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| |  Changes Not Affecting Tumour Size May Better Predict Outcomes to Bevacizumab: Presented at RSNA By Ed Susman CHICAGO -- December 3, 2009 -- Changes seen in imaging studies of tumours following administration of the targeted biologic agent bevacizumab that do not affect tumour size may permit doctors to follow progress of treatment and better predict outcomes, researchers suggested here. “The addition of bevacizumab to cytotoxic regimen is associated with unique morphological changes identifiable on single-phase, contrast-enhanced computer-assisted tomography,” said Piyaporn Boonsirikamchai, MD, University of Texas M. D. Anderson Cancer Center, Houston, Texas, on December 1, in a poster presentation at the Radiological Society of North America (RSNA) 95th Annual Meeting. “These changes, independent of change in tumour size, predict pathological response and thus are a radiographic marker of response,” Dr. Boonsirikamchai reported. The changes seen in the tumours may be subtle, and may be discordant with changes in tumour size as measured by Response Evaluation Criteria in Solid Tumours (RECIST) criteria, the researchers said. “Treatment effect after bevacizumab does not always manifest as a change in tumour size. Non-size-related criteria presented in this poster allow reliable evaluation of the treatment,” Dr. Boonsirikamchai said. “At pathology they are associated with a decrease in the percentage of residual tumour cells and a decrease in the tumour thickness at tumour/normal liver interface. These criteria correlate with patient’s survival.” The research team analysed computed tomography (CT) scans from 112 patients who were diagnosed with colorectal liver metastases -- 50 patients with resectable disease and 62 patients who had unresectable metastases. Dr. Boonsirikamchai indicated that a major response to bevacizumab was manifested by change of ill-defined tumour masses of heterogeneous attenuation into homogeneously hypoattenuating lesions, and a sharp tumour-liver interface. A minor response was described as a decrease in heterogeneity of tumour attenuation and a better definition of the tumour/liver interface but no sharp interface. The radiologists said they could define recurrence where they observed a reversal of the response pattern with increasing heterogeneity, haziness of margins, or subtle focus of tumour recurrence abutting a treated metastasis. Treatment responses in the patients who were able to undergo surgery were validated after the operation. “After the initial response was determined based on clinical, biological, and radiographic parameters, the patients with unresectable disease were followed until progression,” Dr. Boonsirikamchai said. The poster presentation included numerous CT scans illustrating the changes noted in the study. “Discordance between the morphological changes and RECIST criteria indicates that neither RECIST criteria nor morphological changes alone are sufficient and that both methods need to be part of the response evaluation,” Dr. Boonsirikamchai said. [Presentation title: New CT Findings of Response and Recurrence Independent of Change in Tumor Size in Colorectal Liver Metastasis Treated with Bevacizumab. Abstract LL-GI3742]
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