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Purpose Taxane-based chemotherapy is the primary treatment for premenopausal breast cancer. Although being inconsistent, research suggests that variant alleles alter pharmacokinetics through reduced function of OATP transporters (limiting hepatic uptake), CYP-450 enzymes (hampering drug metabolism), and ABC transporters (decreasing clearance). Reduced function of DNA repair enzymes may hamper effectiveness through dose-limiting toxicities. We investigated whether single-nucleotide polymorphisms (SNPs) were associated with breast cancer recurrence or mortality in premenopausal women diagnosed with breast cancer. Methods We conducted a population-based cohort study of premenopausal women diagnosed with non-distant metastatic breast cancer in Denmark during 2007‒2011, when guidelines recommended adjuvant combination chemotherapy (taxanes, anthracyclines, and cyclophosphamide). Using archived formalin-fixed paraffin-embedded primary tumor tissue, we genotyped 26 SNPs using TaqMan assays. Danish health registries provided data on breast cancer recurrence (through September 25, 2017) and death (through December 31, 2019). We fit Cox regression models to calculate crude hazard ratios (HRs) and 95% confidence intervals (CIs) for recurrence and mortality across genotypes. Results Among 2,262 women, 249 experienced recurrence (cumulative incidence: 13%) and 259 died (cumulative incidence: 16%) during follow-up (median 7.0 and 10.1 years, respectively). Mortality was increased in variant carriers of GSTP1 rs1138272 (HR: 1.30, 95% CI 0.95–1.78) and CYP3A rs10273424 (HR: 1.33, 95% CI 0.98–1.81). SLCO1B1 rs2306283 (encoding OATP1B1) variant carriers had decreased recurrence (HR: 0.82, 95% CI 0.64–1.07) and mortality (HR: 0.77, 95% CI 0.60–0.98). Conclusion Docetaxel effectiveness was influenced by SNPs in GSTP1, CYP3A, and SLCO1B1 in premenopausal women with non-distant metastatic breast cancer, likely related to altered docetaxel pharmacokinetics. These SNPs may help determine individual benefit from taxane-based chemotherapy.

Standard adjuvant chemotherapy for HER2-negative breast cancer consists generally in an anthracycline and taxane-based regimen (A+T). The TC (docetaxel and cyclophosphamide) regimen arises as a potential alternative, although individual randomized controlled trials (RCTs) could not demonstrate the non-inferiority of TC over A+T. This is a systematic review and meta-analysis of RCTs comparing 6 cycles of TC versus sequential A+T in the adjuvant treatment of HER2-negative breast cancer. A systematic literature search was performed to identify RCTs comparing TC versus A+T. Disease-free survival (DFS) and overall survival (OS) were assessed. Subgroup analyses of DFS according to hormone receptor status, lymph node involvement, and menopausal status were performed. Hazard ratios (HRs) and 95% confidence intervals (CI) for DFS and OS were extracted from each trial, and a pooled analysis was conducted using the random-effect model. The Higgins’ I-Squared Test was used to quantify heterogeneity. Seven RCTs were included (12,741 patients). Overall, no difference was observed between TC and A+T in DFS (HR 1.08, 95% CI 0.96–1.20) and OS (HR 1.05; 95% CI 0.90–1.22). A trend favoring A+T was observed in hormone receptor-negative (HR 1.12, 95% CI 0.93–1.34) and N2 patients (HR 1.25; 95% CI 0.82–1.90). Emesis/vomiting, mucositis, thrombocytopenia and sensory neuropathy were significantly more frequent with A+T. As adjuvant treatment of HER2-negative breast cancer, sequential A+T regimen was associated with increased risk of toxicities and no clear survival benefit as compared to 6 cycles of TC. Higher-risk patients may benefit the most from A+T, whilst TC may be an efficacious and less toxic alternative for lower-risk patients.

Taxanes are a standard first-line option for metastatic breast cancer (MBC), but their utility may be limited by primary or acquired resistance. New microtubule-targeting agents have been developed to overcome taxane resistance and provide additional options for improving patient outcomes. This article reviews these alternative microtubule-targeting agents and their potential clinical benefits for MBC patients. Relevant clinical data were compiled through searches within PubMed and congress abstract databases. Ixabepilone, a novel microtubule-stabilizing drug approved by the US Food and Drug Administration (FDA), has proven efficacy across multiple lines of therapy, including patients with taxane-resistant/refractory disease. In phase III trials, ixabepilone plus capecitabine significantly improved progression-free survival compared with capecitabine alone in anthracycline/taxane-pretreated patients. Eribulin has recently been approved by the FDA and by the European Medicines Agency for the treatment of patients with MBC who have received at least two prior chemotherapy regimens for late-stage disease. In a phase III trial, eribulin extended overall survival compared with the physician’s treatment choice in heavily pretreated MBC patients. In addition, several investigational microtubule-targeting agents may have therapeutic potential in MBC. The development of new microtubule-targeting agents helps to address the need for additional effective regimens for patients progressing after standard treatment with anthracycline- and taxane-containing regimens.

The aim of this study is to test the hypothesis that antiangiogenic treatment with sunitinib consolidation can prolong remissions induced by taxane-based chemotherapy in women with metastatic breast cancer. The method involves a two-arm open-label (2:1 randomization) multicenter, randomized phase II trial evaluating the efficacy of sunitinib (arm A) versus no therapy (arm B) in patients with HER-2-negative metastatic breast cancer who achieved an objective response to taxane-based chemotherapy. The results of this study indicates that the primary endpoint of progression-free survival (PFS) > or =5 months was achieved in 10 of 36 patients (28%) in arm A and 4 of 19 patients (21%) in arm B. The median PFS was 2.8 and 3.1 months, respectively. A protocol amendment to the sunitinib dosing schedule was made because 53% (17/32) of patients treated at a starting dose of 50 mg (4 weeks on/2 weeks off) required dose reduction. Changing the starting dose to sunitinib 37.5 mg continuously resulted in dose reductions in 44% (7/16) of patients. Grades III-IV toxicity occurred in 69% of patients in arm A (fatigue 31%, musculoskeletal pain 11%, neutropenia and thrombopenia 8%) and 11% in arm B. The proof-of-principle study does not confirm the hypothesis that sunitinib consolidation therapy can lead to a predefined clinically relevant proportion of patients with PFS of > or =5 months after an objective response to taxanes. Furthermore, toxicity was significant.

Nanoparticle albumin-bound paclitaxel (nab-paclitaxel) has demonstrated clinical benefit in metastatic breast cancer (MBC) in a randomized phase III trial versus paclitaxel (CA012; N = 454) and in a randomized phase II trial versus docetaxel (CA024; N = 300). This retrospective analysis examines whether patients with poor prognostic factors demonstrate similar outcomes to the intent-to-treat (ITT) populations in these trials. This retrospective analysis evaluated the efficacy and safety of previously untreated patients with MBC with the following poor prognostic factors: visceral dominant metastases and short disease-free interval (DFI; ≤2 years). In CA012 (n = 186 first-line patients), nab-paclitaxel demonstrated a significantly higher overall response rate (ORR) versus paclitaxel in patients with visceral dominant metastases (42 vs. 23 %; P = 0.022), whereas the higher ORR for nab-paclitaxel in patients with a short DFI (43 vs. 33 %; P = NS) was not statistically significant. In CA024, a significantly higher ORR for nab-paclitaxel 150 mg/m2 versus docetaxel was observed in patients with visceral dominant metastases (76 vs. 37 %; P