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: NOTCH oncogenic signaling induces epithelial-to-mesenchymal transition (EMT) and tumor stemness that play a critical role in driving tumor progression. Following interaction of NOTCH receptors (NOTCH 1, 2, 3, and 4) with their ligands (DELTA-LIKE 1, 3, 4 and JAGGED 1, 2), γ- secretase complex performs an intra-membrane cleavage releasing the NOTCH intracellular domain (NNICD). NNICD translocates to the nucleus and induces the expression of HEY1 and HES1 transcription factors that in turn orchestrate NOTCH-mediated EMT and stemness reprogramming. Materials and Methods: Parental MCF-7 and unique metastatic MCF-7RAF-1 xenografts with constitutively active MAPK signaling (D’Assoro et al., Oncogene 2014: 33:599-610) were used to define the extent to which increased expression of NOTCH signaling was linked to distant metastases. SKY analysis was performed to assess the grade of chromosomal instability (CIN) in tumor xenografts. Stemness activity was assessed by culturing breast cancer cells under non-adherent conditions to generate mammospheres. Expression of CD24 luminal marker was characterized by FACS analysis and immunofluorescence. Global transcriptome analysis was performed using Affymetrix® microarray. Highly invasive MDA-MB 231 breast cancer cells were used to perform a tail vein cancer cell-seeding assay. The LY411575 γ-secretase inhibitor (Pan-NOTCH inhibitor) was used to block NOTCH signaling in MDA-MB 231 cells. Results: Metastasis Initiating Cells (MICs) isolated from the lungs of nude mice carrying MCF-7RAF-1 xenografts exhibited a higher degree of genomic stability than primary tumor xenografts that was characterized by the absence of centrosome amplification and non-clonal chromosomal abnormalities. MICs also showed higher mammosphere forming capacity that was linked to lower expression of luminal marker CD24. Significantly, global transcriptome analysis showed that expression of NOTCH3 and HES1 stemness genes was increased in MICs. To corroborate the role of NOTCH signaling in inducing metastatic seeding, MDA-MB 231 breast cancer cells were pre-treated with 1 µM of LY411575 After 72 hours viable cells were injected into the tail vein of immune-compromised mice to develop lung metastases. While animals injected with untreated MDA-MB 231 cells developed lung metastases, those injected with the LY411575-treated MDA-MB 231 cells failed to develop lung metastatic lesions. Conclusions: These preliminary findings demonstrate the role of NOTCH stemness signaling in promoting metastatic seeding of breast cancer cells. Since NOTCH signaling is a “druggable target”, these results also provide the rationale to develop novel NOTCH-targeted therapies to inhibit tumor stemness and early onset of distant metastases. Citation Format: Alexey Leontovich, Jeffrey Salisbury, Candace L. Haddox, Lisa Mills, Tufia Haddad, James McCubrey, Matthew Goetz, James Ingle, Evanthia Galanis, Antonino B. D'Assoro. NOTCH signaling promotes metastatic seeding and growth of human breast cancer cells [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 4851. doi:10.1158/1538-7445.AM2017-4851

Abstract Previous studies have implicated estrogen as a regulator of epidermal growth factor receptor (EGFR) expression in breast tumors. We therefore speculated that estrogen might modulate serologic soluble EGFR (sEGFR) concentrations in breast cancer patients. Accordingly, we measured serum sEGFR concentrations in postmenopausal women with metastatic breast cancer (MBC) treated with letrozole, an aromatase inhibitor that blocks estrogen synthesis. Serum specimens were obtained prior to and following 1 and 3 months of letrozole therapy. We report that sEGFR concentrations do not differ between MBC patients prior to letrozole treatment and age- and postmenopause-matched healthy women (P = 0.468). In contrast, however, sEGFR concentrations decreased significantly in 76% of MBC patients after both 1 month (P = 0.006) and 3 months (P = 0.003) of letrozole therapy versus pretreatment concentrations. Within the limitations of this study, we found no evidence for an association between pretreatment sEGFR concentrations or decreased treatment sEGFR concentrations and either progression-free or overall survival. Nonetheless, we conclude that future prospective studies are warranted to determine if baseline and/or longitudinal serum sEGFR concentrations may be useful for predicting disease progression and survival, and/or for monitoring responsiveness to aromatase inhibitors or other endocrine therapies in breast cancer patients.

