Response-guided neoadjuvant sacituzumab govitecan for localized triple-negative breast cancer: results from the NeoSTAR trial

BACKGROUND

Sacituzumab govitecan (SG), a novel antibody-drug conjugate (ADC) targeting TROP2, is approved for pre-treated metastatic triple-negative breast cancer (mTNBC). We conducted an investigator-initiated clinical trial evaluating neoadjuvant (NA) SG (NCT04230109), and report primary results.

PATIENTS AND METHODS

Participants with early-stage TNBC received NA SG for four cycles. The primary objective was to assess pathological complete response (pCR) rate in breast and lymph nodes (ypT0/isN0) to SG. Secondary objectives included overall response rate (ORR), safety, event-free survival (EFS), and predictive biomarkers. A response-guided approach was utilized, and subsequent systemic therapy decisions were at the discretion of the treating physician.

RESULTS

From July 2020 to August 2021, 50 participants were enrolled (median age = 48.5 years; 13 clinical stage I disease, 26 stage II, 11 stage III). Forty-nine (98%) completed four cycles of SG. Overall, the pCR rate with SG alone was 30% [n = 15, 95% confidence interval (CI) 18% to 45%]. The ORR per RECIST V1.1 after SG alone was 64% (n = 32/50, 95% CI 77% to 98%). Higher Ki-67 and tumor-infiltrating lymphocytes (TILs) were predictive of pCR to SG (P = 0.007 for Ki-67 and 0.002 for TILs), while baseline TROP2 expression was not (P = 0.440). Common adverse events were nausea (82%), fatigue (76%), alopecia (76%), neutropenia (44%), and rash (48%). With a median follow-up time of 18.9 months (95% CI 16.3-21.9 months), the 2-year EFS for all participants was 95%. Among participants with a pCR with SG (n = 15), the 2-year EFS was 100%.

CONCLUSIONS

In the first NA trial with an ADC in localized TNBC, SG demonstrated single-agent efficacy and feasibility of response-guided escalation/de-escalation. Further research on optimal duration of SG as well as NA combination strategies, including immunotherapy, are needed.

Abstract P2-14-19: Surgical and long-term outcomes of patients receiving neoadjuvant pertuzumab-containing regimens for HER2-positive localized breast cancer

Background: The addition of pertuzumab to trastuzumab and chemotherapy significantly improves the pathologic complete response (pCR) rate in HER2+ localized breast cancer in the preoperative setting. Although many patients are converted to breast conserving therapy (BCT) candidates by neoadjuvant HER2-directed therapy, a significant proportion opt for a mastectomy for various reasons. Among mastectomy procedures, nipple sparing mastectomy (NSM) is frequently chosen instead of non-nipple sparing mastectomy (NNSM). In this study, we evaluated the surgical and long-term outcomes of HER2+ patients receiving neoadjuvant pertuzumab-containing regimens.

Methods: We performed a retrospective review of localized breast cancer patients treated with neoadjuvant pertuzumab-containing regimens from 2011 to 2016, who underwent BCT or mastectomy at an academic institution and two community-based practices. Disease characteristics, treatment regimens, surgical outcomes, and recurrence data were extracted from the electronic medical records.

Results: Among 90 patients with stage II-III HER2+ breast cancer, 45 received AC-THP (50.0%), 26 received THP (with adjuvant AC) (29.0%), and 19 received TCHP (21.0%). The majority of patients had grade 3 tumors (61.1%), clinical stage II disease (80.0%), invasive ductal carcinoma (86.7%), and ER+ disease (65.6%). Thirty-seven (41.0%) patients underwent BCT and 53 (59.0%) patients underwent mastectomy. Among the mastectomy patients, 38 (71.7%) patients underwent bilateral mastectomies, specifically 33 (62.0%) patients underwent a NSM and 20 (38.0%) patients underwent a NNSM. The type of surgery that patients underwent stratified by type of neoadjuvant regimen is outlined in the Table 1 below. Most patients who underwent BCT and mastectomy received radiation, including 36 (97.3%) BCT, 24 (72.7%) NSM, and 18 (95.0%) NNSM. Over a median follow-up period of 33 months, 6 patients (6.7%) had recurrences with 2 (2.2%) local recurrences and 4 (4.4%) distant recurrences. The 2 local recurrences occurred in one patient who underwent BCT and one patient who underwent NNSM followed by post-mastectomy radiation.

Conclusions: Among mastectomy patients, NSM was more commonly pursued than NNSM. Rates of local recurrence following pertuzumab-containing regimens for HER2-positive localized breast cancer were low overall, regardless of the type of surgery. Data on plastic surgery approaches and complication rates will be presented at the meeting.

Table 1.Type of surgery in patients receiving neoadjuvant HER2-directed therapy. AC-THP (N = 45)TCHP (N = 19)THP (N = 26)BCT46.7%47.4%26.9%NNSM26.7%10.5%23.1%NSM26.7%42.1%50.0%

Citation Format: Haddad SA, Spring LM, Jimenez RB, Vidula N, Comander A, Shin JA, Coopey SB, Gadd MA, Hughes KS, Taghian A, Smith BL, Isakoff SJ, Moy B, Bardia A, Specht MC. Surgical and long-term outcomes of patients receiving neoadjuvant pertuzumab-containing regimens for HER2-positive localized breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P2-14-19.