Rethinking Low-Risk Papillary Thyroid Cancers < 1cm (Papillary Microcarcinomas): An Evidence Review for Recalibrating Diagnostic Thresholds and/or Alternative Labels

Active surveillance of low-risk papillary thyroid microcarcinoma

Recently, the incidence of thyroid carcinoma has been increasing rapidly worldwide. This is interpreted as an increase in the incidental detection of small papillary thyroid carcinomas by the widespread use of high-resolution imaging techniques such as ultrasonography. However, the mortality rates of thyroid carcinoma have not changed, suggesting that small papillary thyroid carcinomas may be overdiagnosed and overtreated. Active surveillance management has been introduced from Japan since the 1990s, as one of the measures to prevent overtreatment of low-risk papillary thyroid microcarcinoma. Based on the favorable outcomes, active surveillance has been gradually adopted worldwide as an alternative to immediate surgery. The management should be carried out with strict eligibility criteria and close monitoring for cancer progression, under a multidisciplinary team. In addition, an adequate shared decision-making is mandatory for individual patients. Papillary thyroid microcarcinomas with clinically apparent lymph node metastasis, distant metastasis, or invasion to adjacent organs should have surgery.

Cancer overdiagnosis: a challenge in the era of screening

"Screening" is a search for preclinical, asymptomatic disease, including cancer. Widespread cancer screening has led to large increases in early-stage cancers and pre-cancers. Ubiquitous public messages emphasize the potential benefits to screening for these lesions based on the underlying assumption that treating cancer at early stages before spread to other organs should make it easier to treat and cure, using more tolerable interventions. The intuition is so strong that public campaigns are sometimes launched without conducting definitive trials directly comparing screening to usual care. An effective cancer screening test should not only increase the incidence of early-stage preclinical disease but should also decrease the incidence of advanced and metastatic cancer, as well as a subsequent decrease in cancer-related mortality. Otherwise, screening efforts may be uncovering a reservoir of non-progressive and very slowly progressive lesions that were not destined to cause symptoms or suffering during the person's remaining natural lifespan: a phenomenon known as "overdiagnosis." We provide here a qualitative review of cancer overdiagnosis and discuss specific examples due to extensive population-based screening, including neuroblastoma, prostate cancer, thyroid cancer, lung cancer, melanoma, and breast cancer. The harms of unnecessary diagnosis and cancer therapy call for a balanced presentation to people considering undergoing screening, even with a test of accepted benefit, with a goal of informed decision-making. We also discuss proposed strategies to mitigate the adverse sequelae of overdiagnosis.

Active Surveillance of Papillary Thyroid Cancer: Frequency and Time Course of the Six Most Common Tumor Volume Kinetic Patterns

Background: The change in size of the papillary thyroid cancer (PTC) nodule during active surveillance has traditionally been characterized as either stable, increasing, or decreasing based on changes in maximal tumor diameter or tumor volume. More recently, it has been observed that the changes in tumor size observed during observation are more complex with tumor volume kinetic patterns that can be characterized either as stable (Pattern I), early increase in volume (Pattern II), later increase in volume (Pattern III), early increase in volume followed by stability (Pattern IV), stability followed by an increase in volume (Pattern V), or a decrease in tumor volume (Pattern VI). Methods: The frequency, time course, and clinical correlates of these six tumor volume kinetic patterns were analyzed in a cohort of 483 patients with low-risk PTC up to 1.5 cm in maximal diameter followed with active surveillance at our center for a median of 3.7 years. Results: The cumulative incidence of an increase in tumor volume for the entire cohort was 15.9% [confidence interval (CI) 11.8-20.0] at 5 years. At 5 years, most tumors demonstrated stability (78.8%, Pattern I) with 10.0% showing early growth (Pattern II), 4.1% late growth (Pattern III), 1.9% growth then stability (Pattern IV), 0.6% stability then growth (Pattern V), and 5.6% with a decrease in tumor volume (Pattern VI). Tumor volume doubling time during exponential growth significantly differed across the kinetic patterns, with median values of 2.4, 7.1, and 3.3 years for Patterns II, III, and IV, respectively (p < 0.01). Similarly, the time to a change in tumor volume was significantly different across the kinetic patterns, with median values of 1.5, 3, 1.6, 4.7, and 4.1 years for Patterns II, III, IV, V, and VI, respectively (analysis of variance, p < 0.01). Clinical correlates at baseline were not associated with tumor volume kinetic pattern. Conclusions: These six kinetic tumor volume patterns provide a comprehensive description of the changes in PTC tumor volume observed during the first 5 years of active surveillance.