(RxWiki News) Generally speaking, cancer takes years – even decades – to develop. So a recent study suggests this fact needs to be taken into account when recommending cancer screenings.
Breast and colorectal cancer screenings should be limited to people who are expected to live at least 10 years, according to a new study. While no one should be denied screening, the study authors emphasized, the harms may outweigh the benefits for those with shorter life expectancies.
"Talk with your doctor about when and how often you should have cancer screenings."
The University of California in San Francisco researchers designed the study to look at how long a person needs to live in order to benefit from cancer screenings.
Other studies have looked at the benefits of screening is (i.e., how many lives saved). No other research has studied the timing of these benefits.
Current guidelines recommend that healthy older patients be screened. The rationale here is that complications from screenings can cause immediate harm, while the benefits of screening sometimes aren’t seen for years.
The goal of this study was to estimate the amount of time it takes for a person to benefit from breast and colorectal cancer screenings.
The researchers analyzed results from five breast and four colorectal cancer screening trials which focused on patients 50 years and older. The trials were published over a 22-year period – from 1986 to 2008.
The trials involved patient populations of just under 40,000 to more than 150,000 individuals. The study members were followed for anywhere from eight to 20 years.
Colorectal cancer screenings
- After five years, screening prevented an average of just under three colorectal cancer deaths for every 10,000 people screened.
- This benefit increased with time – reaching 23 colorectal cancers prevented among 10,000 people after 15 years.
- The authors translated this to absolute terms, meaning how long it actually took to prevent deaths. For colorectal cancer, it took an average of nearly five years to prevent one death for every 5,000 people screened; it took 10.3 years to prevent one death for 1,000 people screened.
Breast cancer screenings
- After five years, an average of four deaths were prevented for every 10,000 women screened.
- 19 breast cancer deaths were prevented after 15 years among 10,000 women screened.
- Absolute terms found it took about three years to prevent one breast cancer death in 5,000 women screened and 10.7 years to prevent one death in every 1,000 women who were screened.
The authors noted that one in every 10 people screened will have a false-positive result, and more will possibly receive unnecessary treatment.
Because of these results, the authors suggest that people who are likely to live 10 or more years should be guided to have breast and colorectal cancer screens. If life expectancy is 3-5 years, though, the individual “probably should be discouraged from screening since the potential risks likely outweigh the very small probability of benefit,” the authors wrote.
"The detection method in older patients should be geared to those cancers which carry a immediate risk of mortality," Christopher Ruud, MD, of the Austin Cancer Centers, told dailyRx News. "For example it might be more appropriate to use physical exam rather than mammography to find breast cancer in women over 80. Physical exams would be more specific, identifying only larger lumps which need removal," said Dr. Ruud, a breast cancer specialist, who was not involved in the study.
The researchers concluded that considering this time-lag information could help both patients and doctors make more informed decisions about screening for these cancers.
This study was published January 8 in the British Journal of Medicine.