Tchou, Julia

504 Background: Axillary surgery in breast cancer is used for staging and therapeutic purposes, but axillary lymph node dissection (ALND) confers high risk of complications including lymphedema. Accordingly, trials have focused on right-sizing axillary surgery, with options ranging from complete omission of surgery, sentinel lymph node (SLN) surgery, targeted axillary dissection (TAD), or ALND. Identifying a biomarker to reliably predict nodal burden would facilitate accurate selection of surgical management. We evaluated whether the presence or absence of ctDNA in the blood pre and post NAC is associated with residual nodal burden. Methods: I-SPY2 is a prospective, multicenter NAC trial for patients with clinical stage II-III high-risk breast cancer. Patients are randomized to novel NAC agents, with pathologic complete response being the primary endpoint. As part of the trial, serial ctDNA is assessed with a highly sensitive tumor-informed assay using up to 16 patient-specific tumor mutations (Signatera) at baseline, 3 weeks, 12 weeks, and post-NAC. We determined whether ctDNA positivity or negativity post-NAC, and the change in ctDNA status baseline/post-NAC (-/-, -/+, +/+, +/-) are associated with ypN category (N0, N1, N2). Results: ctDNA status was available post-NAC in 495 patients and change in ctDNA status from baseline was available in 493. At baseline, ctDNA was detected in 160/220 (72.3%) cN0 patients and 227/273 (83.2%) cN+ patients (p=0.006). Post-NAC, ctDNA was detected in 11/220 (5%) cN0 patients and 34/273 (12.5%) cN+ patients (p=0.004). While baseline ctDNA status was not associated with ypN category, there was a significant association between post-NAC ctDNA status and ypN category. For ctDNA + patients post-NAC, 33.3% were ypN0, 31.1% were ypN1, and 35.6% were ypN2 at surgery; in contrast, for ctDNA - patients post-NAC, 67.1% were ypN0, 23.1% were ypN1, and 9.8% were ypN2 (p<0.0001). Dynamic ctDNA changes were also associated with ypN category, with significantly more ypN0 patients among ctDNA -/- or ctDNA +/- cases, and more ypN2 patients in those who did not clear ctDNA (+/+) (p=0.0001, Table). Conclusions: To our knowledge this is the first study to demonstrate a significant relationship between ctDNA and ypN category, which has important surgical implications. CtDNA negativity was associated with low likelihood of ypN2 disease, making these patients excellent candidates for SLN surgery or TAD. Ongoing analyses will incorporate receptor subtype and timing of clearance of ctDNA. CtDNA in breast cancer may help tailor surgical management of the axilla, potentially reducing patient morbidity without compromising prognostic information. ctDNA baseline/post-NAC ypN0 (n=317) ypN1 (n=116) ypN2 (n=60) ctDNA -/- (n=105) 72.4% 19.1% 8.6% ctDNA -/+ (n=1) 0.0% 100.0% 0.0% ctDNA +/+ (n=44) 34.1% 29.6% 36.4% ctDNA +/- (n=343) 65.9% 23.9% 10.2%

Neoadjuvant chemotherapy (NAC) increases rates of successful breast-conserving surgery (BCS) in patients with breast cancer. However, some studies suggest that BCS after NAC may confer an increased risk of locoregional recurrence (LRR). We assessed LRR rates and locoregional recurrence-free survival (LRFS) in patients enrolled on I-SPY2 (NCT01042379), a prospective NAC trial for patients with clinical stage II to III, molecularly high-risk breast cancer. Cox proportional hazards models were used to evaluate associations between surgical procedure (BCS vs mastectomy) and LRFS adjusted for age, tumor receptor subtype, clinical T category, clinical nodal status, and residual cancer burden (RCB). In 1462 patients, surgical procedure was not associated with LRR or LRFS on either univariate or multivariate analysis. The unadjusted incidence of LRR was 5.4% after BCS and 7.0% after mastectomy, at a median follow-up time of 3.5 years. The strongest predictor of LRR was RCB class, with each increasing RCB class having a significantly higher hazard ratio for LRR compared with RCB 0 on multivariate analysis. Triple-negative receptor subtype was also associated with an increased risk of LRR (hazard ratio: 2.91, 95% CI: 1.8–4.6, P < 0.0001), regardless of the type of operation. In this large multi-institutional prospective trial of patients completing NAC, we found no increased risk of LRR or differences in LRFS after BCS compared with mastectomy. Tumor receptor subtype and extent of residual disease after NAC were significantly associated with recurrence. These data demonstrate that BCS can be an excellent surgical option after NAC for appropriately selected patients.

