You learn as a doctor to never say never.
This past Wednesday I was a member of a panel that was brought together by the Centers for Medicare and Medicaid Services (CMS) to review the clinical indications for using PET scans in cancer.
While trying to make decisions regarding the effectiveness and benefits of PET scans in various cancers, I made a discovery that was a surprise to me: something that I previously thought was a far out theory for cancer treatment may in fact be plausible after all.
For those not familiar with PET scans, they are an imaging procedure which utilizes radioactive glucose to point out where cancer is located in the body.
The technique has been around for a while, and more recently PET scan information has been merged with CT scans to produce images that are very helpful to doctors determine whether a cancer has spread, and if so where it is in the body.
For some cancers, there is also some evidence that PET scans may highlight how aggressive a cancer may be, or whether or not the cancer has actually responded to chemotherapy.
The issue facing Medicare is that PET scans are increasing in frequency. Because they are expensive—they cost several thousand dollars for each one—there has been concern about the impact of this technology, and whether it really makes a difference in the treatment of cancer patients.
As a result, CMS has been conservative in their approach to paying for these scans. A couple of years ago they started paying for the use of PET scans in some cancers, but for others they required that patients and doctors participate in a data collection effort (called the National Oncology PET Registry, or NOPR) to determine whether PET scans really made a difference in the diagnosis, treatment, staging and monitoring of patients with cancer.
At our meeting on Wednesday, we were asked to review the data in the medical literature regarding research studies that had been done on PET scans show they make a difference. We also had the opportunity to hear about the latest information that came from the NOPR program.
The bottom line was that the panel agreed for some cancers it was reasonably clear that PET made a difference in some aspects of cancer care, while for others there was little evidence of impact or the evidence was equivocal.
In the not too distant future, CMS will take a look at all of this information and make a coverage decision regarding PET scans in those circumstances where they are not now routinely approved for payment.
That was the “headline” purpose of the meeting. However, for me, it was a small detail in a slide presentation that got my attention
You may recall last February there was an international uproar about a paper published in a medical journal that described some laboratory and animal experiments using a commonly available chemical called dicholoroacetic acid, or DCA.
A scientist at the
The simple summary of the theory was based on the observations of a Dr. Warburg back in the early 1930’s, who proposed that cancer cells get their energy through a different pathway than normal cells. Correct the defect in that pathway, and you could kill the cell.
The paper published in 2007 expanded on that hypothesis and demonstrated that the use of DCA in cell cultures and in animals with cancer could kill cancer cells.
The research got a lot of international attention, in part because the scientist (who was not a cancer doctor or researcher) said that this chemical was already approved for human use and could move directly into clinical trials. The other claim was that no one was interested in funding those trials because the chemical was cheap and commonly available. As a result, there would be no profit for a company that would take the clinical trial process forward towards approval for use in cancer treatment.
My position was that, like so many other “breakthroughs” in the lab, this work needed more investigation both in the lab and the clinic to see if there really was merit to the hypothesis. I didn’t say the research was wrong or that it was bad, but I did say that caution was appropriate. What was not appropriate were the claims on the internet that this was a cure for cancer.
There were millions of emails circulating the internet, and I did a blog on the topic which got a lot of exposure. There were comments pro and con, but the difficult part—for me, at least—is that some doctors started to prey on the desperation of patients with cancer by setting up clinics and administering DCA directly to patients.
Fast forward, and the uproar has passed to a large degree. I don’t know if patients are still getting DCA in clinics. A couple of months ago a colleague told me that some clinical cancer researchers were planning on starting clinical trials.
Enter the PET scan meeting on Wednesday.
When one of the doctors was presenting his information, there was a comment on a slide that PET scanning was based in part on the Warburg hypothesis—the very same 1930’s research mentioned above.
That’s when the light bulb lit up.
The Warburg theory rests on how cancer cells metabolize glucose. In PET scans, cancer cells have an abnormal glucose metabolism, and that is why they become visible on the scan after an injection of glucose “tagged” with a radioactive tracer.
More importantly, as was pointed out several times this past Wednesday, the biology behind PET scans is not specific for a certain cancer, but is common to many different types of cancer.
In short, the abnormal glucose metabolism is common in the biology of cancer cells, and that is why PET scans work in so many cancers.
As I started to think about those facts, the link between Warburg, the Canadian researcher, PET scans and the potential treatment implications became more apparent to me.
So maybe the DCA researcher wasn’t so “far out” after all. And it doesn’t take a huge leap to think about the fact that if researchers could take advantage of this phenomenon, it could indeed be a possible approach to the treatment of cancer.
I actually asked one of my expert colleagues at the Wednesday meeting about that possibility. He told me that in fact several researchers were pursuing exactly that question. They are trying to find out if the same abnormal glucose metabolism that makes a PET scan useful can be applied to the treatment of cancer.
I still remain very cautious about the use of DCA in patients. I don’t believe it is a magic bullet, or even that it will have any benefit in the treatment of cancer. We simply don’t have the research that supports that conclusion. As I often say, it is a long road from the bench to the bedside.
But this experience should also serve as a reminder to all of us that you can never say never. You always have to be open to new thoughts and new ideas, and you always have to be prepared to readdress your prior thoughts and opinions based on new and/or additional information.
I continue to believe that conquering cancer isn’t going to come from one magic bullet. The approach is going to be multi-faceted and strategic.
But if we are able to capture the power and theory behind the PET scan, then perhaps we will have another arrow in our quiver as we move forward on this vital journey to reduce the pain and suffering of this terrible disease.