Citations

Purpose Endoxifen is a tamoxifen metabolite with potent antiestrogenic activity. Patients and Methods We performed a phase I study of oral Z-endoxifen to determine its toxicities, maximum tolerated dose (MTD), pharmacokinetics, and clinical activity. Eligibility included endocrine-refractory, estrogen receptor–positive metastatic breast cancer. An accelerated titration schedule was applied until moderate or dose-limiting toxicity occurred, followed by a 3+3 design and expansion at 40, 80, and 100 mg per day. Tumor DNA from serum (circulating cell free [cf); all patients] and biopsies [160 mg/day and expansion]) was sequenced. Results Of 41 enrolled patients, 38 were evaluable for MTD determination. Prior endocrine regimens during which progression occurred included aromatase inhibitor (n = 36), fulvestrant (n = 21), and tamoxifen (n = 15). Patients received endoxifen once daily at seven dose levels (20 to 160 mg). Dose escalation ceased at 160 mg per day given lack of MTD and endoxifen concentrations > 1,900 ng/mL. Endoxifen clearance was unaffected by CYP2D6 genotype. One patient (60 mg) had cycle 1 dose-limiting toxicity (pulmonary embolus). Overall clinical benefit rate (stable > 6 months [n = 7] or partial response by RECIST criteria [n = 3]) was 26.3% (95% CI, 13.4% to 43.1%) including prior tamoxifen progression (n = 3). cfDNA mutations were observed in 13 patients ( PIK3CA [n = 8], ESR1 [n = 5], TP53 [n = 4], and AKT [n = 1]) with shorter progression-free survival ( v those without cfDNA mutations; median, 61 v 132 days; log-rank P = .046). Clinical benefit was observed in those with ESR1 amplification (tumor; 80 mg/day) and ESR1 mutation (cfDNA; 160 mg/day). Comparing tumor biopsies and cfDNA, some mutations ( PIK3CA, TP53, and AKT) were undetected by cfDNA, whereas cfDNA mutations ( ESR1, TP53, and AKT) were undetected by biopsy. Conclusion In endocrine-refractory metastatic breast cancer, Z-endoxifen provides substantial drug exposure unaffected by CYP2D6 metabolism, acceptable toxicity, and promising antitumor activity.

Abstract Background: PARP inhibitors (PARPis) are active in cancers with homologous recombination (HR) defects. Preclinical studies have shown that secondary mutations or alterations in gene expression (e.g., downregulation of 53BP1, Ku70, Ku80 or DNA-PKcs) restore HR and confer PARPi resistance. In addition, low PARP1 expression can diminish PARP trapping and cause PARPi resistance. ARIEL2 Part 1 is a phase 2 study of the PARPi rucaparib in platinum sensitive, relapsed high grade serous or endometrioid ovarian cancer (OC). Pretreatment OC biopsies were previously assayed for HR gene mutations and loss of heterozygosity (LOH), a genomic scar that reflects HR deficiency. Two tumor groups (BRCA wildtype [wt]/LOH high and BRCA1 or BRCA2 mutant) have objective response rates of 29.3% and 80%, respectively, as well as progression free survival (PFS) of 5.7 and 12.8 months, respectively, on rucaparib (E. Swisher et al., Lancet Oncol., in press). Common AEs included nausea (80%), asthenia/fatigue (78%), constipation (46%), and vomiting (44%). The present studies tested the hypotheses that i) lower PARP1 expression and/or ii) lower expression of NHEJ components 53BP1, DNA-PKcs, Ku80, Ku70, or LIG4, may correlate with diminished response rate as well as PFS in pts treated with rucaparib on ARIEL2. Methods: Immunohistochemical assays were developed for 53BP1, DNA-PKcs, Ku80, Ku70, LIG4, and PARP1 and validated in formalin fixed, paraffin embedded cell lines differing in analyte expression. Available pretreatment OC biopsies from ARIEL2 Part 1 were stained and scored for % of tumor nuclei that were negative (0), weak (1+), moderate (2+) or strong (3+). Modified H-scores were correlated with clinical characteristics and outcome measures. Results: Pretreatment biopsies from 62-68 pts were successfully stained for each repair protein. Across the samples, PARP1 H-scores varied from 0 to 300 (median 160). Focusing on the BRCA wt/LOH high group (n = 38), there was no significant difference in PFS of pts with low (<100), intermediate (100-200) or high (>200) PARP1 H-score (p = 0.57). Expression of DNA-PKcs, Ku70, Ku80, and LIG4 was generally lower (median H-scores 20-60) and did not individually correlate with response or PFS. In contrast, there was a trend toward improved PFS in BRCA wt/LOH high OC pts expressing intermediate or high 53BP1 (H-score ≥ 100, n = 10) compared to pts with low 53BP1 (H-score <100, n = 25), with median PFS 20.7 vs. 5.5 months (p = 0.073), respectively. Staining of additional pretreatment biopsies is planned. Conclusions: In the BRCA wt/LOH high group, pretreatment PARP1 expression does not correlate with rucaparib response. In contrast, BRCA wt/LOH high OC pts with low 53BP1 have a trend toward shorter PFS with rucaparib, suggesting that 53BP1 downregulation might correlate with clinical PARPi resistance in BRCA wt/LOH high OC. Citation Format: Andrea E. Wahner Hendrickson, Kevin K. Lin, Daniel W. Visscher, Rachel M. Hurley, Mitch Raponi, Thomas C. Harding, Linda M. Murphy, Jill M. Wagner, Heidi Giordano, Iain McNeish, Elizabeth M. Swisher, Scott Kaufmann. DNA repair protein expression and response of homologous recombination deficient ovarian cancer to the poly(ADP-ribose) polymerase (PARP) inhibitor rucaparib in the ARIEL2 Part 1 study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4676. doi:10.1158/1538-7445.AM2017-4676

