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Background:\ud \ud Biomarkers for cyclin-dependent kinase 4/6 inhibitors, such as palbociclib, for patients with hormone receptor-positive/HER2-negative metastatic breast cancer are lacking. Thymidine kinase is a proliferation marker downstream of the cyclin-dependent kinase 4/6 pathway. We prospectively investigated the prognostic role of serum thymidine kinase activity (sTKa), in patients treated with Palbociclib + fulvestrant.\ud \ud Patients and methods:\ud \ud PYTHIA was a phase II, single-arm, multicentre, trial that enrolled 124 post-menopausal women with endocrine-resistant hormone receptor-positive/HER2-negative metastatic breast cancer. Serum samples were collected pre-treatment (pre-trt; n = 122), at day 15 of cycle 1 (D15; n = 108), during the one week-off palbociclib before initiating cycle 2 (D28; n = 108) and at end of treatment (n = 76). sTKa was determined centrally using Divitum®, a refined ELISA-based assay with a limit of detection of 20 Divitum Units (Du)/L. The primary study endpoint was progression-free survival, assessed for its association with pre- and on-treatment sTKa.\ud \ud Results:\ud \ud Data from 122 women were analysed. Pre-treatment sTKa was not associated with clinical characteristics and moderately correlated with tissue Ki-67. Palbociclib + fulvestrant markedly suppressed sTKa levels at D15, with 83% of patients recording levels below limit of detection. At D28, sTKa showed a rebound in 60% of patients. At each timepoint, higher sTKa was associated with shorter progression-free survival (each p < 0.001), with the strongest effect at D15.\ud \ud Conclusions:\ud \ud STKa is an independent prognostic biomarker in patients treated with palbociclib. High pre-treatment sTKa and its incomplete suppression during treatment may identify patients with poorer prognosis and primary resistance. This warrants validation in prospective comparative trials.\ud \ud Clinicaltrials.gov identifier:\ud \ud NCT02536742; EudraCT 2014-005387-15.

I-GMIB-anti-human epidermal growth factor receptor type 2 (HER2)-VHH1 is a targeted radionuclide theranostic agent directed at HER2-expressing cancers. VHH1 is a single-domain antibody covalently linked to therapeutic I via the linker -succinimidyl 4-guanidino-methyl-3-iodobenzoate (SGMIB). The phase I study was aimed at evaluating the safety, biodistribution, radiation dosimetry, and tumor-imaging potential of I-GMIB-anti-HER2-VHH1 in healthy volunteers and breast cancer patients. In a first cohort, 6 healthy volunteers were included. The biodistribution of I-GMIB-anti-HER2-VHH1 was assessed using whole-body (anterior and posterior) planar images obtained at 40 min and at 2, 4, 24, and 72 h after intravenously administered (38 ± 9 MBq) I-GMIB-anti-HER2-VHH1. Imaging data were analyzed using OLINDA/EXM software to determine the dosimetry. Blood and urine samples were obtained over 72 h. In the second cohort, 3 patients with metastatic HER2-positive breast cancer were included. Planar whole-body imaging was performed at 2 and 24 h after injection. Additional SPECT/CT images were obtained after the whole-body images at 2 and 24 h if there was relevant uptake in known cancer lesions. No drug-related adverse events were observed throughout the study. The biologic half-life of I-GMIB-anti-HER2-VHH1 in healthy subjects was about 8 h. After intravenous administration, the compound was eliminated from the blood with a 2.5-h half-life. The drug was eliminated primarily via the kidneys. The drug was stable in circulation, and there was no increased accumulation in the thyroid or stomach. The absorbed dose to the kidneys was 1.54 ± 0.25 mGy/MBq, and to bone marrow it was 0.03 ± 0.01 mGy/MBq. SPECT/CT imaging in patients with advanced breast cancer showed focal uptake of I-GMIB-anti-HER2-VHH1 in metastatic lesions. Because of its favorable toxicity profile and its uptake in HER2-positive lesions, this radiopharmaceutical can offer new therapeutic options to patients who have progressed on trastuzumab, pertuzumab, or trastuzmab emtansine, given its difference in mode-of-action. A dose escalation is planned in a subsequent phase I/II study to assess the therapeutic window of this compound (NCT04467515).

