Significance of risk factor analysis and dissection for station 4L lymphatic metastasis in left lung cancer: a systematic review and meta-analysis

BACKGROUND: The effect of 4L lymph node dissection on the prognosis of left lung cancer is currently controversial. Therefore, a meta-analysis was conducted to compare the difference in prognosis between the dissection group and the non-dissection group, and assess the independent risk factors for 4L lymphatic metastasis. METHODS: A systematic literature retrieval from PubMed, Embase and CNKI was conducted to identify relevant studies up to October, 5, 2020. The data concerning the overall survival (OS) rate, disease-free survival (DFS) rate, and risk factors for 4L lymphatic metastasis were extracted and analyzed. RESULTS: L10 lymphatic metastasis was an independent risk factor for positive L4 lymph node result (Z=4.89, P<0.05). The probability of positive L4 with positive L10 was 5.11 times of that with negative L10. L5 lymphatic metastasis was an independent risk factor for positive L4 lymph node result (Z=3.92, P<0.05). The probability of positive L4 with positive L5 was 3.92 times of that with negative L5. L7 lymphatic metastasis was not an independent risk factor for positive L4 lymph node result. Positive L4 lymph node decreased the survival rate of relevant patients while L4 lymph node dissection increased the survival rate of relevant patients (Z=2.81, P<0.05 or Z=4.18, P<0.05). Positive L4 lymph node reduced the DFS time of relevant patients while L4 lymph node dissection prolonged the DFS time of relevant patients (P<0.05, Z=2.72). CONCLUSIONS: If the intraoperative pathological examination indicates positive station 10L lymph node, station 4L lymph node will be dissected, which may be a good choice at present. Positive L4 lymph node may reduce the survival time and DFS time of relevant patients while dissection of positive station 4L lymph node may prolong the survival time and DFS time of relevant patients. The intraoperative rapid frozen section pathological examination of station 10L lymph node may be a good choice.