Peripheral lung cancer refers to lung cancer that occurs below the tertiary bronchus and accounts for about one-third of lung cancer. Early stage I and II lung cancers account for nearly one-third of these cancers. Surgical resection is the standard treatment modality for early-stage peripheral lung cancer, but radical surgery can be performed in only about 20% of lung cancers [1], and the high risk of pneumonectomy and high postoperative disability rate, together with patient reasons for not being able to or refusing surgery, require non-surgical treatment. The 5-year survival rate of radical radiotherapy is only 4-10%, and conventional radiotherapy is difficult to control local tumors, and the treatment outcome is still unsatisfactory [2]. In recent years, image-guided percutaneous ablative minimally invasive treatment has gained increasing attention because of its low side effects and significant efficacy, and its ability to induce the body’s immune response and even achieve in situ radical treatment.
Ablation has been recognized as the first-line curative treatment for small hepatocellular carcinoma, and the use of ablation for lung cancer has demonstrated good efficacy and safety and is gaining increasing attention [3]. In this paper, we review the research progress about percutaneous ablation therapy for early peripheral lung cancer.
I. Overview of percutaneous ablation treatment technology
(1) Percutaneous ablation and CT-guided percutaneous ablation treatment needs to be performed under the guidance of images. CT-guided percutaneous ablation is simple and easy to perform, and its wide applicability is recognized both at home and abroad, especially in the ablation treatment of lung cancer.
(2) Treatment methods of percutaneous ablation Percutaneous ablation therapy uses temperature change to ablate tumor under CT guidance, including radiofrequency thermal ablation (RFA), microwave (MWA) thermal ablation, and argon-helium gas direct cooling cryoablation (CryoA).
1.Percutaneous radiofrequency ablation Under the guidance of CT, the treatment electrode (unipolar or bipolar) is directly inserted into the tumor, and the radioelectromagnetic wave with frequency 100~500kHz and power 100~300W is used to form a circuit in the patient’s body. ~100°C, causing protein denaturation of cancer cells, lipid layer dissolution, cell membrane destruction and coagulation necrosis of tissue cells. At the same time, it can make the vascular tissues around the tumor tissue coagulate to form a reaction zone, stop the blood supply to the tumor and prevent the tumor from metastasis. After surgery, the necrotic tissue is gradually absorbed and fibrotic, and can activate the immune function of the body.
Unlike microwave antennas and cryoprobes, the design of radiofrequency ablation electrodes continues to advance and has been updated for several generations, representing the direction of development of percutaneous ablation technology. From the initial monopolar single needle (1G), it has evolved into cooled monopolar (2G), then monopolar multi needle (3G), then monopolar grouped multi needle (4G), and currently cooled bipolar dual needle (5G), and bipolar multi needle mode (6G) have emerged. The most representative RF ablation electrode is the umbrella-shaped RF electrode needle design. This electrode can better fix the tumor and reduce the damage, and also can clearly show the intended treatment area on the CT image, the relationship with the surrounding tissue structure, and also can easily implement the effect of conformal ablation according to the different shapes of the tumor by individually adjusting the position and size of the sub-electrodes.
The newly developed monopolar multi-needle conformal ablation electrode needle (Figure 1) is the pinnacle of the development of ablation electrodes as it can achieve the effect of conformal ablation of the largest tumors in a short time with a single needle puncture. The tapered tip of this electrode is very sharp, which reduces the damage during puncture. The 12 electrode sub-needles can be released in half and unfolded in an asymmetric umbrella shape, which can be evenly and conformally distributed inside the tumor according to the shape of the tumor. Each sub-needle can be injected with liquid, which can be used for electrolyte perfusion ablation or drug injection. The temperature measurement point is set in the center of the main needle and the four sub-needles, and the ablation temperature is controlled by the center temperature not to exceed 100°C, which can reduce the gas production due to water boiling, prevent the coking and stagnation of the needle, and retain the tumor antigen to the maximum extent to facilitate the stimulation of the body immunity.