BACKGROUND Multigene panels are routinely used to search for predisposing mutations in families considered at high risk of breast cancer. The number of variants of unknown significance (VUS) thereby identified increases with the number of sequenced genes. We aimed to determine whether tumor sequencing can help reclassify germline VUS based on second events hitting the same gene. METHODS Whole-exome sequencing (WES) was performed on whole-blood DNA from 70 unrelated breast cancer patients referred for genetic testing and without BRCA1, BRCA2, TP53 or CHEK2 mutations. Rare variants considered as a VUS based on ACMG guidelines were retained in a list of 735 genes. WES was performed on matched tumor DNA to look for somatic second hits (copy number alteration or second mutation) in the same genes. RESULTS Sixty-eight patients (97%) carried at least one germline VUS (4.7 ± 2.0 variants per patient). Of the 329 VUS, 55 (17%) presented a somatic second hit in the paired tumor tissue. Two were a second somatic mutation, whereas 53 were copy number alterations. This resulted in relative tumor enrichment or depletion of the germline variant for 28 and 25 VUS, respectively. Estimation of tumor mutation burden and homologous recombination deficiency through mutational signatures and allelic imbalance analysis could highlight bi-allelic gene inactivation in relevant cases. Clinical measures were proposed for six patients carrying a germline variant on PALB2, PMS2, PMS1, MUTYH or NTHL1. Variant disclosure without clinical measures was proposed for five patients carrying a variant on MRE11A, ATM, WRN or TP53 (functional testing ongoing for the latter). Germline and tumor DNA analysis of an affected relative of the patient carrying the germline MRE11A variant demonstrated the co-segregation of the variant as well as the presence of the same somatic second hit. Seven VUS on clinically actionable breast cancer predisposing genes (PALB2, BRCA2, CDH1, ATM and BARD1) were downgraded to probably benign variants as the germline variant was depleted in the tumor. One patient presented a significant tumor enrichment of a germline VUS in the C-terminal domain of the oncogene ERBB2. In vitro expression of this variant caused downstream signaling pathway activation. CONCLUSION Tumor sequencing is a powerful approach to refine VUS in cancer-predisposing genes in high-risk breast cancer patients. In this series, the strategy provided clinically relevant information for 11 out of 70 patients (16%). Citation Format: Cedric Van Marcke, Raphaël Helaers, Céline A Schoonjans, Martine Berlière, Anne De Leener, Jean-Luc Canon, Peter Vuylsteke, Jean-Pascal Machiels, Nisha Limaye, Miikka Vikkula, Francois P Duhoux. Tumor sequencing is useful to reclassify germline variants in unexplained high-risk breast cancer families [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-03-03.

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Ovarian cancer is the fifth largest cancer killer in women. Improved understanding of the molecular pathways implicated in the pathogenesis of ovarian cancer has led to the investigation of novel targeted therapies. Ovarian cancer is characterized by an imbalance between pro- and antiangiogenic factors in favor of angiogenesis activation. Various antivascular strategies are currently under investigation in ovarian cancer. They can schematically be divided into antiangiogenic and vascular-disrupting therapies. This paper provides a comprehensive review of these new treatments targeting the tumor vasculature in this disease. Promising activities have been detected in phase II trials, and results of phase III clinical trials are awaited eagerly.

