Natural history of early colorectal cancer

Since superficial tumors have been found, their peculiar pathologic feature s have evoked questions concerning their biologic behavior, their natural h istory. The aim of the present study was to elucidate the natural history o f colorectal cancers (CRCs) including superficial cancers, using a retrospe ctive radiologic method. Forty nine cancers that had had initial configurat ions of early cancer seen by previous radiography and that were examined pa thologically were the subject of the present study. Growth speeds [doubling time (DT) calculation] and configurational changes at the various stages ( invasion depth) were compared between polypoid growth (PG) and nonpolypoid growth (NPG). Growth speeds of mucosal cancer and submucosal cancer were al so compared. The results showed that early CRC grows slowly (DT 31.2 months ) when the cancer is limited to the mucosa. However, as tumors grow down to the submucosa, their growth speed accelerates (DT 25.8 months). The DT of these early cancers were longer than that of advanced cancers. The patholog ic growth pattern (NPG or PG) of the CRCs did not affect the tumor growth s peed. In respect to tumor configuration, when the tumor is limited to the s ubmucosa the antecedent growth pattern may be easily deduced. It seems diff icult, however, to know the initial growth patterns in advanced cancers bec ause cancers with polyloid growth frequently change to a nonpolypoid growth pattern when in advanced stages. Among 32 advanced cancers, only 6 (19%) d erived from IIc/IIc+IIa cancer. The most common (more than 70%) origin of a dvanced cancer seems to be IIa, Is. and Isp Lesions. These results suggest that NPG cancers or superficial depressed cancers are not the main origins of advanced cancers, and that these cancer do not show extraordinarily rapi d growth.