BRAF p.V600E genetic testing based on ultrasound-guided fine-needle biopsy improves the malignancy rate in thyroid surgery: our single-center experience in the past 10 years

In recent decades, the incidence of thyroid cancer in several countries has markedly increased, resulting in thyroid cancer representing 3% of the global incidence of all cancers (Li et al. 2020; Miranda-Filho et al. 2021). A recent study only found a rapid increase in the incidence of the papillary thyroid cancer (PTC) subtype, with small increases or decreases in other subtypes (follicular, medullary, and anaplastic) (Miranda-Filho et al. 2021). PTC is the main type of thyroid cancer, accounting for about 90% (Davies and Hoang 2021). The development of thyroid cancer is very complex, and the prognosis for thyroid cancers of different pathological types is very different, which requires standardized clinical management and treatment. In patients with indeterminate thyroid nodules, the subtype can be determined by diagnostic surgery, only 23% of postoperative pathologic findings are thyroid cancers, while the remaining 77% of patients undergo unnecessary thyroid surgery (Ianni et al. 2020).

Ultrasound examination is one of the most accurate physical diagnostic methods to assess the risk of malignancy in patients with thyroid nodules before surgical treatment (Russ et al. 2017). When thyroid nodules are suspected to be malignant by ultrasound examination, UG-FNAB is suggested to identify the benign and malignant nodules and provide a basis for the subsequent clinical treatment plan according to the 2015 American Thyroid Association (ATA) guidelines (Haugen et al. 2016). However, some thyroid nodules cannot be characterized by cytological examination. As a new diagnostic method, genetic testing using molecular markers (such as BRAF, RAS, and RET) is recommended for the auxiliary diagnosis of patients with thyroid nodules when cytological results are uncertain (Alexander et al. 2012; Duick et al. 2012). BRAF p.V600E mutation is the most common gene mutation in PTCs. Its incidence varies significantly with geography. Some studies suggest that BRAF p.V600E is associated with 40% to 50% of PTCs in the United States but is identified in up to 80% of PTCs in Asia (Yip and Sosa 2016). Previous review has shown that “Despite a high specificity for thyroid cancer, BRAF p.V600E mutation has a low overall sensitivity and therefore has a limited diagnostic value as a single screening test (Jinih et al. 2017)”. However, another study has pointed out that “BRAF p.V600E mutation is potentially useful adjunct to thyroid nodules, especially indeterminate samples classified as Bethesda System for Reporting Thyroid Cytopathology (BSRTC) III (Du et al. 2021)”. UG-FNAB and BRAF p.V600E genetic testing have been used in Qilu Hospital, but their effect on the incidence of malignant tumors during surgery in the past 10 years is not clear.

Thyroid cancer is one of the most common endocrine malignant tumors. In 2020, 580,000 new cases of thyroid cancer were reported worldwide (Sung et al. 2021), making it the 11th most common cancer type. Thyroid cancer is expected to become the fourth most common cancer by around 2030. As shown in Table 1, during the 10-year period (2012–2021), the number of surgically removed malignant thyroid tumors soared from 454 to 3103, while the number of surgical beds increased only by 20 in Qilu Hospital. The latest data show that thyroid cancer incidence rates have increased in many countries and this epidemiological pattern has been largely attributed to an overdiagnosis effect (Pizzato et al. 2022). An increase in the number of thyroid cancers resected was observed in this study. However, this may or may not be the same as an increase in the incidence of thyroid cancer in the population. More accessible healthcare for example can account for more thyroid cancers coming to clinical attention without there actually being an increase in the incidence. The age of onset tended to decrease, with no significant change in gender ratio. Female patients accounted for about 3/4 of the total number of patients.

The prognosis of different types of thyroid neoplasms varies greatly (Cabanillas et al. 2016). Many large-sample studies have shown that clinical lymph node metastasis is an important factor affecting the survival of patients with thyroid cancer (Adam et al. 2015; Zhou et al. 2020). The prognosis of thyroid cancer is poor when the tumor has obvious extra-glandular invasion resulting in the invasion of surrounding important structures such as the larynx, trachea, and esophagus (Wang et al. 2016). Different treatment methods were selected according to different pathological types and clinical stages, such as active monitoring, affected side lobectomy plus isthmus resection, and total/near-total thyroidectomy (Filetti et al. 2019; Haugen et al. 2016). It is one of the most important challenges for clinicians to correctly diagnose benign and malignant thyroid nodules using effective diagnostic methods.

Current methods for differentiating benign and malignant thyroid tumors include ultrasound, preoperative FNAB, UG-FNAB, rapid intraoperative frozen section diagnosis, routine postoperative pathology, and molecular pathological examination (Filetti et al. 2019; Haugen et al. 2016). Ultrasound is the primary imaging method for risk assessment of thyroid nodules (Russ et al. 2017; Tessler et al. 2017). In the high-risk population (e.g., head and neck radiation exposure or radiation exposure in childhood, systemic radiation therapy) (Zupunski et al. 2019), thyroid ultrasound screening should be performed as early as possible. It has been suggested that the accuracy, sensitivity, specificity, positive predictive value, and negative predictive value of ultrasonography for malignant thyroid nodules were 68–70%, 84–91%, 33–49%, 67–71%, and 68–70%, respectively (Liu et al. 2021). The ATA guidelines indicate that the risk of malignancy for highly suspected malignant nodules is approximately 70–90%, and ultrasound results determine which nodules require fine-needle cytology biopsy (Haugen et al. 2016). FNAB is the first recommendation for suspected thyroid nodules due to its widely accepted safety and accuracy (Layfield et al. 2009).

