A lower apatinib dose provides equivalent efficacy and reduced toxicity: A phase II, single-arm study of apatinib and oral etoposide in metastatic breast cancer

Introduction : The effectiveness of antiangiogenic drugs in metastatic breast cancer is still unclear. Apatinib is a small tyrosine kinase inhibitor that inhibits vascular endothelial growth factor receptor 2 (VEGFR-2). We performed this clinical trial to evaluate the efficacy and safety of apatinib and oral etoposide in patients with HER2-negative locally advanced or metastatic breast cancer(MBC). Methods : Patients with HER2-negative MBC previously treated with anthracycline and taxanes and failed ≥1 prior chemotherapy regimens were recruited. The starting dose of apatinib was 500 mg and 425 mg in patients with Eastern Cooperative Oncology Group (ECOG) scores of 0-1 and 2, respectively. The etoposide capsules were given at 50 mg/m 2 on days 1 to 10 for 21 days. The primary end point was progression-free survival (PFS) which is assessed every 6 weeks (RECIST v1.1). Secondary end points included objective response rate (ORR), disease control rate (DCR), overall survival (OS), and safety. Results : Thirty-one eligible patients were enrolled. The median follow-up time was 11 months. The median PFS for all patients was 6.93 months (95% confidence interval (CI), 5.97–7.90), and 6.93 months(95% CI 5.27-8.60) and 6.56 months (95% CI 1.41-11.73) for patients with apatinib 425mg and 500mg once daily, respectively. The ORR was 35.5% (11/31). The DCR was 87.1% (27/31). The median OS was 20.37 months (95% CI, 11.39– 29.34). The median PFS of patients who had hypertension and proteinuria was longer than that for those without hypertension and proteinuria. The most common grade 3/4 treatment-related adverse events(AE) were hypertension (12/31, 38.71%), fatigue (3/31, 9.68%), thrombocytopenia (3/31, 9.68%). Conclusion : Apatinib combined with etoposide capsules is effective and tolerable pretreated, metastatic HER2-negative breast A lower apatinib and toxicity.


Introduction
Breast cancer is the most common malignant tumour and the second leading cause of cancer-related death in women worldwide [1]. The median survival time of patients after metastasis is 9 months to 3 years [2,3]. In China, HER2-negative breast cancer accounts for approximately 65% of all breast cancers [4]. which has no specific targeted drug for this type of breast cancer.The treatment for HER2-negative metastatic breast cancer, especially in second and later lines, requires more new drugs or combined regimens.
Tumour angiogenesis is closely related to tumour growth and metastasis,, and antiangiogenic strategies are some of the most important strategies for advanced breast cancer. Bevacizumab has shown some efficacy in the treatment of metastatic breast cancer, and chemotherapy as a first-line and second-line treatment for HER2-negative advanced breast cancer has significantly extended median progression-free survival (PFS) [5,6]. Preclinical studies have shown that antiangiogenic drugs combined with chemotherapy can improve the efficacy of chemotherapeutic drugs and reverse the resistance of tumour cells [7-9], which indicates this combination therapy may be a potential treatment.
Apatinib is an oral small molecule tyrosine kinase inhibitor(TKI) that selectively inhibits vascular endothelial growth factor receptor 2(VEGFR2), which exhibits some efficacy in in triple-negative and non-triple-negative metastastic breast cancer by monotherapy [10,11]. Oral etoposide is one of the options for patients with metastatic breast cancer, achieving a median PFS of 5 months and a median overall survival(OS) of 16 months with manageable toxicity [12]. We suppose that apatinib and etoposide capsules are effective and tolerablein patients with breast cancer. Therefore, this study aimed to explore the efficacy and safety of apatinib combined with etoposide capsules in pretreated metastatic HER2-negative breast cancerpatients from the NCT03535961 trial.

Study designand participants
Patients included in the trial were 18-to-75-year-old females with histologically or cytologically diagnosed HER2-negative locally advanced or metastatic breast cancerwho received at least one regimen of chemotherapy after metastasis, includinga taxane and anthracycline, with an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2. The patients had measurable lesions as defined by the Response Evaluation Criteria In Solid Tumors (RECIST) 1.1.Patients who had previously received small molecule antiangiogenic TKIs and patients with uncontrolled hypertension were excluded from the trial.
The study was approved by the Ethics Committee of the Cancer Hospital of the Chinese Academy of Medical Sciencesandperformed in accordance with the Declaration of Helsinki.
Every patient signed written informed consent.

