Following nearly 30 percent of successful breast cancer treatments, tumors return, claiming 685,000 lives worldwide every year. Now, we may have a new method for significantly reducing those recurring cases.
A study led by researchers from the University of Pennsylvania shows that actively targeting dormant tumor cells (DTCs) lingering in the bone marrow and other parts of the body can keep patients cancer-free.
Currently, patients who’ve been treated for breast cancer are carefully monitored to see if the tumor returns. This new approach doesn’t involve waiting and monitoring: instead, drugs are used to attack the root causes of a relapse.
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“Right now, we just don’t know when or if someone’s cancer will come back – that’s the problem we set out to solve,” says medical oncologist Angela DeMichele from the University of Pennsylvania.
“Our study shows that preventing recurrence by monitoring and targeting dormant tumor cells is a strategy that holds real promise, and I hope it ignites more research in this area.”
It’s only in the last few years that these dormant cells were confirmed as potential targets for treatment. Other recent studies have pointed to pathways and drugs that might be used to reach DTCs, leading the researchers to hydroxychloroquine (which treats autoimmune diseases), everolimus (an existing anti-cancer drug), or both.
The results of a series of tests on 51 people who had previously had breast cancer and were confirmed to have DTCs were quite dramatic. Individually, the drugs cleared up to 80 percent of the DTCs, but together they were even more effective, wiping out 87 percent of the dormant cells.
In the group that took both hydroxychloroquine and everolimus, all of the participants remained cancer-free after three years. For those who took either drug on its own, the survival rate was still an impressive 92-93 percent.
The same positive results were seen in tests on mouse models of cancer, run before the human trials to test the effectiveness of the approach. The animal testing also enabled the researchers to get a closer look at the mechanisms by which the drugs were working.
“Surprisingly, we’ve found that certain drugs that don’t work against actively growing cancers can be very effective against these sleeper cells,” says cancer biologist Lewis Chodosh from the University of Pennsylvania.
“This tells us that the biology of dormant tumor cells is very different from active cancer cells.”
Not all breast cancer survivors have these DTCs left in their system, but for those who do, the early signs for this treatment are promising. The next steps are to run trials with a larger number of participants and to test different drug combinations and doses.
Right now, breast cancer that comes back is virtually impossible to eliminate completely, which leads to a large proportion of the overall deaths from the disease, casting a shadow over how effectively it can be tackled the first time around.
“The lingering fear of cancer returning is something that hangs over many breast cancer survivors after they celebrate the end of treatment,” says DeMichele.
The research has been published in Nature Medicine.
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