Thyroid FNAB is gradually accepted in China. Some hospitals began applying UG-FNAB around the 1990s. At present, most general hospitals use thyroid UG-FNAB as a preoperative diagnostic method in China. Qilu Hospital is one of the thyroid FNAB microcosms among Chinese hospitals. Thyroid FNAB has been performed in the Department of Endocrinology in Qilu Hospital since 1991. UG-FNAB is performed for thyroid nodules since 2015. As shown in Fig. 1, with the implementation of UG-FNAB, the number of non-ultrasound-guided FNAB cases decreased sharply. However, the number of UG-FNAB cases increased rapidly from 2186 cases in 2015 to 5588 cases in 2021. It should be noted that these data are slightly affected by the impact of COVID-19 on medical treatment in China in 2020. But in 2021, COVID-19 had no discernible impact. Possible reasons for the increase in the number of thyroid UG-FNAB cases in the past 10 years are as follows: (1) Along with the rapid economic development, health awareness of people has improved, and health examination has become more popular in China. More asymptomatic thyroid nodules were detected. (2) Different national guidelines (Nabhan and Ringel 2017) and clinicians' personal experience lead to different nodular criteria for UG-FNAB selection. Guidelines for the implementation of FNAB have been published by the ATA and the National Comprehensive Cancer Network (NCCN) from the United States and the European Society for Medical Oncology (ESMO) and the European Thyroid Association (ETA) from Europe (Filetti et al. 2019; Haddad et al. 2018; Haugen et al. 2016; Russ et al. 2017). In all of these guidelines, FNAB is recommended for thyroid nodules sized ≥ 10 mm with a highly suspicious pattern. A recent study has indicated that the implementation of FNAB is considered necessary for a detailed and accurate assessment of the ultrasound appearance of thyroid nodules, rather than categorizing them solely on the basis of size (Shimura et al. 2021). (3) Patients are increasingly concerned about the nature of thyroid nodules and request UG-FNAB for thyroid nodules (Singh Ospina et al. 2020). As shown in Fig. 2, after thyroid FNAB was implemented in Qilu Hospital in 2015, the malignancy rate in thyroid surgery increased significantly (from 35.97% in 2012 to 64.79% in 2015). This suggests that preoperative UG-FNAB may reduce the number of unnecessary diagnostic thyroid surgeries. However, the inadequate or non-diagnostic aspiration rate of FNAB pathology are still relatively high (Chen et al. 2015).

BRAF p.V600E is the most common mutation in PTC. As BRAF p.V600E mutation leads to the continuous activation of the RAS–RAF–MEK–ERK pathway, it enhances the mitotic capacity of cells, ultimately leading to abnormal cell proliferation and tumorigenesis (Roth et al. 2018). Meta-analysis revealed that BRAF mutation is associated with lymph node metastasis, tumor stage, extrathyroidal extension, tumor size, and classic PTC (Li et al. 2012). In cases with a high BRAF p.V600E positive rate, such as patients diagnosed with PTC by FNAB, BRAF p.V600E genetic testing is unlikely to be helpful. In other cases, such as patients with uncertain and suspicious Bethesda classification, the presence of the BRAF p.V600E mutation may aid in diagnosis (Han et al. 2016). Molecular detection results need to be interpreted in combination with individual clinical manifestations, imaging results, and FNAB cytology results. After BRAF p.V600E genetic testing was implemented in Qilu Hospital in May 2019, the number of tests increased rapidly (Fig. 1). Meanwhile, as shown in Fig. 2, the malignancy rate in thyroid surgery increased significantly, from 85.22% in 2019 to 90.33% in 2021. These findings suggest that BRAF p.V600E testing may reduce the number of unnecessary diagnostic thyroid surgeries.

To further determine whether UG-FNAB and BRAF p.V600E genetic testing can improve the malignancy rate in thyroid surgery, we analyzed data on the malignancy rates in thyroid surgery during different time periods (Table 2) and within the same time period (Table 3). In this study, the 10-year period was divided into three stages, with the implementation of UG-FNAB in 2015 and the implementation of BRAF p.V600E genetic testing in 2019 as the dividing lines. There was a significant difference in the malignancy rate in thyroid surgery between the three stages (P < 0.001) (Table 2). Table 3 shows the data after the implementation of BRAF p.V600E genetic testing in Qilu Hospital. From May 2019 to December 2021, the malignancy rate in thyroid surgery was significantly different between the Non-FNAB, UG-FNAB, and UG-FNAB-BRAF groups (P < 0.001). These results suggest that the implementation of UG-FNAB and BRAF p.V600E genetic testing in Qilu Hospital has had a huge impact on the overall quality of life and healthcare costs of patients by reducing the number of unnecessary diagnostic thyroid surgeries. These unnecessary surgical excision of benign tumors mainly included nonfunctional, minimal thyroid adenoma, nodular goiter, thyroid cyst, etc.

There were likely other influences on the malignancy rate during this decade. For example, the gradual use of ultrasound evaluation system, Bethesda system for reporting thyroid cytopathology, optimization of cytological preparation method and FNA biopsy protocols, and more experienced and skilled operators may have influenced the diagnostic rate and ultimately malignancy rate in post-op specimens.

The current study has several limitations. First, this was a retrospective study, so the results may be biased. Second, our study is a single-center study, which cannot fully represent the overall situation in China but only describe a specific clinical experience. Third, this study only counted the number of thyroid operations, punctures, and BRAF p.V600E genetic testing cases and the malignancy rate in thyroid surgery in Qilu Hospital during the 10-year period, without further specific analyses of thyroid nodule ultrasound results, thyroid nodule size, metastasis, and other indicators. These will be considered in future studies. Fourth, our data showed that FNA and BRAF p.V600E genetic testing were selected according to doctors' experience, patients' wishes and medical expenses for thyroid nodule patients in the past 10 years, and these two examination methods may be overused.