Parallels Between Low-Risk Prostate Cancer and Thyroid Cancer: A Review.

IMPORTANCE: Across many countries, a rapid escalation of the incidence of thyroid cancer has been observed, a surge that nonetheless underestimates the true extent of the disease. Most thyroid cancers now diagnosed comprise small, low-risk cancers that are incidentally found and are unlikely to cause harm. In many ways, prostate cancer similarly harbors a well-behaved subclinical reservoir, a long natural history, and superlative outcomes that have made active surveillance the de facto guideline recommendation for low-risk disease. This review highlights the parallels and differences between prostate cancer and thyroid cancer regarding screening, diagnosis, risk stratification, and considerations for active surveillance. OBSERVATIONS: Prostate cancer and thyroid cancer have undergone recalibrated, de-escalatory shifts to counter changing epidemiologic landscapes. The US Preventive Services Task Force has issued cautionary recommendations on screening via prostate-specific antigen testing or neck ultrasonography, while the thresholds to performing biopsy have increased. Comparable changes to cancer terminology and staging have also helped alleviate patient anxiety and minimize pressure for overtreatment. Long-term, randomized prospective clinical trials for prostate cancer have established active surveillance as a first-line treatment approach for properly stratified low-risk patients, while observational trials for thyroid cancer have also made strides in defining risk and eligibility for surgery. Caveats requiring deeper investigation include aggressive disease in older patients, underestimation of the extent of the disease, and patient-physician bias in shared decision making. For prostate cancer, survival may not improve and function will likely worsen after intervention; for thyroid cancer, patients are younger, surgery is safer, and the bar for surveillance will likely be higher. CONCLUSIONS AND RELEVANCE: Despite similarities in biological indolence between low-risk prostate and thyroid malignant neoplasms, key distinctions in life expectancy and treatment sequelae may ultimately confer somewhat disparate management paradigms for the 2 diseases. Nevertheless, the experience forged by prostate cancer trials serves as a model for thyroid cancer management, potentially reshaping the perception of active surveillance into a credible, valuable treatment modality.