Leukemia/Lymphoma Study for Twins at Fox Chase

Dr. Mitchell R. Smith is recruiting identical twins for a blood-cancer study

This week, my aunt is in town visiting us, as she does every summer. On the itinerary: patronizing the fabulous malls of the Garden State, seeing the new Harry Potter—oh yeah, and participating in a twin cancer study.

My mom and her sister are identical twins. My mom has a chronic form of leukemia—the sort of thing you typically live with, rather than die from—and she sees doctors at Fox Chase Cancer Center. She recently learned that Dr. Mitchell R. Smith, director of the lymphoma service at Fox Chase, is recruiting pairs of identical twins for a study about blood cancers, and both my mom and aunt were eager to participate. When I learned that Dr. Smith is still in need of participants, I scheduled a chat with him to get more information.

How long has the study been in progress? It was about a year and a half ago that we had thought about this, when we happened to have a set of twins. We did the study on them and had some interesting results. But it’s hard to convince people [of these findings] with one set, so we’re trying to expand it at this point. We think if we had 10 sets, we’d have pretty solid evidence. We just had a second set come in, and we’ve identified a third set that’s eligible.

Ten pairs of twins? Compared to studies I read about in the news, that sounds like a really small size. It is a small group, but it’s not a common event—identical twins plus lymphoma incidence.

Does the study take a long time? What kind of commitment does it require? We take a few tubes of blood and take it off to lab. That’s it.

No questionnaires about lifestyle, diet or medical history? What can you tell from the blood samples? We’re asking, in the case of a lymphoma for example, why does it grow when the immune system should recognize and kill it? We think there’s something there in the immune system. So we take the blood and test the patient cells with their own immune cells and then compare the patient cells to the “normal” immune cells in their twin.

When you say “test the patient cells,” what kinds of cells are you referring to? We’re talking about the lymphoma cells. We’re asking, What happens when the patient’s immune system tries to attack the lymphoma cells? It’s clear that they are unable to do that, because the lymphoma grows. Are the lymphoma cells immune to the attack, or is there something wrong with the patient’s immune system? Or is it both?

Can you explain the significance of studying identical twins in a study of this type? Sure. We want to look at identical immune cells. The idea is, we’re interested in what we call “natural killer cells,” which vary quite a bit from person to person. In identical twins, you have as close as you can get to identical genes in the natural killer cell. They’re not truly identical, because they’ve been exposed to things in the patient’s life, but because these cells are part of the innate immune system, they don’t “learn” as much from previous immune conditions. Down the road, this might have implications for the development of vaccines, too.

Are you focusing only on people from Philadelphia? No. We’re happy to facilitate as best we can. If people live far away, I imagine we could get them to a lab or work with them to get their samples. It just happens to be patients we see [at Fox Chase] so far. We haven’t gone out advertising for patients yet. We wrote the study just for that first pair of twins, and the results were interesting, so we’re expanding the study.

What was interesting about that pair’s results? It looked like there was a very specific change on the surface of the natural killer cells, which prevented them from recognizing the lymphoma. If we find that [this specific change] is a theme, we could try to turn the recognition signal back on.

Once you’ve found 10 pairs and studied all their samples, what happens next? Will you publish a paper? Will the participants be notified of your findings? We submit an abstract, usually to the American Society of Hematology, then present the data there and follow it with a paper. And perhaps we might get money from grants to do more research. We don’t always have a formal mechanism for informing people of our results, but for a study of this size where people are kindly donating their blood, we’ll probably get in touch with participants.

If people want to participate in the study, how can they find out more? Pairs of identical twins where one—or even both—has leukemia or lymphoma can call me at 215-728-2674 or email me at mitchell.smith@fccc.edu.