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Prevalence of EGFR Mutations in Patients with Adenocarcinoma: Moving Beyond Never-Smokers

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The question of “who should be tested?” for an epidermal growth factor receptor (EGFR) mutation and potentially other molecular markers is among the most timely questions in lung cancer management today. The field has changed dramatically since the initial description of the mutation, associated with a high probability of an impressive and often prolonged response to EGFR tyrosine kinase inhibitor (TKI) therapy, back in 2004. For several years after that, mutations had been known to be neither absolutely necessary (occasional patients would have phenomenal responses despite not having a mutation identified) nor sufficient (response rates to EGFR TKIs among patients with an EGFR mutation have been in the 65-75% range, not 100%) to see a gratifying response. Moreover, it was also known that certain clinical/demographic characteristics, such as being Asian, female, a never-smoker, and having an adenocarcinoma or bronchioloalveolar carcinoma (BAC) tumor histology was associated with a higher probability of a significant response to EGFR TKIs as well, and that these characteristics are associated with a higher probability of having a lung cancer with an activating EGFR mutation (it has been clarified in the last few years that particular mutations in exons 19 and 21 are far more common than others and are the ones most consistently associated with a dramatic response, as discussed in Dr. Pennell’s terrific review of the subject).

Though I had previously felt there to be a potential role to be played by “clinical selection” of patients who might be best served by starting with an EGFR TKI inhibitor, such as for a never-smoker presenting with a lung adenocarcinoma, or potentially anyone with a BAC, the IPASS trial clearly illustrated that EGFR mutation status was a reliable means of selecting which patients are better served by prioritizing an EGFR TKI over standard chemotherapy, while clinical selection failed: as I described in my post “Confessions of a Former Clinical Selector“, the trial highlighted that even Asian never-smokers with a lung adenocarcinoma did better with chemotherapy than an EGFR TKI if they didn’t have an EGFR mutation.

Since then, multiple trials have confirmed that while a difference in overall survival (OS) hasn’t been clearly demonstrated, patients with an EGFR mutation have a very significantly improved progression-free survival (PFS) after starting an EGFR TKI compared with standard chemotherapy. Accordingly, testing for EGFR mutations has become far more common, though not a uniform practice. The National Comprehensive Cancer Network (NCCN) guidelines for non-small cell lung cancer (NSCLC) now call for EGFR mutation testing in all patients who don’t have a squamous NSCLC tumor (since mutations are known to be unlikely — though are still seen rarely — in patients with a squamous tumor). Surveys of oncologist practices in the US over time have shown that more oncologists are testing than previously, but only perhaps a third to 40% of patients are being tested, and the probability of someone being tested having an EGFR mutation is about 40%, quite a bit higher than the 10-15% prevalence of the EGFR mutation among NSCLC patients in North America. This means that oncologists are being selective about who to test, and they’re focusing on patients who have a higher probability of testing positive.

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World Lung Conference Day 2, 7/5/2011

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Plenary Session: Lung Cancer in Never Smokers

The day started if with Dr. Thun from the American Cancer Society. He reviewed environmental factors contributing to Lung Cancer in never smokers. He started by reminding us that although only 10% of lung cancer deaths in men and 15-20% of lung cancer deaths in women are due to nonsmoking cancer, the burden of suffering caused by non-smoking lung cancer is actually rather high. If non-smoking lung cancer were treated as its own disease, separate from smoking-driven lung cancer, it would rank eighth among the most common fatal cancers in America! He reviewed environmental factors known to cause lung cancer: secondhand smoke, radon, asbestos, certain metals, some organic chemicals, radiation, air pollution, tubercoulosis, and other chronic inflammatory conditions. Others exposures likely also play a role, but have yet to be proven: human papilloma virus and chronic inhalation of cooking fumes and incense. Indoor air pollution from cooking, coal burning, and smoking men may explain the extraordinarily high rate of nonsmoking lung cancer among women in some areas of Northern China.

Dr. Pierre Massion of Vanderbilt took the stage second to talk about the molecular pathogenesis of never smokers. He reminded us of the different histologic tendencies of never smokers—less SqCC, more adenocarcinoma including the multiple subtypes once called BAC. He reviewed genes associated with susceptibility including cyp1a1, gstm1, xrcc1, gpc5, and fam38b. He pointed out the role of genetic differences in key molecules in inflammatory pathways: IL-1b, IL6, and IL1RN. Finally, insults from the environment may be expressed differently based on variations in genetic susceptibility.

Dr. Massion then used the figure, reproduced below, from Pao et al, Lancet Oncology 2011 to remind us how far we have come in understanding the molecular drivers in nonsmoking cancer:

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Studies have shown particular genomic signatures in never smokers. But not only is the DNA changed, but DNA modifiers (epigenetics) are also changed and we have defined specific genes whose expression is modified.

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The EML4-ALK Mutation Enters the Lung Cancer Clinic

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Dr. Pinder previously summarized the early story of the newly identified EML4-ALK mutation in NSCLC, which traces back only a couple of years. Amazingly, in that short time, treatments targeting this mutation have already been identified and administered to patients who are benefiting from these novel agents at this very moment. Still, one of the leading issues with this story of progress is that the EML4-ALK mutation appears to be present in less that 5 percent of the overall NSCLC population, so people may ask how valuable this discovery really is.

That really depends on a couple of factors. First, screening for an EML4-ALK mutation will be much more appealing and feasible if we have some hints of which pateints are more or less likely to have one of these mutations. Second, we need to have a treatment that helps the people we screen who have the ALK mutation.

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Interview with Dr. Suresh Ramalingam on First Line and Maintenance Therapy for Advanced NSCLC

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The ASCO meeting I’m at right now is so busy that there really isn’t time to write a new post (though I’m still “tweeting from the meeting”). Though the talk show hows just air re-runs of old shows when they’re on vacation, I’m trying to continue to add new content to the website during this time (and it’s about as far from a vacation as anyone has in Orlando).

Here’s an interview I did with Dr. Suresh Ramalingam, medical oncologist and Director of the Thoracic Oncology Program at Winship Cancer Institute at Emory University. It covers the current status of initial treatment for advanced NSCLC, including controversies and shifting standards for first line and then the transition into maintenance therapy. There’s also an associated slide set (as a pdf file), a transcript, and a link to the audio (mp3) version.

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ramalingam-first-line-and-maintenance-rx-transcript

Ramalingam First Line and Maintenance Rx for Adv NSCLC Audio Podcast


Interview with Dr. Ramalingam on First Line Advanced NSCLC and Maintenance Therapy

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The ASCO meeting I’m at right now is so insanely busy during the days and nights that it’s next to impossible to carve out the time to write posts during the meeting. While the talk show hosts just show re-runs while they’re on vacation, we’re at least going to put up some new content, even if it’s from work previously done (and this is far from a vacation).

This podcast features Dr. Suresh Ramalingam, Director of the Thoracic Oncology Program from Winship Cancer Institute at Emory University in Atlanta. We discussed recent data that have led to changes in our current treatment standards for first line treatment of advanced NSCLC, as well as emerging evidence leading to debates about maintenance therapy after a fixed amount of initial chemotherapy. The video version includes synchronized figures. The audio is an mp3 file.

Ramalingam interview Adv NSCLC and Maintenance Aud

I’ll add the figures and transcript very soon.


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