Analysis of radiation-induced liver disease using the Lyman NTCP model.
OBJECTIVE
To describe the dose-volume tolerance for radiation-induced liver disease (RILD) using the Lyman-Kutcher-Burman (LKB) normal tissue complication probability (NTCP) model.


METHODS
A total of 203 patients treated with conformal liver radiotherapy and concurrent hepatic arterial chemotherapy were prospectively followed for RILD. Normal liver dose-volume histograms and RILD status for these patients were used as input data for determination of LKB model parameters. A complication was defined as Radiation Therapy Oncology Group Grade 3 or higher RILD < o r =4 months after completion of radiotherapy. A maximal likelihood analysis yielded best estimates for the LKB NTCP model parameters for the liver for the entire patient population. A multivariate analysis of the potential factors associated with RILD was also completed, and refined LKB model parameters were obtained for patient subgroups with different risks of RILD.


RESULTS
Of 203 patients treated with focal liver irradiation, 19 developed RILD. The LKB NTCP model fit the complication data for the entire group. The "n" parameter was larger than previously described, suggesting a strong volume effect for RILD and a correlation of NTCP with the mean liver dose. No cases of RILD were observed when the mean liver dose was <31 Gy. Multivariate analysis demonstrated that in addition to NTCP and the mean liver dose, a primary hepatobiliary cancer diagnosis (vs. liver metastases), bromodeoxyuridine hepatic artery chemotherapy (vs. fluorodeoxyuridine chemotherapy), and male gender were associated with RILD. For 169 patients treated with fluorodeoxyuridine, the refined LKB model parameters were n = 0.97, m = 0.12, tolerance dose for 50% complication risk for whole organ irradiated uniformly [TD50(1)] = 45.8 Gy for patients with liver metastases, and TD50(1) = 39.8 Gy for patients with primary hepatobiliary cancer.


CONCLUSIONS
These data demonstrate that the liver exhibits a large volume effect for RILD, suggesting that the mean liver dose may be useful in ranking radiation plans. The inclusion of clinical factors, especially the diagnosis of primary hepatobiliary cancer vs. liver metastases, improves the estimation of NTCP over that obtained solely by the use of dose-volume data. These findings should facilitate the application of focal liver irradiation in future clinical trials.
Dawson
Laura A
LA
Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48109-0010, USA. dawson@umich.edu
Normolle
Daniel
D
Balter
James M
JM
McGinn
Cornelius J
CJ
Lawrence
Theodore S
TS
Ten Haken
Randall K
RK
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D016013:Likelihood Functions; D008113:Liver Neoplasms / Q000209:etiology*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009362:Neoplasm Metastasis; D009381:Neoplasms, Radiation-Induced; D011379:Prognosis; D011874:Radiometry; D013997:Time Factors