1. Introduction

Breast cancer is one of the most common malignancies among women, and poses a serious threat to their health.[1] The incidence of breast cancer has been increasing over the decades, with more than 1 million cases every year across the world.[2] In Europe, North America, Australia and Latin American states, breast cancer has become the leading incidence cancer of malignant tumors in women.[3,4] Increasing attention has been paid to the diagnosis and treatment of human epidermal growth factor receptor-2 -positive (HER2-positive) breast cancer in the research field of breast cancer, The anti-HER2-targeted therapy has become the recognized standard treatment for patients with HER2-positive breast cancer. In recent years, with the application of the first anti-HER-targeted therapy (i.e., trastuzumab), the survival rate of patients with HER2-positive breast cancer and gastric cancer has improved significantly.[5,6] However, with disease progression and tumor metastasis, trastuzumab has limited ability for disease control, with cardiac toxicity and drug resistance.[7,8] In June 2012, the US Food and Drug Administration (FDA) approved pertuzumab combined with trastuzumab and chemotherapy as the first-line treatment for patients with metastatic HER2-positive breast cancer.[9]Pertuzumab can bind the dimerization domain of HER2, suppress the heterodimerization of HER2 with other HER receptors, and also cooperate with trastuzumab to inhibit tumor progression.[10] According to the American Society of Clinical Oncology guidelines, for patients with high-risk, early stage HER2-positive breast cancer, clinicians could add adjuvant pertuzumab persisting for 1 year based on the combination of trastuzumab and chemotherapy.[11] However, studies have shown that pertuzumab has adverse effects.[12,13] The present meta-analysis aimed to assess the efficacy and safety of treatment with and without pertuzumab for HER2-positive breast cancer.

2. Data and methods 2.1. Inclusion criteria 2.1.1. Study design.

Randomized controlled trial (RCT) of treatment with pertuzumab for HER2-positive breast cancer, whether blind or not.

2.1.2. Study subjects. ① The pathological diagnosis was HER2-positive breast cancer. ② ≥18 years old. ③ According to Eastern Cooperative Oncology Group, the physical performance status should be 0 or 1 (0 represents fully active and capable of all activities freely; 1 represents limited physical activity but suffers from ambulatory and mild or sedentary work).[14] ④ Left ventricular ejection fraction ≥ 50%. 2.1.3. Interventions.

The treatment of experimental group is treatment in combination with pertuzumab, while the treatment of control group is treatment in combination without pertuzumab. All the treatments of both group are not limited by the dosage and course of treatment.

2.1.4. Outcome indicators.

Efficacy outcomes: progression-free survival (PFS) and overall survival (OS). Safety outcomes: incidence of serious adverse events (SAEs), incidence of grade ≥ 3 adverse events (AEs) and incidence of common AEs. The adverse effects include: neutropenia, diarrhea, anemia, febrile neutropenia, alopecia, nausea, and rash. Grade refers to the severity of the AE. The Common Terminology Criteria for Adverse Events (CTCAE) Version 4.0 displays Grades 1 through 5 with unique clinical descriptions of severity for each AE based on the general guideline.

2.2. Exclusion criteria ① The clinical trial was not completed. ② The purpose of the trials were inconsistent with our study’s. ③ The studies reported non-randomized control trials, such as observational studies, retrospective studies, etc. ④ Abstracts only without full text, duplicate publications or incomplete data. ⑤ The review, reviews, expert views, experience summaries, individual cases, animal experiments and other nonclinical trial studies. 2.3. Search strategy

Studies were identified by searching PubMed (January 1966 to July 2022), EMbase (January 1974 to July 2022), ClinicalTrials.gov, Cochrane Library, and web of science, using medical subject headings (MeSH) and the keywords: “Breast Cancer,” “Breast Neoplasm (s),” “BreastTumor (s),” “Mammary Neoplasm (s),” “Mammary Cancer (s),” “Pertuzumab,” “Perjeta,” “HER2,” “c-erbB-2 Genes” and “HER2 Gene,” and so on. In the light of the characteristics of the different databases, corresponding search strategies were used.

2.4. Data extraction and quality evaluation

Literature screening and data extraction were independently conducted by 2 authors. The articles that lacked original data or did not meet the inclusion criteria were excluded. If more than 1 publication reported results from the same trial or included the same or overlapping patient cohorts, only the outcomes from the largest and most recent publications were included.[15] The following information was recorded from eligible studies: basic information of the studies including title, first author’s name, year of publication, publishing journal, etc; The basic characteristics of the studies, including the number of cases and age; Interventions; Primary outcome indicators; The risk assessment of bias.

