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Purpose: Chemotherapy-related amenorrhea (CRA) is a surrogate for ovarian toxicity and associated risk of infertility and premature menopause. Here, we compare CRA rate with paclitaxel (T)-trastuzumab (H) to that with ado-trastuzumab emtansine (T-DM1)., Methods: Patients with T1N0 HER2 + early-stage breast cancer (eBC) enrolled on the ATEMPT trial and were randomized 3:1 to T-DM1 3.6 mg/kg IV every (q) 3 weeks (w) × 17 vs. T 80 mg/m 2 with H IV qw × 12 (4 mg/kg load → 2 mg/kg), followed by H (6 mg/kg IV q3w × 13). Enrollees who self-reported as premenopausal were asked to complete menstrual surveys at baseline and every 6-12 months for 60 months. 18-month CRA (no periods reported during prior 6 months on 18-month survey) was the primary endpoint of this analysis., Results: Of 512 ATEMPT enrollees, 123 who began protocol therapy and answered baseline and at least one follow-up menstrual survey were premenopausal at enrollment. 76 had menstrual data available at 18 months without having received a gonadotropin-releasing hormone agonist or undergone hysterectomy and/or oophorectomy. Median age was 45 (range 23-53) among 18 who had received TH and 46 (range 34-54) among 58 who had received T-DM1. The 18-month rate of CRA was 50% after TH and 24% after T-DM1 (p = 0.045)., Conclusion: Amenorrhea at 18 months was less likely in recipients of adjuvant T-DM1 than TH. Future studies are needed to understand how T-DM1 impacts risk of infertility and permanent menopause, and to assess amenorrhea rates when T-DM1 is administered after standard HER2-directed chemotherapy regimens., (© 2021. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

Studies on well characterized, large populations of estrogen receptor (ER)/progesterone receptor (PgR)/HER2-negative [triple-negative (TN)] breast cancer (BC) patients with long-term follow-up are lacking. In this study, we analyze clinical outcomes of TN BC and implications of epidermal growth factor receptor (EGFR) expression. Clinical and biologic features, time to first recurrence (TTFR), and overall survival (OS) were compared in 253 TN versus 1,036 ER positive, PgR positive, HER2-negative [estrogen-driven (ED)] BC. Compared to ED, TN tumors were larger (p = 0.02), more proliferative (high S-phase 54 vs. 17 %, p < 0.0001), more aneuploid (64 vs. 43 %, p < 0.0001) and more likely EGFR positive (≥10 fmol/mg by radioligand-binding assay, 49 vs. 7 %, p < 0.0001). Among TN, EGFR-positive BC were larger (p = 0.0018), more proliferative (p < 0.0001), and more aneuploid, (p < 0.0001) than EGFR-negative BC. Adjuvant-treated TN patients had shorter TTFR (p = 0.0003), and OS (p = 0.0017), than ED patients. However, in untreated patients, no differences in TTFR and OS were observed at 8 years median follow-up. Among TN patients, EGFR expression was not associated with worse outcome. TN tumors have a worse outcome in systemically treated patients but not in untreated patients. EGFR expression, does not predict for worse long-term survival.

We studied resistance to endocrine and HER2-targeted therapies using a xenograft model of estrogen receptor positive (ER)/HER2-overexpressing breast cancer. Here, we report a novel phenotype of drug resistance in this model. MCF7/HER2-18 xenografts were treated with endocrine therapy alone or in combination with lapatinib and trastuzumab (LT) to inhibit HER2. Archival tumor tissues were stained with hematoxylin and eosin and with mucicarmine. RNA extracted from tumors at early time points and late after acquired resistance were analyzed for mucin4 (MUC4) expression by microarray and quantitative reverse transcriptase-PCR. Protein expression of the MUC4, ER, and HER2 signaling pathways was measured by immunohistochemistry and western blotting. The combination of the potent anti-HER2 regimen LT with either tamoxifen (Tam + LT) or estrogen deprivation (ED + LT) can cause complete eradication of ER-positive/HER2-overexpressing tumors in mice. Tumors developing resistance to this combination, as well as those acquiring resistance to endocrine therapy alone, exhibited a distinct histological and molecular phenotype-a striking increase in mucin-filled vacuoles and upregulation of several mucins including MUC4. At the onset of resistance, MUC4 mRNA and protein were increased. These tumors also showed upregulation and reactivation of HER2 signaling, while losing ER protein and the estrogen-regulated gene progesterone receptor. Mucins are upregulated in a preclinical model of ER-positive/HER2-overexpressing breast cancer as resistance develops to the combination of endocrine and anti-HER2 therapy. These mucin-rich tumors reactivate the HER2 pathway and shift their molecular phenotype to become more ER-negative/HER2-positive.

