Tumor Volume Kinetic Analyses Might Explain Excellent Prognoses in Young Patients with Papillary Thyroid Carcinoma

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.

Criteria for follow-up of thyroid nodules diagnosed as follicular neoplasm without molecular testing - The experience of a high-volume thyroid centre in Japan

BACKGROUND

Clinical management of follicular neoplasms (FNs) using molecular testing of thyroid-aspirated materials is not routinely performed in Japan. This article aims to identify low-risk FN nodules that can be followed up without molecular testing.

METHODS

The relationship between preoperative findings, factors influencing surgical decision, and the risk of malignancy (ROM) was examined in 356 thyroid nodules with cytological diagnosis of FN at Kuma Hospital from January to December 2020.

RESULTS

ROMs of FN with cytology results favouring malignancy (41.2%) were significantly higher than those favouring benign (7.7%) or borderline (8.2%) (p < .001). Moreover, ROMs of FN with ultrasonography results of high suspicion (54.5%) were significantly higher than those with low (4.5%) or intermediate suspicion (0%) (p < .0001). There was a large difference in overall ROM in tumours bordering 30 mm in size (<30 mm; 3.6%, ≥30 mm; 20.0%). ROMs of FNs with a tumour volume doubling rate (TVDR) of 1.0/year or more (28.6%) were higher than those of FNs with a lower TVDR (9.9%) (p < .05). The ROMs of FNs with or without one or more of the following four findings suggestive of malignancy: cytological findings favouring malignancy, ultrasonography findings of high suspicion, tumour size ≥30 mm, and TV-DR ≥1.0/year, were 14.6% and 1.0%, respectively.

CONCLUSION

FNs with no cytological findings favouring malignancy, no ultrasonography findings of high suspicion, tumour size <30 mm and TV-DR <1.0/year, are considered low risk and can be followed up without the need for molecular testing.

Tumor Volume Doubling Time in Active Surveillance of Papillary Thyroid Microcarcinoma: A Multicenter Cohort Study in Korea

Background: Some papillary thyroid microcarcinomas (PTMCs) may progress with tumor enlargement or development of new lymph node (LN) metastasis during active surveillance (AS). This study evaluated the relevant predictors of disease progression, especially new cervical LN metastasis. Methods: This was a long-term follow-up study conducted using a previous multicenter cohort of AS in Korea. After excluding 54 (14.2%) patients with a short follow-up duration, 326 PTMC patients were evaluated for tumor kinetics, including changes in tumor volume (TV) and TV doubling time (TVDT). Results: During a median follow-up duration of 4.9 years, 17 (5.2%, 95% confidence intervals [CI] 2.7-7.6%) patients showed a maximal diameter increase of ≥3 mm after a median of 4.0 years follow-up, while 9 (2.8%, CI 1.0-4.5%) developed new LN metastasis after a median of 2.2 years follow-up. New cervical LN metastasis occurred exclusively of a maximal diameter increase of ≥3 mm. The prevalence of new development of LN metastasis was higher in patients with TVDT <5 years (7.4%) than in those with TV ≥50% (3.2%). Furthermore, only TVDT <5 years was significantly associated with LN metastasis (p = 0.002). In univariate and multivariate analyses, TVDT <5 years was an independent risk factor for disease progression with respect to new development of LN metastasis (hazard ratio [HR] = 6.51, CI 1.73-24.50; p = 0.002) and tumor enlargement (HR = 20.89, CI 5.78-75.48; p < 0.001). Finally, 86 (22.6%) patients underwent delayed surgery, and the most common reason was patient anxiety. Conclusions: TVDT <5 years is a predictor of disease progression during AS in terms of new LN metastasis development as well as tumor enlargement. Determination of TVDT in the early phase of AS could help in predicting disease progression, tailoring follow-up intensity of AS and in determining if early surgical intervention is needed.

How to identify indolent thyroid tumors unlikely to recur and cause cancer death immediately after surgery-Risk stratification of papillary thyroid carcinoma in young patients

Current histopathological diagnosis methods cannot distinguish the two types of thyroid carcinoma: clinically significant carcinomas with a potential risk of recurrence, metastasis, and cancer death, and clinically insignificant carcinomas with a slow growth rate. Both thyroid tumors are diagnosed as "carcinoma" in current pathology practice. The clinician usually recommends surgery to the patient and the patient often accepts it because of cancer terminology. The treatment for these clinically insignificant carcinomas does not benefit the patient and negatively impacts society. The author proposed risk stratification of thyroid tumors using the growth rate (Ki-67 labeling index), which accurately differentiates four prognostically relevant risk groups based on the Ki-67 labeling index, ≥30%, ≥10 and <30%, >5 and <10%, and ≤5%. Indolent thyroid tumors with an excellent prognosis have the following four features: young age, early-stage (T1-2 M0), curatively treated, and low proliferation index (Ki-67 labeling index of ≤5%), and are unlikely to recur, metastasize, or cause cancer death. Accurate identification of these indolent tumors helps clinicians select more conservative treatments to avoid unnecessary aggressive (total thyroidectomy followed by radio-active iodine) treatments. Clinicians can alleviate the fears of patients by confirming these four features, including the low proliferation rate, in a pathology report immediately after surgery when patients are most concerned.