Background The role of different subtypes of tumour infiltrating lymphocytes (TILs) in breast ductal carcinoma in situ (DCIS) is still poorly defined. This study aimed to assess the prognostic significance of B and T lymphocytes and immune checkpoint proteins expression in DCIS. Methods A well characterised DCIS cohort ( n = 700) with long-term follow-up comprising pure DCIS ( n = 508) and DCIS mixed with invasive carcinoma (IBC; n = 192) were stained immunohistochemically for CD20, CD3, CD4, CD8, FOXP3, PD1 and PDL1. Copy number variation and TP53 mutation status were assessed in a subset of cases ( n = 58). Results CD3+ lymphocytes were the predominant cell subtype in the pure DCIS cohort, while FOXP3 showed the lowest levels. PDL1 expression was mainly seen in the stromal TILs. Higher abundance of TILs subtypes was associated with higher tumour grade, hormone receptor negativity and HER2 positivity. Mutant TP53 variants were associated with higher levels of stromal CD3+, CD4+ and FOXP3+ cells. DCIS coexisting with invasive carcinoma harboured denser stromal infiltrates of all immune cells and checkpoint proteins apart from CD4+ cells. Stromal PD1 was the most differentially expressed protein between DCIS and invasive carcinoma ( Z = 5.8, p < 0.0001). Dense TILs, stromal FOXP3 and PDL1 were poor prognostic factors for DCIS recurrence, while dense TILs were independently associated with poor outcome for all recurrences (HR = 7.0; p = 0.024), and invasive recurrence (HR = 2.1; p = 0.029). Conclusions Immunosuppressive proteins are potential markers for high risk DCIS and disease progression. Different stromal and intratumoural lymphocyte composition between pure DCIS, DCIS associated with IBC and invasive carcinoma play a potential role in their prognostic significance and related to the underlying genomic instability. Assessment of overall TILs provides a promising tool for evaluation of the DCIS immune microenvironment.

Purpose: Advanced stage MOC have poor chemotherapy response and prognosis and lack biomarkers to aid Stage I adjuvant treatment. Differentiating primary mucinous ovarian carcinoma (MOC) from gastrointestinal (GI) metastases to the ovary is also challenging due to phenotypic similarities. Clinicopathological and gene expression data were analysed to identify prognostic and diagnostic features. Experimental Design: Discovery analyses selected 19 genes with prognostic/diagnostic potential. Validation was performed through the Ovarian Tumor Tissue Analysis consortium and GI cancer biobanks comprising 604 patients with MOC (n=333), mucinous borderline ovarian tumors (MBOT, n=151), upper GI (n=65), and lower GI tumors (n=55). Results: Infiltrative pattern of invasion was associated with decreased overall survival (OS) within 2-years from diagnosis, compared with expansile pattern in Stage I MOC (hazard ratio HR 2.77 (1.04-7.41, p=0.042). Increased expression of THBS2 and TAGLN were associated with shorter OS in MOC patients, (HR 1.25 (95% CI 1.04-1.51, p=0.016)) and (1.21 (1.01-1.45, p=0.043)) respectively. ERBB2 (HER2)-amplification or high mRNA expression was evident in 64/243 (26%) of MOCs, but only 8/243 (3%) were also infiltrative (4/39, 10%) or Stage III/IV (4/31, 13%). Conclusions: An infiltrative growth pattern infers poor prognosis within 2-years from diagnosis and may help select Stage I patients for adjuvant therapy. High expression of THBS2 and TAGLN in MOC confer an adverse prognosis and is upregulated in the infiltrative subtype which warrants further investigation. Anti-HER2 therapy should be investigated in a subset of patients. MOC samples clustered with upper GI, yet markers to differentiate these entities remain elusive, suggesting similar underlying biology and shared treatment strategies.

