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Findings

Survival varies by type of cancer
Survival varies by age
The data
Conclusion

A diagnosis of cancer does not usually mean that death is imminent. The five-year survival of Canadians diagnosed with invasive cancer is predicted to be, on average, 62% of that of an otherwise similar group of people without cancer. Of course, the term “cancer” is used to refer to myriad malignancies—each of which confers a distinct illness and prognosis. Some cancers are far more lethal, and within a shorter time-span, than are others.

With records from the Canadian Cancer Registry (CCR) linked to the Canadian Vital Statistics Death Database, relative survival statistics have been calculated. Cohort-based survival estimates from cancer are routinely published by Statistics Canada1; the most recent pertained to cases diagnosed from 1992 to 2000. This report provides predicted survival estimates for cases diagnosed in 2004 to 2006. Duration- and age-specific relative survival estimates are derived for 23 of the most commonly occurring cancers in people aged 15 through 99; five-year survival estimates for cases diagnosed in 2004 to 2006 are compared with those diagnosed in 1992 to 1994.   

Survival varies by type of cancer

For all cancers combined, the five-year relative survival ratio (RSR) was estimated at 62%—meaning that the predicted probability of surviving five years following a diagnosis of cancer in the years 2004 to 2006 was about three-fifths the survival probability of persons not diagnosed with cancer (Table 1). The ten-year RSR was nearly as high: 58%. Five-year RSRs ranged from 6% for pancreatic cancer to 98% for cancer of the thyroid. Relative survival was high for cancers of the prostate (96%) and testis (95%), skin melanoma (89%), and breast cancer (88%). Cancer sites for which five-year RSRs were low included esophagus (13%), lung and bronchus (16%), and liver (18%).

Table 1 Predicted relative survival ratios, by type of cancer and survival duration, population aged 15 to 99 at diagnosis, Canada excluding Quebec, 2004 to 2006

With some important exceptions for individual cancers, relative survival exhibited a general pattern of a fairly substantial decline in the year following diagnosis, a somewhat more gradual fall over the next two years, then a smaller decline over the interval from three to five years after diagnosis. From five to ten years after diagnosis, the decline in survival was typically, but not invariably, small.

In the year after diagnosis, the most lethal cancer was pancreatic, with a one-year RSR of 21%. Other cancers with low one-year RSRs were esophageal (37%), lung and bronchus (39%) and liver (40%). From one to three years after diagnosis, RSRs for multiple myeloma, ovarian and esophageal cancer fell the most steeply of all cancers—each by slightly over 20 percentage points.

In the period from three to five years after diagnosis, the RSRs with the greatest declines were those for multiple myeloma and ovarian cancer, which fell by 13 and 11 percentage points, respectively. From five to ten years after diagnosis, RSRs for most cancers declined by less than 5 percentage points. The most notable exceptions included multiple myeloma and cancer of the larynx, which declined by 15 and 11 percentage points, respectively.

Among cancers with high survival, breast cancer had a relatively large RSR decline of 6 percentage points after five years. For cancers of the prostate, testis and thyroid, the RSR at ten years from diagnosis remained nearly at the same level as at one year (Figure 1).

Figure 1 Ten-year cumulative relative survival ratios, selected cancers, Canada excluding Quebec, 2004 to 2006

Survival varies by age

Relative survival differed by age. For most cancers, the RSR was higher at younger than older ages, and for some cancers, the survival advantage at younger ages was quite marked. For example, at ages 15 through 44, the five-year RSR for cancer of the brain was 58%, compared with 9% at ages 65 through 74, and 4% at ages 75 through 99 (Table 2).

Table 2 Predicted five-year relative survival ratios (RSR), by type of cancer and age group, population aged 15 to 99 at diagnosis, Canada excluding Quebec, 2004 to 2006

For other cancers, when diagnosis occurred before age 75, relative survival was similar across the four age groups 15 to 44, 45 to 54, 55 to 64 and 65 to 74, but was lower among people diagnosed between ages 75 and 99. To illustrate, the five-year RSR for colorectal cancer in the four younger age groups ranged from 65% to 68%, but was 58% in the oldest age group. The RSR for breast cancer was 87% to 90% in age groups younger than 75, but 82% among people diagnosed at ages 75 to 99.

Associations between age and survival emerge more clearly when finer age groups are examined. Breast cancer five-year relative survival has been reported elsewhere as 82% when diagnosed before age 40, and prostate cancer, as 82% for men aged 80 to 99.20  

From 1992-1994 to 2004-2006, five-year relative survival for a number of cancers increased—usually slightly, but in some cases, appreciably (Figure 2). For example, the age-standardized RSR for non-Hodgkin lymphoma rose from 51% to 63%; that for leukemia, from 44% to 54%; and for liver, from 9% to 17%. For other cancers, age-standardized RSRs were stable (bladder, corpus uteri and pancreas) during the period. Increases in RSRs over time may reflect diagnosis at an earlier stage of the disease—when treatment is more effective or from which point survival is artefactually longer—or improvements in treatment.

