Evaluation of lung tumor using three-dimensional stereoscopic imaging by CT scan

The effect of chemotherapy in lung cancer is evaluated by the response rate (the ratio of tumor area on plane roentgen film before and after chemotherapy), but it is preferable to evaluate tumor size by volume rather than by area. We therefore hypothesized that the doubling time after chemotherapy calculated by accurate volume measurement would predict survival time better than the conventional response rate. To clarify this hypothesis, we studied twenty-two primary lung cancer patients treated with anticancer agents. The response rate, the doubling time after chemotherapy and the survival time after chemotherapy were evaluated. To calculate doubling time, we measured tumor volume using three-dimensional stereoscopic imaging by serial CT scan using a personal computer. To determine the accuracy of this measurement, we compared clay models of known volume (five different shapes) and surgically resected lung cancers. We found the difference between the real volume and volume as determined by CT measurement was 6% in clay models and 11% in resected lung cancers. The correlation coefficient of the response rate and survival time after chemotherapy and that of doubling time after chemotherapy and survival time were 0.165 and 0.527, respectively. We conclude that measurement of tumor volume by serial CT images using personal computer is accurate and the doubling time after chemotherapy calculated by this method predicts survival time better than the conventional response rate. (author)