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Iressa vs. Standard Chemo in Asian Never- or Light Ex-Smokers: Results of the IPASS Trial
The European Society for Medical Oncology (ESMO) Congress, similar to ASCO but based in Europe, has been going on in Stockholm, where the results of a study called the First Line Iressa versus Carboplatin/Paclitaxel in Asia Study (taking some liberties to force it into the acronym “IPASS”) was presented in the Presidential Symposium by my friend and Hong Kong-based colleague Tony Mok. This study, as shown in the schema below, randomized 1217 Asian patients with advanced NSCLC who had not received prior systemic therapy to either the oral EGFR inhibitor iressa (gefitinib) or the standard chemotherapy carboplatin/taxol (paclitaxel):
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Longterm Survival with Iressa in BAC
One of my earliest posts when I started OncTalk was on the use of oral inhibitors of the epidermal growth factor receptor (EGFR), one of the growth signals that is often over-active in cancer cells, against advanced bronchioloalveolar carcinoma (BAC), a unique subtype of lung cancer that tends to grow within the lungs, sometimes slowly, and not progress elsewhere. These EGFR inhbitors like iressa (gefitinib) and tarceva (erlotinib) have certainly been well studied in NSCLC in general, but both of these drugs have been a focus of particular attention as a treatment for BAC. In fact, the largest trial that has yet been conducted in advanced BAC is one that I led, called SWOG 0126, that gave iressa at 500 mg by mouth daily (actually twice the dose that was eventually settled on, but possibly a more effective dose) to 135 eligible patients with advanced BAC. My colleagues and I published the results of this trial a couple of years ago (abstract here), but this year at ASCO I presented the results with longer-term follow up (abstract here), which yielded some interesting findings.
Obviously, the response rates and side effects didn’t change with a couple of years of longer-term follow up. Nor did the median progression-free and overall survival numbers, since those reflect the point at which half of the patients will have demonstrated progression or have died:
It’s worth noting that while this study enrolled both patients who had never been previously treated and some other patients who had received prior chemotherapy, both the chemo-naive and previously treated patients had the same progression-free and overall survival results, as shown in the superimposed curves shown above.
Comparison of Iressa to Single Agent Chemo in First Line treatment for Elderly Advanced NSCLC Patients: The INVITE Trial
In addition to a direct comparison of iressa to chemo in the second line setting for advanced NSCLC (see recent post on INTEREST trial), as conducted with the INTEREST trial I described in a recent post, a very similar comparison of Iressa to chemo was also performed in another setting where single-agent chemo is also the treatment of choice. Specifically, the INVITE trial evaluated iressa vs. navelbine as a single agent in previously untreated advanced NSCLC (abstract here).
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As discussed in one of my early posts, there is room to debate whether single agent approaches or older patients should receive single-agent chemo or standard platinum-based doublets (particularly carboplatin-based instead of the more challenging cisplatin doublets). Among the most commonly used single chemo agents in the elderly population is navelbine (also known as vinorelbine), based on it being proven to improve survival compared with supportive care alone in the memorably named ELVIS trial (Elderly Lung Cancer Vinorelbine Italian Study – paper here). We’ve seen the results of a trial in which tarceva was compared to the chemo doublet of carbo/taxol in patients with a marginal performance status (not the same population as elderly), and as I described in a prior post, the recipients of chemo fared better than those who received tarceva. So did the INVITE trial show similar results for gefitinib in the elderly compared to a single chemo agent? Continue reading
The INTEREST Trial of Chemo vs. Iressa as Second Line Treatment for Advanced NSCLC
In a post several months ago, I described the results of a trial from Japan, designated V-15-32, that directly compared Iressa to Taxotere as a second line therapy. Although overall comparable, the study showed that Japanese patients receiving Iressa had a higher response rate, but despite that had a lower median and one year survival. Although Iressa overall has not shown the same degree of clinical benefit as the very similar drug Tarceva, these results were perhaps a bit surprising because EGFR inhibitors have been most effective in Asia, where a higher proportion of lung cancer patients are never-smokers and/or have an EGFR mutation. But the Japanese trial had the problem that more patients randomized to Taxotere received a potentially effective therapy (different agent with potential activity in previously treated patients) after the trial drug than patients on the Iressa arm.
One of the trials presented at the Presidential Symposium at the recent World Conference on Lung Cancer in Seoul, Korea, was called the INTEREST trial (I don’t remember what the acronym stands for, except that it was a major stretch), led in North America by my friend Ed Kim from MD Anderson Cancer Center. This trial (abstract here) had almost the exact same design as the Japanese study, again randomizing previously treated patients to either Iressa 250 mg daily or Taxotere IV every three weeks.
