I still need to add a post on the more recent history of managing Pancoast tumors, but I wanted to add an important and potentially relevant bit of information I learned today. I'm attending a small meeting in New York and had the opportunity to talk with some folks from the company that makes Tarceva, OSI Pharmaceuticals, who relayed some potentially relevant news people here should know. In follow-up of concerns voiced by several OncTalk members, I had previously asked people at the company what information they have on metabolism of tarceva in people taking a class of drugs called proton pump inhibitors (PPIs), drugs like protonix, nexium, prevacid, and prilosec that block the stomach's ability to make gastric acid. These agents are very helpful in treating gastro-esophageal reflux disease (GERD, or just "heartburn"), and they generally have few side effects. I was told by the folks I spoke to that they were looking into it.

As I described in a prior post back in May, there have been some lingering questions about whether these drugs limit the stomach's ability to absorb oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) like iressa and tarceva. Most of the evidence on this potential interaction is with Iressa, which really isn't commonly used any more in the US, but Iressa and tarceva are similar in so many ways that there would be reason to suspect that the same issue may exist for the commonly used tarceva.

I was just told that they're providing additional information to the FDA based on pharmacokinetic studies (measuring blood levels of drugs over time) that apparently do show that people on PPIs have lower circulating drug levels of tarceva. The person I spoke to didn't have any details available about what the research demonstrated or what the FDA would be doing, but I imagine it may add some language in the official package insert document that advises for doctors to consider this potential interaction when starting someone on tarceva. I don't believe there are data out there to say what would be the "right" dose to use in someone who was continuing on one of these drugs that keeps the stomach from being an acidic environment and thereby limit absorption, but I would be inclined based on this information to advise patients on one of the proton pump inhibitors to stop it if it wasn't definitely necessary while they were on tarceva. In some other situations when people need an acidic environment to absorb a medication, you can take it with something acidic at the same time, like orange juice, coca cola, or vitamin C (ascorbic acid), but I'd probably prefer to avoid the issue by having someone suspend taking both a PPI and tarceva at the same time.

I'll let you know more when I have more to tell.