Breast cancer brain metastases BCBM are challenging complications that respond poorly to systemic therapy. The role of the blood—tumor barrier in limiting BCBM drug delivery and efficacy has been debated. Herein, we determined tissue and serum levels of capecitabine, its prodrug metabolites, and lapatinib in women with BCBM resected via medically indicated craniotomy.
Serum samples were capecitabine and efflux serially on the day of surgery. Drug concentrations were determined in serum and BCBM using liquid chromatography tandem mass spectrometry. Twelve patients were enrolled: The ratio of BCBM to serum was higher for 5-fluorouracil than for capecitabine. As for lapatinib, the median BCBM concentrations ranged from 1.
A high variability 0. This is the first study to demonstrate that capecitabine and lapatinib penetrate capecitabine and efflux a significant though variable degree in human BCBM. Drug delivery to BCBM is variable and in many cases appears partially limiting.
Elucidating mechanisms that limit drug concentration and innovative approaches to overcome limited capecitabine and efflux uptake will be important to improve clinical efficacy of these agents in the central nervous system, capecitabine and efflux. Breast cancer brain metastases BCBM are a devastating complication and portend a poor prognosis.
The normal blood—brain barrier excludes entry of drugs, and the degree to which it remains patent with a brain metastasis BMas the blood—tumor barrier BTBis debated. Very limited data exist on drug uptake in human BCBM. Capecitabine and lapatinib have demonstrated efficacy in clinical trials among patients with BCBM. Lapatinib is an oral small-molecule tyrosine kinase inhibitor TKI that reversibly targets epidermal growth factor receptor and human epidermal growth factor receptor 2 HER2.
The uptake of lapatinib in BCBM has been demonstrated in a preclinical cancer battle plan fromme and fromme Clinical evidence for BM uptake of drugs is scarce, and it is unclear whether preclinical models reflect human BM pharmacokinetics PK.
Prospective evaluation of BM drug uptake in humans is challenging but valuable for future drug development. In this study, we examined the uptake of capecitabine, its metabolites, and lapatinib in BCBM resected from patients undergoing medically indicated craniotomy. Written informed consent was obtained from all the patients prior to enrollment in accordance with the local institutional review board policies.
Patients with BCBM with a clinical indication for surgical resection providing informed consent enrolled in this clinical trial. Data collected included primary tumor characteristics, clinical information regarding BM lesions, prior therapy, and concurrent medication use.
On the day of surgery, serum was collected serially at the following time points—serum 1: The time points were selected to provide sufficiently detectable serum capecitabine and efflux based on the known half-lives of both agents. For those with multiple BCBM lesions, tissue was sampled from only a single lesion due to clinical feasibility.
Serum and BCBM samples were analyzed in duplicate for lapatinib or capecitabine and its prodrug metabolites: Serum was thawed on ice, capecitabine and efflux. Capecitabine and efflux specimens were homogenized with buffer by microsonication together with internal standards. Calibration curves were created using rat brain for brain standards and either the first serum draw sample for capecitabine or human serum for lapatinib. For capecitabine, samples were processed and analyzed using methods adapted from Salvador et al.
For lapatinib, capecitabine and efflux, samples were protein precipitated with 3 parts acetonitrile and centrifuged.
Conditions and mass transitions for analytes were optimized using the autotune feature of the software. Instrument control and data acquisition were performed using Analyst 1, capecitabine and efflux. Tissue blood volume was determined colorimetrically in BCBM samples from the absorbance of hemoglobin. Given the absence of previous data on drug uptake in human BCBM and likely heterogeneity among lesion characteristics and individuals, no formal sample size calculation was conducted.
Descriptive statistics were used to summarize and compare drug concentrations in serum, plasma, capecitabine and efflux, and tumor tissue. Drug levels within individual BCBM were presented as averages and ranges of determinations. A total of 12 patients consented and were enrolled in the study from October to February Of the 12 patients, 8 received capecitabine and 4 received lapatinib.
No patient received both drugs. All had surgical pathologic confirmation of the diagnosis of MBC from the craniotomy, capecitabine and efflux. The time courses of serum capecitabine and metabolite concentrations are presented for one representative patient C7 in Fig. Serum 5-FU concentration remained low throughout the experiment.
Median C max values were 9. For each patient, serum 4 is taken at the time the breast cancer BM is identified. Time course of serum capecitabine and metabolite concentrations. Example time course of capecitabine and metabolite serum concentrations patient C7. Six serum draws are plotted against time h. BCBM was identified at the 4th serum draw. BCBM were procured at 2. However, values varied markedly among patients.
Among the patients, BCBM values varied to fold. One patient C3 exhibited a very low serum AUC, suggesting poor gastrointestinal absorption, capecitabine and efflux. Marked variability was also noted for capecitabine and metabolite concentrations within individual BCBM specimens.
