Metastatic patterns in patients with carcinomas of the lower esophagus and upper rectum.

The frequency of metastatic involvement of eight target organs was examined in people dying as a consequence of squamous cell carcinomas of the lower third of the esophagus or adenocarcinomas of the upper third of the rectum. In both groups, there was a stronger association of metastatic incidence in the target organs with organ blood flow per gram in patients with liver metastases than without. The results suggest that this association, which is consistent with the 'mechanical' hypothesis of metastatic pattern, is only seen in people with advanced disease and that in the others temporal limitations imposed by death or cure prevent full development of the pattern. The data suggest that in accord with the 'cascade' theory, cancer cells must first form metastases in the liver, that cells from these metastases not the primary cancer, then form metastases in the lungs; cancer cells from the lung metastases then subsequently disseminate with a trend towards an arterial pattern. Data from animal experiments suggest that owing to the inefficiency of the metastatic process in terms of cancer cells, this sequential process is slow relative to tumor development and that this time base affects expression of metastatic pattern. This proposed scheme for metastatic pattern development provides evidence in favor of Ewing's 'mechanical' hypothesis for two histologic types of cancer, each growing in one designated primary site. It does not exclude a role for 'seed and soil' effects in these and other cancers.