Abstract PD9-02: Personalized ctDNA as a predictive biomarker in high-risk early stage breast cancer (EBC) treated with neoadjuvant chemotherapy (NAC) with or without pembrolizumab (P)

Background: In the I-SPY 2 TRIAL, the addition of P to standard NAC resulted in more than doubling of the pathologic complete response (pCR) rates for both hormone receptor-positive (HR+)/HER2- and triple-negative (TN) early breast cancer (EBC) patients (pts) compared to NAC only (Nanda et al, JAMA Oncol, 2020). At 3 years, distant recurrence-free survival (DRFS) rates in pts with pCR following NAC+P was >95%. We hypothesized that ctDNA can serve as a predictive biomarker of response and survival in pts treated with NAC.

Methods: A personalized ctDNA test (Signatera) was performed on 511 serial plasma samples from 138 pts with high-risk HR+/HER2- (n=77) or TN (n=61) stage II/III EBC. Pts received P with paclitaxel (Tx) followed by AC (P arm, n=42) or standard NAC only (n=96), an exploratory subset of pts evaluated for P efficacy. Plasma was collected; pretreatment (T0), 3 weeks after treatment initiation (T1), between Tx+/-P and AC regimens (T2), and prior to surgery (T3). ctDNA was deemed positive with a minimum of 2 of the pt specific tumor mutation fragments detected in cfDNA. Association of ctDNA with response and survival was analyzed using logistic and Cox regressions with pCR and DRFS as endpoints. Median follow-up was 2.8 years.

Results: Detection of ctDNA decreased over time (P arm: T0-81%, T1-50%, T2-19%, T3-3%) and NAC only: T0-82%, T1-65%, T2-26%, T3-10%).

ctDNA data at T0 and T1 was available for 96% (132/138) of pts in P arm or NAC only (Table). Among ctDNA+ patients at baseline, clearance at T1 was significantly associated with pCR (OR=1.92, ctDNA+/-; OR=0.27, ctDNA+/+; LR p<0.001). This association remained significant after adjustment for HR status and treatment (LR p<0.001) and P arm or NAC only (P: LR p=0.03; NAC: LR p=0.01).

ctDNA data at T0, T1, and T2 was available for 86% (118/138) pts. (Table). Among all ctDNA+ pts at baseline, dynamics through T2 was associated with pCR (OR=1.44, ctDNA+/-/-; OR=0.33, ctDNA+/+/-, OR=0.12, ctDNA+/+/+; LR p=0.0011). This association remained significant when adjusted for HR status and treatment (LR p<0.001). Analysis within individual treatments showed significant association for NAC (LR p=0.040) and a non-significant trend in NAC+P (LR p=0.063), likely due to smaller sample size.

All pts who achieved pCR were ctDNA- at T3 (n=34). Among those who failed to achieve pCR (n=81), DRFS was significantly better in ctDNA- (n=72/81; 20 in P and 52 in NAC) versus ctDNA+ pts (n=9/81; 1 in P and 8 in NAC) (adjusted HR 0.13; 95% CI 0.05-0.37).

Conclusions: These exploratory results align with our previous findings that early clearance of ctDNA during NAC treatment was significantly associated with increased likelihood of achieving pCR. Additionally, we show that ctDNA clearance can be an early surrogate marker for therapy response assessment. Residual ctDNA after neoadjuvant treatment was a significant predictor of metastatic recurrence and death. Personalized monitoring of ctDNA during the course of NAC is feasible and provides information that can be combined with imaging and pathology, and may help to optimize decision making for de-escalation or escalation of therapy. Larger studies are ongoing.

ctDNA dynamics and pCRctDNA status at T0 and T1 (n=132)ctDNA status at T0, T1, and T2 (n=118)ctDNA-/-ctDNA+/-ctDNA+/+ctDNA-/-/-ctDNA+/-/-ctDNA+/+/-ctDNA+/+/+Total, n (%)24 (18)28 (21)80 (61)22 (19)24 (20)43 (36)27 (23)pCR, n (%)9 (38)15 (54)11 (14)9 (41)12 (50)8 (19)2 (7)No pCR, n (%)15 (63)13 (46)69 (86)13 (59)12 (50)35 (81)25 (93)

Citation Format: Mark Jesus M Magbanua, Denise Wolf, Derrick Renner, Svetlana Shchegrova, Lamorna Brown Swigart, Christina Yau, Gillian Hirst, Hsin-Ta Wu, Ekaterina Kalashnikova, Antony Tin, Amy Delson, Douglas Yee, Angela DeMichele, Raheleh Salari, Angel Rodriguez, Bernhard Zimmermann, Himanshu Sethi, Alexey Aleshin, Paul Billings, Laura Esserman, Minetta Liu, Rita Nanda, Laura van ‘t Veer, I-SPY 2 Investigators. Personalized ctDNA as a predictive biomarker in high-risk early stage breast cancer (EBC) treated with neoadjuvant chemotherapy (NAC) with or without pembrolizumab (P) [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PD9-02.