The risk of bias in the included studies was evaluated using the RCT bias assessment tool, that is using the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0 (https://training.cochrane.org/handbook):[16,17] Random sequence generation (selection bias); Allocation concealment (selection bias); Blinding of participants and personnel (performance bias); Blinding of outcome assessment (detection bias); Incomplete outcome data (attrition bias); Selective reporting (reporting bias); Other biases. The risk of bias was rated as high/ low/unclear.[18]

2.5. Statistical methods

We followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines to perform this meta-analysis using the R software (version 4.2.1, https://www.r-project.org/).[19,20] The hazard ratio (HR) and 95% confidence interval (CI) were pooled for PFS and OS, the number of events extracted directly from clinical trials was used to calculate the risk ratio (RR) and 95% CI for AEs. The Cox proportional hazards model or stratified and unstratified Cox proportional hazards regression model was used to estimate the hazard ratio and confidence interval in the included studies[21–27] expect the APHINITY[28] and PEONY[29] studies. Heterogeneity in the results of the included studies was evaluated both visually through forest plots and P values using the I-squared (I2). If statistically significant heterogeneity was observed (I2 ≥ 50%), the pooled effect was calculated using a random-effect model; otherwise, a fixed-effect model was employed (I2 < 50%).[30] Sensitivity analysis was performed by recalculating the pooled outcome estimates after excluding each study 1 at a time (leave-1-out procedure).[31]

3. Results 3.1. Studies inclusion

A total of 6447 studies were initially searched and identified. These studies are processed by screening the titles and/or abstracts, removing duplicates, and removing articles with similar data and study designs. Finally, 9 eligible studies were included. The Preferred Reporting Items for Systematic reviews and Meta-Analyses flow diagram detailing the inclusion and exclusion of publications is shown in Figure 1.

Figure 1.:

Flow diagram of the trial search and selection process.

3.2. Basic characteristics of the included studies

Of the 9 RCTs included, there were 8055 patients, including 4083 patients in the experimental group and 3972 patients in the control group. The basic characteristics of the included studies are presented in Table 1.

Table 1 - Basic characteristics of included studies. First Author Trial name, yr Treatment status Treatment arms Populations Eiffcacy endpoint Follow-up (m) Grade ≥ 3 AEs Serious AEs Sandra M[21] CLEOPATRA,2020 Metastatic A: D + H + P A:402 OS A: 99.9 NR NR B: D + H + pla B:406 PFS B: 98.7 Binghe Xu[22] PUFFIN,2020 Metastati/Locally recurrent A: D + H + P A:122 PFS A: 13.7 A: 70.5% A:19.7% B: D + H + pla B:121 ORR B:13.1 B: 69.2% B:19.2% Ander[23] PHEREXA,2017 Metastatic A: H + P + cap A:228 OS A: 25.3 A: 51.8% A:24.6% B: H + cap B:224 PFS B: 28.6 B: 59.6% B:23.9% Edith A[24] MARIANNE, 2019 Advanced A: TDM-1 + P A:366 OS A: NR A: 48.6% NR B: TDM-1 B: 361 B: 54.0 B: 47.1% Mothaffar[25] PERTAIN, 2018 Metastatic/locally recurrent A: H + P + AI A: 129 PFS A: 31.0 A: 50.4% A: 33.1% B: H + AI B: 129 DoR B:NR B: 38.7% B: 19.4% Gunter[28] APHINITY, 2017 Early A: H + P or chemotherapy A: 2400 OS A: 45.4 A:64.2% NR B: 2405 IDFS B: NR B: 57.3% B: H + pla or chemotherapy Zhimin Shao[29] PEONY, 2019 Early/locally advanced A: H + P + D A: 219 tPCR NR A: 48.6% A: 10.1% B:H + D B:110 B: 41.8% B: 8.2% Luca Giann[26] NEOSPHERE, 2016 Early/locally advanced A: H + P + D A: 107 pCR NR NR NR B: H + D B: 107 PFS DFS Yutaka[27] PRECIOUS, 2022 Advanced A: H + P + chemotherapy A: 110 PFS 14.2 NR NR B: H + chemotherapy B:109

A = Experimental group, AEs = adverse events, AI = aromatase inhibitor, B = Control group, cap = Capecitabine, D = Docetaxel, DFS = disease free survival, DoR = duration of response, H = Trastuzumab, IDFS = invasive disease free survival, ORR = objective response rate, NR = not reported, P = Pertuzumab, Pla: Placebo, pCR = pathological complete response, PFS = progression-free survival T-DM1 = Trastuzumab emtansine, tPCR = total pathologic complete response.

3.3. Quality evaluation

The 9 included studies were all RCTs, among them, 3 studies illustrated the randomized methods, and 5 studies were double-blind trials. The baseline of Patient Demographics and Disease Characteristics are reported in all the studies. Based on the risk of bias assessment of the studies, the overall quality assessments was moderate. The risk of bias summary and bias graph of the included studies are shown in Figures 2 and 3.

