chemotherapy Drug Concession and never once suggested the need for any clinical trials to show when drugs were selected with and without the presence of profit differential (which included oral-dose drugs), clinical outcomes would be the same. It is a real credit to oncologists who utilize assay-testing in their management of their cancer patients, despite the fact that their use constrained their freedom to choose and doubtlessly reduced their incomes.

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.

The present system exists to serve the clinical investigators and the clinical oncologists, but not to serve the best interests of the cancer patients. I think it is time to set aside empiric one-size-fits-all treatment in favor of recognizing that breast, lung, ovarian and other forms of cancer represent heterogenous diseases, where the tumors of different patients have different responses to chemotherapy. It requires individualized treatment based on testing the individual properties of each patient's cancer.

gdpawel's picture
Posts: 538
Joined: May 2001

The clinical utility and clinical accuracy of cell culture drug resistance testing (chemosensitivity testing) with cell-death endpoints has now been proven beyond doubt.

Data on it may be reviewed at http://www.htaj.com/chemosensitivity_and_resistance_testing.wmv (a 27 minute video on .wmv format)

and http://weisenthal.org/faqw.htm

The cost of drugs is enormous. Patients are followed with serial CT scans, MRIs and even Pet Scans, just to see if a tumor is growing or shrinking. Not to mention the hospitalizations for toxicity, bone marrow transfusions, etc. The point is, the cost of ineffective therapy is truly enormous and assay-testing is particulary good at identifying ineffective therapy.

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