More young people are getting colorectal cancer. We're working together to find out why.

By Dr. Kevin Wang, Medical Oncology Fellow in the Eliot Phillipson Clinician-Scientist Training Program at the Princess Margaret Cancer Centre, University Health Network

A worrying trend has emerged in the last few decades: more young people are being diagnosed with certain kinds of cancer, including colorectal cancer. In fact, the American Cancer Society reported  that 20 per cent of colorectal cancer diagnoses in 2019 were in patients under the age of 55, which is about double the rate seen in 1995.

As a medical oncologist in training, I regularly see and treat patients in their 30s and 40s who have been diagnosed with colorectal cancer. Unfortunately, these younger patients are also more likely to be diagnosed at advanced stages of the disease, which means that their cancers are more difficult to treat. Many are only offered palliative treatment.

Although we know that some patients are genetically predisposed to colorectal and other gastrointestinal cancers, the steep rise in number of patients diagnosed at a young age strongly suggests that environmental and lifestyle exposure, including for example diet and obesity, are contributing factors. But to find out exactly what’s causing this worrying trend, we need data, and lots of it.

One way to investigate the potential underlying cause of a tumour – its etiology – is to search for "scars” in the tumour's DNA that provide clues about how the cancer arose. These are called "mutational signatures". In fact, mutational signatures have been used to better understand the genetic backgrounds of more common forms of colorectal cancers and are also being applied to the study of early-onset cancers.

As part of a team led by Drs. Steven Gallinger and Robert Grant at the Princess Margaret Cancer Centre, we've launched a new project that aims in part to identify the molecular profiles and mutational signatures common in young-onset colorectal cancers that may help explain why these cancers are becoming more frequent.

The project is a collaboration with the Ontario Familial Colorectal Cancer Registry, which has been collecting personal and family health information as well as blood and tumour samples from Ontario residents diagnosed with colorectal cancer and their family members since 1997. The registry collects the detailed epidemiological data needed to understand participants’ circumstances leading up to their diagnosis. With funding from the Marathon of Hope Cancer Centres Network, we are generating complementary comprehensive genomic data from some of the registry's samples.

We plan to use this rich bank of information – comprehensive genomic sequencing paired with detailed health and epidemiological data – to reveal connections between mutational signatures of unknown etiology and environmental and lifestyle factors. This will provide insights into why these cancers are occurring, which can then be used to fuel further research studies looking at new methods of prevention and/or treatment.

This project highlights the value of large collaborative efforts and of long-term follow-up studies. The Ontario Familial Colorectal Cancer Registry has, for over two decades, collected detailed information about patients’ lifestyles, histories, and family health. By leveraging this valuable resource and complementing it with detailed genomic data as made possible through the Marathon of Hope Cancer Centres Network, we are gathering the scale and scope of data needed to start answering the “needle in a haystack” question of why the rate of young-onset colorectal cancers is increasing.

This study is a good representation of the increasingly complex questions we need to answer to advance cancer research and improve care, and indeed it’s only by working together that we will be able to tackle these difficult problems. As a clinician-scientist, my goal is to find new ways of providing better care to my patients, and I'm dedicated to working as part of a team to make that happen.

Multidisciplinary collaborations also help advance research with wider-ranging implications. For example, if we can gain a better understanding of why colorectal cancers are becoming more frequent in younger patients, this will lead not only to better screening options that help us identify these cancers at an earlier stage but will also fuel research around more effective prevention strategies.

Although I've focused on colorectal cancer here, it's important to remember that early-onset cancers are also becoming more frequent in other cancer types, including breast, stomach and liver cancers. I believe we have an opportunity to redefine how team science can be leveraged to answer complex and crucial questions across cancer research, and that we must capitalize on this opportunity for the benefit of patients everywhere.