TORONTO – The prognosis gets better for people diagnosed with cancer – sometimes substantially – after they’ve survived a year or more, says a new Statistics Canada report that estimates five-year survival ratios for the first time.
The charts and tables released Wednesday cover patients diagnosed between 2004 and 2006, with estimates based on records from the Canadian Cancer Registry linked to the Canadian Vital Statistics Death Database.
“When people are given a prognosis or you’re trying to look at people with cancer, their risk of dying isn’t … the same through that first five-year period – it’s typically concentrated in the first year or first couple years,” senior analyst and epidemiologist Larry Ellison said from Ottawa.
“There’s more risk in the beginning. So if you can get past that initial period and be a survivor, then you’ve gone through the worst stretch and … your outlook is a lot better.”
The report cites relative survival rates. Relative survival compares the observed survival of those with cancer to the expected survival for comparable people in the general population.
Statistics Canada says the estimated five-year relative survival ratio for pancreatic cancer is six per cent at diagnosis, but rises to 28 per cent for one-year survivors and 88 per cent for five-year survivors.
The initial prognosis for those diagnosed with esophageal cancer is 13 per cent, but the relative survival ratio rises to 83 per cent after five years. For colon cancer, the percentage climbs from 63 per cent to 97 per cent.
“For almost all the individual cancers studied, the relative probability of living an additional five years improved when measured at increasingly longer periods after diagnosis, the effect being strongest in the first one to two years,” the report stated.
One exception was chronic lymphocytic leukemia. The five-year relative survival ratio was just under 80 per cent at diagnosis of the disease, and did not appear to improve over the subsequent five years.
Among more common cancers, breast cancer starts out with a relative survival rate of 88 per cent at diagnosis, but the outlook for five-year survivors living an additional five years was 93 per cent.
An official at the Canadian Cancer Society welcomed the results and said health-care providers can use the information to adjust their plans for followup care for cancer patients.
“It’s certainly helpful for predicting prognosis of cancer patients over time, as well as for the patients themselves – this information can give them a better understanding of how they can expect their cancer to progress over time,” said epidemiologist Prithwish De.
But he emphasized that the information applies to whole populations of people with cancer, so it’s not applicable to individuals.
“Each individual cancer patient has their own profile in terms of what their survival will be and that depends on type of treatment, what type of cancer they have and so on,” he explained.
Treatments might explain part of the results in terms of improved survival over time, but De said more research needs to be done to find out what role treatment actually plays, versus other types of factors that impact survival.
“We need to look at ways to improve survival rates initially especially for those cancers that have very poor survival during their first year after a cancer diagnosis,” he said.
“So doing further research to understand what are some of the ways that we can improve care and treatments following an initial cancer diagnosis.”