The Study: The 4L mediastinal lymph node station (left lower paratracheal) lies amongst the aorta, recurrent laryngeal nerve, and the thoracic duct. This high-stakes realty means it sometimes go undissected in patients even with left sided lung cancers. In this large retrospective study, outcomes for 657 patients with left sided lung cancers who did (~20%) or did not (~80%) have 4L nodes dissected were compared. As expected, the N1 nodal stations had the highest frequency of metastases at a rate of around 25%. Station 4L along with station 5 was the most commonly involved N2 station at around 15%, beating out the subcarinal nodes. Even more interesting, though, was that dissection of 4L was associated with improved disease-free and overall survival. What was the biggest predictor of having a 4L metastasis? A positive hilar node. This data suggests that there could be a benefit to more routine dissection and clearance of disease at 4L, particularly when there is hilar disease. And left hilar nodal involvement may be a reason to include 4L in radiation target volumes.
Bottom Line: Station 4L is a frequent site of mediastinal lymph node mets from lung cancer that may go undissected. | Wang, J Clin Oncol 2018