By age 45, more than 80 per cent of childhood cancer survivors will grapple with serious or life-threatening effects stemming from their treatments. These repercussions range from heart disease to colorectal and breast cancer, according to a recent Canadian study.
The study, published Monday in the Canadian Medical Association Journal (CMAJ), found that adult survivors of childhood cancer are at elevated risk of sickness and death compared to the general population.
The risk of colorectal cancer is two to three times higher than for the general population. Additionally, females who received chest radiation therapy during childhood have a breast cancer risk similar to individuals with a genetic mutation predisposing them to the disease.
“I think people believe that you treat a child with cancer, you cure them, and then it’s fantastic and that we move on,” said Dr. Paul Nathan, co-author of the study and an oncologist in the division of haematology and oncology at SickKids in Toronto.
“But the problem is we cure them with pretty heavy chemotherapy or radiation or surgery or transplants, often a combination that has long-term problems as a consequence,” he told Global News.
Around 1,000 children get cancer every year in Canada, according to a 2021 study by the Public Health Agency of Canada (PHAC). But almost 84 per cent of children survive a cancer diagnosis after five years.
Although the survival rate is high, Nathan said, children are particularly vulnerable to cancer treatment because their bodies and organs are still developing. Chemotherapy and radiation, crucial though they may be, can trigger long-term side effects that manifest years later. Despite this, Nathan noted that many cancer survivors may remain unaware of these potential complications.
The Ontario-based researchers said they were well aware of the challenges surrounding follow-up screenings after childhood cancer treatments, which is why they decided to look at data to see how many people were adhering them.
The researchers analyzed Ontario data from 3,241 childhood cancer survivors diagnosed between 1986 and 2014. Focusing on those exposed to radiation treatments or certain chemotherapies, the study assessed their elevated risk for breast cancer, colorectal cancer or cardiomyopathy (heart disease).
Of the entire group, 2,806 (87 per cent) were at risk for at least one of these late effects, 345 (11 per cent) were at risk for two and 90 (three per cent) were at risk for three late effects.
“We’ve shown conclusively that if you’ve had certain chemotherapies or radiation or bone marrow transplants, your risk for these late effects or late toxicities is even higher,” Nathan said.
Guidance exists but is rarely used
The North American Children’s Oncology Group has developed a series of long-term follow-up guidelines aimed at monitoring adults who battled cancer during childhood.
For instance, people exposed to radiation therapy targeting the head, brain, neck, or spine during childhood are at risk of thyroid cancer. Because of this, the guideline recommends yearly thyroid exams.
Females who received chest radiation during childhood may also face increased breast cancer risk, and yearly breast exams starting at puberty are recommended, along with annual mammograms eight years post-radiation.
In terms of undergoing chemotherapy as a child, there are several potential late effects including, acute myelogenous leukemia (AML), which is cancer of the blood and bone marrow. Yearly physicals after exposure to the agent are recommended.
Although the guideline exists, the authors of the CMAJ study say the number of survivors who followed the screening recommendations was low. The study found only 13 per cent were complying with colorectal cancer screening recommendations, six per cent were following breast cancer screening guidelines and 53 per cent were adhering to cardiomyopathy screening recommendations.
Those older at diagnosis were more likely to follow the cancer screening guidelines. In contrast, the study found, younger age at diagnosis was associated only with a higher likelihood of following screening guidance for cardiomyopathy.
Regarding the age range of these complications appearing, Nathan said it depends on the patient.
“They can happen at any time. Some of our patients have these problems from the day they start treatment and they persist throughout their lives. But for many of them, they don’t develop until later,” he said. “There’s a period where the damage is subclinical or we’re not able to see what’s going on until it manifests itself. And that can take years or decades.”
Why do patients stop going?
Dr. Jennifer Shuldiner, a co-author of the study and scientist at Women’s College Hospital in Toronto, said the guidelines are very complex, they’re very long and they’re also constantly changing.
To use the guidelines, a patient or physician must also know the treatment that was received during childhood, which could have been decades past, she said.
“So the person often might not know what treatment they received. And then if they have a family physician, the family physician might not have access to that information or would have trouble finding that information. So that kind of complicates the situation,” Shuldiner added.
In Canada, there are numerous clinics available for childhood cancer survivors, though they are primarily located in major cities. And for patients in their 30s, 40s, or 50s, who are significantly removed from their cancer treatment, she said attending follow-up appointments can present challenges. Factors such as lack of awareness about the risks, accessibility issues, and associated costs childcare or parking fees) may contribute to patients foregoing these appointments.
The study found that despite primary care physician visits, survivors’ adherence to breast and colorectal cancer surveillance guidance was low. Primary care physician visits were associated only with higher adherence to cardiomyopathy surveillance.
“This may reflect practical barriers; compared with other surveillance tests, echocardiography is more readily available and less restrictive for primary care physicians in Ontario to arrange than a multitarget stool DNA test,” the authors said.
What's next?
Building on the findings, the researchers said they will soon be launching a province-wide study to see if surveillance reminders for childhood cancer survivors and their family doctors will prove to complete these potentially life-saving tests.
“It would be to use the same process by which people get sent reminders for colon cancer checks or pap smear checks or breast cancer screening, which currently does happen in the general population in Ontario and also happens in the high-risk population,” Nathan explained.
The idea, he said, would be to contact these high-risk groups and their doctors, reminding them of the needed tests.
“We are hoping that if we can show that the system works and it’s cost-effective, that a body like Ontario Health would be willing to take it as one of the programs,” he said, adding that it’s a bonus if other provinces follow suit.
Meanwhile, he suggested that childhood cancer survivors can head to the Pediatric Oncology Group of Ontario website to find further information about accessing treatment.
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