Procedures
The starting dose of apatinib was 500 mg and 425 mg in patients with ECOG scores of 0-1 and 2, respectively,and apatinib was taken orally each day. The etoposide capsules were given at 50mg/m 2 on days 1 to 10 for 21 daysper cycle.The tumour response was evaluated every 6 weeks according to RECIST v1.1 until the disease progressed or intolerable adverse reactions occurred. Blood pressure was monitored twice a day for the first 3 weeks and at least once a day after blood pressure stabilized. Routine blood and urine tests were performed weekly, physical examinations were performed every 3 weeks, liver and kidney functions were monitored, and electrocardiograms and tumour marker tests were performed every 6 weeks.
Dosage adjustment was recommended if haematological toxicity above grade 3 or nonhematological toxicity above grade 2 (except for hair loss) occurred, including withdrawal and reduction.
The first reduced dose was 425 mg/day and the second reduced dose was 250 mg/day for patients with an apatinib starting dose of 500 mg. Patients with a starting dose of 425 mg were adjusted to 250 mg/day first and 250 mg every other day second. The first and second adjustments of etoposide dose were 35 mg/m 2 on d1-10 and 35 mg/m 2 on d1-7, respectively. When adverse reactions of grade 3 and above occurred, dose adjustments were made according to the protocol. When adverse reactions were of grade 2 or below, researchers were allowed to adjust the doses according to the specific conditions. Adverse events were graded using Common Terminology Criteria for Adverse Events (CTCAE) 4.0.

Outcome
The primary endpoint of this study was progression-free survival(PFS), and the secondary endpoints were overall survival(OS), safety, objective response rate(ORR) and disease control rate(DCR). The PFS duration was defined as the interval between the initiation of treatment and disease progression. The overall survival duration was defined as the interval between the initiation of treatment and death for any reason.

Statistical analysis
Simon's two-stage design with a one-sided α = 0.05 and 80% test efficiency was used to determine the number of patients that needed to be enrolled [13]. Previous studies have shown that the ORR of apatinib monotherapy for patients with metastatic non-triplenegative breast cancer is 16.7%, and the ORR of etoposide capsule monotherapy is 21.3% [10,14]. We estimated thatthe response rate of apatinib combined with etoposide was 40%. Under such conditions, at least 2 of 10 patients needed to respond for the trial to move to the next stage. Another 21 patients needed to be recruited in the second stage, for a total of 31 patients. If 10 or more patients responded to this therapy, the regimen would be considered a success.
Patients receiving ≥1 cycle of apatinib were included for survival and safety analysis. PFS and OS were estimated based on a Kaplan-Meier curve. A log-rank test was used to compare the mPFS in different subgroups. Factors with p <0.1 in the Kaplan-Meier single factor analysis were included in the Cox regression model for analysis. SPSS 23.0 and GraphPad Prism 7.0 were used for data analysis.

Results
Thirty-four patients were screened from May 2017 to May 2019. Two patients withdrew their informed consent. Because 1 patient had only bone metastases and no measurable lesions, 31 patients were included in the final survival and safety analyses (Fig. 1). The basic clinicopathologicaland median PFS data are shown in Table 1.
The results of the subgroup analysis are shown in Table 2. Factors with p <0.1 in the univariate analysis were included in the multivariate analysis, and the HR of hormone receptor status on mPFS was 2.354 (95% CI 0.903-6.135; p = 0.08), which reach a marginal statistical significance.The results of thesubgroup analysis are shown in Table 1.
As of the date of data analysis, 17 patients were still alive, with a median OS of 20.37 months (95% CI 11.39-29.34).

