Preoperative Preparation

The incidence and presentation of pulmonary metastatic disease is variable among different pediatric solid tumors. A multidisciplinary approach to patient care and timing of operative intervention is requisite to ensure optimal patient outcomes, as primary diagnosis and size and number of lesions will be critical in the decision making.

Imaging

Computerized tomography (CT) remains the primary method for evaluating pulmonary tumors. It is important to remember that CT imaging may be adversely affected by atelectasis. This can be avoided with the help of non-sedated or sedated scans with pulmonary recruitment maneuvers performed immediately prior to imaging[1]. With advances in artificial intelligence, new methods of computer-aided detection of pulmonary nodules on CT imaging are also being investigated[2]. Often, pulmonary nodules are round or ovoid, well-demarcated, and located in the periphery of the lung[3][4]. Generally, the likelihood of malignancy is higher when more than three nodules are present, nodules are greater than or equal to five mm, or there is bilateral lung disease[3][5][6][7].

Surgical Approach

While both are safe and viable options for pulmonary metastasctomy, video assisted thoracoscopic surgery (VATS) versus thoracotomy in the management of pulmonary metastases continues to be an important topic of discussion[8]. COG AOST2031 study is a phase III trial comparing the effect of open thoracic surgery (thoracotomy) to thoracoscopic surgery (VATS) in the treatment of patients with osteosarcoma with pulmonary metastases (NCT05235165). Enrollment is currently open and should be considered for eligible patients. Like all treatment methods, there are advantages and disadvantages to both, and consideration of the trial, as well as optimal type and timing of intervention, should be determined on a patient-by-patient basis by a pediatric surgeon.

VATS

A minimally invasive approach is a good surgical option for patients with limited disease burden.[9] While there is some evidence to suggest thoracotomy allows for identification and removal of additional nodules palpated intraoperatively but not observed on imaging, there is no evidence of survival benefit. Advances in localization techniques in recent years have also enabled effective minimally invasive surgery (MIS) when nodule(s) cannot be clearly seen or felt intraoperatively[10]. There is also no proven downside to waiting for smaller nodes that might be missed initially to grow slightly larger and be excised with a second VATS procedure. In the event a patient requires further operative intervention in the future, re-exploration is easier and potentially safer following VATS than thoracotomy. Recovery following VATS may also be faster and less painful compared to open operations. In addition, patients typically have a lower narcotic requirement following MIS[11]. Although newer forms of post-operative pain control used during open operations, such as regional anesthesia and intercostal nerve cryoablation, have allowed for enhanced recovery, they are not routinely required in patients undergoing VATS and can carry their own potential side effects or complications.

Thoracotomy

Open procedures should be offered to patients who have numerous or deep pulmonary lesions or are expected to have a challenging resection (i.e. repeat surgery, excessive scar tissue, nodules near the hilum or adherent to surrounding structures). As previously mentioned, CT imaging remains the primary method of diagnosis of pulmonary nodules. Open procedures allow for manual palpation, which may more reliably confirm removal of all nodules present[12][13]. Palpation has been shown to identify occult nodules not seen by CT or other imaging in 20-25% of cases[14][15]. While VATS often requires a generous stapled wedge resection, open surgery can allow for resection with a smaller margin of normal lung tissue. Unlike VATS, additional localization procedures are not generally required prior to open operative intervention. Recovery after thoracotomy is still longer than recovery after VATS on average[11]. However, modern surgical and pain control techniques, including muscle sparing thoracotomy, regional anesthesia, and intercostal nerve cryoablation, have improved pain control and recovery times after thoracotomy[16][17].

Unilateral vs Bilateral Intervention + Staged vs Concurrent

Unilateral Disease at Presentation

For patients with unilateral metastases at diagnosis, particularly in cases of osteosarcoma, contralateral exploration was historically recommended in an attempt to clear any disease not currently visible on preoperative imaging. However, ipsilateral versus contralateral recurrence following resection of pulmonary metastases occurs at a similar incidence. Contralateral exploration has not been shown to improve survival rates, and with advances in diagnostic imaging, contralateral thoracotomy may not be indicated with unilateral involvement on preoperative imaging.

Bilateral Disease at Presentation

When bilateral disease is present, a decision must be made between performing staged or concurrent thoracotomies during the same operation. When considering each option, size and number of metastases, location (central versus more peripheral), primary diagnosis and the patient’s clinical condition. Concurrent thoracotomies allow for a reduction in anesthesia, total inpatient hospital days and time with chest tubes. It may reduce the burden on the patient and their family by completing all the surgical resection at one operation. However, the degree of resection and the patient’s mobility must also be considered. For patients with lower extremity primary lesions, ambulation with crutches or other assistive devices can be much more challenging after a bilateral thoracotomy. Post-operative pulmonary toilet is also potentially more difficult after a bilateral procedure. Intra-operatively, caution must be taken when operating on the second side, as single lung ventilation will be required on the first lung immediately post-procedure. Concurrent thoracotomy may be best for patients with lower burden of disease rather than those that may require a larger resection. Staged thoracotomy allows for improved recovery from anesthesia and the procedure, with increased ease of mobility. However it may lead to increased delays to resumption of systemic therapy.

Anesthetic Considerations including pain management

The provision of single lung ventilation either using a bronchial blocker or double lumen endotracheal tube (with its position checked with a flexible bronchoscope), optimizes visualization on the operative side and avoids excessive thoracic insufflation. Particularly when thoracotomy is performed, a multi-disciplinary plan for postoperative pain control should be provided, with an emphasis on minimizing narcotic medications. Regional anesthesia, with a thoracic epidural, paravertebral, or erector spinae catheter are effective modes of postoperative analgesia[17][18]. Alternatively, intraoperative performance of intercostal nerve cryoablation provides durable postoperative pain control and is associated with a reduction in opiate utilization[19][20]. As VATS has become increasingly popular, studies have been done to evaluate the optimal postoperative pain control regimen. A systematic review of randomized controlled trials evaluating various postoperative pain management strategies between January 2010-January 2021 was done, with the overall goal of developing recommendations for optimal pain management after VATS[21]. They recommend administration of acetaminophen and NSAIDs or COX2 inhibitors preoperatively or intraoperatively and continuation of these in the post-operative period. While paravertebral or erector spinae plane blocks were preferred, intraoperative dexmedetomidine was considered a viable option when basic and regional analgesia cannot be provided. Importantly, they recommend reserving opioids as rescue analgesics in the post-operative period.