OBJECTIVE: To detect the mode of yearly biological cycle of malignant biological behavior of hepatocellular carcinoma (HCC). METHODS: Twenty-one kinds of CT signs reflecting various degrees of malignant biological behavior were determined. A total of 360 patients were collected by random sampling of 30 patients each month. CT signs of each patient were fitted in corresponding group of yearly cyclic data respectively by cosine curves and analysed in terms of sequence characteristics (cosinor). RESULTS: With a 95% confidence, 10 CT signs showed biological rhythm (P<0.05). The acrophase of CT features for highly-invasive growth concentrated between -60° and -120° from March to April. For low-invasive growth, however, the CT features were relatively low and concentrated between -180° and -270° from July to September. No acrophase was shown between -120° and -180° from May to June, and between -270° and -330° from October to November. CONCLUSION: Between CT signs of the highly-invasive and those of low-invasive growth of HCC, a sequential difference in biological cycles can be observed.
