Abstract

Abstract Abstract #6053 Background: Assessment of tumor response to chemotherapy has traditionally relied on the bidimensional tumor measurement guidelines proposed by the World Health Organization (WHO, 1979) and more recently on the unidimensional Response Evaluation Criteria in Solid Tumors (RECIST, Therasse et al., 2000). MRI is being used increasingly to monitor breast cancer response to preoperative chemotherapy and allows both linear and volumetric assessment of tumor size. The purpose of this study was to compare pre- and post-treatment RECIST, WHO, and volumetric measures of tumor size on MRI for predicting recurrence free survival (RFS) in patients undergoing preoperative chemotherapy.
 Materials & Methods: 56 patients with locally advanced breast cancer were imaged with MRI (1.5T GE scanner) before and after 4 cycles of preoperative chemotherapy. Tumor longest diameter (LD) at physical exam (ClinLD) was recorded before (N=56) and after (N=48) treatment. Fat suppressed, contrast enhanced, T1-weighted sagittal 3DFGRE images (TE/TR=8/4.2ms, flip=20°, 2mm thick, 18-20cm FOV, 256x192 matrix) were acquired for tumor size measurements.
 All MRI LD measurements were made manually following RECIST and WHO guidelines. Tumor volume was measured with a semi-automated tumor segmentation algorithm based on a specific enhancement ratio calculation. Univariate Cox proportional hazards analysis was used to assess the value of clinical, pathology, RECIST, WHO, and volume measurements for predicting RFS. Variables with p<0.15 were combined in a stepwise multivariate model to determine the greatest predictive value.
 Results: 23 patients have recurred since surgery (mean time 132 weeks). The mean RFS in the non-recurrent group is 330 weeks. Results for univariate and multivariate analysis are show in the Table. Final tumor volume was most predictive of recurrence free survival, and was the only variable found to be an independent significant predictor in the multivariate analysis. Age, tumor grade, and positive lymph node status were not significant predictors.
 Discussion: Post-chemotherapy tumor volume calculated via a semi-automatic algorithm was found to be a significant predictor of RFS for patients undergoing preoperative chemotherapy, out-performing manual 1D RECIST, 2D WHO, and clinical measurements. The results support previous work demonstrating the value of MRI tumor volume for predicting patient outcome.
 
 Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 6053.

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