Phenotypic discordance between primary and metastatic breast cancer in the large-scale real-life multicenter French ESME cohort

Expression of hormone receptor (HR) for estrogens (ER) and progesterone (PR) and HER2 remains the cornerstone to define the therapeutic strategy for breast cancer patients. We aimed to compare phenotypic profiles between matched primary and metastatic breast cancer (MBC) in the ESME database, a National real-life multicenter cohort of MBC patients. Patients with results available on both primary tumour and metastatic disease within 6 months of MBC diagnosis and before any tumour progression were eligible for the main analysis. Among the 16,703 patients included in the database, 1677 (10.0%) had available biopsy results at MBC diagnosis and on matched primary tumour. The change rate of either HR or HER2 was 27.0%. Global HR status changed (from positive = either ER or PR positive, to negative = both negative; and reverse) in 14.2% of the cases (expression loss in 72.5% and gain in 27.5%). HER2 status changed in 7.8% (amplification loss in 45.2%). The discordance rate appeared similar across different biopsy sites. Metastasis to bone, HER2+ and RH+/HER2- subtypes and previous adjuvant endocrine therapy, but not relapse interval were associated with an HR discordance in multivariable analysis. Loss of HR status was significantly associated with a risk of death (HR adjusted = 1.51, p = 0.002) while gain of HR and HER2 discordance was not. In conclusion, discordance of HR and HER2 expression between primary and metastatic breast cancer cannot be neglected. In addition, HR loss is associated with worse survival. Sampling metastatic sites is essential for treatment adjustment.

[Concurrent radiation therapy and dual HER2 blockade in breast cancer: Assessment of toxicity]

PURPOSE

The tolerance of the concurrent use of radiotherapy, pertuzumab and trastuzumab is unknown. The purpose of this study was to evaluate the toxicity of this association in patients treated for HER2 positive metastatic and/or locally recurrent unrespectable breast cancer.

MATERIAL AND METHODS

A retrospective study was performed in our institution for all consecutive patients treated with concurrent irradiation, pertuzumab and trastuzumab. The radiotherapy was performed while pertuzumab and trastuzumab were administrated as a maintenance treatment at the dose of 420mg (total dose) and 6mg/kg respectively every 3 weeks without chemotherapy. Toxicity was assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. Left ventricular ejection fraction (LVEF) was measured at baseline and then every 3-4 months.

RESULTS

We studied 77 patients. treated in between 2013 and 2019 with median follow-up of 38 months (range 0-264 months). Median age was 53 years (33-86). There were 50 patients (64.9%) with metastatic and 27 patients (35.1%) with recurrent disease. All patients received docetaxel followed by P-T as first line treatment and they received 34 cycles (10-85) of pertuzumab and trastuzumab. All patients experienced partial or complete response according to RECIST criteria. Irradiation volumes were whole breast (41 patients, 53.2%) and chest wall (29 patients, 37.7%) at a dose of 50Gy with a median duration of 39 days. Radiotherapy of lymph nodes was performed in 53 patients (68.8%) as following: supraclavicular-infraclavicular and axillary lymph nodes in 52 patients (67.5%), and internal mammary nodes in 31 patients (40.3%). For 20 patients. (26.0%) radiotherapy was palliative: bone irradiation (12 patients, 15.6%), whole-brain radiotherapy (2 patients, 2.6%), cerebral metastasis irradiation (6 patients). As early toxicity we observed: radio dermatitis as following: 36 patients (46.8%) presented grade I, 17 patients (22.1%) presented grade II, and 3 patients (3.9%) presented grade III. One patient (1.3%) presented grade II esophagitis. One patient (1.3%) presented asymptomatic decrease of LVEF during treatment and 6 patients (7.7%) presented a decrease of LVEF. There was no radiation-induced pneumonitis. As late toxicity, we observed 1 (1.3%) case of grade I and 1 (1.3%) with grade II telangiectasia. There was 1 case (1.3%) of grade III cardiac toxicity, 8 months after the concurrent treatment.

CONCLUSION

The concurrent use of radiotherapy, pertuzumab and trastuzumab is feasible with good tolerance. Larger prospective data with longer follow-up is needed to confirm these results.

Total orbital exenteration with temporalis muscle transfer and secondary healing

OBJECTIVE

To evaluate the outcomes of orbital exenteration with temporalis muscle flap repair of the socket and secondary healing of the anterior surface of the flap in ocular, conjunctival, and eyelid malignancies.

DESIGN

Retrospective single-centre study.

PARTICIPANTS

Consecutive patients who underwent total exenteration for malignancy with temporal muscle flap repair of the socket between December 2009 and January 2016.

METHODS

We report the outcomes of this surgical technique in terms of healing without fistula formation and time to epithelialization.