ImportancePathologic complete response (pCR) after neoadjuvant chemotherapy (NAC) in breast cancer strongly correlates with overall survival and has become the standard end point in neoadjuvant trials. However, there is controversy regarding whether the definition of pCR should exclude or permit the presence of residual ductal carcinoma in situ (DCIS).ObjectiveTo examine the association of residual DCIS in surgical specimens after neoadjuvant chemotherapy for breast cancer with survival end points to inform standards for the assessment of pathologic complete response.Design, Setting, and ParticipantsThe study team analyzed the association of residual DCIS after NAC with 3-year event-free survival (EFS), distant recurrence-free survival (DRFS), and local-regional recurrence (LRR) in the I-SPY2 trial, an adaptive neoadjuvant platform trial for patients with breast cancer at high risk of recurrence. This is a retrospective analysis of clinical specimens and data from the ongoing I-SPY2 adaptive platform trial of novel therapeutics on a background of standard of care for early breast cancer. I-SPY2 participants are adult women diagnosed with stage II/III breast cancer at high risk of recurrence.InterventionsParticipants were randomized to receive taxane and anthracycline-based neoadjuvant therapy with or without 1 of 10 investigational agents, followed by definitive surgery.Main Outcomes and MeasuresThe presence of DCIS and EFS, DRFS, and LRR.ResultsThe study team identified 933 I-SPY2 participants (aged 24 to 77 years) with complete pathology and follow-up data. Median follow-up time was 3.9 years; 337 participants (36%) had no residual invasive disease (residual cancer burden 0, or pCR). Of the 337 participants with pCR, 70 (21%) had residual DCIS, which varied significantly by tumor-receptor subtype; residual DCIS was present in 8.5% of triple negative tumors, 15.6% of hormone-receptor positive tumors, and 36.6% of ERBB2-positive tumors. Among those participants with pCR, there was no significant difference in EFS, DRFS, or LRR based on presence or absence of residual DCIS.Conclusions and RelevanceThe analysis supports the definition of pCR as the absence of invasive disease after NAC regardless of the presence or absence of DCIS.Trial RegistrationClinicalTrials.gov Identifier NCT01042379.

Abstract Background: Patients who achieve a pathological complete response (pCR- defined as no invasive cancer) after neoadjuvant chemotherapy (NAC) for breast cancer (BC) have improved outcomes, but there is still controversy about the significance of residual ductal carcinoma in situ (DCIS) on local recurrence rate (LRR). The I-SPY 2 TRIAL is an adaptive neoadjuvant platform trial evaluating novel experimental regimens in comparison to standard chemotherapy in women with high-risk breast cancer. The purpose of this study is to determine if residual DCIS after NAC in early BC affects LRR in patients with or without residual invasive disease in the I-SPY 2 TRIAL. Methods: 933 I-SPY 2 patients with residual cancer burden (RCB) and follow-up data were included in this analysis. Residual DCIS was defined as any carcinoma in situ &gt; 0% on RCB evaluation. Local recurrence was defined as recurrence in breast, chest wall or locoregional nodes and/or skin and subcutaneous tissue. We stratified our cohort into four groups: those without residual invasive disease (defined as RCB0) ± residual DCIS, and those with residual invasive disease (RCB&gt;0) ± residual DCIS. We estimated LRR within each group using the Kaplan Meier method; and used Cox proportional hazards models to assess LRR differences between groups, with: patients with no residual disease (invasive or in situ) as reference group. Results: Among 933 patients assessed, median follow up time was 3.9 years. RCB 0 status was achieved in 337 patients (36%). Of these, 267 (29%) had no residual DCIS, which represents our reference group, and 70 (7%) had residual DCIS. Among 596 (64%) patients who had RCB&gt;0, 296 (32%) had residual DCIS. For patients with RCB0 without DCIS and RCB0 with DCIS, the LRR at 3 years were similar: 2% vs 3% respectively (Hazard ratio: 1.29 [0.26-6.39]). Results were also similar in the RCB&gt;0 group, with a LRR of 10% at 3 years in those without residual DCIS, and 11% in those with residual DCIS. Both RCB&gt;0 groups had significantly higher LRR when compared to the patients with RCB0 without DCIS (Hazard ratio: 5.25 [2.20-12.5]) and HR 5.85 [2.47-13.9] respectively). Conclusion: There was no association between residual DCIS and LRR after neoadjuvant chemotherapy, regardless of resolution of invasive disease. Further work is needed to determine whether residual DCIS should drive locoregional therapy decisions after neoadjuvant chemotherapy for invasive breast cancer. Citation Format: Marie Osdoit, Christina Yau, W. Fraser Symmans, Judy C. Boughey, Smita M. Asare, Ron Balassanian, Jodi M. Carter, Yunn-Yi Chen, Kimberly Cole, Laila Khazai, Molly Klein, Dina Kokh, Gregor Krings, Sunati Sahoo, Gretchen Ahrendt, Akiko Chiba, Cheryl Ewing, Constantine Godellas, Nora Jaskowiak, Brigid Killelea, Helen Krontiras, Rachael Lancaster, Julie Lang, M. Catherine Lee, Arpana Naik, Roshni Rao, Julia Tchou, Shannon Tierney, Eleni Tousimis, Tod Tuttle, Anne Wallace, I-SPY 2 TRIAL Consortium, Bev Parker, Laura J. Esserman, Rita A. Mukhtar. The impact of residual ductal carcinoma in situ on breast cancer recurrence in the neoadjuvant I-SPY2 TRIAL [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P3-08-16.