The presence of lymphatic invasion (LI) indicates a worse prognosis for patients with pathologically node-positive lung adenocarcinoma, compared with its absence, indicate Japanese study findings.
Three-year recurrence-free survival (RFS) rates were 48% versus 85% in node-positive patients with and without LI, after a median 42-month follow-up, report the researchers in The Journal of Thoracic and Cardiovascular Surgery.
Indeed, multivariate analysis revealed LI to be the only factor significantly associated with RFS (defined as the length of time until a sign or symptom of cancer after primary surgical treatment) for the 41 node-positive patients in the cohort of 609 patients with stage T1 N0 M0 disease.
While Morihito Okada (Hiroshima University) and colleagues accept that their study was limited by the small number of node-positive participants, they caution that their findings strongly support “the significance of LI status as a predictive factor, particularly in patients whose lymph node status is clinically negative and pathologically positive.”
“That is, poor prognosis should be defined according to not only lymph node status but also LI status”, they add.
The team included patients’ LI, blood vessel invasion, pleural invasion and lymph node metastasis status as well as their lepidic component (LC) ratio in the initial analysis. The LC ratio threshold used was 30%, which is also an indicator of high- or low-grade malignancy.
While positive LI status was the only factor to significantly predict poor RFS for pathologically node-positive patients, an LC ratio above the threshold, positive LI status, blood vessel invasion, pleural invasion and the presence of lymph node metastasis all significantly predicted poor RFS for node-negative patients.
In the analysis of LI status alone, 3-year RFS rates were significantly lower in both pathologically node-positive and node-negative patients with positive LI, at 48% and 71%, compared with their respective counterparts without LI, at 85% and 93%.
The difference in the predictive ability of LI compared with lymphatic metastasis in this population could lie in the difficulty in examining all slices of a tissue specimen, note Okada and colleagues. Some slices – including the tumour – could be pathologically assessed but missed if deemed to have only slight LI.
The team suggests that in addition to LI status indicating prognosis, it could also affect the selection of patients with lung cancer who require adjuvant therapy.
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