RESULTS

Twenty-nine patients underwent surgery using this technique. Diagnoses consisted of 18 conjunctival melanomas, 2 choroidal melanomas, 6 squamous cell carcinomas, 2 sebaceous cell carcinomas, and 1 basal cell carcinoma. Mean age at surgery was 70.7 years and mean follow-up was 27.4 months. On histological analysis, tumour excision was complete in 25 patients, of whom 3 had an orbital recurrence after exenteration (3 conjunctival melanomas). Four patients had incomplete tumour excision, of whom 3 underwent postoperative orbital radiotherapy with no subsequent orbital recurrences. Complete epithelialization of the socket occurred in mean 7.9 weeks (range 2-16 weeks). Flap necrosis occurred in 1 patient after postoperative radiotherapy (with sino-nasal fistula formation); 2 other patients developed sino-orbital fistulas.

CONCLUSION

After orbital exenteration, spontaneous epithelialization of the socket may take up to several months. Use of a temporalis muscle flap can reduce the duration of socket healing postoperatively, even if left to heal by secondary intention. This may facilitate early postoperative radiotherapy when indicated. Aesthetic results are acceptable and local surgical complications are rare.

Circulating tumor DNA as a dynamic biomarker of response to palbociclib and fulvestrant in metastatic breast cancer patients

Background

Following the PALOMA-3 study results, the combination of palbociclib, a CDK4/6 inhibitor, with fulvestrant, a selective estrogen receptor degrader, has become a standard therapy in women with estrogen receptor-positive (ER+) HER2-negative (HER2−) metastatic breast cancer (MBC). Palbociclib has been shown to increase the progression-free survival (PFS) overall but no predictive biomarker of palbociclib efficacy has been validated so far. We thus evaluated whether early changes of circulating tumor DNA (ctDNA) levels are associated with palbociclib plus fulvestrant efficiency.

Methods

ER+ HER2− MBC patients were included in a prospective observational cohort before treatment initiation. Tumor response was assessed by radiological evaluation (RECIST v1.1) every 3 months. Plasma samples were collected before treatment (baseline), at day 15 (D15), at day 30 (D30), and at disease progression. We searched for somatic mutations from archived tumor tissues by targeted deep sequencing. For patients with somatic mutations identified, circulating tumor DNA (ctDNA) was tracked using digital droplet PCR. Ratios of ctDNA levels ([D15/baseline] and [D30/baseline]) were then correlated with prospectively registered patient characteristics and outcomes.

Results

Twenty-five of the 61 patients enrolled had a somatic mutation testable in plasma (N_PIK3CA = 21, N_TP53 = 2, N_AKT1 = 2). At baseline, 84% of patients had detectable ctDNA levels but ctDNA levels had no prognostic impact on PFS (p = 0.10). Among those patients, ctDNA was still detected in 82% at D15 and 68% at D30. ctDNA clearance observed at day 30 was associated with longer PFS (HR = 7.2, 95% CI = 1.5–32.6, p = 0.004). On the contrary, a [D30/baseline] ctDNA ratio > 1 was associated with a shorter PFS (HR = 5.1, 95% CI = 1.4–18.3, p = 0.02) and all 5 patients with increased ctDNA levels at D30 showed disease progression after 3 months under palbociclib-fulvestrant. Finally, at the time of radiological tumor progression, ctDNA was detected in all patients tested.

Conclusion

Our study demonstrates that the efficiency of palbociclib and fulvestrant can be monitored by serial analyses of ctDNA before radiological evaluation and that early ctDNA variation is a prognostic factor of PFS.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01411-0.

Abstract PS12-03: Letrozole and palbociclib versus 3rd generation chemotherapy as neoadjuvant treatment in luminal breast cancer: Survival results of the UNICANCER-NeoPAL study

Background Palbociclib is a CDK4/6 inhibitor with demonstrated survival benefits in combination with endocrine therapy in advanced luminal breast cancer (LBC). Its potential role in early breast cancer is currently explored. The NeoPAL trial compared letrozole-palbociclib (LETPAL) combination to standard chemotherapy (CT) as neoadjuvant treatment in patients with high-risk LBC. Both LETPAL and CT were associated with poor pathological response, and equivalent clinical responses, while LETPAL let to encouraging biomarker responses in Prosigna®-defined high-risk LBC. We now evaluate the survival outcomes of both groups.