Background Breast cancers (BC) that arise in individuals heterozygous for a germline pathogenic variant in a susceptibility gene, such as BRCA1/2, PALB2 and RAD51C, have been shown to exhibit bi-allelic loss in the respective genes, and be associated with triple-negative (TN) BC and distinctive somatic mutational signatures. Tumour sequencing thus presents an orthogonal approach to assess the role of candidate genes in BC development. Methods Exome sequencing was performed on paired normal-breast tumour DNA from 124 carriers of germline loss-of-function (LoF) or missense (MS) mutations carriers in 15 known and candidate BC predisposition genes identified in the BEACCON case-control study. Bi-allelic inactivation and association with tumour genome features including mutational signatures and homologous recombination deficiency (HRD) score were investigated. Results BARD1-carrying TN BC (4/5) displayed bi-allelic loss and associated high HRD scores and mutational signature 3, as did a RAD51D-carrying TN BC and ovarian cancer. Bi-allelic loss was less frequent in BRIP1 BCs (4/13) and had low HRD scores. In contrast to other established BC genes, BCs from carriers of CHEK2 LoF (6/17) or MS (2/20) carriers had low rates of bi-allelic loss. Exploratory analysis of BC from carriers of LoF mutations in candidate genes such as BLM, FANCM, PARP2 and RAD50 found little evidence of bi-allelic inactivation. Conclusions BARD1 and RAD51D behave as classic BRCA-like genes with bi-allelic inactivation but this was not observed for any of the candidate genes. However, as demonstrated for CHEK2, the absence of bi-allelic inactivation does not provide definitive evidence against the gene’s involvement in BC predisposition.

IntroductionPeople of Ashkenazi Jewish (AJ) ancestry are more likely than unselected populations to have a BRCA1/2 pathogenic variant, which cause a significantly increased risk of breast, ovarian and prostate cancer. Three specific BRCA1/2 pathogenic variants, referred to as BRCA-Jewish founder mutations (B-JFM), account for >90% of BRCA1/2 pathogenic variants in people of AJ ancestry. Current practice of identifying eligible individuals for BRCA testing based on personal and/or family history has been shown to miss at least 50% of people who have one of these variants. Here we describe the protocol of the JeneScreen study—a study established to develop and evaluate two different population-based B-JFM screening programmes, offered to people of Jewish ancestry in Sydney and Melbourne, Australia.Methods and analysisTo rmeasure the acceptability of population-based B-JFM screening in Australia, two screening programmes using different methodologies have been developed. The Sydney JeneScreen programme provides information and obtains informed consent by way of an online tool. The Melbourne JeneScreen programme does this by way of community sessions attended in person. Participants complete questionnaires to measure clinical and psychosocial outcomes at baseline, and for those who have testing, 2 weeks postresult. Participants who decline testing are sent a questionnaire regarding reasons for declining. Participants with a B-JFM are sent questionnaires 12-month and 24-month post-testing. The questionnaires incorporate validated scales, which measure anxiety, decisional conflict and regret, and test-related distress and positive experiences, and other items specifically developed or adapted for the study. These measures will be assessed for each programme and the two population-based B-JFM screening methods will be compared.Ethics and disseminationInstitutional Human Research Ethics Committee approval was obtained from the South Eastern Area Health Service Human Research Ethics Committee: HREC Ref 16/125.Following the analysis of the study results, the findings will be disseminated widely through conferences and publications, and directly to participants in writing.

BackgroundAshkenazi Jewish (AJ) people have a higher incidence of BRCA1/2 pathogenic variants (PVs) than unselected populations. Three BRCA-Jewish founder mutations (B-JFMs) comprise >90% of BRCA1/2 PVs in AJ people. Personal/family cancer history-based testing misses ≥50% of people with B-JFM.MethodsWe compared two population-based B-JFM screening programmes in Australia—using (1) an online tool (Sydney) and (2) in-person group sessions (Melbourne).ResultsOf 2167 Jewish people tested (Sydney n=594; Melbourne n=1573), 1.3% (n=28) have a B-JFM, only 2 of whom had a significant cancer family history (Manchester score ≥12). Pretest anxiety scores were normal (mean 9.9±3.5 (6–24)), with no significant post-result change (9.5±3.3). Decisional regret (mean 7.4±13.0 (0–100)), test-related distress (mean 0.8+/2.2 (0–30)) and positive experiences (reverse-scored) (mean 3.4±4.5 (1–20)) scores were low, with no significant differences between Sydney and Melbourne participants. Post-education knowledge was good overall (mean 11.8/15 (±2.9)) and significantly higher in Melbourne than Sydney. Post-result knowledge was the same (mean 11.7 (±2.4) vs 11.2 (±2.4)). Participants with a B-JFM had higher post-result anxiety and test-related distress and lower positive experiences, than those without a B-JFM, but scores were within the normal range. Family cancer history did not significantly affect knowledge or anxiety, or pretest perception of B-JFM or cancer risks. Most participants (93%) were satisfied/very satisfied with the programme.ConclusionBoth B-JFM screening programmes are highly acceptable to Australian Jewish communities. The programme enabled identification of several individuals who were previously unaware they have a B-JFM, many of whom would have been ineligible for current criteria-based testing in Australia.

