Many Canadian cancer patients who survive the first year after their diagnosis end up surviving for many years more, Statistics Canada reports in a new study.
The study is the first to look at the prognoses for Canadians who have already lived at least one year after a cancer diagnosis. It found that the outlook for these patients tends to improve – sometimes dramatically -- after that first year.
For example, the estimated five-year relative survival ratio for someone diagnosed with pancreatic cancer is just 6 per cent at the time of diagnosis. That may be in part because pancreatic cancer is often not diagnosed until its later states. ("Relative survival" compares the survival of those with cancer to the expected survival for comparable people in the general population.)
But among those who survive the first year, their chance of living another four rises to 28 per cent. And among five-year survivors, it rises to 88 per cent.
Similarly, among those with esophageal cancer, the initial survival odds are around 13 per cent, but that rises to 83 per cent once patients have survived the first five years.
For five-year survivors from colon cancer -- a cancer with an initial estimated five-year relative survival ratio of 63 per cent -- the prognosis is 97 per cent after the first year.
These estimates were calculated based on records from the Canadian Cancer Registry linked to the Canadian Vital Statistics Death Database. The data covers patients diagnosed between 2004 and 2006.
They are based on average survival for the population at large; any individual's prognosis could be different depending on their situation.
The study authors note that most survival estimates are presented as the probability of surviving a given length of time after diagnosis, such as five years.
"However, these estimates are less informative for people who have survived one or more years, as the risk of death due to cancer is often greatest in the first few years. After this initial period, the prognosis can improve substantially, so the earlier estimates no longer apply," they write.
On average, for cancers with an initial five-year survival ratio of at least 80 per cent, survival odds rose to at least 95 per cent after five years' survival. The one exception was breast cancer, whose five-year relative survival ration is 93 per cent after five years.
But for some other forms of cancer, the odds of survival did not necessarily improve. There was no apparent improvement in survival prospects during the first five years after diagnosis for chronic lymphocytic leukemia, with its estimated five-year relative survival ratio remaining at around 80 per cent and did not appear to improve over the next five years.
"For most cancers, the outlook for people who have survived one or more years after diagnosis is better than that at diagnosis, sometimes substantially so," the study authors write.
"…These results could assist people who have survived one or more years after a cancer diagnosis in adjusting their view of the future, and help cancer care providers in planning follow-up."