Patients and Methods NeoPAL (UCBG10/4, NCT02400567) is a randomized, parallel, non-comparative phase II study. Postmenopausal women with ER-positive, HER2-negative, Prosigna®-defined luminal B, or luminal A and node-positive, stage II-III breast cancer, not candidate for breast-conserving surgery, were randomly assigned to either letrozole (2.5 mg daily) and palbociclib (125 mg daily, 3 weeks/4) during 19 weeks (LETPAL), or to FEC100 (5FU 500 mg/m2, epirubicin 100 mg/m2, cyclophosphamide 500 mg/m2) x3 21-day courses followed by docetaxel 100 mg/m2 x3 21-day courses (CT). Secondary endpoints included progression-free survival (PFS) and invasive-disease free survival (iDFS), all measured from the date of randomization. Exploratory objectives aimed at evaluating the impact of PEPI score and residual cancer burden (RCB) on survival outcomes in both arms.

Results 53 pts were randomized in each arm (both with 11% Luminal A N+ and 89% Luminal B). 23 of the 53 pts in the LETPAL arm received postoperative adjuvant chemotherapy. Median follow-up is 40.4 months [0-56.6]. 11 progressions have been observed (10 metastatic events, 1 regional progression), of which 3 were in the LETPAL and 8 in the control arm. Two additional iDFS events were observed in the LETPAL arm (secondary malignancies). PFS (HR = 1.01; 95%CI [0.36; 2.90], p=0.98) and iDFS (HR= 0.83; 95%CI [0.31; 2.23], p=0.71) did not differ between both arms. 40 months PFS rate is 86.7% (78.0-96.4) and 87.2% (78.1-97.4) in LETPAL and CT arms respectively. PEPI (PEPI II/II vs I: HR 0.80, 95%CI 0.18-3.67) and RCB scores (RCB II/III vs 0/I: HR 1.36; 95%CI 0.17-10.6) did not appear as independent predictors of PFS or iDFS.

Conclusions Despite its small size, NeoPAL suggests that a neoadjuvant LETPAL strategy, together with selected postoperative administration of chemotherapy, may spare chemotherapy in some pts with luminal breast cancer while allowing very good long-term outcomes.

Citation Format: Suzette Delaloge, Sylvain Dureau, Véronique D'Hondt, Isabelle Desmoulins, Pierre-Etienne Heudel, François Duhoux, Christelle Levy, Florence Lerebours, Marie Ange Mouret-Reynier, Florence Dalenc, Jean-Sébastien Frenel, Christelle Jouannaud, Laurence Venat-Bouvet, Suzanne Nguyen, Cécile Callens, David Gentien, Jerome Lemonnier, Anne Vincent-Salomon, Hélène Manduzio, Paul-Henri Cottu. Letrozole and palbociclib versus 3rd generation chemotherapy as neoadjuvant treatment in luminal breast cancer: Survival results of the UNICANCER-NeoPAL study [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 PS12-03.

PD-L1 Expression after Neoadjuvant Chemotherapy in Triple-Negative Breast Cancers Is Associated with Aggressive Residual Disease, Suggesting a Potential for Immunotherapy

The consequences of neoadjuvant chemotherapy (NAC) for PD-L1 activity in triple-negative breast cancers (TNBC) are not well-understood. This is an important issue as PD-LI might act as a biomarker for immune checkpoint inhibitors' (ICI) efficacy, at a time where ICI are undergoing rapid development and could be beneficial in patients who do not achieve a pathological complete response. We used immunohistochemistry to assess PD-L1 expression in surgical specimens (E1L3N clone, cutoff for positivity: ≥1%) on both tumor (PD-L1-TC) and immune cells (PD-L1-IC) from a cohort of T1-T3NxM0 TNBCs treated with NAC. PD-L1-TC was detected in 17 cases (19.1%) and PD-L1-IC in 14 cases (15.7%). None of the baseline characteristics of the tumor or the patient were associated with PD-L1 positivity, except for pre-NAC stromal TIL levels, which were higher in post-NAC PD-L1-TC-positive than in negative tumors. PD-L1-TC were significantly associated with a higher residual cancer burden (p = 0.035) and aggressive post-NAC tumor characteristics, whereas PD-L1-IC were not. PD-L1 expression was not associated with relapse-free survival (RFS) (PD-L1-TC, p = 0.25, and PD-L1-IC, p = 0.95) or overall survival (OS) (PD-L1-TC, p = 0.48, and PD-L1-IC, p = 0.58), but high Ki67 levels after NAC were strongly associated with a poor prognosis (RFS, p = 0.0014, and OS, p = 0.001). A small subset of TNBC patients displaying PD-L1 expression in the context of an extensive post-NAC tumor burden could benefit from ICI treatment after standard NAC.

