The Phenomenon of Overdiagnosis in Cancer

Overdiagnosis triggers overtreatment, and all of our treatments carry some harm

Abstract
JNCI
This article summarizes the phenomenon of cancer overdiagnosis—the diagnosis of a “cancer” that would otherwise not go on to cause symptoms or death. Archives JNCI 2010.

This article summarizes the phenomenon of cancer overdiagnosis—the diagnosis of a “cancer” that would otherwise not go on to cause symptoms or death. We describe the two prerequisites for cancer overdiagnosis to occur: the existence of a silent disease reservoir and activities leading to its detection (particularly cancer screening). We estimated the magnitude of overdiagnosis from randomized trials: about 25% of mammographically detected breast cancers, 50% of chest x-ray and/or sputum-detected lung cancers, and 60% of prostate-specific antigen–detected prostate cancers. We also review data from observational studies and population-based cancer statistics suggesting overdiagnosis in computed tomography–detected lung cancer, neuroblastoma, thyroid cancer, melanoma, and kidney cancer. To address the problem, patients must be adequately informed of the nature and the magnitude of the trade-off involved with early cancer detection. Equally important, researchers need to work to develop better estimates of the magnitude of overdiagnosis and develop clinical strategies to help minimize it.

Early detection has forced clinicians and researchers to contemplate a more expansive and, to many, counterintuitive definition of the word “cancer.” What most of us were taught in medical school is captured by the terse definition contained in the medical dictionary—“a neoplastic disease the natural course of which is fatal”. It was a simple definition that was largely accurate in an era when patients were diagnosed with cancer because they had signs and symptoms of the disease.

But that all changed after we became technologically able to advance the time of diagnosis and detect cancer early—before it produces signs and symptoms. Now it has become evident that the word “cancer” encompasses cellular abnormalities with widely variable natural courses: Some grow extremely rapidly, others do so more slowly, others stop growing completely, and some even regress. Clinicians are left with the realization that the word “cancer” is less a prediction about disease dynamics and more a pathological description made at a single point in time. Continued adherence to the dictionary definition of cancer, however, can lead to harm—including overuse of anticancer therapies.

Although not yet contained in medical dictionaries, recently, a new word has appeared in the medical literature to describe a side effect of our technological progress: “overdiagnosis.” This article is intended to summarize the phenomenon.

Read Overdiagnosis in Cancer, Oxford JournalsMedicine & Health JNCI,
J Natl Cancer Inst Volume 102, Issue 9Pp. 605-613, March 5, 2010.
Full PDF.

Residual Risk of Breast Cancer Recurrence Five Years after Adjuvant Systemic Therapy

Breast cancer patients who undergo AST are at risk of late recurrences

Residual Risk of Breast Cancer Recurrence 5 Years After Adjuvant Therapy
JNCI, Oxford University Press USA journal, source for cancer news and information.

About 1 in 5 breast cancer survivors who have completed 5 years of adjuvant systemic therapy (AST) suffer a recurrence within the 10 years after their treatment, according to a 2008 study published in the Journal of the National Cancer Institute.

Context and Caveats

Prior knowledge:

Adjuvant and neoadjuvant systemic therapy (AST) improves the survival of breast cancer patients, but there is still a risk that the disease will recur years later.

Study design:

Disease recurrence among breast cancer patients who were disease free 5 years after AST (the landmark) was estimated 5 and 10 years after landmark. Multivariable analysis was used to identify factors associated with recurrence.

Contributions:

Rates of recurrence-free survival at 5 years and 10 years after landmark were 89% and 80%, respectively. The risk of recurrence 5 years after therapy increased with tumor stage (stage 1: 7%, stage II: 11%, and stage 3: 13%) and was also associated with tumor grade, hormone receptor status, and endocrine therapy.

Implications:

Breast cancer patients who undergo AST are at risk of late recurrences, and this risk is associated with certain characteristics of the original tumor.

Limitations:

HER2/neu status was not included in the analysis because the data were not available; aromatase inhibitor treatment was not included because too few women received it.

Sources and full study:

Residual Risk of Breast Cancer Recurrence 5 Years After Adjuvant Therapy, JNCI, June 2008, Vol 100, Issue 16Pp. 1179-1183.

For DES Daughters