Figure 1: Monopolar multi-needle conformal ablation electrode needle
Radiofrequency ablation host design is more automated, using temperature dominant control, computer automatic temperature control at 95.0±0.5 ℃, to achieve the best ablation state; impedance-assisted control, to prevent energy idle, greatly improving the treatment efficiency. The treatment takes 10~30 minutes to form a spherical thermal coagulation foci of 3~8 cm in diameter with adjustable size, ablating and killing tumor cells.
2.Transcutaneous microwave ablation Under CT-guided percutaneous puncture, the unipolar treatment antenna is inserted directly into the tumor interior, and the microwave with frequency of 915~2450MHz and power of 100W emitted from the antenna is used to produce thermal effect by rapid rotation of polar water molecules in the surrounding tissues and friction to heat the tumor and achieve the purpose of in situ ablation of tumor. Unlike radiofrequency ablation, microwave therapy does not require the formation of a circuit of electric current. The microwave antenna has developed from the initial single-pole antenna to a pin-pole cooled single-pole antenna, increasing the range of treatment. Because the microwave antenna has not been able to break through the bottleneck of the single-pole design, clinical treatment, the use of multi-needle combination puncture mode to achieve conformal ablation.
3.Percutaneous argon-helium cryoablation Under CT-guided percutaneous puncture, a unipolar cryotherapy probe is inserted directly into the tumor, and according to the Joule-Thompson principle, argon gas can be released rapidly in the probe tip to freeze the lesion to -120~-160 ℃, and helium gas can be released rapidly in the probe tip to rapidly thaw and re-temperature the ice ball. The formation of ice balls by freezing can cause cell dehydration, protein denaturation, cell membrane and cell structure rupture, resulting in irreversible coagulation and necrosis of tumor cells in the frozen area. Cryoprobes are usually used in multiple needle combinations and are conformal to treat larger tumors. Cryoablation forms an ice ball that is clearly visible on CT images. Like microwave antennas, the cryoprobe has not been able to break through the bottleneck of monopolar design. For clinical treatment, multiple needle combination puncture mode is used to achieve conformal ablation.
(3) Anatomical characteristics of early peripheral lung cancer and temperature field distribution of ablation Lung cancer is a solid tumor, heat can easily accumulate and transfer in solid tumor tissues, with a slow decreasing distribution. This is conducive to the application of physical hot and cold ablation in the treatment of lung cancer. Especially, radiofrequency ablation treatment relies on the high-frequency current in the tissue to generate heat, and the current density of tumor tissue is greater than that of alveolar tissue, which is especially suitable for the treatment of peripheral type isolated early lung cancer [4]. The US FDA published the RFA operation for lung tumors with reference to soft tissue ablation regulations [5].
In the case of RF ablation, for example, the temperature of the treatment site is accurately reflected by the thermometric couples distributed at the tip of the needle for the treatment of peripheral type lung cancer, and when the treatment temperature reaches the required level, the device will reduce the power and maintain it for a certain period of time. Normally, the temperature of the treatment center reaches 95°C and is maintained for 10 minutes, and the temperature of the RF sub-electrode can also reach 90°C. Due to the “heat loss effect”, a regular heat field distribution is formed, and the temperature of the tissue far away from the sub-electrode starts to decrease, from 10°C for every 5 mm outward, and the temperature of the sub-electrode can be maintained at 50°C for 20 mm away. When RF ablation reaches the edge of the tumor, the temperature reaches 51.4 ~72.6°C for 10 minutes, which can cause tumor cell degeneration and necrosis to achieve the therapeutic effect [6].