In vitro bone metastasis dwelling in a 3D bioengineered niche

Bone is the most frequent metastasis site for breast cancer. As well as dramatically increasing disease burden, bone metastases are also an indicator of poor prognosis. One of the main challenges in investigating bone metastasis in breast cancer is engineering in vitro models that replicate the features of in vivo bone environments. Such in vitro models ideally enable the biology of the metastatic cells to mimic their in vivo behavior as closely as possible. Here, taking benefit of cutting-edge technologies both in microfabrication and cancer cell biology, we have developed an in vitro breast cancer bone-metastasis model. To do so we first 3D printed a bone scaffold that reproduces the trabecular architecture and that can be conditioned with osteoblast-like cells, a collagen matrix, and mineralized calcium. We thus demonstrated that this device offers an adequate soil to seed primary breast cancer bone metastatic cells. In particular, patient-derived xenografts being considered as a better approach than cell lines to achieve clinically relevant results, we demonstrate the ability of this biomimetic bone niche model to host patient-derived xenografted metastatic breast cancer cells. These patient-derived xenograft cells show a long-term survival in the bone model and maintain their cycling propensity, and exhibit the same modulated drug response as in vivo. This experimental system enables access to the idiosyncratic features of the bone microenvironment and cancer bone metastasis, which has implications for drug testing.

ShallowHRD: detection of homologous recombination deficiency from shallow whole genome sequencing

Summary

We introduce shallowHRD, a software tool to evaluate tumor homologous recombination deficiency (HRD) based on whole genome sequencing (WGS) at low coverage (shallow WGS or sWGS; ∼1X coverage). The tool, based on mining copy number alterations profile, implements a fast and straightforward procedure that shows 87.5% sensitivity and 90.5% specificity for HRD detection. shallowHRD could be instrumental in predicting response to poly(ADP-ribose) polymerase inhibitors, to which HRD tumors are selectively sensitive. shallowHRD displays efficiency comparable to most state-of-art approaches, is cost-effective, generates low-storable outputs and is also suitable for fixed-formalin paraffin embedded tissues.

Availability and implementation

shallowHRD R script and documentation are available at https://github.com/aeeckhou/shallowHRD.

Supplementary information

Supplementary data are available at Bioinformatics online.

Combination of Olaparib and Radiation Therapy for Triple Negative Breast Cancer: Preliminary Results of the RADIOPARP Phase 1 Trial

PURPOSE

Preclinical studies have evidenced that triple-negative breast cancer (TNBC) cell lines are more sensitive to poly (ADP-ribose) polymerase inhibitors. This provides a strong rationale for developing a new therapeutic approach for TNBC management based on poly (ADP-ribose) polymerase inhibition. The primary goal of the RADIOPARP phase 1 trial was to evaluate the dose-limiting toxicities (DLT) and the maximum tolerated dose of olaparib combined with locoregional radiation therapy.

METHODS AND MATERIALS

RADIOPARP was a single institutional phase 1 trial which evaluated olaparib-radiation therapy combination in patients with inflammatory, locoregionally advanced or metastatic TNBC who received neoadjuvant chemotherapy. Radiation therapy delivered 50 Gy to the breast or to the chest wall. Lymph nodes could be included in target volumes according to local guidelines. The dose-finding toxicity-based study was conducted in sequential and adaptive Bayesian scheme using the time-to-event continual reassessment method, with 4 olaparib dose levels (50 mg, 100 mg, 150 mg, and 200 mg twice per day).

RESULTS

Twenty-four patients with Eastern Cooperative Oncology Group Performance Status of 0 or 1 were enrolled from September 2017 to November 2019. Twenty-one patients (87.5%) received the olaparib-radiation therapy combination after breast surgery owing to residual disease after neoadjuvant chemotherapy, and the 3 other patients (12.5%) had unresectable tumors which were refractory to neoadjuvant chemotherapy. All patients received full course combination treatment as follows: 4 patients (pts) at 50 mg twice a day, 8 pts at 100 mg twice a day, 7 pts at 150 mg twice a day, and 5 pts at 200 mg twice a day. No DLT was observed.

CONCLUSIONS

Olaparib was escalated to the maximum target dose of 200 mg twice a day without DLT. Further follow-up is needed to evaluate the late toxicities. Pending the long-term results of the RADIOPARP trial, we suggest using 200 mg of olaparib twice per day for future trials.

Characterization of Stromal Tumor-infiltrating Lymphocytes and Genomic Alterations in Metastatic Lobular Breast Cancer

PURPOSE

Invasive lobular carcinoma (ILC) represents the second most common histologic breast cancer subtype after invasive ductal carcinoma (IDC). While primary ILC has been extensively studied, metastatic ILC has been poorly characterized at the genomic and immune level.