Hava Izci,1 Gilles Macq,2 Tim Tambuyzer,2 Harlinde De Schutter,2 Hans Wildiers,1,3 Francois P Duhoux,4 Evandro de Azambuja,5 Donatienne Taylor,6 Gracienne Staelens,7 Guy Orye,8 Zuzana Hlavata,9 Helga Hellemans,10 Carine De Rop,11 Patrick Neven,1,3 Freija Verdoodt2 1KU Leuven - University of Leuven, Department of Oncology, Leuven, B-3000, Belgium; 2Belgian Cancer Registry, Research Department, Brussels, Belgium; 3University Hospitals Leuven, Multidisciplinary Breast Center, Leuven, B-3000, Belgium; 4Department of Medical Oncology, King Albert II Cancer Institute, Cliniques Universitaires Saint-Luc, Brussels, Belgium; 5Institut Jules Bordet and l’Université Libre de Bruxelles (U.L.B), Brussels, Belgium; 6CHU UCL Namur, Site Sainte-Elisabeth, Namur, Belgium; 7Multidisciplinary Breast Center, General Hospital Groeninge, Kortrijk, Belgium; 8Department of Obstetrics and Gynecology, Jessa Hospital, Hasselt, Belgium; 9Department of Medical Oncology, CHR Mons-Hainaut, Mons, Hainaut, Belgium; 10Department of Obstetrics and Gynaecology, AZ Delta, Roeselaere, Belgium; 11Department of Obstetrics and Gynaecology, Imelda Hospital, Bonheiden, BelgiumCorrespondence: Hava Izci, KU Leuven, Department of oncology, Herestraat 49 Box 7003-06, Leuven, 3000, Belgium, Email hava.izci@kuleuven.bePurpose: High-quality population-based cancer recurrence data are scarcely available, mainly due to complexity and cost of registration. For the first time in Belgium, we developed a tool to estimate distant recurrence after a breast cancer diagnosis at the population level, based on real-world cancer registration and administrative data.Methods: Data on distant cancer recurrence (including progression) from patients diagnosed with breast cancer between 2009– 2014 were collected from medical files at 9 Belgian centers to train, test and externally validate an algorithm (i.e., gold standard). Distant recurrence was defined as the occurrence of distant metastases between 120 days and within 10 years after the primary diagnosis, with follow-up until December 31, 2018. Data from the gold standard were linked to population-based data from the Belgian Cancer Registry (BCR) and administrative data sources. Potential features to detect recurrences in administrative data were defined based on expert opinion from breast oncologists, and subsequently selected using bootstrap aggregation. Based on the selected features, classification and regression tree (CART) analysis was performed to construct an algorithm for classifying patients as having a distant recurrence or not.Results: A total of 2507 patients were included of whom 216 had a distant recurrence in the clinical data set. The performance of the algorithm showed sensitivity of 79.5% (95% CI 68.8– 87.8%), positive predictive value (PPV) of 79.5% (95% CI 68.8– 87.8%), and accuracy of 96.7% (95% CI 95.4– 97.7%). The external validation resulted in a sensitivity of 84.1% (95% CI 74.4– 91.3%), PPV of 84.1% (95% CI 74.4– 91.3%), and an accuracy of 96.8% (95% CI 95.4– 97.9%).Conclusion: Our algorithm detected distant breast cancer recurrences with an overall good accuracy of 96.8% for patients with breast cancer, as observed in the first multi-centric external validation exercise.Keywords: machine learning, breast cancer, distant metastases, recurrences, algorithm, administrative data

It is estimated that four in five women will give birth while one in eight women will be diagnosed with breast cancer at some point in her lifetime. It is also known that pregnancy at a young age is associated with a marked decrease in the risk of breast cancer and that this protection is different according to breast cancer subtypes. This thesis explores the impact of reproductive history on breast cancer biology and provides the molecular characterization of breast cancer diagnosed during pregnancy. The last part investigates the effect of RANKL inhibition on the biology of breast cancer in young women. In the first study, we investigated the impact of parity and age at first pregnancy on the clinicopathological features, the genomic and transcriptomic landscape, and the immune microenvironment of 313 breast cancers. For the first time, we highlighted a link between reproductive history and the genomic landscape of subsequent breast cancer. We demonstrated that, independently of clinicopathological features, age at first birth is associated with specific genomic alterations that could explain the differences in risk reduction associated with pregnancy according to breast cancer subtypes. This study represents a first step toward the recognition that reproductive factors matter in order to fully understand breast cancer biology and advocates that reproductive history should be routinely collected in future studies addressing the biology of breast cancer but also of other female cancers. The second study is focused on the molecular characterization of breast cancer diagnosed during pregnancy (BCP). We conducted a comparative analysis of a unique cohort of BCP patients and non-pregnant control patients by integrating gene expression, copy number alterations, and whole-genome sequencing data. We showed that BCP has unique molecular characteristics including an enrichment of non-silent mutations, a higher frequency of mutations in mucin gene family and an enrichment of mismatch repair deficiency mutational signature. This provides important insights into the biology of BCP and suggests that these features may be implicated in promoting tumor progression during pregnancy. In addition, it provides an unprecedented resource for further understanding of the biology of breast cancer in young women and how pregnancy could modulate tumor biology. In a previous study, the laboratory had reported up-regulation of RANKL in young and pregnant breast cancer patients. Therefore, in the last chapter, we investigated the biological effect of denosumab, a RANKL inhibitor, in a preoperative study including 27 young primary breast cancer patients. We demonstrated evidence that denosumab induces modulation of the tumor immune microenvironment with an increased level of tumor-infiltrating lymphocytes. This effect was likely due to upregulation of inflammatory cytokines and depletion of immunosuppressive regulatory T cells within the tumor microenvironment. These findings suggest a role for denosumab in reshaping the tumor immune microenvironment of breast cancer and that its use in combination could improve immunotherapy efficacy., Doctorat en Sciences biomédicales et pharmaceutiques (Médecine), info:eu-repo/semantics/nonPublished