Prognosis of pulmonary lymphangitic carcinomatosis in patients with non-small cell lung cancer

BACKGROUND: The eighth edition of the TNM classification for lung cancer does not provide a definite guideline for pulmonary lymphangitic carcinomatosis. The purpose of this retrospective case-control study is to evaluate the prognosis of pulmonary lymphangitic carcinomatosis in patients with non-small cell lung cancer compared with those with intrapulmonary metastases. METHODS: Non-small cell lung cancer (NSCLC) patients with pulmonary lymphangitic carcinomatosis detected on chest computed tomography scan during staging evaluation between 2000 and 2016 were included. The extent of pulmonary lymphangitic carcinomatosis was classified as being around the primary tumor (cLy1), at a distance from the tumor but confined to the same lobe (cLy2), in other ipsilateral lobes (cLy3), or affecting the contralateral lung (cLy4). Overall survival rates of the subjects were compared with those with intrapulmonary metastases. RESULTS: A total of 103 subjects with pulmonary lymphangitic carcinomatosis were analysed. The 5-year overall survival rates of the subjects with pulmonary lymphangitic carcinomatosis (n=103) and intrapulmonary metastases (n=111) were 33% and 21%, respectively. The 5-year overall survival rates of cLy1 (n=28), cLy2 (n=40), cLy3 (n=26) and cLy4 (n=9) were 54%, 35%, 12% and 11%, respectively. On multivariable analyses after adjusting for possible confounders, the subjects with cLy1 and cLy2 had better overall survival (adjusted hazard ratio for death, 0.34 and 0.49; 95% confidence interval, 0.24–0.73 and 0.30–0.80; P<0.001 and 0.004, respectively) and the subjects with cLy4 had worse overall survival (adjusted hazard ratio, 2.21; 95% confidence interval, 1.03–4.70; P=0.040) compared with those with intrapulmonary metastases. CONCLUSIONS: The subjects with cLy1/2 had better overall survival than those with cLy3/4 or intrapulmonary metastases. cLy1/2 seems to be a T descriptor (T3/4) rather than an M1 descriptor.