EXPERIMENTAL DESIGN

We retrospectively assembled the multicentric EuroILC series of matched primary and metastatic samples from 94 patients with estrogen receptor (ER)-positive ILC. Stromal tumor-infiltrating lymphocytes (sTILs) were assessed by experienced pathologists. Targeted sequencing and low pass whole-genome sequencing were conducted to detect mutations and copy-number aberrations (CNAs). We compared the frequencies of the alterations in EuroILC with those from patients with ER-positive metastatic ILC (n = 135) and IDC (n = 563) from MSK-IMPACT.

RESULTS

Low sTIL levels were observed in ILC metastases, with higher levels in the mixed nonclassic histology. Considering ILC metastases from EuroILC and MSK-IMPACT, we observed that >50% of tumors harbor genomic alterations that have previously been associated with endocrine resistance. A matched primary/metastasis comparison in EuroILC revealed mutations (AKT1, ARID1A, ESR1, ERBB2, or NF1) and CNAs (PTEN or NF1 deletion, CYP19A1 amplification) associated with endocrine resistance that were private to the metastasis in 22% (7/32) and 19% (4/21) of patients, respectively. An increase in CDH1, ERBB2, FOXA1, and TBX3 mutations, in CDH1 deletions and a decrease in TP53 mutations was observed in ILC as compared with IDC metastases.

CONCLUSIONS

ILC metastases harbor genomic alterations that may potentially explain endocrine resistance in a large proportion of patients, and present genomic differences as compared with IDC metastases.

Transcriptional and Functional Analysis of CD1c+ Human Dendritic Cells Identifies a CD163+ Subset Priming CD8+CD103+ T Cells

Dendritic cells (DCs) are antigen-presenting cells controlling T cell activation. In humans, the diversity, ontogeny, and functional capabilities of DC subsets are not fully understood. Here, we identified circulating CD88-CD1c+CD163+ DCs (called DC3s) as immediate precursors of inflammatory CD88-CD14+CD1c+CD163+FcεRI+ DCs. DC3s develop via a specific pathway activated by GM-CSF, independent of cDC-restricted (CDP) and monocyte-restricted (cMoP) progenitors. Like classical DCs but unlike monocytes, DC3s drove activation of naive T cells. In vitro, DC3s displayed a distinctive ability to prime CD8+ T cells expressing a tissue homing signature and the epithelial homing alpha-E integrin (CD103) through transforming growth factor β (TGF-β) signaling. In vivo, DC3s infiltrated luminal breast cancer primary tumors, and DC3 infiltration correlated positively with CD8+CD103+CD69+ tissue-resident memory T cells. Together, these findings define DC3s as a lineage of inflammatory DCs endowed with a strong potential to regulate tumor immunity.

PLK1 inhibition exhibits strong anti-tumoral activity in CCND1-driven breast cancer metastases with acquired palbociclib resistance

A significant proportion of patients with oestrogen receptor (ER) positive breast cancers (BC) develop resistance to endocrine treatments (ET) and relapse with metastatic disease. Here we perform whole exome sequencing and gene expression analysis of matched primary breast tumours and bone metastasis-derived patient-derived xenografts (PDX). Transcriptomic analyses reveal enrichment of the G2/M checkpoint and up-regulation of Polo-like kinase 1 (PLK1) in PDX. PLK1 inhibition results in tumour shrinkage in highly proliferating CCND1-driven PDX, including different RB-positive PDX with acquired palbociclib resistance. Mechanistic studies in endocrine resistant cell lines, suggest an ER-independent function of PLK1 in regulating cell proliferation. Finally, in two independent clinical cohorts of ER positive BC, we find a strong association between high expression of PLK1 and a shorter metastases-free survival and poor response to anastrozole. In conclusion, our findings support clinical development of PLK1 inhibitors in patients with advanced CCND1-driven BC, including patients progressing on palbociclib treatment.

A subset of activated fibroblasts is associated with distant relapse in early luminal breast cancer

Background

Early luminal breast cancer (BC) represents 70% of newly diagnosed BC cases. Among them, small (under 2 cm) BC without lymph node metastasis (classified as T1N0) have been rarely studied, as their prognosis is generally favorable. Nevertheless, up to 5% of luminal T1N0 BC patients relapse with distant metastases that ultimately prove fatal. The aim of our work was to identify the mechanisms involved in metastatic recurrence in these patients.

Methods

Our study addresses the role that autonomous and non-autonomous tumor cell features play with regard to distant recurrence in early luminal BC patients. We created a cohort of T1N0 luminal BC patients (tumors between 0.5–2 cm without lymph node metastasis) with metastatic recurrence (“cases”) and corresponding “controls” (without relapse) matched 1:1 on main prognostic factors: age, grade, and proliferation. We deciphered different characteristics of cancer cells and their tumor micro-environment (TME) by deep analyses using immunohistochemistry. We performed in vitro functional assays and highlighted a new mechanism of cooperation between cancer cells and one particular subset of cancer-associated fibroblasts (CAF).

