Can magnetic resonance imaging correctly diagnose remaining breast cancer after chemotherapy before surgery?

This review evaluated several studies which compared magnetic resonance imaging (MRI) to mammography, ultrasound and clinical examination after neoadjuvant chemotherapy in breast cancer patients. The aim was to see if MRI more accurately identified patients who had responded well to chemotherapy and obtained a pathological complete response. 

Chemotherapy before surgery in breast cancer patients is known as neoadjuvant chemotherapy (NAC). The aim of NAC is to shrink the cancer in the breast tissue and destroy cancer cells that have spread beyond the breast. This is called a pathologic complete response. Following NAC, if the cancer is still invading nearby breast tissue or lymph nodes, it is called residual cancer. Shrinking the cancer before surgery increases the chances that the cancer will be completely removed during surgery.

MRI is a test that uses magnetic and radio waves to make pictures of tissues, organs and other structures of the body. These pictures can be viewed and stored on a computer. This makes it useful to identify cancer in the breast or that has spread to the surrounding lymph nodes or to other tissues and organs. Mammography uses x-rays to locate and diagnose breast cancers and ultrasound uses sound waves to make pictures of tissues and organs of the body. The authors of this study compared MRI to mammography and ultrasound in correctly identifying residual cancer in patients undergoing NAC for breast cancer.

This article looked at the results of 44 clinical studies which included overall 2050 patients newly diagnosed with breast cancer. All patients were treated with NAC and underwent MRI afterwards, to see if there was any residual cancer before surgery. Some patients also underwent mammography, ultrasound or clinical examination of the affected breast as alternative diagnosis method to MRI.

Results show that MRI correctly detected residual breast cancer. Moreover, MRI was significantly more accurate in detecting residual invasive breast cancer after NAC than mammography, but not when compared to cheaper techniques such as ultrasound and clinical examination.  

Overall this study showed that MRI was very useful in detecting residual cancer after NAC in patients with breast cancer.

A drawback for this research was that definitions for a pathologic complete response varied between the studies included. Also, there were fewer studies comparing MRI to ultrasound than those comparing MRI to mammography. Therefore, to accurately determine whether MRI has more benefits than ultrasound examination in detecting residual breast cancer would require more good quality clinical trials.