Endocrine therapy in patients with breast cancer can be limited by the problem of resistance. Preclinical studies suggest that complete blockade of the estrogen receptor (ER) combined with inhibition of the epidermal growth factor receptor can overcome endocrine resistance. We tested this hypothesis in a phase II neoadjuvant trial of anastrozole and fulvestrant combined with gefitinib in postmenopausal women with newly diagnosed ER-positive breast cancer. After a baseline tumor core biopsy, patients were randomized to receive anastrozole and fulvestrant or anastrozole, fulvestrant, and gefitinib (AFG) for 3 weeks. After a second biopsy at 3 weeks, all patients received AFG for 4 months and surgery was done if the tumor was operable. The primary endpoint was best clinical response by RECIST criteria and secondary endpoints were toxicity and change in biomarkers. The study closed after 15 patients were enrolled because of slow accrual. Median patient age was 67 years and median clinical tumor size was 7 cm. Four patients had metastatic disease present. Three patients withdrew before response was assessed. In the remaining 12 patients, there were two complete clinical responses (17%), three partial responses (25%), five had stable disease (41%), and two (17%) had progressive disease. Most common adverse events were rash in four patients, diarrhea in four, joint symptoms in three, and abnormal liver function tests in three. There were no grade 4 toxicities and all toxicities were reversible. At 3 weeks, cell proliferation as measured by Ki-67 was significantly reduced in the AFG group (P value = 0.01), with a parallel reduction in the expression of the Cyclin D1 (P value = 0.02). RNA microarray data showed a corresponding decrease in the expression of cell cycle genes. These results suggest that AFG was an effective neoadjuvant therapy and consistently reduced proliferation in ER-positive tumors.

We hypothesized that a subset of sporadic triple negative (TN) breast cancer patients whose tumors have defective DNA repair similar to BRCA1-associated tumors are more likely to exhibit up-regulation of DNA repair-related genes, anthracycline-sensitivity, and taxane-resistance. We derived a defective DNA repair gene expression signature of 334 genes by applying a previously published BRCA1-associated expression pattern to three datasets of sporadic TN breast cancers. We confirmed a subset of 69 of the most differentially expressed genes by quantitative RT-PCR, using a low density custom array (LDA). Next, we tested the association of this DNA repair microarray signature expression with pathologic response in neoadjuvant anthracycline trials of FEC (n = 50) and AC (n = 16), or taxane-based TET chemotherapy (n = 39). Finally, we collected paraffin-fixed, formalin-embedded biopsies from TN patients who had received neoadjuvant AC (n = 28), and tested the utility of the LDA to discriminate response. Correlation between RNA expression measured by the microarrays and 69-gene LDA was ascertained. This defective DNA repair microarray gene expression pattern was significantly associated with anthracycline response and taxane resistance, with the area under the ordinary receiver operating characteristic curve (AUC) of 0.61 (95% CI = 0.45-0.77), and 0.65 (95% CI = 0.46-0.85), respectively. From the FFPE samples, the 69-gene LDA could discriminate AC responders, with AUC of 0.79 (95% CI = 0.59-0.98). In conclusion, a promising defective DNA repair gene expression signature appears to differentiate TN breast cancers that are sensitive to anthracyclines and resistant to taxane-based chemotherapy, and should be tested in clinical trials with other DNA-damaging agents and PARP-1 inhibitors.