As one of the most common cancers, lung cancer is the leading cause of cancer death worldwide and its mortality rate exceeds the sum of the three most common cancers (colon, breast, and pancreatic cancer). Due to the lack of clinical symptoms in the early stage, most lung cancers are diagnosed as distant metastasis and the 5-year survival is only 17.8% [17]. With the widespread use of low-dose spiral CT, more pulmonary nodules, especially those with GGO, are found in the early stages. The prevalence of pulmonary nodules detected on by CT is 31% and up to 50% among high-risk patients [18]. Under the guidance of CT, the accuracy of the needle biopsy is 88%, the sensitivity is 90%, and the false negative rate is 22% [19–20]. However, due to limitations of the technique, some pulmonary nodules cannot be clearly diagnosed. As a minimally invasive method for diagnosis and treatment, VATS has been widely used for pulmonary nodules. However, some pulmonary nodules cannot be seen by the naked eye and cannot be clearly palpated by fingers during the operation, bringing further challenges in clinical diagnosis and treatment [21]. Some studies have shown that intraoperative finger-assisted palpation of pulmonary nodules with diameter of > 2 cm on the pleural surface is often possible. However, for small lesions < 1 cm in diameter, preoperative localization is usually recommended [22]. In this retrospective study, all 80 patients with malignant pulmonary nodules < 1 cm in diameter were treated with hook-wire localization.
At present, a variety of preoperative localization methods have been reported. However, each localization method has its advantages and disadvantages [23]. It is difficult to identify pulmonary nodules by methylene blue because it can quickly spread to the pleural surface [24]. Specific radioactive tracers require specialised equipment such as CT-fluorescence [25]. Intraoperative ultrasound detection requires a specific flexible ultrasound probe and the localization is impeded by air, therefore it is difficult to be applied in patients with non-collapsed lung or emphysema [26]. Currently, there is no golden standard for preoperative localization in clinical practice.
Hook-wire localization is widely used and has the advantages of simplicity and ease of operation, short operation time, and reduced surgical injury. Ciriaco et al. report that the average time of CT-guided pulmonary nodules localization is 20 ± 10 min, which is slightly longer than the preoperative localization time in our study, which was similar to the duration reported by Li et al. [28]. Interestingly, Ciriaco et al. report that the VATS time of pulmonary nodules after preoperative localization was 40 ± 7 min compared with 75 ± 12 min without preoperative localization. This indicates that with the help of preoperative localization, pulmonary nodules are identified and removed faster during surgery, which greatly shortens the operation time. In comparison, the average operation time of VATS in our study was 89.02 ± 23.35 min. The discrepancy can be explained by the high proportion of lung segmentectomy and lobectomy in our study population (95%), which complicated the surgery and increased operation time.
Inevitably, the hook-wire preoperative localization also has some disadvantages. For example, the surgical margin cannot be determined after displacement of the localization needle and therefore the complete removal of pulmonary nodules cannot be guaranteed [29]. It has been reported that 3 to 8% of localization needles may be displaced or even detached [30], which was consistent with the occurrence in our study. The causes of hook-wire dislodgement were mostly by coughing and upper body movement. In this situation, we determined the location of pulmonary nodules by the puncture point of the hook-wire on the lung surface.
Pulmonary nodules that are deep in the lung or blocked by the ribs and scapula are difficult to locate, leading to pneumothorax, haemothorax, pain, and death from gas embolisms [31]. Huang et al. reported that in 39 patients undergoing preoperative localization, 5.2% of the patients presented mild parenchymal hemorrhage and 12.8% presented minor pneumothorax [15]. Other reports have described that the incidence of mild parenchymal hemorrhage is 13.9–36% and the incidence of pneumothorax is 7.5–40% [16]. In this study, minor pneumothorax and mild parenchymal hemorrhage occurred in 33.7% and 22.5% of the cases, respectively, which was consistent with previous studies. No serious complications such as massive haemothorax or massive air embolism resulted from these incidents. Interestingly, we found that the length of the localization needle in the pulmonary parenchyma had a significant correlation with the occurrence of mild pulmonary parenchymal hemorrhage, although the depth of pulmonary nodules did not show such correlations. Therefore, we suggest that physicians should be aware of the risk of pulmonary hemorrhage for localization of pulmonary nodules requiring a long needle.
This study has some limitations. Primarily, there was no control group of VATS patients without preoperative localization. This may lead to overestimation of the safety and effectiveness of preoperative hook-wire localization.