In a recent medical news item that you may have missed, an analysis from NORC at the University of Chicago determined that only 14% of cancers in the U.S. are diagnosed by a recommended screening test for breast, cervical, colorectal, or lung cancer. An additional 11% represent prostate cancers detected through PSA screening, which isn't technically recommended. Adding these two percentages together and subtracting from 100% means that 75% of cancers are either detected incidentally or after patients develop symptoms that cause them to seek medical care. Notably, the study was funded by GRAIL, which sells the Galleri blood test for screening for many types of cancer at once (most without currently recommended tests), and the company no doubt plans to use the results to increase demand for its unproven $949 test.
However, there is another way to respond to this analysis. If three-quarters of cancers are detected after symptoms develop, the medical community should focus on improving outcomes by reducing the time from symptoms to cancer diagnosis. In a 2022 JAMA Viewpoint and a more detailed paper in Cancer Prevention Research, Dr. Elizabeth Sarma and colleagues made the case for this approach, arguing that symptom detection should be viewed as a "partner to screening" in primary care. People with possible cancer symptoms don't always seek timely care; a mixed-methods systematic review of 80 studies suggested that older adults often initially attribute symptoms to normal aging, but when they do recognize them as potentially serious, they are quicker to see a doctor than younger persons. Another study found that patients with more than two chronic conditions had a longer diagnostic interval (time from primary care presentation to cancer diagnosis) and a higher likelihood of seeking emergency care, possibly because clinicians incorrectly attributed the symptom to the pre-existing condition rather than cancer.
The diagnostic challenge that family physicians face is that most patients with common symptoms that could be due to cancer don't have cancer. If I ordered a CT scan or referred to a gastroenterologist every adult who presented to my office with abdominal pain, many patients would endure a lot of unnecessary procedures to identify the few with colorectal cancer. A 2019 review found few electronic clinical decision support tools for cancer diagnosis in primary care. However, a Veterans Affairs health system study concluded that visiting a primary care clinician at least annually is associated with substantially lower risks of metastatic disease at time of diagnosis and cancer-related death. So what factors influence our decisions to perform tests or refer patients with symptoms that could represent cancer? A systematic review found that the only factors that consistently prompted more diagnostic workups and referrals were alarm symptoms (e.g., fever or unexplained weight loss) and a "gut feeling" that a serious cause was responsible. This isn't good enough. Alarm symptoms are generally obvious, and gut feelings may overestimate or underestimate risk depending on the physician's training and experience.
Although they perform less cancer screening than we do in the U.S., the United Kingdom is well ahead of us in refining systems for early diagnosis. Dr. Sarma observed that U.K. researchers used data from their national heath system to "generate symptom lists and corresponding positive predictive values ... [that] were used to develop interactive calculators for primary care practice to predict an individual's risk of cancer." She endorsed a three-pronged research agenda: describing pre-diagnostic care pathways for symptomatic cancers; identifying signs and symptoms that can be used to identify patients at higher risk for specific cancers; and improving diagnostic pathways for symptomatic patients by increasing patient awareness and improving point-of-care tests in primary care. Can the U.S. successfully emulate the U.K. model of improving early cancer diagnosis?