LBA506 Background: MA.17R is a Canadian Cancer Trials Group (CCTG) led phase III randomized controlled trial comparing letrozole to placebo after 5 years of aromatase inhibitor (AI) as adjuvant therapy for hormone-receptor positive breast cancer. The primary endpoint was disease-free survival. Quality of life (QOL) was a secondary endpoint. Methods: QOL was measured with the SF-36 (2 summary scores and 8 domains) and menopause-specific QOL (MENQOL) (4 symptom domains) at baseline and every 12 months (mo) up to 60 mo. QOL assessment was mandatory for CCTG centres but optional to centres in other groups. Mean change scores from baseline were calculated at 12 and 36 mo. Between-arm differences were assessed with the Wilcoxon test. Results: 1918 patients were randomized and 1428 patients completed the baseline QOL assessment. Compliance with QOL measures was over 85%. Baseline summary scores for SF-36 physical (PCS, 47.5 for letrozole and 47.9 for placebo) and mental (MCS, 55.5 for letrozole and 54.8 for placebo) were close to population norms (50). No differences were seen between groups in mean change scores for the SF-36 PCS and MCS and the other 8 QOL domains. Patients randomized to letrozole reported worse vasomotor symptoms (12 mo p = 0.02, 36 mo p = 0.03) and worse sexual functioning (12 mo p = 0.01, 36 mo p = 0.01). Further analyses with follow up to 60 months will be presented. Conclusions: No differences were seen in overall QOL measured by the SF 36 summary measures between letrozole and placebo groups. Differences existed for vasomotor symptoms and sexual functioning which were worse in the letrozole group and attributed to improvements in mean scores seen for women randomized to placebo. The data indicate that continuation of AI therapy after 5 years prior treatment is not associated with a deterioration of overall QOL. Treatment related vasomotor and sexual functioning alterations occur with ongoing treatment. Clinical trial information: NCT00754845.

LBA1 Background: Five years of aromatase inhibitor (AI) therapy either as up-front treatment or after 2-5 years of tamoxifen has become the standard of care for postmenopausal women with hormone receptor positive early breast cancer. Extending treatment with an AI to 10 years may further reduce the risk of breast cancer recurrence. Methods: We conducted a double-blind, placebo-controlled trial (Canadian Cancer Trials Group MA.17R) to test the efficacy of extending AI treatment for an additional five years using letrozole. The primary endpoint was disease-free survival. Results: A total of 1,918 women with early stage breast cancer were enrolled (median follow-up 75 months, 6.3 years). A total of 165 disease-free survival (DFS) events (67 on letrozole and 98 on placebo) occurred, of which 42 versus 53 were distant recurrences on letrozole and placebo, respectively. There were 200 deaths (100 in each treatment group). The 5 year DFS was respectively 95% for patients receiving letrozole versus 91% for those on placebo (HR 0.66; P = 0.01) from a two-sided log-rank test stratified by nodal status, prior adjuvant chemotherapy, interval between last dose of AI therapy and randomization, and duration of prior tamoxifen at randomization. The 5 year overall survival was respectively 93% for subjects on letrozole and 94% on placebo with a HR of 0.97 (P = 0.83). The annual incidence rate of contralateral breast cancer was 0.21% for subjects on letrozole versus 0.49% on placebo (P = 0.007). Conclusions: Compared to 5 years of AI treatment as initial therapy or preceded by 2-5 years of tamoxifen, extending AI treatment to 10 years significantly improves disease-free survival. Further analyses will provide a comprehensive picture of toxicities and QOL. Clinical trial information: NCT00754845.

BACKGROUNDBreast cancer patients in the MA.27 trial had similar outcomes with steroidal aromatase inhibitor (AI) exemestane and nonsteroidal anastrozole. AIs increase the risk of osteoporosis. This study examined the effects of self‐reported osteoporosis and osteoporosis therapy (OPT) on outcomes.METHODSThe MA.27 phase 3 adjuvant trial enrolled 7576 postmenopausal women. The primary outcome was event‐free survival (EFS), and the secondary outcome was distant disease–free survival (DDFS). Patients were permitted bisphosphonates to prevent or treat osteopenia/osteoporosis. In a multivariate, stratified Cox regression, factors were significant with a 2‐sided Wald test P value ≤ .05.RESULTSOsteoporosis was reported at the baseline by 654 of the 7576 women (8.6%) and in total by 1294 patients. Oral OPT was received at the baseline by 815 of the 7576 women (10.8%) and in total by 2711 patients (36%). With a median follow‐up of 4.1 years, 693 EFS events (9.15%) and 321 DDFS events (4.2%) occurred. Osteoporosis was not associated with EFS or DDFS. Few EFS events occurred before the initiation of OPT, with no substantive evidence of a time‐differing effect on outcomes (nonproportional hazards). OPT (yes vs no) was significantly associated with improved EFS (hazard ratio [HR] for yes vs no, 0.67; 95% confidence interval [CI], 0.57‐0.80; P < .001) and DDFS (HR, 0.57; 95% CI, 0.44‐0.73; P <. 001). Time‐differing (time‐dependent) OPT was not (EFS; P = .45). OPT did not alter the incidence of visceral‐only metastasis (P = .31).CONCLUSIONSOral OPT, administered to postmenopausal breast cancer patients receiving adjuvant AI therapy, was associated with improved EFS and DDFS; the time of OPT initiation (a time‐dependent effect) did not affect the outcome. OPT did not alter the risk of visceral metastasis. Cancer 2017;123:2444–51. © 2017 American Cancer Society.