When my friend told me, “they caught it early,” all I could think was overdiagnosis and overtreatment. However, I kept these thoughts to myself and refrained from even hinting at the possibility. In that moment, I was wearing my supportive-friend-hat, which required setting aside my critical-thinking-PA-hat.
I knew what I was supposed to say, and I stuck to the script. “Oh good,” I told her. After all, maybe it was good they caught her disease early. Maybe this wasn’t an instance of overdiagnosis and subsequent overtreatment. I didn’t know the details of her particular case.
However, what I do know is that in the U.S., we promote preventative medicine as a panacea. If we can catch diseases early, the thinking goes, we can prevent the sequelae and prolong life! This is a compelling promise, and most Americans (clinicians and patients alike) have bought into it, hook, line, and sinker.
But does the promise hold true? With respect to cancer screening in particular, does early detection save lives? We have all been trained to believe that of course it does! In fact, we are so confident in this conclusion that to suggest otherwise is often considered heresy.
However, I wish more people were familiar with the barnyard analogy. Imagine there are three animals — a hummingbird, a rabbit, and a turtle — and each represents a different kind of cancer.
The hummingbird represents a very fast-growing, aggressive cancer. Whether you build a fence around the barnyard or not, the hummingbird is going to get away from you. In this case, screening doesn’t help because the cancer has already spread by the time it’s detectable.
The rabbit is a less aggressive cancer that grows more slowly. Sooner or later, if you didn’t have the fence around the barnyard, the rabbit would run away. In other words, the cancer would spread, causing symptoms and ultimately the patient’s death. However, there’s been a fortunate development: a fence that can keep the rabbit safely contained within the barnyard. This is the kind of cancer where screening is helpful.
The third kind of cancer is represented by the turtle. The good news is, it moves so slowly it would never get beyond the barnyard fence. The patient might die with this cancer, but they won’t die from this cancer. Unfortunately, this is the kind of cancer (also known as indolent disease) that’s often detected as a result of standard screenings.
According to a paper published in The Lancet Oncology, “Indolent disease might account for 15–75% of all cancers, depending on organ type.” These diagnoses and the subsequent treatment regimens end up causing all kinds of side effects and iatrogenic harms — not to mention the stress of the diagnosis itself. Tragically, what these patients go through is completely unnecessary because their cancer wouldn’t have caused a problem in the first place.
The phrase “we caught it early” is best considered as an invitation to think twice. More information is necessary in order to accurately assess the situation. Is this the kind of cancer that’s a hummingbird, a rabbit, or a turtle?
The trouble is, it’s not necessarily possible to make this distinction. Nevertheless, we owe it to our patients to ask the hard-hitting questions. Namely, is there solid evidence that screening for this cancer in an average-risk person improves overall mortality?
The answer might surprise you.
Shannon Casey, PA-C, is a physician assistant and former assistant teaching professor in the Department of Family Medicine at the University of Washington. She writes at The Medical Atlas.
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