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The INTEREST trial was run around the world, accruing 1466 patients from 149 centers in 24 countries, making it the largest trial in previously treated patients with NSCLC that has ever been conducted. The Taxotere dose was also 75 mg/m2 every 3 weeks, the FDA-approved standard in the US based on a proven survival benefit in North American trials, while the Japanese V-15-32 trial used 60 mg/m2, which is the standard in Japan and appears to be a dose with the same general toxicity and effectiveness as a higher dose in North American/European populations. Otherwise, the INTEREST trial asked the same question as the Japanese trial but in a broader audience. Specifically, one of the reasons it was so big is that it was looking to see whether the two approaches could be proven to have the SAME survival/clinical benefit, which requires more patients than showing that one is better than another. The trial was also designed to look at whether patients with EGFR gene amplification as measured by the FISH test. Continue reading
Biologic and Molecular Correlates of Clinical Benefit in French Trial of Iressa in BAC
The study I was just discussing, the French trial of Iressa at 250 mg daily for advanced BAC (abstract here), provided interesting clinical information, especially when viewed in the context of previous work on EGFR inhibitors in BAC. But in 2007 we’re also interested in the next generation of questions, including trying to identify which patients are more or less likely to benefit from Iressa or other EGFR tyrosine kinase inhibitor therapy. In addition to the clinical portion of the trial, the French investigators evaluated several clinical, pathologic, and molecular variables that were associated with disease control (DCR: response or stable disease) vs. progressive disease (PD) in a separate reported part of the study (abstract here).
From the 88 eligible patients enrolled on the BAC trial, they had tissue submitted from 65, of whom the expert pathologists felt that 50 had BAC or adenoBAC, evenly split between mucinous (M) and non-mucinous(NM) BAC, while the others didn’t have tumor tissue in their submitted specimen or had an adenocarcinoma that the experts didn’t think could be called BAC (this is typical — expert reviews of pathology submitted as “BAC” from various hospitals often show high rates of disagreement, with a less strict definition in the “real world”). Not suprisingly, the patients with tissue submitted, like those on the trial in general, had a higher rate of non-smokers (>40%, and from France, no less!), and more than half of the BAC patients were women (pretty much the only lung cancer setting where we see this). The tumor tissue was tested for EGFR by protein expression (immunohistochemistry, or IHC), gene amplification (by a process called FISH, and another called CISH), and also for EGFR mutations; they also checked for ras mutations, which I described in a prior post as being likely associated with a lower likelihood of benefit on EGFR inhibitors. Finally, they checked for thyroid transcription factor-1 (TTF-1), which is a marker of thyroid and lung tissue that helps us determine whether a cancer is actually from the lung or thyroid vs. another part of the body (they can tell the difference between lung and thyroid from other protein stains in the unusual cases where there’s a question between those sites as the primary tumor site). About 70% of lung adenocarcinomas express TTF-1.
First, the investigators compared the M-BAC to NM-BAC tumors and found differences in several regards. Although there were no gender differences and never-smokers were found in similar proportions between the two types of BAC, NM-BAC was much more likely to be associated with TTF-1 expression, EGFR protein overexpression (by IHC; about 35%) and gene amplification (by FISH and CISH; 10% range)) and EGFR mutations (12% of the population) than M-BAC tumors. They didn’t differ in their frequency of ras mutations (about 1/4 of both groups). So they have some differences that might explain differences in how the different types of BAC tumors respond to EGFR inhibitor therapy.
And when they looked at the characteristics of the patients who achieved disease control vs. those who showed PD, they saw that the patients who had stable disease or better were significantly more likely to be women, never-smokers, have NM-BAC, have a tumor that expresses TTF-1, and also a higher likelihood of having an EGFR mutation. In contrast, those with ras mutations were more likely to be the ones who showed progression. Here’s the summary:
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This isn’t a large enough study to say anything definitive, but it’s a step forward in giving us hints about biological differences between M-BAC and NM-BAC, and it also helps provide some insight about why people with NM-BAC may be more likely to respond better and have longer survival on Iressa and Tarceva trials. In addition, this biological information may be useful outside of BAC. Perhaps the patients with TTF-1 positive tumors are the ones more likely to respond to EGFR inhibitors. We’ve never really looked at that, but that marker is a routine part of testing lung tumors. It’s readily available everywhere, and it doesn’t take days or weeks to obtain, unlike the mutation work. There are several other interesting leads here, so we need to follow up and see what holds up in other studies of EGFR inhibitors.
EGFR inhibitors (Tarceva, Iressa) and Stomach Acid
Several members have raised questions in the last several weeks around the question of whether antacids like garden variety Rolaids or Tums, a class of drugs called histamine H2 blockers like zantac and tagamet, and also proton pump inhibitors (PPIs) like prilosec (the “magic purple pill”), protonix, nexium, etc. that effectively shut down stomach acid may actually be problematic if taken in combination with Iressa or Tarceva (I’m going to focus primarily on Tarceva here, since that’s the drug marketed in the US right now). This issue isn’t one that has been highlighted in the general research and teaching about these oral agents. We do know that absorption is variable, but the reason it is recommended that they be taken on an empty stomach is that it’s more predictable in that setting. Taking these agents with food tends to increase absorption, but unpredictably, so the best way to have a good idea of what’s going into the body is to take the recommended amount (or a dose reduction, as needed) on an empty stomach.
