Recent research shows that melanoma cases rise during midlife and then drop again in very old age. This is changing how scientists understand the links between cancer and ageing.
TheDigger Intelligence Unit
Unraveling the Age-Cancer Paradox
For many years, scientists believed cancer became more dangerous as people got older.
They thought this was due to a build-up of genetic mutations, longer exposure to harmful substances, and a weaker immune system with age.
But new research from Fox Chase Cancer Centre challenges this idea. It shows that melanoma spreads fastest in middle age and then slows down in very old age.
This means that cancer is not just linked to getting older, but also to changes in our immune system and biology throughout life.
The discovery, shared at the American Association for Cancer Research meeting, suggests the link between ageing and cancer is more complicated than once believed.
Things like long-term inflammation, aging cells, genetics, and the environment all work together to affect cancer risk at different ages.
Why Cancer Peaks in Midlife
In mouse studies, researchers saw that cancer spread the least in young mice, peaked in middle-aged mice, and then dropped in very old mice.
This surprising pattern suggests there is a key time in midlife when the immune system is less able to control cancer.
Lead researcher Mitchell Fane, PhD, said that most cancer studies use young mice, which are like humans in their early 20s. “These young mice have a healthy and intact immune system,” he said. “Understanding how therapies affect older patients could yield better treatment options.”
The Guardians WA special group of immune cells called gamma delta (γδ) T cells seems to play a key role. These cells are part of the body’s early defense system, quickly finding and destroying new tumor cells before they can grow or spread.
These cells help keep tumors inactive and stop them from spreading. Young and very old mice had more of these protective cells, while middle-aged mice had fewer.
Researchers also found that melanoma cells in middle age release molecules that weaken or tire out γδ T cells.
This makes it harder for these cells to find and fight tumors. As a result, cancer spreads more easily, showing that cancer can take advantage of weak spots at any age, not just in older people.
When scientists took away γδ T cells from young and old mice, cancer spread much more, proving these cells protect against cancer.
On the other hand, stopping the signals that weaken the immune system helped γδ T cells work better and protected middle-aged mice again.
These results show that cancer is not just a risk for older people. Problems with the immune system at any age can give tumors a chance to grow and spread.
Breaking Barriers in Ageing Research
One reason this discovery took so long is that studies using older mice are rare.
Less than 10 percent of experiments use aged animals because they cost more and need extra care. To fix this, Fane and his colleague Yash Chabra, PhD, set up a special facility for older mice at Fox Chase Cancer Centre, so researchers can use them more easily.
“Now we have a facility with established colonies of older mice, which makes ageing research less expensive and faster,” Fane said. “It also lets us encourage other researchers to test their models in older mice.”
Next, researchers want to see if these patterns happen with other types of cancer and if boosting the immune system in midlife can slow cancer spread.
They also need long-term studies to learn how lifestyle, genetics, and the environment affect the immune system and cancer risk at every age.
What This Means for People
Although cancer risk usually goes up as people get older, it actually drops in those over 80 or 85. The new research suggests that changes in the immune system over time might explain this surprising trend.
Understanding these dynamics could lead to more effective treatments tailored to different age groups, particularly older adults who are often underrepresented in clinical trials.
It also raises the possibility of developing strategies to shore up immune defences in younger and middle-aged individuals, potentially reducing cancer’s lethality before old age sets in.
A New Frontier in Cancer and Ageing
This research shows that cancer and ageing are not simple or predictable. Middle age might be a key time when the immune system weakens, making it easier for cancer to spread.
By learning more about ageing, scientists hope to find new ways to keep cancer inactive and to improve treatments for people of all ages.