Protocol to Improve Intrapulmonary Lymph Node Yield in NSCLC Staging Needed
“Pathologic examination of the surgical resection specimen is the most accurate means of staging NSCLC,” noted Raymond U. Osarogiagbon, MBBS, FACP, of the University of Tennessee Cancer Institute, Germantown, TN. “It enables accurate prognostication, informs decision making about postoperative adjuvant therapy, and facilitates cross comparisons of patient outcomes. Lymph node (LN) stage is the most important prognostic factor after curative-intent resection of NSCLC. Unfortunately, the completeness of pathologic examination of the resection specimen varies, and the overall quality of pathologic LN staging may be poor. For example, only a median of 5 LNs are examined after resection of lung cancer in the United States.”
They investigated completeness of N1 LN examination in NSCLC resection specimens by performing a case-control study of a SPE protocol that used thin gross dissection with retrieval and microscopic examination of all LN-like material on remnant NSCLC resection specimens after routine pathologic examination. Lymph nodes retrieved by the SPE protocol were compared with those examined after routine pathologic examination of the same lung specimens and with those of an external control cohort.
Additional LNs were retrieved in 66 of 73 (90%) patient cases. Metastasis was discovered in 56 (11%) of 514 retrieved LNs from 27% of all patients. Unexpected LN metastasis was found in 6 (12%) of 50 node-negative patients and 3 others had undetected satellite metastatic nodules.
“Given the growing evidence that the number of LNs with metastasis is independently prognostic, it is remarkable that we found additional LN metastasis in 64% of patients who were already known to have node-positive disease,” they reported. “The final pathologic stage was upgraded in 11% of patients. Four of 8 patients whose stage was upgraded became eligible for postoperative adjuvant chemotherapy because of SPE findings.”
The investigators found that although SPE is more meticulous and labor intensive than RPE, “the SPE learning curve can be surmounted after a few patient cases.”
“Finally, we have not provided any outcome data in this study. It is possible that finding occult LN metastasis has no meaningful impact on patient survival, and our effort simply created a type of overdiagnosis bias. Although this seems unlikely, the answer to this criticism can only come from a clinical trial designed to measure survival. We are currently designing such a trial,” they stated. In the meantime, they suggest an improved protocol for dissection and examination of lung resection specimens designed to improve LN yield be adopted.