Abstract Background: The Breast Cancer Surveillance Consortium (BCSC) model predicts invasive breast cancer risk in women with Benign Breast Disease (BBD), and recently incorporated BBD histology into the model. The BCSC has been validated in the Mayo Mammography Health Study, but has yet to be examined in Mayo Clinic’s BBD cohort. The Benign Breast Disease to Breast Cancer (BBD-BC) model predicts risk of both invasive and in situ breast cancer. Here we compare the performance of the BCSC and BBD-BC in Mayo Clinic’s BBD cohort. Methods: Eligible women underwent a breast biopsy with benign findings at the Mayo Clinic between years 1997-2001 and had a 4-view screening mammogram within six months of biopsy. Clinical BI-RADS density assessments using the 4th edition American College of Radiology were available on all mammograms, and were coded as almost entirely fat, scattered fibroglandular densities, heterogeneously dense, and extremely dense. Risk at 5 and 10 years of invasive cancer only (BCSC model) or both invasive and in situ cancer (BBD-BC model) were estimated. In situ cancers were censored at time of diagnosis for both models. Concordance statistics, i.e. model discrimination (higher is better), for each model were calculated using a Cox proportional hazards model with predicted risk as the sole predictor, and were compared using permutation tests. The ratio of total predicted (sum of predicted risk) to observed number of invasive breast cancers was used to assess model calibration. Calibration was not formally compared across models due to differences in how DCIS was treated in the development of each (BCSC censored; BBD-BC event). Results: 999 women met inclusion criteria. BI-RADS density was categorized as fatty in 46 (4.6%), scattered densities in 372 (37.2%), heterogeneously dense in 423 (42.3%), and extremely dense in 158 (15.8%). 62 invasive cancers occurred over a median 13.3yrs of follow-up, with 16 (25.8%) and 48 (77.4%) of the cancers occurring with-in 5 and 10 years. The concordance of the BCSC at 5 years was 0.550 (95% CI 0.409—0.691), compared to 0.719 (95% CI 0.578—0.860) for the BBD-BC (p-value=0.005). At 10 years the BCSC concordance was not significantly different from the BBD-BC, at 0.624 (95% CI 0.542—0.706) and 0.662 (95% CI 0.580—0.744), respectively (p-value=0.306). The BCSC over predicted the number invasive cancers in the BBD cohort at 5 years (predicted-to-observed=1.54; 95% CI 1.01—2.70), but was well calibrated at 10 years (1.06; 95% CI 0.83, 1.47). Conclusions: The BCSC model performed reasonably well in the BBD Cohort 10 years post-biopsy, but overestimated risk at 5 years. Additional study is needed to improve models for prediction of breast cancer risk among women with BBD. Citation Format: Ryan D. Frank, Celine M. Vachon, Stacey J. Winham, Robert A. Vierkant, Marlene H. Frost, Derek C. Radisky, Daniel W. Visscher, Amy C. Degnim. Validation of the BCSC model within the Mayo Benign Breast Disease Cohort [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5299. doi:10.1158/1538-7445.AM2017-5299

