| Budget Amount *help |
¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1996: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
Purpose : To determine the preserved functional capacity of the liver as a probable major determinant of radiation tolerance in radiotherapy for hepatocellular carcinoma which is often accompanied by cirrhosis, and besides to determine the patterns of tumor regression following radiotherapy. Materials and Methods : We used sequential CT scans of 26 patients for the tolerance study and of 18 patients for the tumor-regression study. Tumors were treated with focused proton beams which delivered high doses (140-186 TDF) with sharply defined region. We measured the degree of hypertrophy of the untreated liver volume, by measuring the totalliver volume, tumor volume, and the treated liver volume identified on the follow-up CT scans. The risk of radiation-induced liver failure was estimated using the prediction score (PS) originally used for estimating posthepatectomy liver failure in cirrhotic livers, substituting the planned treated liver volume for the resection liver volume. Tumor regress
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ion was determined in terms of daily decrement (DD : cm^3/day) of a tumor mass. Correlation of the DD with the initial tumor diameter (D : cm) was examined with a regression analysis. Results : The degree of liver hypertrophy was significantly positively correlated with the ratio of the planned treated liver volume to the initial functional liver volume (total liver volume minus tumor volume). The PS agreed well with observed radiation tolerance. The regression equation derived, DD=a^*D^b, showed that the exponent b was 3.0 or larger for the <less than or equal>6-month period and 2.0 or smaller for the >6-month period (6-33). Conclusion : As in surgical treatment, radiation tolerance of the cirrhotic liver is closely related to the preserved functional capacity of the untreated liver volume, which hypertrophies following radiotherapy. The patterns of tumor regression suggest that the clearance depends initially on the tumor volume, subsequently on the tumor surface area, and then it becomes much more moderate. Less
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