II. Treatment strategies and methods of percutaneous ablation for early peripheral lung cancer
Pathologically confirmed early-stage peripheral lung cancer, including adenocarcinoma, squamous carcinoma, small cell carcinoma or metastatic lung cancer, is mainly treated by local eradication of cancer cells. Surgical resection remains the main curative tool, and radical ablation is the preferred option for patients who are inoperable or refuse surgery. Contraindications include tumor located in the hilar region of the lung, invading bronchi above the lobe or tumor is infiltrative; severe failure of major organs; active infection; uncorrectable coagulation dysfunction and hematologic disease with severe abnormal blood picture; poor lung function, massive pleural fluid, impaired consciousness or advanced cachexia, and expected survival less than 3 months. If there is residual tumor after treatment, additional ablation therapy can be performed. When there are tumorigenic high-risk factors, comprehensive treatment such as radiotherapy should be appropriately coordinated.
(I) Treatment planning relies on high quality enhanced CT and PET/CT images before surgery to determine the indications and target areas, including tumor size, shape, number, vascular distribution, and important organ structures, and fully consider factors such as tumor condition, puncture access and tumor surrounding tissues and organs to properly assess the efficacy and risk. The treatment plan includes the development of the ablation target area according to the tumor contour, and the initial decision of the puncture site and the puncture access. The puncture site should be chosen between two intercostal spaces, and the puncture access should avoid the blood vessels, interlobular fissures and alveoli in the thorax. According to the size and shape of the tumor, the ablation target and the treatment power, temperature and time should be calculated, and the three-dimensional temperature should be distributed.
(2) The target area of ablation should include the visible tumor volume (GTV) and the subclinical target volume (CTV) around the GTV. For radical ablation, the plain tumor volume (PTV) should be 10 mm outward of the primary tumor (GTV) (or 5 mm outward of the CTV). For safety reasons, the tumor margin should be at least 5 mm from major anatomical structures such as the heart, large blood vessels, and nerves, and ablation alone is not recommended for lesions > 5 cm due to local treatment limitations.
Figure 2, CT-guided radiofrequency ablation for lung cancer, A localization, B ablation, C PTV at the end of ablation, D PTV after 24 hours
(C) Operation of ablation therapy
1. Position and anesthesia Supine position is appropriate. For lesions close to the back, prone position can be used, and lateral position is avoided as much as possible to reduce displacement and discomfort during treatment. Pre-operative routine sedation, analgesia, cough and hemostasis pretreatment, treatment with local anesthesia, the patient is in the awake state, according to the patient’s feelings, adjust the treatment process. Depending on the situation, general anesthesia can also be used.
2. Breathing training For accurate puncture hits, the patient is instructed to maintain a calm breathing pattern, avoid deep and large breaths, and close the air at the end of expiration, when the residual air volume is minimal and can avoid displacement of the lesion. During CT scanning, positioning and puncture, the patient should be instructed to close the breath in the same breathing state.
3. CT guidance and monitoring The key to successful CT-guided puncture includes: (1) grasp the four-dimensional coordinates of the puncture needle, i.e., CT frame angle, needle angle, needle depth, and control of the patient’s breathing. (2) The puncture needle is located within the CT tomographic level, and the overall clarity makes it easy to grasp the position of the puncture needle. (3) The puncture access avoids important organs and tissues to ensure safety. (4) The error between the needle tip and the target point is less than 5 mm.(5) Minimize the number of punctures into the needle to reduce lung injury producing complications such as pneumothorax, hemothorax and implantation metastasis.
4.CT positioning Fix the positioning ruler on the puncture body surface and CT scan at the maximum tomographic level of the lesion to determine the best skin puncture needle entry point. The angle and length (i.e., the depth of needle entry) of the line between this point and the target point are measured. The laser light is turned on at the bed of the CT scan at the maximum tomographic level of the lesion, and the point where the body projection of the laser localization line intersects with the localization line is the puncture entry point.
5. Puncture guide Place the support frame at the puncture point, insert the single-use guide tightly into the support frame, and adjust the bi-directional angle of the guide to the puncture parameters. Insert the puncture needle into the guide jack and place the needle tip on the puncture point. The CT scan confirms that the tail shadow of the puncture needle passes through the target point (the puncture angle can be adjusted appropriately). The target point is hit by puncturing in the direction of puncture to the corresponding depth.
