Even as incidence of several types of cancers is rising, death rate does not always rise, and that has led several specialists to explore whether all cancer diagnoses need treatments — and whether treatments in some cases can do more harm than good.
Since the 1990s, the incidence of several types of cancer has doubled in the United States among people under 50, but death rates have not risen proportionately. This has led specialists to question whether all cancer diagnoses require treatment.
A study published in September found that eight types of cancer with the fastest-rising incidence in Americans younger than 50 —thyroid, anus, kidney, small intestine, colorectum, endometrium, pancreas, and myeloma— have doubled in incidence since 1992, but their death rates have remained flat.
The rise in early-onset cancer incidence does not consistently signal an increase in clinically meaningful cancer, according to Vishal R Patel, Adewole S Adamson, and H Gilbert Welch, the authors of the study published in JAMA Internal Medicine.
The authors noted that while some of the increase in early-onset cancer is likely clinically meaningful, it appears small and limited to a few cancer sites, and much of the increase seems to reflect heightened diagnostic scrutiny and overdiagnosis.
They warned that such overdiagnosis —under the belief that more screening and testing would lead to more diagnoses and hence greater reduction in mortality— could be counterproductive.
“Interpreting rising incidence as an epidemic of disease may lead to unnecessary screening and treatment while also diverting attention from other more pressing health threats in young adults,” noted Patel, Adamson and Welch in the paper.
When cancer diagnosis may not need treatment
Whether an increase in diagnosis is a false alarm or a danger signal depends on whether deaths rise as well, Welch told The New York Times.
If more lethal cancers are being found, there should be more deaths. But if the death rate remains steady even as cancer cases rise, many of those diagnoses may not have been needed at all. Welch’s research showed exactly that.
In their paper examining the eight fastest-growing cancers, Welch and co-authors reported that colorectal and endometrial cancer showed a slight rise in deaths, whereas others were stable or had falling death rates.
In some cancers, such as thyroid and kidney cancer, overdiagnosis has been well documented, according to the study. For other cancers, the study noted that incidental detection or earlier diagnosis may explain the trends.
While not among the fastest growing (0.6 per cent per year), breast cancer remains the most common early-onset cancer. Despite rising diagnoses in women under 50, the death rate has decreased by approximately half, according to the study.
Can treatments in some cases do more harm than good?
With cancers that are neither growing nor likely to be fatal, doctors face the question of whether treatment could do more harm than good. But there is also the risk that the cancer could progress later if left untreated with damning consequences.
However, evidence suggests that some cancers have very low fatality rates and may not warrant panic.
For example, a study found a third of adults in Finland had undetected thyroid tumours, yet deaths remained below 1 per cent, according to The New York Times.
A similar study cited by the newspaper from South Korea found that the incidence of thyroid cancer soared with the introduction of widespread ultrasound screening, but deaths did not increase. In fact, it was estimated that up to 90 per cent of cancers discovered and treated did not need to be found.
While treatments do save lives, many treatment regimens can cause infertility and organ damage and lead to debt. And, as per the JAMA study and cases from Finland and South Korea cited by The Times, not many patients with cancer needed diagnosis.
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