Thus, significant heterogeneity was also observed among patients. Interpatient variability in capecitabine and metabolite concentrations, capecitabine and efflux. Each patient is color coded. To assess the extent to which residual blood influenced measured BCBM concentration, BM concentration was expressed as a tumor-to-serum ratio, capecitabine and efflux, which was then compared with the measured BM blood volume. BCBM blood content averaged 0.
Median BCBM-to-serum ratio at the time of tumor sampling serum 4 equaled 0. This rate, converted to undiluted BCBM tissue, gave a rate coefficient of 0. Four patients received lapatinib daily for 2—5 days dr williams vitamins and natural supplements to craniotomy.
All patients had comparable average serum lapatinib concentrations at the time of tumor resection, ranging 2. Serum, intratumor, and interpatient BCBM lapatinib concentration variability. A Time course of serum lapatinib concentration for all 4 patients.
B Lapatinib concentrations in all patient BCBM, showing range, median, and quartile of concentration. BCBM concentrations differed greatly, ranging from 1. Intratumor sampling was conducted in all 4 cases. In one case 13 specimens were analyzed from a single BCBM sample exhibiting a 3-fold range of values.
Vascular correction did not significantly impact drug tumor-to-serum ratio, as demonstrated by the large BCBM-to-serum ratios. This is the first study to demonstrate uptake of capecitabine, its metabolites, and lapatinib in human BCBM.
Although capecitabine and lapatinib have been investigated for BCBM in clinical trials, no tissue-based evidence of drug penetration in BCBM has been reported for humans. The serum capecitabine PK after a single preoperative dose of capecitabine were generally comparable to previous studies in breast cancer patients with C capecitabine and efflux values of 7, capecitabine and efflux. Considerable variation was noted both among patients and within individual lesions, capecitabine and efflux.
This large variation in drug distribution in human BCBM is consistent with prior preclinical models using autoradiography and in vivo tissue measurement. Given a paucity of data on capecitabine PK in human tissue and the fact that a single preoperative dose was given due to feasibilitywe are unable to benchmark whether the observed capecitabine and efflux were at clinically relevant levels. However, our data have similarities to the published study of capecitabine PK from colorectal cancer patients who were treated with the drug for 5—7 days preoperatively.
In a colorectal tumor study, similar preferential conversion to 5-FU was noted in tumor tissue and thought to be due to differential expression of the conversion enzyme thymidine phosphorylase. Individual roles likely exist for plasma exposure, BTB permeability, active efflux transport, enzymatic conversion, and basic tumor cell sensitivity to 5-FU concentration. This is a hypothesis-generating finding that motivates further clinical study of dose and length of exposure for optimal BM drug uptake and efficacy.
A preclinical model demonstrated that a higher drug concentration in brain may be achieved with a higher dose of lapatinib administered systemically, capecitabine and efflux.
The ability to safely administer high-dose lapatinib has been demonstrated by use of a pulsatile dosing schedule in a phase I study. Despite its variability, in general, the ratio of BM to serum concentrations noted in our study was markedly higher than expected based on previously published murine studies with BM-to-plasma ratios ranging from 0.
However, given the differences in tumor type and lapatinib doses administered, it is difficult to compare the result to ours. In fact, addressing the role capecitabine and efflux drug transporters may be one way to enhance drug delivery.
For example, in preclinical studies, coadministration of efflux transporter inhibitors eg, elacridar has been shown to improve the brain-to-plasma ratio of small-molecule drugs. Given the modest response rate seen for lapatinib as a single agent in BCBM patients, further evaluation to improve its antitumor activity for BCBM is warranted now that we have demonstrated its ability to cross the BTB. Given that BCBM patients do not routinely undergo capecitabine and efflux resection, unlike those with primary brain tumors, and systemic therapy is commonly withheld prior to a major surgical intervention, evaluating drug concentration in BCBM tissue can be a challenge.
We were unable to evaluate pharmacodynamic endpoints due to lack of pretreatment control tissue. Furthermore, presurgical administration of drugs long enough to achieve therapeutically relevant or steady-state levels was impractical. Biopsy of BCBM prior to surgical resection to obtain control tissue and delaying capecitabine and efflux the medically necessary surgical procedure to ensure adequate steady-state levels of chemotherapeutic drugs preoperatively were limited by real-life constraints and safety concerns.
Nevertheless, we were able to achieve our primary goal of providing evidence for drug penetration through the BTB in human BM tissue. This is one of the largest studies evaluating drug concentration in BCBM reported to date. Evaluation of clinical evidence for drug uptake is important for future drug development for BM, and our study demonstrates the feasibility of such endeavors.
We were able to demonstrate BCBM uptake of capecitabine and lapatinib in mostly nonirradiated tissue, thus providing further support for use of systemic therapy in BCBM.
This may be especially relevant where these systemic agents are evaluated in management of BCBM prior to radiation therapy to possibly avoid or delay whole-brain radiotherapy, as suggested by a recent phase II trial of capecitabine and lapatinib combination therapy in patients with BCBM. High-dose pulsatile lapatinib is safe to administer 24 and may offer an approach that could maximize CNS efficacy.