Researchers from Memorial Sloan Kettering Cancer Center in New York City used MRI-guided biopsy to identify all but one patient with lingering invasive cancer after chemotherapy. The technique achieved a negative predictive value of 95% for invasive cancer, suggesting it has the potential to serve as an alternative to surgical resection.
"These preliminary results suggest that MRI-guided biopsy was an accurate approach for evaluating the extent of residual disease after [neoadjuvant chemotherapy]," wrote the authors, led by radiologist Dr. Elizabeth Sutton.
Patients with breast cancer undergo neoadjuvant chemotherapy in hopes of downstaging their cancer and preventing the need for more invasive treatment options, such as a mastectomy or axillary lymph node dissection. However, the only reliable option for assessing pathologic complete response in these patients is surgical resection, according to the authors.
Understandably, researchers are eager to find alternative, noninvasive methods to diagnose pathologic complete response in patients after neoadjuvant chemotherapy. The authors theorized that MRI-guided biopsy could be one such tool due to the modality's unparalleled sensitivity.
The team tested their hypothesis in a phase I pilot study with patients at their institution. The nonrandomized controlled trial included 20 patients, the sample size needed to determine whether MRI-guided biopsy could achieve a negative predictive value of at least 85%.
All 20 study participants underwent standard-of-care neoadjuvant chemotherapy followed by definitive surgery to treat stage IA to IIIC invasive breast cancer. They also received noncontrast-enhanced MRI before and after their neoadjuvant chemotherapy regimen.
The authors scanned patients with a 1.5-tesla or 3-tesla whole-body MRI scanner equipped with a breast coil. Using MRI guidance and a vacuum-assisted biopsy system, the team removed seven to 12 tissue samples from each patient. The team marked the biopsy incision site at the tumor location before the start of chemotherapy.
On surgical pathology, 11 patients had no evidence of residual cancer, eight patients were diagnosed with residual invasive cancer, and one patient was diagnosed with ductal carcinoma in situ.
The MRI-guided biopsy technique correctly identified all patients without residual invasive cancer. However, the method gave a false-negative result to one patient with residual invasive cancer of less than 0.02 cm on surgical pathology.
When the authors accounted for patients with both residual invasive and in situ breast cancer, MRI-guided biopsy missed an additional cancer diagnosis in one more person. In this case, the technique assigned a false negative result to a woman whose surgical pathology showed ductal carcinoma in situ.
|Performance of MRI-guided biopsy for assessing response to chemotherapy in women with breast cancer
||Invasive cancer only
||Invasive or in situ cancer
|Negative predictive value
|Positive predictive value
Based on these results, MRI-guided biopsy achieved a negative predictive value of 93% for invasive cancer and 86% for both invasive and in situ cancers. Both metrics came in above the 85% threshold deemed acceptable by the authors at the study outset.
"These findings suggest that a negative MRI-guided biopsy result was a reliable indicator of [pathologic complete response], or of limited residual disease, after [neoadjuvant chemotherapy]," the authors wrote.
The authors cautioned their findings cannot be extrapolated to other populations or modalities since the trial was intended to prove feasibility and relied on advanced breast MRI imaging techniques. Nevertheless, they see promise in using MRI as a noninvasive method for assessing neoadjuvant chemotherapy response.
"These preliminary results support the need for further study of our novel method that uses MRI-guided biopsy," the authors concluded.
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