"The Law of 3": prognostic parameters for resected metastatic pulmonary tumors.

Metastatic tumors from various organs are found in pulmonary tissue because of the unique anatomical function of the lungs as a filter for systemic venous return. A retrospective study of the clinical factors used to assess the prognosis of 80 patients who underwent resections of metastatic pulmonary tumors in our surgical department between September 1978 and December 2002 is presented. The overall 5-year survival rate in our study was 31.7%. We demonstrated four significant factors used in predicting the prognosis of patients with resected metastatic pulmonary tumors: diameter of the tumor (</=3.0 cm or >3.0 cm), number of tumors (</=3 or >3), disease-free interval (>/=3 years or <3 years), and ratio of the diameter of the largest tumor to the diameter of the smallest tumor in patients with multiple metastases (</=3 or >3). Based on our results, we have applied the term "the law of 3" to these valuable prognostic factors. Among these parameters, the ratio of the diameter of the largest to the diameter of the smallest tumor may be applicable as a new prognostic parameter for surgery in patients with multiple foci. (Ann Thorac Cardiovasc Surg 2003; 9: 290-4)