Late Cardiac Toxicity after Mediastinal Radiotherapy for Hodgkin Lymphoma: Contributions of Coronary Artery and Whole Heart Dose-Volume Variables to Risk Prediction

Publication date: Available online 27 March 2017
Source:International Journal of Radiation Oncology*Biology*Physics
Author(s): Ezra Hahn, Haiyan Jiang, Angela Ng, Shaheena Bashir, Sameera Ahmed, Richard Tsang, Alexander Sun, Mary Gospodarowicz, David Hodgson
PurposeMediastinal radiotherapy (RT) for Hodgkin Lymphoma (HL) is associated with late cardiotoxicity, but there are limited data to indicate which dosimetric parameters are most valuable for predicting this risk. This study investigated which whole heart dosimetric measurements provide the most information regarding late cardiotoxicity, and whether coronary artery dosimetry was more predictive of this outcome than whole heart dosimetry.Methodsand Materials; A random sample of 125 HL patients treated with mediastinal RT was selected and 3D cardiac dose-volume data was generated from historical plans using validated methods. Cardiac events were determined by linking patients to population-based datasets of inpatient and same-day hospitalizations and same-day procedures. Variables collected for the whole heart and three coronary arteries included: Dmean, Dmax, Dmin, dose homogeneity, V5, V10, V20, and V30. Multivariable competing risk regression models were generated for the whole heart and coronary arteries.ResultsThere were 44 cardiac events documented, of which 70% were ischemic. The best multivariable model included the following covariates: Whole heart Dmean (HR 1.09, p=0.0083), dose homogeneity (HR 0.94, p=0.0034), male gender (HR 2.31, p=0.014), and age (HR 1.03, p=0.0049). When any adverse cardiac event was the outcome, models using coronary artery variables did not perform better than models using whole heart variables. However, in a subanalysis of ischemic cardiac events only, the model using coronary artery variables was superior to the whole heart model and included the following covariates: age (HR 1.05, p<0.001), volume of left anterior descending artery receiving 5Gy (HR 0.98, p=0.003), and volume of left circumflex artery receiving 20Gy(HR 1.03, p<0.001).ConclusionIn addition to higher mean heart dose, increasing inhomogeneity in cardiac dose was associated with a greater risk of late cardiac effects. When evaluating all types of cardiotoxicity the whole heart variable model outperformed the coronary artery models. However, when events were limited to ischemic cardiotoxicity, the coronary artery based model was superior.

Teaser

There are limited data to indicate the potential value of dosimetric parameters other than mean heart dose in predicting late cardiotoxicity after radiation for Hodgkin Lymphoma. We explored the value of these other dosimetric variables. Increasing cardiotoxicity was associated with increasing whole-heart Dmean, increasing cardiac dose inhomogeneity, and also male sex and increasing age; coronary artery dose did not value to predicting all-cause cardiotoxicity. However, when evaluating ischemic cardiac events only, a coronary artery-based model was superior.


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