Author:
Gregory D. Pawelski
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Date Posted: 21:07:32 06/18/06 Sun
In reply to:
Gregory D. Pawelski
's message, "Cell Culture Drug Resistance Testing (CCDRT)" on 00:09:56 05/16/06 Tue
The traditional criteria ever used to evaluate laboratory tests has been the predictive 'accuracy' of the test. The American Society of Clinical Oncology (ASCO) reviews of cell culture assay tests 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.
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 Pet Scans to measure tumor response to treatment. 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.
ASCO says that there is no literature establishing clinical 'efficacy' of assay 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.
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'. This is a diagnostic test and should be held to that criteria, and not to that of therapy.
This laboratory test is 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.
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.
Molecular assays have established absolutely no data relating to assay 'efficacy', and with much less data relating to assay 'accuracy' than exist to support the application of cell culture assays.
ASCO is an organization which has been zealous in its support of an inherently corrupt system which won't allow drugs to be chosen on the basis of tumor biology but instead protects the ability of oncologists to choose drugs largely on the basis of profit margin or least inconvenience to research clinics.
There should an expansion of reimbursement to promote even greater utilization and development of laboratory-based mechanisms for improving the match between tumors and an ever-increasing number of partially effective and very expensive drug therapies.
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