Thu, Nov 23, 2006 - Page 8 News List

Letter: Test tailors cancer treatment

By Gregory Pawelski

I would like to reply to Angelica Oung's article ("Cancer drug shows greater efficacy in Taiwanese patients," Nov. 13, page 2) by noting that there was a recent study in the US describing correlations between cell culture assay results (cell death in response to Iressa exposure) and the survival of patients with non-small-cell lung cancer who had received extensive prior chemotherapy.

These correlations were based on the actual assay results given to the doctors who ordered the laboratory tests. There were striking correlations between the results of the tests and patient survival.

The study utilized a new test called EGFRx, which accurately predicted the survival of patients treated with many emerging drugs. This is important because the EGFRx test could help to solve the growing problem of knowing which patients should receive costly, new treatments that can have harmful side-effects and which treatments will work for some -- but not all -- cancer patients.

Another benefit of the EGFRx test is that it can discriminate between the effects of different drugs and identify situations in which it would be advantageous to provide drug combinations.

The new test relies upon "whole cell profiling," in which living tumor cells are removed from an individual cancer patient and exposed in the laboratory to the new drugs. A variety of metabolic and apoptotic measurements are then used to determine if a specific drug could be successful in killing the patient's cancer cells.

After being exposed to Iressa, cancer cells undergo apoptosis and die. This has been found at the whole-cell level in the cell culture assays and has been reported to be strikingly correlated with patient survival.

The whole cell profiling method differs from other tests in that it assesses the activity of a drug upon the combined effect of all cellular processes, using metabolic and morphologic endpoints.

Other tests, such as those that identify DNA or RNA sequences or individual protein expression, often examine only one component of a much larger, interactive process.

The effects of drugs targeting EGF (Iressa, Tarceva, Erbitux) are poorly predicted by measuring the ostensible target (EGFR), but can be predicted more accurately by measuring the effect of the drugs on the function of live cells.

This is an area of cancer research that had been abandoned by most of the cancer research establishment except for a small band of cell biologists.

If Iressa works for some people, then obviously there must be others out there who would also benefit. This is a great argument for cell culture assay testing for tumors.

Gregory Pawelski

Pennsylvania

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