Results

We found that specific TME features are indicative of relapse in early luminal BC. Indeed, quantitative histological analyses reveal that “cases” are characterized by significant accumulation of a particular CAF subset (CAF-S1) and decrease in CD4⁺ T lymphocytes, without any other association with immune cells. In multivariate analysis, TME features, in particular CAF-S1 enrichment, remain significantly associated with recurrence, thereby demonstrating their clinical relevance. Finally, by performing functional analyses, we demonstrated that CAF-S1 pro-metastatic activity is mediated by the CDH11/osteoblast cadherin, consistent with bones being a major site of metastases in luminal BC patients.

Conclusions

This study shows that distant recurrence in T1N0 BC is strongly associated with the presence of CAF-S1 fibroblasts. Moreover, we identify CDH11 as a key player in CAF-S1-mediated pro-metastatic activity. This is independent of tumor cells and represents a new prognostic factor. These results could assist clinicians in identifying luminal BC patients with high risk of relapse. Targeted therapies against CAF-S1 using anti-FAP antibody or CDH11-targeting compounds might help in preventing relapse for such patients with activated stroma.

The Genomic Landscape of Mucinous Breast Cancer

Mucinous carcinoma of the breast (MCB) is a rare histologic form of estrogen receptor (ER)-positive/HER2-negative breast cancer (BC) characterized by tumor cells floating in lakes of mucin. We assessed the genomic landscape of 32 MCBs by whole-exome sequencing and/or RNA-sequencing. GATA3 (23.8%), KMT2C (19.0%), and MAP3K1 (14.3%) were the most frequently mutated genes in pure MCBs. In addition, two recurrent but not pathognomonic fusion genes, OAZ1-CSNK1G2 and RFC4-LPP, were detected in 3/31 (9.7%) and 2/31 (6.5%) samples, respectively. Compared with ER-positive/HER2-negative common forms of BC, MCBs displayed lower PIK3CA and TP53 mutation rates and fewer concurrent 1q gains and 16q losses. Clonal decomposition analysis of the mucinous and ductal components independently microdissected from five mixed MCBs revealed that they are clonally related and evolve following clonal selection or parallel evolution. Our findings indicate that MCB represents a genetically distinct ER-positive/HER2-negative form of BC.

Abstract A43: Centrosome amplification favors survival and impairs ovarian cancer progression

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy. The most common subtype of EOC is high-grade serous (HGSOC), which responds at least initially to chemotherapy but has a worse overall prognosis. Genomic, transcriptomic, and proteogenomic profiling of HGSOC suggested a whole spectrum of molecular diversity, including homologous recombination pathway deficiencies (HRD). The centrosome is the main microtubule (MT)-organizing center of animal cells. It facilitates the accuracy of chromosome segregation during mitosis and influences cell polarity and migration. The presence of more than two centrosomes in a cell, centrosome amplification, has long been associated with tumorigenesis. However, little is known about the real status of centrosome numbers in human cancers and whether numerical alterations are solely associated with poor prognosis. We screened 100 samples of primary EOCs including 88 HGSOC, using immunofluorescence and state-of-the-art microscopy, to determine the centrosome-nucleus index (CNI). We integrated these data with genomic alterations, HRD status, and patient outcome. We found that EOCs are highly heterogeneous, with infrequent but strong centrosome amplifications leading to higher CNI than in healthy tissues. Strikingly, while a correlation between CNI and genomic alterations, such as aneuploidy or chromosome rearrangements, could not be established, we found that high CNI correlates with increased patient survival and sensitivity to chemotherapy, independently of HRD status. Using ovarian cancer cellular models to manipulate centrosome numbers and patient-derived xenografts (PDXs), we found that higher CNIs can positively impact the response to chemotherapy and inhibit peritoneal cell dissemination.

Citation Format: Jean-Philippe Morretton, Aurelie Herbette, Camille Cosson, Bassirou Mboup, Aurelien Latouche, Pierre Gestraud, Tatiana Popova, Marc-Henri Stern, Fariba Nemati, Didier Decaudin, Guillaume Bataillon, Veronique Becette, Didier Meseure, Andre Nicolas, Odette Mariani, Claire Bonneau, Jorge Barbazan, Anne Vincent-Salomon, Fatima Mechta-Grigoriou, Sergio Roman-Roman, Roman Rouzier, Xavier Sastre-Garau, Oumou Goundiam, Renata Basto. Centrosome amplification favors survival and impairs ovarian cancer progression [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr A43.

