Drs. Matin and Goldberg describe and comment on the invasive techniques currently used for the clinical staging of lung cancer. Although they term this “surgical” staging, in reality, it is part of clinical staging (cTNM) and should be distinguished from the staging that occurs intraoperatively during the resection of a tumor. This latter staging, combined with the final pathologic assessment, is considered to be surgical/pathologic staging (pTNM) and, for obvious reasons, is the most accurate staging of TNM. The staging procedures discussed by the authors should therefore be termed “invasive” rather than “surgical.”
Why Use Invasive Techniques for Clinical Staging?
There are very good reasons to clinically stage patients with lung cancer using invasive techniques. The most important of these is to determine the likelihood of an R0 (complete resection) and to avoid primary surgery in patients with significant mediastinal nodal involvement.
At present, the imaging techniques currently available, with the possible exception of positron emission tomographic (PET) scanning, understage the patient in at least 30% of cases. This is improved by invasive staging. Also, these imaging techniques may result in overstaging, which may potentially deny the patient surgical treatment.
For these reasons, invasive staging very frequently must be used to confirm or deny the imaging result, especially if there is any doubt regarding the accuracy of the clinical stage that may alter the initial treatment.
With the advent of combined-modality therapy in the management of lung cancer, especially induction chemotherapy or chemoradiotherapy for locally advanced disease, it is imperative that patients be clinically staged as accurately as possible. It has been demonstrated quite clearly that patients suffering from lung cancer who have metastases to mediastinal nodes of any significant extent do not benefit from primary surgery, even if the resection is an R0 procedure.[3,4] Most of the invasive staging procedures described by the authors are used to determine whether or not mediastinal lymph node involvement is present. If this is identified prior to surgery, in most instances, patients should be offered a treatment other than primary surgical resection.
Much more difficult is the preoperative identification of “inoperable” T4 disease. Despite the use of mediastinoscopy and thoracoscopy (as described in this article), invasion into the vital structures of the mediastinum, resulting in R1 (microscopic residual) or R2 (gross residual) resections, often cannot be determined until the time of surgery.
Unfortunately, although theoretically valuable, in most instances, thoracoscopy has not proven to be advantageous in identifying mediastinal organ invasion that may preclude a surgical approach. Endoscopic invasive procedures are limited by their inability to dissect deeply enough in the area of vital organs to identify this type of invasion. Preoperative magnetic resonance imaging (MRI) and ultrasonography are probably the best of the inaccurate techniques currently available for this assessment.
Role of Transesophageal Ultrasound
Not mentioned in this review is the use of transesophageal ultrasound to assess organ invasion and to perform ultrasound-guided needle aspiration biopsies of deep subcarinal and para-esophageal posterior mediastinal lymph nodes and masses. This staging approach has proven useful and accurate, especially in confirming massive lymph node involvement in posterior subcarinal lymph nodes inaccessible to the mediastinoscope and, to a lesser extent, in demonstrating inoperable aortic invasion.
All surgeons practicing general thoracic surgery must be adept at all of the invasive procedures discussed by the authors and must be willing to use them to avoid unnecessary thoracotomies resulting in incomplete resections or to alter the overall management of the patient with resectable but locally advanced disease. However, despite all of these staging maneuvers, our ability to clinically stage patients accurately leaves much to be desired. Patients should not be denied a potentially curative surgical option if there is any doubt as to the accuracy of the clinical stage. When in doubt, give the patient the benefit of the doubt!
What the Future Holds
Within the next few years, newer imaging techniques (eg, PET scanning) and newer immunohistochemical techniques to identify micrometastases in lymph nodes and bone marrow may further improve our ability to accurately stage patients with lung cancer prior to therapy, thus allowing for more appropriate treatment. These modalities are currently under investigation in nationwide trials to assess their ability to improve clinical staging.[6,7]
In the future, clinical staging of lung cancer may not require as many of the invasive approaches as we use today. Computed tomographic scans, PET, and as yet undefined serum prognostic factors may allow “one-stop shopping,” decreasing the need for invasive staging.