3 Background: Atypical ductal hyperplasia (ADH) is a high-risk breast lesion usually diagnosed with core needle biopsy. Although upgraded to cancer at surgical excision in ~15 to 25% of cases, routine excision is questioned due to cost and overtreatment. We evaluated clinical, imaging, and histologic features associated with cancer upgrade and developed a multivariate model to predict risk of upgrade. Methods: With IRB approval a single institution retrospective review was performed of patients who underwent surgical excision of ADH diagnosed by core biopsy from 06/2005 to 06/2013. Review was performed of electronic records, breast imagin,g and biopsy slides. Multiple imputations were used for missing data. Association of cancer upgrade with various features was assessed with logistic regression. Results: 409 biopsies with ADH on core biopsy, with later surgical excision, were included. The overall upgrade rate was (16.1%, 95% CI:12.9-20.0%); 10 patients had invasive cancer at excision and 56 DCIS only. Features on core biopsy most strongly associated with upgrade were imaging estimated percent of lesion removed (upgrade 9% for 90% removed, 14% for 50 to 75%, and 27% for < 50% removed), individual cell necrosis (upgrade 34% with necrosis vs. 9.5% without), and # foci of ADH (22% for >1 focus vs 8% for 1 focus). A multivariate predictive model (see Table) showed an average C-statistic of 0.77. Women with no necrosis and either 1 focus with ≥ 50% removal or >1 focus with 90% removal (36% of the sample) have low risk of upgrade (5.0%, 95% CI:1.3-8.7%). Conclusions: ADH on core biopsy with low risk of upgrade to cancer is defined by percent of imaging lesion removed, # of foci of ADH, and lack of individual cell necrosis. If findings are validated, women whose biopsies meet low-risk criteria might be considered for chemoprevention and surveillance rather than surgical excision.[Table: see text]

2 Background: Women with atypical hyperplasia (AH) on breast biopsy have an aggregate increased risk of breast cancer (BC), but accurate personalized risk prediction is desirable to facilitate individual clinical management decisions. Currently used models provide poor BC risk prediction for women with AH. Our goal was to develop and validate an improved risk prediction model for women with AH. Methods: From a cohort of 13,538 women with benign breast disease from 1967-2001, pathology review confirmed 699 with AH. Clinical risk factors and histologic features of the tissue biopsy were recorded, and BC events were ascertained from study questionnaires, tumor registry, and review of medical records. Using a lasso approach, 23 variables were assessed for model inclusion. Lasso-identified features were then fit in a Cox regression model to estimate BC risk. Model discrimination was assessed with C-statistics in the model-building set and in a separate external validation set. Calibration was assessed by comparing observed to predicted breast cancer counts. Results: The model-building set comprised 699 women with 142 BC events (median follow-up 8.1 years), and the external validation set comprised 461 women with 114 BC events (median follow-up 11.4 years). The final model included three covariates: age at biopsy, age squared, and number of foci of AH. Model performance was good, with a C-statistic of 0.622 (SE = 0.027) in the model-building set and 0.594 (SE = 0.029) in the external validation set. The model is well-calibrated, with observed to expected numbers of BCs nearly equal across all post-biopsy follow-up years. Conclusions: We propose a new model for predicting BC risk in women with AH based on age at biopsy and number of foci of atypia. This model provides absolute risk estimates for women with AH, has good discriminatory ability, is well-calibrated, and validates in an external cohort.

18 Background: Benign breast disease (BBD) is diagnosed in 1-2 million women/year in the US, and while these patients are known to be at substantially increased risk for subsequent development of breast cancer, existing models for risk assessment perform poorly at the individual level. Here, we describe a DNA-microarray-based transcriptional model for breast cancer risk prediction for patients with sclerosing adenosis (SA), a lesion found in ¼ of all BBD patients that is characterized by epithelial proliferation, disordered acinar architecture, and stromal fibrosis. Methods: A training set was developed from 86 patients diagnosed with sclerosing adenosis (SA), of which 27 subsequently developed cancer within 10 years (cases) and 59 remained cancer-free at 10 years (controls). A diagonal linear discriminate analysis (DLDA)-prediction model for prediction of cancer within 10 years (SA TTC10) was generated from transcriptional profiles of formalin fixed, paraffin-embedded (FFPE) biopsy-derived RNA. This model was tested on a separate validation case-control set composed of 65 SA patients. Results: The SA TTC10 gene signature model, composed of 35 gene features, achieved a clear and significant separation between case and control with receiver operating characteristic area under the curve of 0.913 in the training set and 0.836 in the validation set. Conclusions: Our results provide the first demonstration that benign breast tissue contains transcriptional alterations that indicate risk of breast cancer development, and that essential precursor biomarkers of malignancy are present many years prior to cancer development. Furthermore, the SA TTC10 gene signature model, which can be assessed on FFPE biopsies, constitutes a novel prognostic biomarker for patients with SA.