PACE: A Randomized Phase II Study of Fulvestrant, Palbociclib, and Avelumab After Progression on Cyclin-Dependent Kinase 4/6 Inhibitor and Aromatase Inhibitor for Hormone Receptor-Positive/Human Epidermal Growth Factor Receptor-Negative Metastatic Breast Cancer

PURPOSE

Cyclin-dependent kinase (CDK) 4/6 inhibitors (CDK4/6is) are an important component of treatment for hormone receptor-positive/human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC), but it is not known if patients might derive benefit from continuation of CDK4/6i with endocrine therapy beyond initial tumor progression or if the addition of checkpoint inhibitor therapy has value in this setting.

METHODS

The randomized multicenter phase II PACE trial enrolled patients with hormone receptor-positive/HER2- MBC whose disease had progressed on previous CDK4/6i and aromatase inhibitor (AI) therapy. Patients were randomly assigned 1:2:1 to receive fulvestrant (F), fulvestrant plus palbociclib (F + P), or fulvestrant plus palbociclib and avelumab (F + P + A). The primary end point was investigator-assessed progression-free survival (PFS) in patients treated with F versus F + P.

RESULTS

Overall, 220 patients were randomly assigned between September 2017 and February 2022. The median age was 57 years (range, 25-83 years). Most patients were postmenopausal (80.9%), and 40% were originally diagnosed with de novo MBC. Palbociclib was the most common previous CDK4/6i (90.9%). The median PFS was 4.8 months on F and 4.6 months on F + P (hazard ratio [HR], 1.11 [90% CI, 0.79 to 1.55]; P = .62). The median PFS on F + P + A was 8.1 months (HR v F, 0.75 [90% CI, 0.50 to 1.12]; P = .23). The difference in PFS with F + P and F + P + A versus F was greater among patients with baseline ESR1 and PIK3CA alterations.

CONCLUSION

The addition of palbociclib to fulvestrant did not improve PFS versus fulvestrant alone among patients with hormone receptor-positive/HER2- MBC whose disease had progressed on a previous CDK4/6i plus AI. The increased PFS seen with the addition of avelumab warrants further investigation in this patient population.

Impact of Neoadjuvant Paclitaxel/Trastuzumab/Pertuzumab on Breast Tumor Downsizing for Patients with HER2+ Breast Cancer: Single-Arm Prospective Clinical Trial

BACKGROUND

The impact of abbreviated neoadjuvant regimens for HER2+ breast cancer on rates of breast conservation therapy (BCT) is unclear. We aimed to determine BCT rates in a single-arm prospective trial of neoadjuvant paclitaxel/trastuzumab/pertuzumab (THP) in patients with stage II-III HER2+ breast cancer.

STUDY DESIGN

BCT eligibility was prospectively recorded before and after THP. Pre- and post-treatment mammogram and breast ultrasound were required; breast MRI was encouraged. Patients with a large tumor to breast size ratio were eligible for downsizing. Multifocal/multicentric tumors, extensive calcifications, and contraindications to radiation were considered BCT contraindications.

RESULTS

Overall, 92 patients who received neoadjuvant THP on trial were included. At presentation, 39 (42.4%) were considered eligible for BCT and 53 (57.6%) were not. BCT-eligible patients were older (median 54 years versus 47 years, respectively, p=0.006) and had smaller tumors by palpation (median 2.5 cm versus 3 cm, respectively, p=0.004). Of 53 BCT-ineligible patients, 28 were candidates for tumor downsizing, whereas 25 had contraindications to BCT. Overall, 51(55.4%) patients underwent BCT. Of the 28 patients who were candidates for downsizing, 22 (78.6%) became BCT-eligible after THP and 18/22 (81.8%) underwent BCT. In total, 44/92 (47.8%) patients experienced breast pathologic complete response (pCR, ypT0), including 11/25 (44.0%) patients with BCT contraindications at presentation.

CONCLUSIONS

De-escalated neoadjuvant systemic therapy led to high BCT rates in this cohort. The impact of de-escalated systemic therapy on local therapy and outcomes in early stage HER2+ breast cancer warrants further investigation.

Abstract P2-07-03: Correlation of immune-related protein expression with hormone receptor (HR) status and pathologic response to neoadjuvant paclitaxel/trastuzumab/pertuzumab (THP) among patients with early-stage HER2+ breast cancer