Figure 3 Guider-assisted CT-guided radiofrequency ablation
The guide can guide a single needle puncture or multiple needle punctures simultaneously. For example, when performing argon-helium cryoablation, multiple probes can be placed on the body surface, scanned once to confirm the direction of the probes, and then punctured sequentially to hit. This greatly improves puncture efficiency and accuracy. The guide can enter the scanning area with the bed to monitor the position of the puncture needle, and the puncture needle can be released from the guide after the hit to reduce the hindrance to the treatment.
6. Dose prescription of ablation therapy Tumors smaller than 3cm rule are treated with single target ablation, and tumors 3~5cm in diameter are treated with 2~3 target ablation. If the tumor is 5cm in diameter or irregular in shape, multi-target (more than 4 targets) ablation should be adopted. Multi-target point target area requires concentric circle needle laying, and avoid cold point area in the target area when filling. Try to avoid the sub-electrode to enter the restricted organ area.
(1) Dose prescription of radiofrequency ablation When the sub-electrode is opened to cover the tumor target area, the pulse power gradually increases the treatment temperature to 95°C. For the tumor target area ≤3cm, it is maintained for at least 10 minutes; for the target area 3~5cm, it is maintained for at least 20 minutes. The process of treatment is monitored by CT at any time during the treatment, and the efficacy of ablation is monitored by the temperature measurement points of the sub-electrodes. When the surrounding normal lung tissue undergoes a hairy glass-like change of more than 10 mm to kill the peripheral part of the most active tumor growth, a coagulation zone is formed between normal lung tissue and tumor to ensure a tumor-free growth zone and prevent tumor recurrence can achieve a radical effect [7].
(2) Dose prescription for microwave ablation The microwave antenna was punctured to the predetermined site under CT guidance, and the thermometric needle was inserted 5 mm beyond the edge of the tumor being heated. For tumor diameter less than 3 cm, one point puncture of 35~40 W is used for 10 minutes; for tumor diameter between 3~5 cm, two or more points are selected, and 45~90 W can be chosen for 10~15 minutes; when the tumor edge temperature reaches about 60°C, the microwave power output is stopped to end the treatment. During the treatment, C T scan of the lesion was repeatedly performed, and the curing time was extended appropriately according to the extent of density change of the lesion and the patient’s symptoms. At the end of the treatment, the patient was instructed to hold his breath and remove the needle while coagulating.
(3) Dose prescription of argon helium cryoablation The cryoprobe is inserted into the center of the tumor under CT guidance, and multiple probes can be inserted at the same time according to the size of the tumor. The size of the lesion is directly proportional to the number of cryoprobes. Radical cryopreservation requires multiple needle combinations, and the ice ball formed by cryopreservation should contain all the tumor tissues as much as possible, and the ice ball freezing range should be larger than the tumor edge by more than 0.5~1cm. In addition, sufficient high-pressure argon gas (≥3600pa) should be ensured. After turning on the argon gas, the probe tip temperature should be lowered to -160°C for 10-15 minutes, and then the argon gas should be turned off and replaced by helium gas to raise the temperature to 20°C for 4-5 minutes for one cycle. One treatment is usually 2 cycles. The ablation area is scanned frequently during the treatment to monitor the response of the tumor and surrounding tissues, as well as the formation of ice spheres and changes in the lung tissue adjacent to the tumor to avoid freezing damage to important structures. The needle can be removed when the CT scan immediately after the completion of cryopreservation shows complete coverage of the lesion by the ice ball and changes in the lung tissue surrounding the lesion by cryoinjury, and a small amount of bioprotein gel can be injected into the puncture needle tract to prevent pneumothorax and bleeding.
