Greater availability of screening tests may be improving survival for some cancers. (CBC)

The long-term prognosis has generally improved for most types of cancer since the 1990s — sometimes markedly, according to new data from the Canadian Cancer Registry.

The overall five-year survival rate of Canadians diagnosed with cancer in the period from 2004 to 2006 is estimated to be 62 per cent of that of an identical group without cancer.

That's up slightly from 60 per cent for cancers diagnosed in the 1998-2000 period. In the 1994-1996 period, the ratio was 57 per cent.

"We are heartened to see that ... the overall five-year survival rate is 62 per cent and that's holding steady," said Gillian Bromfield, senior manager of cancer control policy with the Canadian Cancer Society.

"We want to see that go up. Sixty-two per cent is still in my mind, too low."

The 10-year survival rate is almost as high as the five-year rate — it's estimated at 58 per cent for cancers diagnosed in the 2004-2006 period.

"A diagnosis of cancer does not usually mean that death is imminent," the study notes.

The five-year relative survival ratio compares the observed survival of a group of people with cancer to the expected survival of other individuals assumed to be cancer-free.

For some cancers, the survival ratio has gone up appreciably. Liver cancer, for instance, saw its five-year survival rate almost double from nine per cent in 1992-1994 to 17 per cent. Leukemia's five-year survival ratio went from 44 per cent to 54 per cent and non-Hodgkin's lymphoma rose from 51 per cent to 63 per cent.

Reasons for improvement

For some cancers, long-term survival is very likely. The five-year survival rate for thyroid cancer is 98 per cent; prostate cancer's five-year rate is 96 per cent; and for testicular cancer, it's 95 per cent.

Breast cancer's five-year survival rate is now 88 per cent. It was 87 per cent in the 1998-2000 period.

"Big numbers like this usually don't lie," said Dr. Tom Hudson, president and scientific director of the Ontario Institute for Cancer Research in Toronto.

Hudson attributed the improved survival ratios to:

• Early detection of tumours that tend to be smaller and less aggressive.
• New treatments like Herceptin for 15 per cent of breast cancers.
• Greater availability of screening tests for colorectal and cervical cancers and melanoma.
• Safer forms of chemotherapy that have reduced complications.

But some types of cancer continue to be particularly lethal. The five-year survival rate for cancer of the pancreas is just six per cent; for esophageal cancer, it's 13 per cent; and for lung cancer, the five-year survival ratio is 16 per cent.

Some cancers are particularly lethal in the first year after diagnosis. Pancreatic cancer, for instance has a one-year survival ratio of just 21 per cent — the lowest figure among 23 kinds of cancer studied.

Pancreatic cancer is a major research focus for the Ontario institute, which is part of the International Cancer Genome Consortium. Pancreatic cancer is often identified late and has few therapies, but the genome effort aims to look for new treatments, Hudson said.

For most cancers, the figures tend to show that the younger the patient, the better the outcome. For instance, the five-year survival ratio for brain cancer was 58 per cent among people aged 15 to 44. But it plunged to just nine per cent for those aged 65 to 74 and four per cent for those over 75.

But for other cancers, such as breast cancer and colorectal cancer, the five-year survival rate was similar among four age groups under age 75 — slipping only when diagnosis occurred after age 75.

Cancer become the top killer in Canada in 2007. Cancer is still increasing because the population is increasing and aging, experts say.

The population information is meaningful for newly diagnosed patients, said Hudson. Often their first questions are about understanding their risk, and having valid numbers on survival helps answer those questions, he added.

Cancer incidence data was taken from the July 2010 version of the Canadian Cancer Registry, a database maintained by Statistics Canada. Mortality figures have been calculated for people aged 15 to 99.

Data from Quebec was excluded because of differences in ascertaining the status of some cases.

With files from The Canadian Press