Abstract P6-01-04: Breast ultrasound and mammography and response to neoadjuvant lapatinib, trastuzumab and their combination in HER2 positive breast cancer: Results from Neo-ALTTO (BIG 1-06)
Authors: S Di Cosimo, C Campbell, HA Hazim, G Curigliano, C Criscitiello, R Crescenzo, L de la Pena, MJ Piccart-Gebhart, H Eidtmann, J Baselga, E de Azambuja
Journal: Cancer Research (2016)

Abstract Mammography (Mx) and breast ultrasound (US) are the most commonly used diagnostic imaging modalities to estimate primary tumor size at the time of diagnosis. However, there are uncertainties regarding their use in the context of neoadjuvant therapy to predict pathologic complete response (pCR) or event-free survival (EFS). In this study, we sought to determine the value of Mx and US in predicting outcomes in women with HER2-positive breast cancer treated within the Neoadjuvant Lapatinib and/or Trastuzumab Treatment Optimisation (Neo-ALTTO) trial. METHODS Neo-ALTTO enrolled 455 women with invasive HER2-positive breast cancer and compared rates of pCR to neoadjuvant lapatinib, trastuzumab, and their combination. Each anti-HER2 therapy was given alone for 6 weeks, followed by 12 weeks of the same therapy plus weekly paclitaxel prior to surgery. Mx and US were requested at baseline, week 6 and before surgery. Central imaging review was not pre-planned and two independent investigators (SDC and HAA Jr), blinded to assigned treatment and clinical outcomes, reviewed the measurements reported for each imaging modality and assigned the corresponding RECIST category of response. Responders were defined as patients who had either a partial or complete response (CR + PR). We evaluated the association between radiological response at week 6/surgery with both pCR and EFS. RESULTS A total of 340 (77%) and 267 (61%) pts had an evaluable US and Mx at weeks 6; and 309 (70%) and 248 (56%) pts had an evaluable US and Mx at the time of surgery. Early response (CR + PR) in the primary tumors was observed after 6 weeks of treatment in 32% pts by Mx and in 43% pts by US. pCR rates were twice as high for early responders than non-responders (week 6: 46% vs 23% by US, p =&amp;lt;0.0001; 41% versus 24% by Mx, p= 0.007). The positive predictive value of US and Mx at surgery were 57% and 53%, respectively; the negative predictive values were 72% and 81%. The results according to hormone receptor status were similar to those in the overall patient population.There was no significant relationship between response at ultrasound and/or at mammography at 6 weeks/surgery and EFS. CONCLUSION Our results show that both Mx and US are underused during neo-adjuvant treatment, and further recommendations regarding the use of both imaging modalities should be explored prospectively. US may be used to assess early response to preoperative treatment in patients with HER2 positive breast cancer receiving anti-HER2 therapies, whereas Mx appears to be more useful in detecting residual disease at the time of surgery. Citation Format: Di Cosimo S, Campbell C, Hazim Jr HA, Curigliano G, Criscitiello C, Crescenzo R, de la Pena L, Piccart-Gebhart MJ, Eidtmann H, Baselga J, de Azambuja E. Breast ultrasound and mammography and response to neoadjuvant lapatinib, trastuzumab and their combination in HER2 positive breast cancer: Results from Neo-ALTTO (BIG 1-06). [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P6-01-04.