(iv) Postoperative evaluation and regression After treatment, regular follow-up reviews should be performed to evaluate the efficacy in order to detect local recurrence and new lesions in a timely manner. The assessment of efficacy should be performed 1 month after ablation, and then every 3 months, and complete ablation (CR) should be determined by intensive CT with no enhancement of the lesion or PET-CT with no tumor metabolism. If ablation is incomplete, additional treatment may be added. If CR cannot be obtained after 3 ablations, ablation therapy should be abandoned.
Treatment effect
(a) The treatment success rate is according to the ablation treatment plan, CT positioning, and accurate hitting the target point under the guidance of the guide. The microwave ablation antenna was located in the center of the tumor, and the temperature of the center of GTV reached 95°C, and the temperature of the edge of CTV exceeded 60°C for more than 10 minutes; the argon-helium cryoablation combined with multiple needle puncture completely covered the tumor and formed an ice ball for more than 10 minutes. The success of the treatment can be judged by the hair glass-like changes of the normal lung tissue around the tumor under CT monitoring. The success rate of percutaneous ablation treatment for early peripheral lung cancer exceeds 90%.
(B) Tumor inactivation rate Figure 4 shows early peripheral type lung occupancy (A), lung cancer with hypermetabolic PET-CT (E) and adenocarcinoma on biopsy (G); ablation therapy (C), immediate CT scan, hypointense changes in the ablation area (D), and hairy glass-like changes in the tumor surrounding tissue, with no enhancement on enhanced scan. One week later, it became dense with pneumonia-like changes. Enhanced CT of the treated area showed hypointense without enhancement (B), and PET-CT metabolism disappeared (F). Pathology showed inflammatory congestion of lung tissue, granulation tissue proliferation, and disappearance of cancer cells (H), indicating that heat can effectively ablate or destroy lung cancer tissue [8].
Figure 4 Inactivation of lung cancer by CT-guided radiofrequency ablation
Almost complete cancer cell death was achieved in surgically resected specimens after ablation of primary lung cancer with tumors ≤2 cm [9]. One month after treatment, CT plain scan showed a slightly enlarged shape of the treated area, and enhancement scan showed no vascular enhancement but significant enhancement of surrounding tissues. 6 months later, the treated area showed hypodense changes and no enhancement on enhancement scan. The ablation area gradually shrinks until it disappears, and some of them form scars or cavities. The inactivated area gradually shrinks and the tumor site forms a cavity until it disappears.
The hypermetabolic foci at the original tumor site disappeared without metabolic signal on PET/CT examination, and the mild ring-shaped metabolic increase area around the treated area was an inflammatory response. After 1 to 3 months of treatment, fine needle aspiration biopsy was performed on the treated area, and pathological and cytological examinations were all necrotic tissue, and no tumor cells were detected in the original tumor site. 3 months later, fine needle biopsy showed tumor necrosis, vitreous changes, fibrotic scar formation, and inflammatory cell infiltration. 6 months later, vitreous changes and fibrotic scar formation were observed in the treated area. Most of the surrounding normal tissues showed no damage except for a small number of cells showing degenerative changes with inflammatory cell infiltration [10]. The area should shrink back to its original size about 3 months after treatment. However, if the ablated area continues to increase after 3 months and the lesion appears to intensify, it suggests incomplete ablation and tumor recurrence, which requires additional treatment [11]. The complete inactivation rate of tumor diameter ≤5 cm in 1 treatment reached 90%, and the residual lesions were completely inactivated in the second additional treatment.