Introduction: Up to 25% of cases of ductal carcinoma in situ (DCIS) recur, and half of these recur as invasive breast cancer (IBC). There is no biomarker to predict which DCIS cases will recur but it has been suggested that a biomarker would allow de-escalation of the current paradigm of treating most patients with surgery and/or radiotherapy. However, we hypothesize that not all recurrences are genetically similar to the primary DCIS (i.e. non-clonal) and therefore arise de novo. To test this we assembled a large recurrence cohort to explore the clonal relatedness of primary-recurrence tumor pairs prior to proposing a predictive biomarker (Gorringe et al Mod Pathol 2015). Method: We microdissected and extracted DNA from 65 pairs of primary DCIS and recurrences. Half of these recurrences were IBC. We analyzed 21 pairs by targeted sequencing or low-coverage whole-genome sequencing (LCWGS, 2x depth) and 44 pairs with Whole Exome Sequencing (WES, average depth 95x). We similarly analyzed a set of non-recurrent DCIS cases (n=29) treated with wide local excision and with a minimum of 7 years follow-up. No matched normal samples were available. Several approaches were utilized to investigate clonal relatedness using copy number alterations and mutations (when detected), including the Clonality package (Mauguen et al Biometrics 2018), manual breakpoint inspection (Bollet et al JNCI 2008), and clonality indexes (Schultheis et al JNCI 2016). Phylogenetic analyses were carried out by MEDICC2 (Petkovic et al bioRxiv 2021) on WES samples. Results: 62% of cases were clonal (40/65), 28% were non-clonal. There were 7/65 that were equivocal, although further validation will be performed. There was no significant difference in clonal relatedness whether the recurrence was IBC or DCIS. IBC recurrent cases showed a significantly higher ploidy than the DCIS recurrences. The final phylogenetic analysis with MEDICC2 will be presented, which will take into account any subclonal whole-genome doubling events. Furthermore, clonal primary DCIS showed a significantly higher number of TP53 mutations compared to non-recurrent and non-clonal primaries (p&lt;0.001, Fisher Exact test) and a higher level of copy number events overall. Conclusion: Detailed molecular analysis of a large cohort of matched DCIS primary and their recurrences using high sequencing resolution showed a substantial proportion of recurrences were not genetically related to the primary DCIS. Our observations raise the question of whether a tumor intrinsic biomarker alone would be sufficient to predict DCIS recurrences. Citation Format: Tanjina Kader, Sakshi Mahale, Magnus Zethoven, Hugo Saunders, Dorothea Lesche, David Byrne, Siqi Lai, Lauren Tjoeka, Claire Candido, Maree Pechlevanis, Olivia Craig, Jia-Min Pang, Lisa Devereux, Shona Hendry, Eloise House, Sureshni Jayasinghe, Michael Toss, Islam M. Miligy, Emad Rakha, Stephen Fox, Bruce Mann, Ian Campbell, Kylie Gorringe. Predictive biomarkers of recurrence may not be useful for deescalating treatment of breast ductal carcinoma in situ due to de novo ipsilateral breast carcinoma development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 43.

<p>Supplementary Methods</p>

<p>Supplementary Figures S1-S13</p>