Abstract P5-11-18: Trajectory of patient (Pt) reported physical function (PF) during and after neoadjuvant chemotherapy in the I-SPY 2 trial

Background

Patients (pts) receiving chemotherapy for breast cancer experience toxicities impacting short and long-term quality of life (QOL). Within I-SPY 2, a trial adaptively randomizing stage II/III breast cancer pts to neoadjuvant chemotherapy +/- an investigational agent, we are collecting pt reported outcome (PRO) data to understand the impact of investigational agents on QOL. This PRO sub-study provides a unique opportunity to study QOL longitudinally and explore how pt and tumor characteristics, exposure to investigational therapies, and surgical outcome impact QOL.

Methods

Pts enrolled in this trial receive paclitaxel (T) +/- an investigational agent for 12 weeks followed by 4 cycles of doxorubicin and cyclophosphamide (AC). Surveys include the EORTC QLQ-C30 and BR-23, and PROMIS measures for QOL metrics including but not limited to physical function (PF), anxiety, and depression. Surveys are administered pre-chemotherapy to 2 years post-surgery. PF data from the EORTC and PROMIS instruments was analyzed for 238 pts at 5 sites (UCSF, UCSD, U of Pennsylvania, U of Minnesota, and Swedish Cancer Center). 48 pts completed baseline, inter-regimen (between T and AC), pre-operative and post-surgery surveys. Of the 48 pts 32 completed a 6-month follow up (FUP) and 31 completed a 1-year FUP survey. A linear mixed effect model, adjusting for HER2 status and treatment type was used to evaluate changes in PF over time. Sample size is small and statistics are descriptive rather than inferential.

Results

Median age of pts in this analysis was 50 (range 27-72).

Table 1 shows PROMIS & EORTC PF scores in this cohort.Time Point  PROMISEORTC  nMeanSEMeanSEPre-TreatmentAll4852.51.092.02.0 HER2+1553.51.594.12.2 HER2-3352.11.391.12.8Inter-RegimenAll4845.51.282.22.7 HER2+1548.62.384.44.2 HER2-3344.11.381.23.4Pre-SurgeryAll4843.91.179.42.3 HER2+1545.12.275.34.1 HER2-3343.41.381.32.86-Month FUPAll3248.11.487.41.9 HER2+1247.52.285.03.3 HER2-2048.41.888.92.41 Year FUPAll3148.91.488.43.1 HER2+949.12.988.95.4 HER2-2248.81.788.33.8

At baseline, mean PROMIS PF scores were higher than the US average (mean = 50) but declined as expected throughout treatment. HER2+ patients experienced a similar degree of recovery as HER2- pts post-surgery despite adjuvant treatment with Herceptin. Analysis of post-operative PROMIS PF indicated an average score within the U.S. general population (mean =50) but did not return to higher functioning seen at baseline levels (mean 52.5, p-value < 0.05). Analysis of the EORTC PF sub-scale demonstrated a similar trend; however, the baseline and post-operative difference was not significant (p-value=0.15 for both FUP). Finding supports PROMIS PF ability to measure high functioning cancer patients.

Conclusions: Among a subset of pts who completed all surveys in the I-SPY 2 QOL substudy, PF did not return to baseline at 6-12 months post-operatively. Through transition to an electronic platform of data collection we hope to improve compliance with survey completion. We continue to analyze other QOL measures and plan to correlate QOL data with treatment arm, adverse events, comorbidities, and response to neoadjuvant treatment.

Citation Format: Shah M, Jensen R, Yau C, Straehley I, Berry DA, DeMichele A, Buxton MB, Hylton NM, Perlmutter J, Symmans WF, Tripathy D, Yee D, Wallace A, Kaplan HG, Clark A, Chien AJ, I-SPY 2 Investigators, Esserman LJ, Melisko ME. Trajectory of patient (Pt) reported physical function (PF) during and after neoadjuvant chemotherapy in the I-SPY 2 trial [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-11-18.