Figure 2 Age-standardized five-year relative survival ratios for cases diagnosed in 1992 to 1994 and in 2004 to 2006, by type of cancer, population aged 15 to 99, Canada excluding Quebec

The data

Cancer incidence data are from the July 2010 version of the Canadian Cancer Registry (CCR), a dynamic, person-oriented, population-based database maintained by Statistics Canada. The CCR contains information on cases diagnosed from 1992 onward, compiled from reports from every provincial/territorial cancer registry.

A file containing records of invasive cancer cases and in situ bladder cancer cases (the latter are reported for each province/territory except Ontario) was created using the multiple primary coding rules of the International Agency for Research on Cancer.2 Cancer cases were classified based on the International Classification of Diseases for Oncology, Third Edition3 and grouped using Surveillance, Epidemiology, and End Results (SEER) Program grouping definitions, with mesothelioma and Kaposi’s sarcoma as separate groups.4 

Mortality follow-up through December 31, 2006 was determined by record linkage to the Canadian Vital Statistics Death Database (excluding deaths registered in the province of Quebec), and from information reported by provincial/territorial cancer registries. For deaths reported by a provincial registry but not confirmed by record linkage, the date of death was assumed to be that submitted by the reporting registry.

Analyses were based on all primary cancers—an approach that is becoming standard practice, as the wisdom of restricting analyses to first primary cancers in an individual has been questioned.56 The effect of including multiple cancers in survival analyses has been studied internationally56 and in Canada.7 Data from the province of Quebec were excluded from the analysis primarily because of issues in correctly ascertaining the vital status of cases. Records were also excluded if: age at diagnosis was younger than 15 or older than 99; diagnosis was established through autopsy or death certificate; or the year of birth or death was unknown.

Relative survival was estimated.8 It is defined as the ratio of the observed survival of a group of people with cancer to the expected survival for people in the general population who are assumed to be free of cancer and otherwise have the same characteristics affecting survival as the group with cancer.8 Survival analyses were based on a publicly available algorithm,9 to which minor adaptations were made. Expected survival proportions were derived from sex-specific, complete provincial life tables using the Ederer II approach.10 Further detail on the survival methodology used is provided elsewhere.1

The cohort-based method of cancer survival analysis includes only cases diagnosed within defined calendar years and with the potential to be followed over the full duration of interest (for example, five years). Long-term survival estimates derived using the cohort approach may not reflect the long-term survival experience expected for newly diagnosed individuals if the prognosis has changed recently. To address this issue, period analysis was introduced to derive more up-to-date estimates of long-term survival.1112 With this method, follow-up data do not relate to a fixed cohort of patients. Rather, estimates are based on the assumption that people diagnosed during the period of interest will experience the most recently observed conditional probabilities of survival. When survival is generally improving, a period estimate tends to be a conservative prediction of the survival that is eventually observed.13-16 

Period-based survival estimates using CCR data have been published on an ad hoc basis17-19 and not to the same level of detail as the cohort estimates. Cohort-based survival estimates dating back to cases diagnosed in 1992 are routinely published by Statistics Canada—the latest publication includes cases diagnosed as recently as 2000 and followed to 2005.1 

For this report, relative survival ratios (RSR) for cases diagnosed in 1992 to 1994 were derived using the cohort method; predicted RSRs for 2004 to 2006 were derived using the period method. Age-standardized estimates were calculated using the direct method by weighting age-specific estimates for a given cancer to the age distribution of persons diagnosed with that cancer from 1992 to 2001.

Conclusion

Survival from cancer depends on the type of cancer and the age at diagnosis. Generally, relative survival is greater when cancer is diagnosed in early rather than later adulthood, but for some of the most common cancers, survival is less affected by age. The data suggest that since 1992 to 1994, the prognosis after diagnosis has generally improved somewhat—and notably so for a few cancers.

Statistics derived from an entire population’s cancer survival experience provide a useful indicator of the disease’s burden. These estimates reflect the average survival time of large groups of people and do not necessarily reflect an individual’s chances of surviving for a given period. The prognosis for a specific person diagnosed with cancer will take into account individual factors that may affect survival such as frailty, co-morbidity, stage of disease at detection, treatment modality, and response to treatment. Nonetheless, the data provide excellent information on the impact of various types of cancer following diagnosis.

Acknowledgement

The Canadian Cancer Registry is maintained by Statistics Canada. It is comprised of data supplied by the provincial and territorial cancer registries whose cooperation is gratefully acknowledged.