Is the mediastinal lymphadenectomy during pulmonary metastasectomy of colorectal cancer necessary?

The aim of study was to investigate the pattern of mediastinal lymph node metastases in patients with colorectal cancer metastasis. Twenty-four pulmonary metastasectomies with mediastinal lymphadenectomies were performed on 19 patients (14 unilateral and five bilateral operations). The metastases were centrally localised in eight cases; the primary tumour was colon cancer in 15 patients and rectal cancer in nine cases. The number and the localisation of metastases were recorded, as the clinico-pathological data of the primary tumours. The results were compared with the pattern of metastases in mediastinal lymph nodes. The data were subjected to statistical processing with the chi(2)-test and Mann-Whitney test. Mediastinal lymph node metastases were confirmed in eight cases (33.3%). The proportion of positive lymph nodes was significantly higher for central metastases (62.5% vs. 18.8%, P=0.032). When the pathological stage of the primary tumour was more advanced, the proportion of lymph node metastases displayed a statistically not significant increase. The pattern of lymph node metastases did not correlate with the localisation of the lung metastases, disease-free interval and the diameter of the greatest pulmonary metastasis. The frequency of lymph node metastasis is relatively high, therefore, mediastinal lymphadenectomy during the resection of colorectal cancer metastases is necessary.