Since 2000, cancer has been the main cause of death in Quebec (Institut de la statistique du Québec, 2003). However, the standardized death rate due to cancer, like most other causes of death, has been declining steadily since the early 1990s (ministère de la Santé et des Services sociaux, 2003; ministère de la Santé et des Services sociaux, 2004), while life expectancy at birth of the Quebec population has increased in recent decades. With the number of seniors growing steadily and the risk of cancer increasing with age, there is a parallel increase in the incidence of cancer. In addition, as a result of earlier diagnoses and more effective treatments, cancer patients are surviving longer, leading to a high demand for health care as follow‑up for these individuals.
A number of indicators can be used to monitor cancer and measure the burden that it represents for society. The most well‑known ones are the number of new cases reported annually (incidence), mortality, relative survival, potential years of life lost, or the number of people still living who received a diagnosis of cancer over a period of 5, 10 or 15 years, i.e. prevalence (National Cancer Institute of the United States, 2004). Cancer prevalence statistics are useful in estimating the burden on the health system attributable in particular to the treatments required (surgery, chemotherapy, radiation therapy, support treatments), monitoring to detect recurrence, and changes in health that may be permanent as a result of cancer.
To date, it has been impossible to measure the prevalence of cancer among Quebecers because there is no active follow up of new cases reported annually. However, with the recent linkage of the Tumour File with the Deaths File to calculate survival tables, it is now possible to do it.
This report is a brief descriptive analysis of 5, 10 and 15-year prevalence for the main cancer sites by age and sex in 1999.
We are living in a society where life expectancy continues to lengthen and the number of seniors is growing. Since cancer is especially common after the age of 60, we can expect a steady increase in the number of cases in Quebec in the years ahead. In addition, early screening efforts for certain types of cancer where there are large numbers, such as breast, prostate and colorectal cancer, associated with more and more effective treatments, mean that persons with cancer are living longer. Thus, the demand for social and health care services linked to cancer is likely to increase at a faster pace. In this context, the prevalence of cancer is a crucial indicator in planning the resources required to fight this disease.
However, the results of prevalence need to be properly interpreted in terms of the length of monitoring. Five-year prevalence is especially relevant because it includes people who are receiving primary treatment, suffering significant secondary effects linked to the treatments and who are at high risk of recurrence. The burden for society in terms of the care required by these people is quite high.
Prevalence could be very informative when it comes to planning resources for the population that requires initial treatment, those who are considered cured, those who are in the recovery phase of the disease and those in the ongoing recovery phase. The only direct means of reducing the increase in incidence, and thus prevalence, is to prevent cancer. Doing so involves an intensification of the battle against smoking, the promotion of healthy life styles, and maximum use of effective screening measures. In the next few years, a vaccine against the human papillomavirus, the cause of cervical cancer and linked to other cancer sites, could also become part of the arsenal of means available to prevent cancer.