Tumor invasion in draining lymph nodes is associated with Treg accumulation in breast cancer patients

Tumor-draining lymph node (TDLN) invasion by metastatic cells in breast cancer correlates with poor prognosis and is associated with local immunosuppression, which can be partly mediated by regulatory T cells (Tregs). Here, we study Tregs from matched tumor-invaded and non-invaded TDLNs, and breast tumors. We observe that Treg frequencies increase with nodal invasion, and that Tregs express higher levels of co-inhibitory/stimulatory receptors than effector cells. Also, while Tregs show conserved suppressive function in TDLN and tumor, conventional T cells (Tconvs) in TDLNs proliferate and produce Th1-inflammatory cytokines, but are dysfunctional in the tumor. We describe a common transcriptomic signature shared by Tregs from tumors and nodes, including CD80, which is significantly associated with poor patient survival. TCR RNA-sequencing analysis indicates trafficking between TDLNs and tumors and ongoing Tconv/Treg conversion. Overall, TDLN Tregs are functional and express a distinct pattern of druggable co-receptors, highlighting their potential as targets for cancer immunotherapy.

Single-Cell Analysis Reveals Fibroblast Clusters Linked to Immunotherapy Resistance in Cancer

A subset of cancer-associated fibroblasts (FAP⁺/CAF-S1) mediates immunosuppression in breast cancers, but its heterogeneity and its impact on immunotherapy response remain unknown. Here, we identify 8 CAF-S1 clusters by analyzing more than 19,000 single CAF-S1 fibroblasts from breast cancer. We validate the five most abundant clusters by flow cytometry and in silico analyses in other cancer types, highlighting their relevance. Myofibroblasts from clusters 0 and 3, characterized by extracellular matrix proteins and TGFβ signaling, respectively, are indicative of primary resistance to immunotherapies. Cluster 0/ecm-myCAF upregulates PD-1 and CTLA4 protein levels in regulatory T lymphocytes (Tregs), which, in turn, increases CAF-S1 cluster 3/TGFβ-myCAF cellular content. Thus, our study highlights a positive feedback loop between specific CAF-S1 clusters and Tregs and uncovers their role in immunotherapy resistance. SIGNIFICANCE: Our work provides a significant advance in characterizing and understanding FAP⁺ CAF in cancer. We reached a high resolution at single-cell level, which enabled us to identify specific clusters associated with immunosuppression and immunotherapy resistance. Identification of cluster-specific signatures paves the way for therapeutic options in combination with immunotherapies.This article is highlighted in the In This Issue feature, p. 1241.

Pitfalls in assessing stromal tumor infiltrating lymphocytes (sTILs) in breast cancer

Stromal tumor-infiltrating lymphocytes (sTILs) are important prognostic and predictive biomarkers in triple-negative (TNBC) and HER2-positive breast cancer. Incorporating sTILs into clinical practice necessitates reproducible assessment. Previously developed standardized scoring guidelines have been widely embraced by the clinical and research communities. We evaluated sources of variability in sTIL assessment by pathologists in three previous sTIL ring studies. We identify common challenges and evaluate impact of discrepancies on outcome estimates in early TNBC using a newly-developed prognostic tool. Discordant sTIL assessment is driven by heterogeneity in lymphocyte distribution. Additional factors include: technical slide-related issues; scoring outside the tumor boundary; tumors with minimal assessable stroma; including lymphocytes associated with other structures; and including other inflammatory cells. Small variations in sTIL assessment modestly alter risk estimation in early TNBC but have the potential to affect treatment selection if cutpoints are employed. Scoring and averaging multiple areas, as well as use of reference images, improve consistency of sTIL evaluation. Moreover, to assist in avoiding the pitfalls identified in this analysis, we developed an educational resource available at www.tilsinbreastcancer.org/pitfalls.

The path to a better biomarker: application of a risk management framework for the implementation of PD-L1 and TILs as immuno-oncology biomarkers in breast cancer clinical trials and daily practice

Immune checkpoint inhibitor therapies targeting PD-1/PD-L1 are now the standard of care in oncology across several hematologic and solid tumor types, including triple negative breast cancer (TNBC). Patients with metastatic or locally advanced TNBC with PD-L1 expression on immune cells occupying ≥1% of tumor area demonstrated survival benefit with the addition of atezolizumab to nab-paclitaxel. However, concerns regarding variability between immunohistochemical PD-L1 assay performance and inter-reader reproducibility have been raised. High tumor-infiltrating lymphocytes (TILs) have also been associated with response to PD-1/PD-L1 inhibitors in patients with breast cancer (BC). TILs can be easily assessed on hematoxylin and eosin-stained slides and have shown reliable inter-reader reproducibility. As an established prognostic factor in early stage TNBC, TILs are soon anticipated to be reported in daily practice in many pathology laboratories worldwide. Because TILs and PD-L1 are parts of an immunological spectrum in BC, we propose the systematic implementation of combined PD-L1 and TIL analyses as a more comprehensive immuno-oncological biomarker for patient selection for PD-1/PD-L1 inhibition-based therapy in patients with BC. Although practical and regulatory considerations differ by jurisdiction, the pathology community has the responsibility to patients to implement assays that lead to optimal patient selection. We propose herewith a risk-management framework that may help mitigate the risks of suboptimal patient selection for immuno-therapeutic approaches in clinical trials and daily practice based on combined TILs/PD-L1 assessment in BC. © 2020 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

