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Editorial |
Section of Thoracic Surgery, Evanston Northwestern Healthcare, Burch 100, 2650 Ridge Avenue, Evanston, Illinois 60201
Correspondence: Address correspondence and reprint requests to: Michael J. Liptay, MD; E-mail: m-liptay{at}northwestern.edu.
Lymph node involvement is the single most important locoregional prognostic factor in nearly all solid tumors. Sentinel node mapping has become the standard of care in breast cancer and melanoma. Its use has also been reported in several other tumor sites, including the lung.1,2
The patterns of lymphatic drainage of the lung and pleural space are poorly understood. The staging of lung cancer with lymph node involvement is imprecise, and often unpredictable patterns of nodal spread confuse the actual prognosis.3
In this issue of the Journal, Parungo et al.4 present a novel method of nodal evaluation that uses intraoperative near-infrared fluorescent imaging. The technique is exciting and offers promise to aid surgeons in the operating room with the potential for real-time evaluation of the lymph nodes with a non-radioactive, nontoxic substance.
Our experience with intraoperative sentinel node mapping in lung cancer has been primarily with 99mTc sulfur colloid injected directly into the tumor at the time of resection.1,5 In more than 250 cases, we have found it to be accurate in approximately 80% of the cases studied. Two issues have affected the utility of this technique. First, the "shine through" radioactivity of the primary tumor affects readings of proximal lymph nodal stations and frequently makes in vivo sentinel node identification of N1 nodes unreliable. With ex vivo on-table dissection and separate Geiger counter readings, more accurate assessments are possible. Second, the use of a radioactive substance requires nuclear medicine physicians to be present for at least a portion of the procedure and limits its universal application secondary to this and other governmental regulatory requirements. The study presented in this issue highlights a promising technique that may simplify and improve the intraoperative sentinel node mapping of individuals with resectable lung cancers.
The authors present an elegant technique that used near-infrared fluorescence imaging to evaluate pleural lymphatic drainage in pigs and rats. Reproducible results were noted in both species: superior mediastinal nodes were the first site of pleural space drainage. These results may translate into clinically applicable techniques if the technologies used (imaging system and tracer) are readily available. More importantly, the technology needs to be studied in pathologic states and human subjects to assess the utility in both lung cancer and mesothelioma.
At least theoretical difficulties with mesothelioma may arise when the pleural space is obliterated by tumor that impairs lymphatic flow. We and others5 have encountered difficulty with sentinel node mapping in lung cancer with clinically positive enlarged nodes that do not map secondary to occluded afferent lymphatic channels. It also remains unclear how the general drainage of the pleural space will correlate with the actual lymphatic spread of an intraparenchymal lung tumor with visceral pleural invasion.
The authors are to be commended for their report on a very promising technology to study lymphatic drainage of pleural tumors. Further studies and practical application in human subjects with lung cancer and mesothelioma are anxiously awaited.
Received for publication September 10, 2004. Accepted for publication November 19, 2004.
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