The efficacy of radiofrequency ablation was routinely evaluated by intensive CT, PET/CT or biopsy histology after ablation. Intensive CT immediately after ablation showed no enhancement in the ablated area, and PET/CT showed tumor disappearance without metabolism (Figure 5). The complete necrosis rate was 69-100% for tumors ≤3 cm in diameter and 40% for tumors more than 3 cm in diameter [12]. on PET/CT, ablation was more complete for tumors ≤3.5 cm in diameter, and tumors ≥3.5 cm in diameter often had residual [13]. Morphological changes of tumors after ablation therapy are often later than metabolic changes, so FDG-PET is more accurate than enhanced CT scan to determine the efficacy [14]. By comparing the changes of tumor tissue metabolism before and after ablation treatment, the recent therapeutic effect of ablation can be accurately judged, and more precise therapeutic target areas can be provided for further radiotherapy or re-ablation treatment.
(III) Survival benefit
1.Radiofrequency ablation Due to tumor necrosis and inflammation response, the lesion scope often exceeds the tumor itself after treatment. The extent of tumor on imaging increases for a short time and slowly decreases over time. Studies have shown survival rates of 78%, 57%, 36%, 27%, and 27% at 1, 2, 3, 4, and 5 years after radiofrequency ablation of stage I non-small cell lung cancer, respectively; the mean survival time was 42 months [15]. A multicenter study also confirmed that percutaneous radiofrequency ablation for primary NSCLC smaller than 3.5 cm resulted in 2-year overall survival of up to 75% [16]. The local recurrence rate for radiofrequency ablation of stage I NSCLC ranged from 3.0% to 38.1% (mean 11.2%), with a mean disease progression-free time of 15.0 to 26.7 months (mean 21 months) and 1-, 2-, and 3-year survival rates of 63% to 85%, 55% to 65%,15% to 46%, respectively [17]. Radiofrequency ablation may become an effective alternative to lobectomy for early inoperable lung cancer [18].
2. Microwave ablation Microwave ablation by percutaneous puncture for early peripheral lung cancer can also achieve curative effect. Compared with RFA, MWA uses radiation antennas, which do not require the formation of a current loop, and requires the simultaneous use of multiple treatment antennas to achieve synergistic effects [19]. The 1-year local control rate of microwave ablation is 67%, the mean time to recurrence is 16.2 months, and the local recurrence rate of the tumor is 22% [20]. The efficiency of monopolar microwave ablation for peripheral type lung cancer was 57.1%, and the ablation area shrunk solid in about 3 months and almost disappeared after 1 year, with cytologically confirmed tumor tissue necrosis after treatment and no significant side effects or complications [21].
3, cryoablation Argon-helium cryoablation has good efficacy for both primary and secondary intrapulmonary tumors [22]. With an overall survival rate of 88% at 2 and 3 years, a median overall survival of 68 months, a disease-free survival rate of 78% at 2 and 67% at 3 years, and a disease-free survival of 46 months for stage I lung cancer treated with argon-helium cryoablation, cryoablation is a viable option for patients with inoperable stage I lung cancer [23].
Compared with partial lobectomy, local recurrence was slightly higher with percutaneous radiofrequency ablation or cryoablation for stage I non-small cell lung cancer, but overall survival was not significantly different, at 87.1% (surgery), 87.5% (radiofrequency) and 77% (cryoablation), respectively [24]. Surgical resection pathology two weeks after percutaneous ablation treatment showed a complete ablation rate of 67%. An average of 8 mm beyond the complete ablation margin still showed ablation without histologically damaging changes in the surrounding lung parenchyma, confirming the safety and controllability of radiofrequency ablation. The combined application of ablation with surgery and radiotherapy has a complementary effect, and the combined application can increase the therapeutic effect [25].
(iv) Quality of life
Most patients in the ablation treatment group showed pain reduction, weight gain, and improved KPS scores after treatment, and the quality of survival was significantly improved 3-6 months after treatment. The rate of complications, nausea, vomiting, weight loss, bone marrow suppression, and decreased immunity, which affected the quality of survival, was greatly reduced with ablation therapy compared with systemic chemotherapy. Physiological status, social family, emotional and functional status were significantly improved, confidence in treatment increased, and treatment compliance increased; meanwhile, tumor-related symptoms such as cough, pain, shortness of breath, and fatigue were reduced in patients, and the quality of survival was significantly improved [26].
