Media coverage out of the annual American Society of Clinical Oncology meeting in Chicago today is focused on the presentation and simultaneous publication online in The Lancet Oncology of a study that showed that cancer cells released from a woman’s tumor could be found in her bloodstream, even when the tumor is stage I or II and has not obviously spread, and that even after standard treatment women who had these circulating tumor cells were more likely to have a recurrence than women who did not.
While this sounds like big news, it actually confirms what we have always known.
Twenty years ago in the first Breast Book I wrote, any breast cancer large enough to be detected has already spread. But a smaller cancer has obviously sent fewer cancer cells into the blood stream than a bigger one, and an aggressive cancer has sent off more cells than a slower-growing cancer.
What has changed since then is that we now have the technology to detect these cells. Over the past few years, European researchers have published three studies showing that about 20 to 23 percent of newly diagnosed women have detectable cancers cells in their blood stream prior to starting treatment. The study presented at ASCO was conducted by a US research group, and it shows similar results.
The French REMAGUS study and the German SUCCESS study as well as the current study from the U.S. looked at whether there was a relationship between finding these cells in the blood before treatment and a higher chance of recurrence and or death. All three studies looked at slightly different populations of women but they all reported that finding cancer cells in the blood was an independent predictor of recurrence and survival.
The recent study, led by Anthony Lucci, a surgical oncologist at M. D. Anderson Cancer Center in Houston, found one or more CTCs in a 7.5ml blood sample in 73 (24 percent) of the 302 women they studied. And the presence of these CTCs accurately predicted both recurrence and overall survival. Fifteen percent (11) of the women who tested positive for CTCs had a recurrence, compared to 3 percent (7) of the women who did not have CTCs. And 10 percent (7) of the women with CTCs died during the five-year study period, compared to 2 percent (5) of those who did not have CTCs.
The study also showed a correlation between having a high concentration of CTCs (three or more per 7.5ml of blood), and survival and progression, with 31 percent (5) of the women in this category experiencing a recurrence or dying during the 5-year study.
Currently, a blood test is not routinely done in women with breast cancer to look for CTCs. Should you ask to have it done? No. And here’s why.
Despite the extensive media coverage, as the researchers themselves point out in their article, this study suggests that in the future we might one day be able to use the presence of CTCs to guide treatment choices for women with early-stage cancer. It’s even possible that a blood test might one day take the place of lymph node dissection. But that day is not today.
The key is that the women in all of these studies received the best treatment we had for their type of cancer and yet they still recurred. This means we need to figure out what we can do differently and brings up questions about these cells.
Chemotherapy kills dividing cells. Could these cells be dormant (not dividing) and therefore protected from the chemotherapy until a later date when they settle down in a new location? Or are they a completely different type than the cancer cells in the tumor? A recent provocative study showed that the cells detected in the blood stream are not all of the same type as those in the tumor and so may need a different treatment than the main lesion. All these things need to be worked out before we know what to do with this information.
This study, like the three previously published European studies, tells us that you can find CTCs in the blood of women with breast cancer. But like the three previous studies, it doesn’t provide any information about whether the presence or absence of these CTCs tells us more than the tools that we currently useER, PR, and HER2 status or gene signature tests, like the OncotypeDX score, to determine the best treatment strategy. The researchers say they are now studying whether CTC results provide additional information on top of what we learn from an Oncotype DX score to guide treatment decisions and that’s precisely the kind of information we need to have to know if CTC testing is useful.
Also, and this is very important, having CTCs does NOT mean you are destined to get metastatic disease. In fact, most of the women with CTCs did not have a recurrence and did not die during the study. And, right now, knowing that you do or do not have them would not change the treatment you are offered. So, basically, knowing that you have them will only make you worry or worry more than you already do. That’s not to say that one day this information might be helpful. But right now, we don’t know.
Bottom line: This study tell us again that CTCs can be found in the blood of women with breast cancer. And it tells us that there is a correlation between their presence and survival. However, it does not provide any evidence that breast cancer patients should have a CTC test, or provide any guidance on how to use that information.