[Hereditary breast carcinomas pathologist's perspective]

Breast cancers occurring in the context of a hereditary mutation of a predisposition gene represent 5 to 10% of all breast cancers, 20 to 25% of which being due to a mutation in the BRCA1 or BRCA2 genes. Authorization to market PARP inhibitors for breast cancer patients with hereditary BRCA1 and 2 mutations has recently been obtained. Given the annual frequency of breast cancer, morphological identification could facilitate the patient care process to limit the search for BRCA1 and 2 mutations to patients whose tumors have very specific characteristics. However, only a few morphological features have been recognized and differ depending on the mutated genes. Breast cancer occurring as part of a mutation in the BRCA1 gene is in 85% of cases of high-grade non-specific type invasive carcinomas with very limited contours, contain numerous lymphocytes in the stroma and are of triple-negative phenotype. Carcinomas associated with mutations in the BRCA2 genes and genes more recently recognized as associated with a risk of development of breast cancer (CHECK2, BMPR1A, BRIP1, PALB2, MUTYH) are most often non-specific invasive carcinomas, although other histological types are possible, grade III, luminal B phenotype. Breast cancer occurring in the context of a constitutional mutation of TP53 occurs in women under 35 years old are of non-specific histological type and with an amplification of HER2 in two thirds of the cases. Those associated with a PTEN mutation are readily of the apocrine type. Finally, very rarely, certain lobular-type breast cancers can occur in the context of a constitutional mutation of the CDH1 gene, which codes for the protein E-cadherin. The morphological and phenotypic characteristics may suggest to the pathologist a carcinoma of the breast occurring in a context of hereditary mutation. However, at the present time the only situations where a morphological sorting makes it possible to accelerate the genetic analysis are those of an invasive carcinoma of non-specific type of triple-negative phenotype in a woman of less than 50 years or that of a diagnosis of HER2 breast cancer amplified in a woman under 31 years of age (Chompret criteria). Family background and personal history are of great importance in the genetic counseling indication decision trees. Unfortunately, to date, no quality antibody has been developed against BRCA1 and 2 to help the pathologist identify hereditary cases. The immunohistochemical analysis of RAD51 could facilitate the identification of tumors possibly sensitive to PARP inhibitors. Progress to identify hereditary cancers is expected thanks to the development of artificial intelligence algorithms from digitized histological slides.

Early Modulation of Circulating MicroRNAs Levels in HER2-Positive Breast Cancer Patients Treated with Trastuzumab-Based Neoadjuvant Therapy

Circulating microRNA (ct-miRNAs) are able to identify patients with differential response to HER2-targeted therapy. However, their dynamics are largely unknown. We assessed 752 miRNAs from 52 NeoALTTO patients with plasma pairs prior and two weeks after trastuzumab. Increased levels of ct-miR-148a-3p and ct-miR-374a-5p were significantly associated with pathological complete response (pCR) (p = 0.008 and 0.048, respectively). At a threshold ≥ the upper limit of the 95%CI of the mean difference, pCR resulted 45% (95%CI 24%–68%), and 44% (95%CI 22%–69%) for ct-miR-148a-3p and ct-miR-374a-5p, respectively. Notably, ct-miR-148a-3p retained its predictive value (OR 3.42, 95%CI 1.23–9.46, p = 0.018) in bivariate analysis along with estrogen receptor status. Combined information from ct-miR-148a-3p and ct-miR140-5p, which we previously reported to identify trastuzumab-responsive patients, resulted in greater predictive capability over each other, with pCR of 54% (95%CI 25%–81%) and 0% (95%CI 0%–31%) in ct-miR-148a/ct-miR-140-5p high/present and low/absent, respectively. GO and KEGG analyses showed common enriched terms between the targets of these ct-miRNAs, including cell metabolism regulation, AMPK and MAPK signaling, and HCC progression. In conclusion, early modulated ct-miR-148-3p may inform on the functional processes underlying treatment response, integrate the information from already available predictive biomarkers, and identify patients likely to respond to single agent trastuzumab-based neoadjuvant therapy.