Breast cancer patients with HER2-positive disease are more likely to be nonsurgical candidates for clinical trials after neoadjuvant systemic therapy if they have eradicated both invasive and ductal carcinoma in situ (DCIS) disease, according to research presented in a recent webcast from the annual meeting of the American Society of Breast Surgeons.
While there is a high rate of pathologic complete response (pCR) in HER2-postive breast cancer after neoadjuvant systemic therapy, it is difficult to determine which patients have achieved pCR because standard imaging generates a high rate of false negatives, noted Susie Sun, MD, from the University of Texas MD Anderson Cancer Center, Houston.
“Although radiological imaging such as mammograms, ultrasounds, and MRIs have been shown to be unreliable in identifying patients with pCR, we have previously determined that patients with clinically significant residual disease can be accurately identified using a combination of multimodality imaging and image-guided, vacuum-assisted biopsy to the tumor bed,” Dr. Sun said in her presentation.
In the Multicenter Trial for Eliminating Breast Cancer Surgery in Exceptional Responders With Neoadjuvant Systemic Therapy, Dr. Sun and colleagues enrolled 280 patients with T1-T2, N0-N1 HER2-positive breast cancer who had undergone HER2-targeted therapy, followed by surgical resection and axillary surgery. The researchers studied both the effects of neoadjuvant therapy patients with pCR and the clinicopathologic characteristics of residual disease to determine how patients with pCR differed from those with residual disease.
After neoadjuvant systemic therapy, 55.4% of pCR invasive cancer was eradicated in patients, 37.5% of both pCR invasive and DCIS cancer was eradicated in patients, and 17.9% of patients had eradication of only residual DCIS. Compared with patients where DCIS was not identified at initial biopsy, DCIS identification was associated with a higher likelihood of residual disease (69% vs. 57%; P = .04). The researchers found patients having hormone receptor–positive/HER2-positive disease was associated with a higher rate of predictive residual disease (26.6%), compared with patients who had hormone receptor–negative/HER2-positive disease (49.2%; odds ratio, 2.7; 95% confidence interval, P less than .0001).
“For the currently occurring trial, evaluating the safety of eliminating surgery for patients who are exceptional responders to neoadjuvant systemic therapy, eradication of both the invasive and DCIS components are necessary because DCIS may serve as a nidus for carcinoma in the future,” said Dr. Sun.
The researchers also studied the effectiveness of multimodality imaging on identifying pathologic response. The multimodality imaging consisted of a mammogram and ultrasound for all patients, and approximately 13% of patients had MRI in addition to mammogram and ultrasound. The multimodality imaging response after neoadjuvant systemic therapy had a sensitivity of 97.1% and a negative predictive value of 70.6% for detecting residual disease in the breast and lymph nodes.
“[O]ur study found that multimodality imaging was not reliable in assessing for pathologic response within the breast or lymph nodes,” said Dr. Sun. “Therefore, imaging alone cannot be used to select patients for no surgery. This requires patients who have image-guided percutaneous biopsy to safely select patients for inclusion and elimination of surgery trial.”
In a discussion session, Dr. Sun clarified the combination of multimodality imaging and image-guided percutaneous biopsy was used to select HER2-positive patients for a clinical trial, and is not standard of practice to determine pCR at the University of Texas MD Anderson Cancer Center.
Dr. Sun reported no relevant financial disclosures.