Breast Imaging Before Chemotherapy Predicts Need for Radiation: Presented at ASTRO

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Title: Breast Imaging Before Chemotherapy Predicts Need for Radiation: Presented at ASTRO
URL: http://www.pslgroup.com/dg/22DD32.htm
Doctor's Guide
September 29, 2008

By Martha Kerr, BSN

BOSTON -- September 29, 2008 -- Magnetic resonance imaging (MRI) may help determine whether a patient with invasive breast cancer would derive benefit from radiation therapy, researchers noted here at the American Society for Therapeutic Radiology and Oncology (ASTRO) 50th Annual Meeting.

Increased kinetics correlate with metastases to the axillary nodes, stated lead investigator Christopher R. Loiselle, MD, University of Washington, Seattle, Washington. His study suggests that a breast tumour's activity on MRI may help predict whether cancer has spread to the lymph nodes, allowing women with smaller tumours and negative nodes to avoid radiation therapy.

Dr. Loiselle and colleagues conducted a retrospective review of the records of 167 consecutive patients with invasive breast cancer who were treated with external-beam radiotherapy from January 2006 to November 2007.

Subjects were included in the study if they had undergone surgical staging by sentinel-node biopsy or axillary dissection prior to chemotherapy. Individuals were excluded if they received neoadjuvant chemotherapy prior to surgery.

MRI kinetic data were analysed and calculated for each patient's primary tumour using a computer-aided evaluation program. Differences in peak enhancement, percentage of rapid enhancement, and percentage of washout between the node-positive and node-negative groups were evaluated.

Of the 46 patients meeting the study criteria, 32 patients (70%) were node-negative and 14 patients (30%) were node-positive.

The peak enhancement of the primary tumour was significantly greater in node-positive patients, where there was a mean difference of 245% over baseline. In node-negative patients, there was a mean difference of 144% over baseline (P = .0027).

The percentage of rapid enhancement was also significantly greater in node-positive patients, with a mean of 48%, compared to node-negative patients with a mean of 29% (P = .0436).

The percentage of washout was not different between groups (P = .9524).

"In the past, decisions regarding radiation therapy were made after surgery and before chemotherapy," Dr. Loiselle said. "When you give chemotherapy first, and then perform the surgery to remove the cancer and sample the lymph nodes, you reduce your ability to know whether there was cancer in the axillary lymph nodes before the patient was treated with chemotherapy."

"This raises the question: Is there another way to stage those lymph nodes? Our study showed that tumour characteristics as seen on an MRI scan may be the answer," Dr. Loiselle said. "MRI is evolving rapidly as a diagnostic tool for breast cancer -- particularly among women with high risk for the disease -- because not only does it give us traditional anatomic information about tumours, but information about the biology of the tumour as well."

[Presentation title: Dynamic Contrast Enhanced MRI Kinetics and Invasive Breast Cancer: A Potential Prognostic Marker for Radiation Therapy. Abstract 2018]

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