(v) Immune function Thermal ablation inactivates tumor and subclinical lesions, and also has the secondary (or distal) effect of activating the immune system of patients, which can improve the immune function of the body to a certain extent [27]. The main mechanisms are: ① thermal therapy destruction can release the confinement factors and macrophage movement inhibitory factors secreted by tumor cells; ② lymphocytes infiltrating the tumor necrosis area and their released lymphokines may have an important role in adjusting and activating the immune system of the body; ③ radiofrequency treatment fully exposes and releases antigens in the cytoplasm and nucleus, thus increasing antigenicity; ④ antigens in the nucleus of cancer cells modified by high temperature P53 and C-myc, etc. can stimulate specific lymphocyte immune effects. The percentage of CD3+, CD4+ and NK cells and the ratio of CD4+/CD8+ cells increased significantly after ablation treatment, and the killing activity of NK cells also increased. Radiofrequency ablation can effectively destroy the microvasculature of tumor tissue, inhibit the formation of blood vessels and reduce the blood supply to the tumor.
IV. Safety and complications
Ablation is mainly done under local anesthesia, which is mildly traumatic. The awake state is conducive to the operator’s timely communication with the patient to grasp the progress of treatment and prevent the patient from damage caused by over-treatment. Like any other medical and surgical treatment, ablation has complications. The complications of ablation are similar to those of CT-guided lung biopsy, including: pneumothorax, pleural effusion, fever, chest pain, cough, hemoptysis, etc. Most of them are mild, and only a few require special treatment.
Major complications of ablation therapy for lung tumors refer to those requiring treatment or having adverse consequences, such as pneumothorax or pleural effusion requiring closed chest drainage. Secondary complications are those that do not require treatment or have no adverse consequences, mainly a small amount of pneumothorax or coughing up blood. Side effects are those that occur as a result of concomitant treatment and rarely cause actual damage, mainly pain.
The most common complication is pneumothorax, mostly due to electrode needle puncture, with an incidence ranging from 30 to 60%, with no more than 20% requiring drain placement [28]. Advanced age and emphysema are more likely to occur and can occur intraoperatively or postoperatively; a small amount of gas can be left undisposed of, and moderate to large amounts of gas can be pumped by thoracentesis or placement of a closed chest drainage device, which is mostly absorbed in 2-3 days. Treatment with a one-step hit on the tumor using a guide guided puncture is associated with low complications especially pneumothorax rarely occurs [29]. Usually radiofrequency is used with a 15-17 G ablation electrode needle slightly thicker than the biopsy needle and the incidence of pneumothorax is not higher than that of lung biopsy.
Complications associated with ablation therapy include pleural effusion, pleurisy, and other rare complications are pneumonia, lung abscess, hematochezia, pulmonary hemorrhage, and acute respiratory distress syndrome. There are no serious complications such as infection, hemorrhage, or death from radiofrequency ablation therapy for lung tumors. Hematochezia is associated with puncture injury or tissue inflammatory reaction after treatment, and symptomatic treatment can be given to stop bleeding [29].
V. Conclusion
Percutaneous ablation for early peripheral lung cancer is minimally invasive, safe, reliable, repeatable, with low complications and tolerable, and is expected to be the treatment of choice for early peripheral lung cancer that cannot be treated surgically. Compared with surgery, the advantages of ablation include precise control, complete destruction, repeatability, disease control and reduced mortality, relatively low cost, simplicity of approach, and even outpatient implementation. The key to the future development of radiofrequency ablation lies in technological advances, while the combination of ablation with chemotherapy and radiation therapy will greatly improve the local control rate of tumors, improve the quality of life and prolong the survival of patients. Multi-center controlled trial studies, standardization of treatment, improvement of technology, monitoring of the treatment process, strict indications for treatment and prevention of complications will enable ablation to develop from an alternative means to a standard treatment method.