When Lisa Dutton was declared free of breast cancer in 2017, she took a moment to celebrate with family and friends, even though she knew her cancer journey might not be over. As many as one-third of people whose breast tumours are cleared see the disease come back, sometimes decades later. Many other cancers are known to recur in the years following an initial treatment, some at much higher rates.
“It’s always in the back of your mind, and that can be stressful,” says Dutton, a retired health-care management consultant living in Philadelphia, Pennsylvania.
Cancer-fighting immune cells could soon be engineered inside our bodies
As part of her treatment, Dutton had enrolled in a clinical trial called SURMOUNT. This would monitor her for sleeping cancer cells, which many researchers now think might explain at least some cancer recurrence1. These dormant tumour cells evade initial treatment and move to other parts of the body. Instead of multiplying to form tumours right away — as is typical for metastatic cancer, in which cells spread from the main tumour — the dormant cells remain asleep. They are hidden from the immune system and not actively dividing. But later, they can reawaken and give rise to tumours.
Even though Dutton understood that her treatment might not have removed all signs of cancer, she says she was floored in 2020 when dormant cells were found in her bone marrow for the first time.
Researchers are discovering dormant tumour cells, also known as disseminated cancer cells, in association with breast, prostate, lung, colon2 and other cancers, and these cells are increasingly implicated in some metastatic cancers. An estimated 30% of people who have been successfully treated for cancer might harbour these cells, although unpublished work suggests they could be even more common.
Over the past decade, a flurry of efforts have attempted to identify and understand dormant cells, with the ultimate goal of treating them. A handful of clinical trials are now under way to test potential therapies.
Although the first trial Dutton enrolled in only monitored the cells, she has since enrolled in a second, called CLEVER, that aims to eliminate them3. As such trials move ahead, open questions about the sleeper cells, including what induces dormancy and how to fight it, are drawing more researchers into the field.
“We’re starting to see multiple groups converging on some of the same ideas, which is always very affirming,” says Cyrus Ghajar, a cancer biologist at the Fred Hutchinson Cancer Center in Seattle, Washington. The trials under way are “a testament to just how much progress has been made”.
A silent threat
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