Prepared by staff in Prevention and Cancer Control. Citation: Cancer Care Ontario. Cancer Fact: Survival improving for the four most common cancers in Ontario. June 2016. Available at http://www.cancercare.on.ca/cancerfacts. Prepared by staff in Prevention and Cancer Control. Survival improving for the four most common cancers in Ontario (June 2016) The five-year relative survival ratio for all cancers combined improved in Ontario, from 47.6% in 1983–1987 to 62.5% in 2008–2012. The four most common cancers in Ontario—prostate, female breast, colorectal and lung—all experienced an increase in their five-year relative survival ratios. The five-year relative survival ratio is an important indicator of the effectiveness of cancer treatments and cancer control programs. The age-standardized five-year relative survival ratio (RSR) from cancer in Ontario has improved over the past three decades, rising from 47.6% in 1983–1987 to 62.5% in 2008–2012. This means that people diagnosed with cancer between 2008 and 2012 were estimated to be 62.5% as likely to survive for another five years as people of the same age and sex in the general population. The five-year RSR also increased for most individual types of cancer between 1983–1987 and 2008–2012, including the four most commonly diagnosed cancers in Ontario: prostate, female breast, colorectal and lung. Together these account for almost half of all cancers diagnosed in 2012. Improvements in survival over time can be attributed to more effective treatments, as well as greater use of early detection—screening increases survival by allowing cancers to be detected at earlier stages when they are usually more treatable. Even small improvements in survival can reflect a large number of avoided premature deaths. The five-year RSR was highest for prostate cancer (93.9% in 2008–2012), which has had a consistently high RSR over all the time periods shown in the figure. The five-year RSR for breast cancer rose from 72.8% in 1983–1987 to 86.1% in 2008–2012, due, in part, to the implementation of the Ontario Breast Screening Program in the late 1980s. The five-year RSR for colorectal cancer increased from 50.2% in 1983–1987 to 64.5% in 2008–2012, while the RSR for lung cancer rose from 13.6% to 19.6% over the same time period. Although this increase in lung cancer appears modest, it actually represents a considerable improvement because survival is so low for this cancer type. Lung cancer consistently had the lowest survival of the four most common types of cancer over the six time periods shown in the figure because most cases are not detected until they are at an advanced stage and the cancer has spread beyond the lungs. Survival statistics are a key indicator of the effectiveness of cancer treatment and control programs. The first five years after diagnosis are critical for examining survival, and usually involve services such as primary treatment and close clinical assessment for recurrence. After five years, the use of the healthcare system and the chance of recurrence both decrease. For more information on the burden of cancer in Ontario through four major types of indicators—incidence, mortality, survival and prevalence—see Ontario Cancer Statistics 2016, available at www.cancercare.on.ca/OCSreport.