rcandelaria@mdanderson.org

To investigate which pretreatment and midtreatment ultrasound breast tumor characteristics are predictive of pathologic complete response (pCR) status in triple negative breast cancer (TNBC) patients treated with neoadjuvant chemotherapy

As a substudy of an active, single-institution, IRB-approved clinical trial of Stage I-III TNBC patients, this imaging analysis included the first 125 patients who underwent surgery. Ultrasound was performed on all patients before (pretreatment) and after (midtreatment) completion of four cycles of AC (Adriamycin and cyclophosphamide) chemotherapy. Patients subsequently received taxane-based chemotherapy or an investigational therapy as guided by midtreatment response. Review of ultrasound images was performed while blinded to pathology results (i.e., pCR versus non-pCR) from definitive surgery. Tumor size was based on the largest dimension on ultrasound. Tumors with a nonmass finding of abnormal, altered echotexture compared to surrounding breast tissue were described as 'infiltrative'. The appearance of the tumor at midtreatment was designated as 'mass', 'architectural distortion', 'flat tumor bed', or 'clip only/no visible tumor bed'. Midtreatment response pattern was described as 'complete', 'concentric shrinkage', 'fragmented', 'stable' or 'progression'. Logistic regression analyses were performed with p values less than 0.05 considered statistically significant.

Mean patient age was 53 years, range 27-77. Fifty-five of 125 patients (44%) achieved pCR while 70 of 125 (56%) had non-pCR. On pretreatment ultrasound, tumors that were <= 5 cm in size (p=0.029) or tumors that did not have an associated infiltrative/nonmass appearance (p=0.0081) were more likely to achieve pCR. On midtreatment ultrasound, tumors which no longer had the appearance of a space-occupying mass (p<0.0001) or tumors that showed a complete or concentric shrinkage response pattern were more likely to result in pCR (p=0.010).

Ultrasound pretreatment tumor size, associated nonmass/infiltrative component assessed at pretreatment, midtreatment tumor appearance and tumor response pattern at midtreatment are variables that may be useful to predict pCR in TNBC.

Ultrasound can be an accessible, informative tool during pretreatment and midtreatment to identify TNBC patients who are less likely to achieve pCR and may benefit from investigational therapies.