Background: Immunological differences between HER2+ breast tumors that are HR+ versus HR- have not been widely explored. DAPHNe was a single-arm prospective clinical trial enrolling patients with clinical anatomic stage II-III HER2+ breast cancer to neoadjuvant treatment with THP. Here, we examine differential expression of immune-related proteins between HR+/HER2+ and HR-/HER2+ tumors in pre-treatment biopsies from trial participants, and analyze correlates of pathologic response to THP, overall and by HR status. Methods: A baseline research biopsy was required in all participants prior to initiation of neoadjuvant therapy. All patients received 12 weeks of neoadjuvant THP; 5 patients also received neoadjuvant AC given incomplete clinical response to THP, and are excluded from residual cancer burden (RCB) analyses. The trial primary endpoint, feasibility of de-escalation to antibody doublet therapy only (HP) following pCR, was previously reported. Protein expression profiling of baseline research biopsies was performed on the NanoString GeoMx® platform using a 58-protein immune cell profiling panel. Regions of interest (ROI; up to 12 per slide) were identified by a pathologist based on tumor cell, immune cell, and/or T cell presence, and all ROI were segmented into tumor vs stroma. Protein data quality controls were normalized by isotypes. Linear mixed effect models were used for differential expression comparisons; p-values were estimated using Satterthwaite’s method. Results: 97 pre-treatment breast tumor specimens were analyzed: 64 patients had HR+ tumors, 32 HR-, 1 unknown; 67 patients had favorable (RCB 0/1) response to preop therapy, 30 patients had unfavorable response (RCB 2/3). Multiple significant differences were observed between protein expression in HR+ versus HR- tumors (Table 1). Multiple immune cell types, as well as checkpoint proteins PD-L1 and IDO1, were higher in HR- patients, whereas checkpoint proteins B7-H3 and TIM3 were higher in HR+ patients. In the overall population, higher HER2 and PD-L1 expression were significant predictors of favorable RCB response, while higher ER alpha and Bcl-2 expression were significant predictors of unfavorable RCB response (Table 2). Conclusions: As anticipated, the strength of HER2 expression and ER expression were the most significant predictors of favorable and unfavorable RCB response to neoadjuvant THP, respectively. This highly multiplexed protein expression analysis demonstrated significant differences between the immune microenvironment of HR+ and HR- HER2+ breast tumors, implying that distinct immunological targets should be explored in the treatment of HER2+ breast cancer according to HR status.

Table 1.Differences between HR+/HER2+ and HR-/HER2+ patientsStroma compartmentTumor compartmentHigher in HR+ER alpha* (fold-change 2.25)ER alpha* (8.94)Fibronectin (1.68)Bcl-2* (1.98)B7-H3 (1.44)Fibronectin* (1.90)PR (1.69)TIM-3 (1.37)Higher in HR-CD27* (fold-change 1.36)IDO1 (1.50)IDO1 (1.77)S100B (1.44)CD45 (1.45)MART1 (1.33)CD3 (1.35)CD20 (1.34)STING (1.33)CD4 (1.30)ICOS (1.30)CD45RO (1.28)CD40 (1.28)CD127 (1.27)VISTA (1.25)PD-L1 (1.24)4-1BB (1.21)*FDR p-value < 0.05 (otherwise, p-value < 0.05). Table 2: Predictors of RCB response

Overall populationHigher in RCB 0/1HER2* (fold-change 3.75)PD-L1 (1.25)Higher in RCB 2/3ER alpha* (2.44)Bcl-2 (1.46)HR+/HER2+ patientsStroma compartmentTumor compartmentHigher in RCB 0/1HER2* (fold-change 4.28)HER2* (4.21)CTLA4 (1.64)Higher in RCB 2/3Bcl-2* (2.18)*FDR p-value < 0.05 (otherwise, p-value < 0.05).HR-/HER2+ patients are not shown in Table 2 as only 2 HR- patients had unfavorable RCB response.

Citation Format: Adrienne G. Waks, Ying Huang, Tyler Hether, Esther R Ogayo, Sapana Kadel, Jillian Alberti, Sara M Tolaney, Ian E Krop, Prajan Divakar, Otto Metzger, Madison L O'Donnell, Sarah Church, Eric P Winer, Jennifer L. Guerriero, Elizabeth A Mittendorf. Correlation of immune-related protein expression with hormone receptor (HR) status and pathologic response to neoadjuvant paclitaxel/trastuzumab/pertuzumab (THP) among patients with early-stage HER2+ breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P2-07-03.

Abstract P5-13-15: High dimensional flow cytometric analysis or the peripheral immune profile and response to HER2-targeted antibody therapy

