Background: Proton-pump-inhibitors (PPIs) are frequently prescribed for the management of anticancer drug-related gastrointestinal symptoms. Palbociclib is a weak base with pH-dependent solubility and potential drug-drug interaction at the absorption level may affect clinical pharmacokinetics. The current study was aimed at investigating the effect of co-administration of PPIs and palbociclib on progression-free survival (PFS) in metastatic breast cancer (mBC) patients. Patients and methods: Patients affected by estrogen receptor-positive, human epidermal growth factor receptor 2negative mBC, who were candidates for first-line treatment with palbociclib, were enrolled in this retrospective observational study. Patients were defined as 'no concomitant PPIs' if no PPIs were administered during palbociclib treatment, and as 'concomitant PPIs' if the administration of PPIs covered the entire or not less than two-thirds of treatment with palbociclib. All clinical interventions were made according to clinical practice. Results: A total of 112 patients were enrolled in the study; 56 belonged to the 'no concomitant PPIs' group and 56 to the 'concomitant PPIs' group. Seventy-one patients were endocrine-sensitive and received palbociclib and letrozole, and 43 were endocrine-resistant and were treated with palbociclib and fulvestrant. The most prescribed PPI was lansoprazole. Patients taking PPIs had a shorter PFS than those taking palbociclib and endocrine therapy alone (14.0 versus 37.9 months, P < 0.0001). Multivariate analysis confirmed concomitant PPIs as the only independent predictive factor for shorter PFS (P ¼ 0.0002). PFS was significantly longer in estrogen-sensitive mBC with no concomitant PPIs compared with patients taking PPIs or estrogen-resistant patients, with and without PPIs (P < 0.0001). No correlation with adverse events was found when considering grade >2 hematological toxicities [Common Terminology Criteria for Adverse Events (CTCAE) scale]. Conclusions: The present study demonstrates that concomitant use of PPIs in mBC patients treated with palbociclib has a detrimental effect on PFS. Therefore, it is recommended to prescribe PPIs with caution in these patients, strictly adhering to the indications in the summary of product characteristics (RCP).

Bevacizumab in combination with taxanes in HER2‐negative metastatic breast cancer (MBC) patients has shown improved progression‐free survival (PFS), despite the lack of clear overall survival (OS) benefit. We performed a retrospective analysis to evaluate the impact of paclitaxel‐bevacizumab and of maintenance therapy with bevacizumab (BM) and endocrine therapy (ET) in the real‐world practice. We identified 314 HER2‐negative MBC patients treated in 12 cancer centers. Overall, the median PFS and OS were 14 and 40 months, respectively. Among the 254 patients potentially eligible for BM, 183 received BM after paclitaxel discontinuation until progression/toxicity. PFS and OS were improved in patients who had received BM in comparison with those potentially eligible but who did not receive BM (P< 0.0001 and P = 0.001, respectively). Results were confirmed when adjusting for propensity score. Among the 216 hormone‐receptor positive patients eligible for BM, a more favorable PFS and OS were observed when maintenance ET was administered (P < 0.0001). Multivariate analysis showed that PS, BM, number of disease sites and maintenance ET were related to PFS, while response and maintenance ET were related to OS. In hormone‐receptor positive patients, BM produced a significant PFS and a trend towards OS benefit only in absence of maintenance ET (P = 0.0007 and P = 0.06, respectively). In the triple‐negative subgroup, we observed a trend towards a better OS for patients who received BM (P = 0.06), without differences in PFS (P = 0.21). Our results confirmed the efficacy of first‐line paclitaxel‐bevacizumab in real‐world practice; both BM and maintenance ET significantly improved PFS and OS compared to no maintenance therapies. J. Cell. Physiol. 232: 1571–1578, 2017. © 2016 Wiley Periodicals, Inc.

CDK4/6 inhibitors (CDK4/6i) are recommended in patients with estrogen receptor (ER)-positive, HER2-negative advanced breast cancer (ABC). Up to now, no prognostic biomarkers have been identified in this setting. We retrospectively analyzed the expression of progesterone receptor (PR) and Ki67, assessed by immunohistochemistry, in 71 ABC patients treated with CDK4/6i and analyzed the impact of these markers on progression-free survival (PFS). The majority of patients 63/71 (88.7%) received palbociclib, 4 (5.6%) received ribociclib, and 4 (5.6%) received abemaciclib. A higher median value of Ki67 was observed in cases undergoing second-line treatment (p = 0.047), whereas the luminal B subtype was more prevalent (p = 0.005). In the univariate analysis of the first-line setting, luminal A subtype showed a trend towards a correlation with a longer PFS (p = 0.053). A higher continuous Ki67 value led to a significantly shorter PFS. When the interaction between pathological characteristics and line of treatment was considered, luminal B subtype showed a significantly (p = 0.043) worse outcome (Hazard Ratio (HR) 2.84; 1.03–7.82 95% Confidence Interval (CI)). PFS in patients undergoing endocrine therapy plus CDK4/6i was inversely correlated with Ki67 expression but not with PR, suggesting that tumor proliferation has a greater impact on cell cycle inhibitors combined with endocrine therapy than PR expression.