CONTINUING TRENDS IN THE PREVALENCE OF RIGHT-SIDED LESIONS AMONG COLORECTAL CARCINOMAS

The shift of colorectal carcinoma location toward the proximal colon h as been reported. This study documents that this statistically signifi cant trend has continued through 1992. An increase in transverse and d escending colon cancers is now apparent also. Only 59% of all large-bo wel cancers occurred distal to the descending colon between 1978 and 1 992. Both right-sided and distal large-bowel cancers have significantl y decreased in size, yet the incidence and frequency of lymph node met astases have not changed over a 65-year interval (from 1928 to 1992). This constant proportion of lymph node metastases may suggest distinct biological subsets of cancers (lymph node avid vs lymph node avoidanc e). The progression from small size with fewer metastases to large siz e with more lymph node metastases occurs only in some of the smallest distal colorectal cancers.