Background: DAPHNe was a prospective trial designed to assess adherence to de-escalated antibody doublet therapy in the adjuvant setting among HER2+ breast cancer patients experiencing a pathologic complete response (pCR) following neoadjuvant taxol (T), trastuzumab (H) and pertuzumab (P). Peripheral blood mononuclear cells (PBMC), were collected from all patients at baseline and after THP completion. The goal of this study was to determine if a patient’s peripheral blood immune profile at baseline, or the longitudinal change with treatment, could predict response to THP. Methods: Blood samples were subjected to high dimensional (28-30 parameter) flow cytometry with comprehensive T- and NK-cell panels. A fully automated computational analysis strategy was undertaken consisting of unsupervised clustering of the high dimensional data into groups of cells with similar immunophenotypic signatures. Clustering was performed using 2 algorithms: Fingerprint-based clustering (Fluster) and High Throughput Mapper (HiTMapper). Clusters were tested using the Wilcoxon rank-sum test for correlation with the clinical response. Responders were those with pCR (=residual cancer burden [RCB] 0) or RCB 1; non-responders were those with RCB 2/3 disease. P values were adjusted with the Benjamini-Hochberg method to control for FDR. In addition to P values, effect size was evaluated using the nonparametric Cliff’s Delta measure. An effect was determined to be large if the magnitude of Delta was >0.4 which corresponded to one cohort coming ahead 70% of the time. In addition, groups of clusters were evaluated using multivariate statistical modeling or dimensionality reduction to determine if there was an association with pCR. Results: Matched baseline and pre-op PBMC were available to perform the NK panel in 66 patients and the T cell panel in 40. In both groups 70% were responders and 30% were non-responders. No cluster produced by Fluster or HiTMapper differed significantly between responders and non-responders however, in the T cell panel, several clusters had a large effect size (table) suggesting the clusters are good at differentiating some, responders from non-responders. Both algorithms agreed that the median responder has more CD4 naïve and CD8 naïve cells than the median non-responder. While no individual cluster differed significantly between responders and non-responders, cross-validated logistic regression analyses showed that 2 clusters, activated CD4 central memory clusters, and activated CD4 naïve clusters, predicted responder status with AUC of 0.70 and 0.68 respectively. Numerous clusters showed robust and significant longitudinal changes between baseline and pre-op samples. Stratifying longitudinal changes by response status revealed no significant differences between responders and non-responders, however evaluation of effect size suggested a naïve CD4 cluster that increased in non-responders and decreased in responders. The latter could be explained as naïve T cells acquiring a memory phenotype in response to treatment in responders. Conclusion: High dimensional flow cytometry suggested a potential role for monitoring several T cell subsets to predict response in HER2+ patients receiving THP. Additional analyses to include cyTOF evaluation of PBMCs are ongoing to further characterize the peripheral immune profile of these HER2+ patients.

T cell clusters with high effect sizeMajor PhenotypeOther markersMethodp-valueeffect sizeCD4 CM.actCD38, CD226HiTMapper0.351-0.469CD4 Naive.act.2CD38, CD226HiTMAPPER0.4-0.413CD4 Naive.act.4CD226HiTMapper0.351-0.490CD4 Naive.act.5CD38HiTMapper0.351-0.524CD8 Naive 1CD226HiTMapper0.396-0.427CD3 Neg-Fluster0.3190.476CD3 Neg3CD45RA, CD185, CD197Fluster0.3190.476CD3 Neg4CD45RA, Eomes,tBETFluster0.4240.413CD4 Naive-Fluster0.319-0.517CD8 Naive1-Fluster0.319-0.469Unassigned 20 (CD4)CD45RA, CD27-, CD28-Fluster0.364-0.441

Citation Format: Esther R Ogayo, Adrienne Waks, Wade Rogers, Matei Ionita, Kenechukwu Adigwe, Jillian Alberti, Sapana Kadel, Jonni Moore, Tari King, Ian Krop, Sara Tolaney, Eric Winer, Jennifer Guerriero, Elizabeth Mittendorf. High dimensional flow cytometric analysis or the peripheral immune profile and response to HER2-targeted antibody therapy [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P5-13-15.

Partial impairment of immune functions in peripheral blood leukocytes from aged men with Down's syndrome

Down's syndrome (DS) has been considered a model of accelerated aging and of Alzheimer's disease. We investigated immunologic functions using peripheral blood leukocytes in order to correlate the production of cytokines and development of neuropathological changes of Alzheimer type in aged persons with DS. Cytokine production (IL-1beta, IL-2, IL-6, IL-8, and TNF-alpha), phytohemagglutinin (PHA)-stimulated proliferation of nonadherent monocytes, and superoxide anion production from polymorphonuclear leukocytes were measured. PHA-stimulated proliferation in aged individuals (>30 years old) with DS was significantly lower than that of age- and sex-matched controls (DS vs control, 55,707+/-5810 vs 88,310+/-6994 cpm, P < 0.001). PHA-stimulated IL-2 production was also significantly decreased in aged individuals with DS (DS vs control, 7.1+/-2.1 vs 10.7+/-1.3 ng/ml). Interestingly, the decrease of proliferation and IL-2 production in aged males with DS is significantly greater than in aged women with DS. PHA-stimulated proliferation and IL-2 production of nonadherent monocytes in females was not significantly reduced. IL-1beta production by LPS-activated adherent monocytes was significantly decreased in older adults with DS compared with non-DS controls. Other immune parameters measured in DS were not significantly different from that of age-matched controls. We conclude that there is partial impairment of T lymphocytes in aged persons with DS that is significantly greater in males than in females.

[Early isotopic synoviorthesis during rheumatoid polyarthritis (RP)]

The authors report the results of 1258 chemical synovectomies carried out in subjects with rheumatoid polyarthritis on joints at Steinbrocker stage I and of 470 chemical synovectomies carried out during the first year of evolution of rheumatoid polyarthritis. Comparison with the results of chemical synovectomy carried out later demonstrate the superiority of early chemical synovectomy.