Testing for the presence of specific cancer protein fingerprints in the blood of lung cancer patients will be an important means of identifying a subgroup whose tumors are more likely to shrink when treated with the drug erlotinib.

The test will be critical when other testing methods are unavailable, according to new data presented at the second European Lung Cancer Conference in Geneva, (Switzerland), which took place from April 28-May 1, 2010.

Erlotinib belongs to a class of drugs that specifically inhibits a cell-surface molecule known as the epidermal growth factor receptor (EGFR). This molecule is highly expressed in some forms of cancer, including lung cancer. By blocking this receptor, drugs such as erlotinib aim to slow tumor growth and proliferation.

Prof. David Carbone from the Vanderbilt-Ingram Cancer Center (Nashville, TN, USA) and colleagues in Canada analyzed blood samples from the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG) BR.21 study, which demonstrated that erlotinib improved survival compared to placebo in patients with advanced non-small-cell lung cancer who had already tried one or two other drugs.

In the new study, scientists analyzed blood samples that had been taken from some patients before they started treatment in the BR.21 study. They performed this analysis on patients who received the drug and on patients who received the placebo, looking for specific proteomic profiles already known to predict outcomes in patients treated with EGFR-blockers.

Other methods available to analyze the EGFR pathway of lung cancers include sequencing of the EGFR gene, or a technique known as fluorescence in-situ hybridization (FISH) to assess EGFR gene copy number, in which tumor tissue samples are directly studied under a microscope.

Prof. Carbone commented, "FISH overall was a better predictor of benefit, but can only be done with adequate biopsy tissue, which was available in this study only in 22% of patients. With the serum test, 99% of patients had a successful determination of proteomic status."

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