Safety
Most of the adverse reactions were mild to moderate (Table 3)

Discussion
This study first explored the application of apatinib combined with etoposide capsules in locally advanced and metastatic HER2-negative breast cancer. In this study, the ORR was 35.5%, the median PFS was 6.93 months, and the median OS was 20.37 months.
The median PFS associated withapatinib monotherapy for metastatic non-triple-negative breast cancer and triple-negative breast cancer was 4.0 months (95% CI 2.8-5.2) and 3.3 months(95% CI 1.7-5.0), respectively [10,11]. In previous studies, the median PFS associated with etoposide monotherapy for advanced breast cancer was between 2.6 and 5.0 months, and the median OS was between 11.0 and 24.0 months [12, [14][15][16]. Although this study has limitations in comparison with other studies directly, it can be seen from the data that the median PFS and median OS were longer in patients who received apatinib and etoposide capsules than in those who received either one of the two drugs alone.
Antiangiogenic drugs combined with chemotherapy increased the PFS in locally advanced and metastatic HER2-negative breast cancer after second-line treatment. The results of this study are equivalent to or even better thanthose of similar studies. In the RIBBON-2 study, the median PFS was 7.2 months with standard chemotherapy regimens combined with bevacizumab for the second-line treatment of patients with metastatic HER2-negative breast cancer [6]. Treatment with gemcitabine or capecitabine combined with sorafenib yielded an median PFS of 3.4 months as a first-line treatment after metastasis in breast cancer patients [17]. Most of the antiangiogenic drugs and chemotherapy drugs tested so far have obtained a small benefit in terms of the median PFS, but no clinical benefit of OS has been seen yet. However, the occurrence of adverse events is greatly increased, which has substantially limited the use of such regimens in clinical practice. In this study, we achieved a median PFS of 6.93 months and a median OS of 20.37 months. The response was comparable to or even better than that insimilar studies, and the adverse reactions were manageable that no bleeding or febrile neutropenia occurred. At the same time, Chinese scholars have shown that apatinib combined with etoposide capsules has achieved good results in advanced ovarian cancer,in which the median PFS was 8.1 months,the ORR reached 54% (19/35), and the toxicities were well tolerated [18]. In addition, apatinib and etoposide capsules are administered orally, which reduces the durationand the cost of hospitalization, so this combination is suggested to be one of the treatment options for patients with locally advanced and metastatic breast cancer.
In this study, different starting doses of apatinib were given on the basis of the patient's ECOG score. There was no significant difference in the median PFS (6.56 months vs 6.93 months,p = 0.56) in the 500 mg group and 425 mg group, but fewer adverse events were observed in the 425 mg group. Therefore, we recommend 425 mg apatinib as the starting dose for combination therapy. In addition, there was no significant difference in the median PFS between patients treated in the second-line, third-line, or further in this study protocol (p = 0.82), indicating that apatinib and etoposide capsules can be used in patients who progress after multiline treatment.
In previous studies, the single dose of apatinib was 500-850 mg once per day. We observed in our clinical practice that some patients were intolerant to the 500 mg dose in the combination strategy of chemotherapy and apatinib. Therefore, we administered 500 mg once daily to patients with superior physical status and 425 mg once daily to patients with relatively worse status. For etoposide capsules, previous clinical research has recommended 50 mg-60 mg/m 2 for 14 consecutive days or 10 days in a 21-day cycle.
We learned from clinical experience that most patients were unable to tolerate the dosage. Considering that our research protocol used a combination treatment, we choose the 50 mg/m2/d on d1-10 and a 21-day cycle as the starting dose for etoposide.
Nonetheless, 38.7% of apatinib was taken in reduced doses due to intolerable adverse reactions.
It is worth noting that this study showed that the occurrence of hypertension and proteinuria may be a positive predictor for efficacy. Previous studies have shown that the occurrence of adverse reactions such as hypertension and proteinuria may be one of the predictive markers for the efficacy of antiangiogenic drugs. In a clinical study of sunitinib in advanced renal cell carcinoma [19], patients with hypertension had longer PFS and OS than patients without hypertension (median OS 41.6 versus 16.4 months, p < 0.0001, medianPFS 12.9 versus 5.6 months, p < 0.0001, respectively). A cohort study of patients with metastatic gastric cancer treated with apatinib showed that the mPFS was prolonged   Figure 1 Clinical profile.

Figure 2
Waterfall plot for the best percentage change in target lesion size Kaplan-Meier graph for progression-free survival in patients who had hypertension(A) and proteinuria(B) (n=31)