It’s certainly understandable that the absorption from the stomach and gastrointestinal tract be moderated in part by stomach acid or lack thereof, since it’s the job of stomach acid to help digest food (it’s not just to cause heartburn), but there has never been any instruction on having antacids and/or PPIs be considered contra-indicated medicines (advised to not be taken at the same time). In fact, the Iressa package insert does mention that zantac and sodium bocarbonate (antacids), given to keep the pH above 5 (outside of the highly acidic range, which is the low numbers like 1-2), reduce Iressa absorption by 44% in one of the studies by the manufacturer (AstraZeneca). Member NeilB was kind enough to e-mail me this link to a chart in a summary article about the EGFR inhibitors, which notes some of the key drug interactions observed with EGFR tyrosine kinase inhibitors like Iressa and Tarceva. Another official document summarizing extensive pharmacologic information on Tarceva tablets (here) also documents that tarceva absorption appears to be diminished in the absence of an acidic stomach environment and suggests that “caution should be exercised when these medicinal products are prescribed with erlotinib” (Tarceva) (page 19 of this pdf document). Continue reading
The Iressa/Tarceva Saga, Part II
Iressa was approved by the US FDA in May of 2003 as a third-line therapy, and for the next 18 months it was the only EGFR inhibitor on the market. At the ASCO conference a year later, Frances Shepherd, from the Princess Margaret Hospital in Toronto and chair of the Lung Cancer Committee for the NCI-Canada, first presented the positive results of the BR.21 trial randomizing patients in a 2:1 fashion to either Tarceva or a placebo as second- or third-line treatment for NSCLC; this was subsequently published in the New England Journal of Medicine (abstract here). I’ve summarized the trial and the demonstrated survival benefit in a prior post. So we came out of that meeting knowing that at least one EGFR inhibitor had a proven significant benefit, and while Iressa was the only EGFR TKI on the market, it continued to be prescribed and generally presumed to have similar benefit, given that the two drugs had the same mechanism of action, very similar side effect profile, and shared characteristics for patient populations who seemed to demonstrate the most impressive responses, such as Asians and patients with adenocarcinomas, especially BAC. I also gave an oral presentation confirming responses, some dramatic and long-lasting, for Iressa in BAC, at that ASCO meeting in 2004 (subsequently published, abstract here).
For a little more than six months, we expected the approval of Tarceva based on the proven benefit, and we saw similar characteristics with Iressa. Most of us in the field considered the two drugs to be like Coke and Pepsi, with some mild distinctions, but more similar than different. We were waiting on a trial of Iressa against placebo, but until November of 2004, Iressa was the only commercially available option, so there wasn’t much of a question of which drug to prescribe. People began to switch with Tarceva’s approval, but the big shocker came in December of 2004, when the first announcement of the ISEL (for Iressa Survival Evalaution in Lung Cancer ) trial was released, indicating that there was no significant survival benefit of Iressa compared to a placebo (abstract here).
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Shortly after that, the FDA no longer allows new prescriptions of Iressa, but patients who aren’t progressing can stay on it, and it’s also in other clinical trials. It continues to be widely used outside of the US, especially in Asia, and we’ll talk about why. Continue reading
EGFR Inhibitors Iressa and Tarceva: A Tale of Two TKIs (Part I)
I haven’t really covered the history or issues of directly comparing the two oral inhibitors of the epidermal growth factor receptor, or EGFR, which are Iressa (gefitinib) and Tarceva (erlotinib). This is really because over the last few years, gefitinib has had disappointing results in some important trials and is no longer readily used or available, while the remarkably similar drug Tarceva has been approved by the US FDA and is a standard treatment for patients with advanced NSCLC that has previously been treated with chemotherapy. So you already know where we are in the story in early 2007. While it appears that Iressa for lung cancer is no longer very relevent for clinical management of lung cancer in the US, several trials of Iressa are still emerging that compare it to chemotherapy, so it’s important to review the similarities and differences of Iressa and Tarceva as we consider whether the effects with Iressa can be generalized to the “class” of EGFR inhibitors.
We’ll step back for a moment to say that the molecular target for both drugs is EGFR, which is expressed on some normal body tissues, including skin (it’s an epidermal growth factor), but it’s also expressed on 40-80% of NSCLC tumors and many other kinds of cancers. In fact, in lab studies using test tube as well as animal models, activating the receptor leads to activities in cancer cells that lead to cancer cell growth and division, as well as decreased likelihood of the cancer cell dying and a higher chance of it invading tissues and spreading elsewhere in the body.
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In people, several types of cancers that have high degrees of expression of the protein on the tumor cells have been shown to be more aggressive and be associated with more aggressive behavior and worse survival outcomes. On the other hand, drugs that inhibit EGFR, which can be antibodies that block EGFR on the outside of the cell (such as Erbitux (cetuximab) and Vectabix (panitumumab) or tyrosine kinase inhibitors (such as Iressa and Tarceva) that act on the inside of the cell on the back end of the receptor, block the cancer-promoting effects of an activated EGFR molecule. So Iressa and Tarceva act on the same part of the EGFR molecule.
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