[Spontaneous change of malignancy of solid malignant tumors : statistical investigations of colorectal and pancreatic carcinoma].

The distribution curves of grades of malignancy for colorectal carcinomas and pancreatic carcinomas have not been stable over the years and investigations have shown a clear variability in the temporal distribution. Colon carcinomas were found to diminish considerably in aggressiveness in different time periods and colorectal carcinomas were found to increase in aggressiveness in some years. However, the distribution curve of grades of malignancy varies in both carcinomas over time and this variation follows a random distribution. In contrast to colorectal carcinomas, pancreatic carcinomas have not been followed up for very long time periods. While the distribution curve of malignancy was unchanged in most countries an increase in malignancy was observed in two countries. For colorectal and pancreatic carcinomas increases in malignancy are linked to a highly significant decrease in the number of cancers with lowest grades of malignancy. Even though the exact nature of variations in these malignancy distribution curves is incompletely understood, these variations appear important for comparative outcome statistics in cancer therapy as the aggressiveness of these malignancies has a direct bearing on the overall prognosis.