Figure 2.:

The risk of bias summary.

Figure 3.:

The risk of bias graph.

4. Effectiveness and safety analysis 4.1. PFS

There were 6 studies[21–23,25–27] reported PFS with no heterogeneity (P = .82, I2 = 0%). There were 1098 cases in the experimental group and 1096 cases in the control group. The pooled results using a fixed-effects model demonstrated that the risk of PFS in the experimental group was significantly higher than that in the control group [HR = 0.72, 95% CI (0.65,0.80), P < .01], which indicated that treatment with pertuzumab could reduce the risk of tumor progression, as shown in Figure 4.

Figure 4.:

Forest plot of PFS (progression-free survival).

4.2. OS

There were 4 studies[21,23,24,28] which reported OS, with low heterogeneity (P = .06, I2 = 59%). There were 3396 cases in the experimental group and 3396 cases in the control group. Heterogeneity was not significant. In this light, the pooled estimates using a random effects model indicated that the overall survival of the patients in the experimental group was significantly longer than that of the control group [HR = 0.80, 95% CI (0.66,0.96), P = .02], as shown in Figure 5. The sensitivity analysis yielded an estimated absolute rate of 0.72 (95% CI, 0.63–0.83) after sequential exclusion of the MARIANNE studies, indicating the heterogeneity source, as shown in Figure 6.

Figure 5.:

Forest plot of OS (overall survival).

Figure 6.:

Sensitivity analysis of OS (overall survival).

4.3. SAEs

There were 5 studies[22,23,25,26,29] which reported the incidence of SAEs with no heterogeneity between studies (P = .42, I2 = 0%). There were 802 and 680 patients in the experimental and control groups, respectively. The pooled estimates using a fixed-effects model indicated no significant difference in the incidence of SAEs between the experimental group and that of the control group [RR = 1.18, 95% CI (0.96,1.44), P = .12], as shown in Figure 7.

Figure 7.:

Forest plot of SAEs (serious adverse events).

4.4. Grade ≥ 3 AEs

There were 6 studies[22–25,28,29] which reported the grade ≥ 3 adverse effects, with low heterogeneity between the studies (P = .04, I2 = 56%). There were 3425 and 3339 patients in the experimental and control groups, respectively. The pooled estimates using a random effects model indicated no significant difference between the incidence of grade ≥ 3 AEs in the experimental and control groups [RR = 1.06, 95% CI (0.96,1.16), P = .23], as shown in Figure 8. Using sensitivity analysis, it is found that the PHEREXA study is the source of heterogeneity, as shown in Figure 9.

Figure 8.:

Forest plot of grade ≥ 3 AEs (adverse events).

Figure 9.:

Sensitivity analysis of grade ≥ 3 AEs (adverse events).

4.5. Grade ≥ 3 AEs subgroups

For the incidence of grade ≥ 3 adverse effects, including febrile neutropenia, diarrhea, and anemia in both groups, no significant study heterogeneity was observed. The pooled estimates using a fixed-effects model showed that there was no significant difference in the incidence of febrile neutropenia between the 2 groups [RR = 1.09, 95% CI (0.94,1.28), and P = .26]. The incidence rates of diarrhea and anemia in the experimental group were both significantly higher than those in the control group [RR = 2.36, 95% CI (1.98,2.81), P < .01; RR = 1.43, 95% CI (1.17,1.75), P < .01, respectively], as shown in Figure 10.

Figure 10.:

Forest plot of grade 3 AEs (adverse events) subgroups.

4.6. Common AEs subgroups

For common AEs, there was no heterogeneity in the incidences of neutropenia, nausea, alopecia, and rash in either group. The pooled estimates using a fixed-effects model showed no significant difference in the incidence of neureopenia, nausea and alopecia between the 2 groups [RR = 0.94, 95% CI (0.85, 1.05), P = .28], [RR = 1.04, 95% CI (0.95, 1.14), P = .39], [RR = 1.01, 95% CI (0.93, 1.10), P = .85]. The incidence of rash in experimental group was significantly higher than that in the control group [RR = 1.62, 95% CI (1.38,1.90), and P < .01], as shown in Figure 11.

Figure 11.:

Forest plot of common AEs (adverse events) subgroups.

