What Does '5-Year Survival' in Breast Cancer Really Mean?
Researchers question the meaning of 5-year survival and stress the importance of context in the discussion of survivorship related to breast cancer.
The Centers for Disease Control and Prevention (CDC) recently reported an increase in the proportion of persons with cancer who survive 5 years or more after diagnosis, to about 2 of every 3 persons.1
The increase is attributed to improved early detection and treatment of cancer. The 5-year relative survival rate was defined as the proportion of persons surviving 5 or more years after cancer diagnosis compared with the proportion of survivors expected in a set of comparable cancer-free persons.1
For the clinician treating one of the 231,840 women and 2,350 men estimated to be diagnosed with breast cancer in 20152—and the nearly 3 million United States women with a history of breast cancer alive today3—what does “5-year survival” really mean?
Who and when it was first determined 5 years would be a benchmark for cancer survivorship is uncertain. Richard Manrow of the National Cancer Institute (NCI) told Cancer Therapy Advisor that the rationale for is use “is that most recurrences of cancer—of all types—usually occurs within the first 5 years of treatment given with curative intent.”
Riccardo Capocaccia, PhD, of the Department of Preventive and Predictive Medicine at the Fondazione Istituto Nazionale Tumori in Milan, Italy, said 5 years is considered “a historical legacy that we accept for consistency and comparability reasons. However, in some cases, such as breast or prostate cancers, it is too short a period to detect substantial survival variations. On the contrary, for lung, liver, or pancreatic cancer, 1- or 3- year survival are more informative indicators.”
Dr. Capocaccia and colleagues recently published a study on the life expectancy of patients with colon, breast, and testicuclar cancer using the NCI's Surveillance, Epidemioliogy, and End Results (SEER)-based population data.4
The impetus for the study, He told Cancer Therapy Advisor, arose from his commitment to write a chapter on prevention and health promotion for a book devoted to the quality of life of long-term survival, defined as those alive 5 years or more after diagnosis.
“I felt it useful to give figures on the expectation of life in those patients, compared to people of the same age and sex but never diagnosed of cancer,” he said. However, “I found a lot of data on cancer patients' life expectancy at diagnosis, but none at different times after the diagnosis or the main treatment.”
Their study estimated life expectancy of patients with cancer and corresponding differences with respect to cancer‐free persons by age and time since diagnosis.
They found that “during the first years after cancer diagnosis, young patients face a much higher loss in life expectancy than older ones. Thereafter, the patients' life expectancy gradually approaches, but never reaches, that of the general population.”
This is important in that “reaching the same life expectancy of cancer-free people is often indicated as the condition for defining survivors as ‘cured from cancer,'” their study reported.
For breast cancer, the initial drop in life expectancy varied from 8.7 years among those ages 40 to 44 years to 2.4 years at ages 70 to 74 years.
Although those diagnosed at age 72 years never reached 5‐year conditional relative survival greater than 95%, at 12 years postdiagnosis, a less than 1‐year difference in life expectancy was reached, they found.4
“Life expectancy by age and time from cancer diagnosis is an informative indicator of the persisting impact of the disease on patients,” Dr. Capocaccia said. “Soon after diagnosis, young patients face a higher loss in life expectancy, with respect to cancer-free people of the same age, than older ones.”
He said “5-year survival” and “life expectancy” each have “different advantages and disadvantages, and should be used for different aims.”
For example, “5-year survival is very informative on what happens in the period immediately following diagnosis. It is mainly used to compare cancer outcome between different treatments (in the clinical trials setting) or between populations and time periods (in the public health setting),” he said.
“Its interpretation is in some cases made difficult by the lead-time phenomenon (anticipation of diagnosis without actual postponement of death) and by diagnosis of cancers that would have not become clinically relevant during patients' life (typically a fraction of prostate, thyroid, and, to some extent, breast cancers). A correct interpretation of survival rates needs, in these cases, supplementary information on stage at diagnosis and on soundness of diagnostic examinations.”