5. Discussion

Monoclonal antibodies have been included as a the standard therapy for oncology drug therapy.[32] In addition to the development of new monoclonal antibodies, great efforts have been made to develop combinatorial drugs of monoclonal antibodies internationally.[33] Monoclonal antibodies usually target a single transduction pathway.[34] While tumors can overcome the blockade of metastasis to other pathways, blocking 1 pathway usually has a limited effect. By combining monoclonal antibodies, the 2 signal transduction pathways can be blocked simultaneously, producing an additive or synergistic effect on tumor growth.[35] At present, most clinical studies on therapy combined with monoclonal antibody are still in the early stages (preclinical or phase Ⅰ/Ⅱ). HER2 overexpression plays an important role in breast cancer pathogenesis.[36,37]Pertuzumab monoclonal antibody (pertuzumab) is a monoclonal antibody drug, whose mechanism of action could be combined with the HER2 extracellular domain Ⅱ region, inhibiting HER2 heterodimerization, and blocking the receptor-mediated signal transduction pathway. Considering that the domain Ⅱ region is located on the opposite side of the domain Ⅳ region, pertuzumab complements trastuzumab in the action mechanism, whose combination could strengthen the blocking effect of HER2 downstream signaling.[38] In clinical applications, the pertuzumab monoclonal antibody further improved treatment efficacy in HER2-positive breast cancer patients without increasing cardio-toxicity.[39] In 2012, the US FDA approved pertuzumab as a first-line treatment for HER2-positive advanced breast cancer and accelerated its approval for preoperative neoadjuvant therapy in early breast cancer patients in 2013.[40] The US FDA has approved pertuzumab in combination with trastuzumab and docetaxel for the treatment of patients with HER2-positive metastatic breast cancer who have not received prior anti-HER2 therapies or chemotherapy for metastatic diseases in 2013.[41] The US FDA has approved pertuzumab for adjuvant treatment of HER2-positive early breast cancer in 2019.[42] In a word, the pertuzumab could be used in the treatment of HER2-positive breast cancer in any stage.

Nine clinical trials with a total of 8055 patients were included in the present study, all of which were multi-center randomized clinical trials. In the 7 studies of these 9 studies, patients in the experimental groups were administered pertuzumab combined with trastuzumab plus traditional chemotherapy drugs (taxanes: docetaxel, paclitaxel, nab-paclitaxel), while patients in the control groups were administered trastuzumab plus the same chemotherapy drugs as in the experimental group, such as docetaxel. In 1 study, patients were administered pertuzumab in combination with trastuzumab and aromatase inhibitor drugs. In another study, patients were administered pertuzumab combined with trastuzumab plus capecitabine versus trastuzumab plus capecitabine alone. In only 1 study, patients in the experimental groups were administered pertuzumab combined with TDM-1, while patients in the control groups were administered TDM-1. The results of this study showed that TDM-1 combined with pertuzumab did not significantly improve the OS of patients with HER2-positive advanced breast cancer compared to TDM-1 alone, illustrating that the therapeutic efficacy of TDM-1 combined with pertuzumab in HER2-positive advanced breast cancer remains to be verified. The PRECIOUS study showed that treatment combined with pertuzumab could prolong PFS in patients with HER2-positive breast cancer. The chemotherapeutic drugs in our study are recommended in National Comprehensive Cancer Network guidelines that can be used for early, advanced, recurrent or metastatic HER2 positive breast cancer. Accordingly, different chemotherapeutic drugs included in our paper are in line with the current clinical benefits. Therefore, the outcomes of trials that used different treatment regimens are also combined, which is consistent with National Comprehensive Cancer Network guidelines.[43]

In this meta-analysis, the results of efficacy evaluation showed that treatment combined with pertuzumab reduced the risk of progression of HER2-positive breast cancer compared with treatment without pertuzumab in PFS [HR = 0.72, 95% CI (0.65,0.80), P < .01]. In terms of OS, the treatment combined with pertuzumab reduced the risk of death in progressive HER2-positive breast cancer compared with treatment without pertuzumab [HR = 0.80, 95% CI (0.66,0.96), P = .02]. However, OS analysis showed a statistically low amount of heterogeneity. In the sensitivity analysis, the MARIANNE study was found to be a source of heterogeneity. In view of the source of heterogeneity, patients in the experimental group were administered a combination of pertuzumab and TDM-1, while the control group was administered the single-agent TDM-1. Nonetheless, in other studies, patients in the experimental group were administered pertuzumab combined with trastuzumab and traditional chemotherapy drugs, while patients in the control group were administered trastuzumab with the same chemotherapy drugs as the experimental group. Thus, the analysis revealed the cause of the heterogeneity.

The results of the safety evaluation showed that the incidence of SAEs in the group with pertuzumab was not significantly different from that of the group without pertuzumab in treating patients with HER2-positive breast cancer [RR = 1.18, 95% CI (0.96,1.44)]. In terms of grade ≥ 3 adverse events, the incidence of grade ≥ 3 AEs in the group with pertuzumab was not significantly different from that of the group without pertuzumab [RR = 1.06, 95% CI (0.96,1.16)]. Because there was study heterogeneity, a sensitivity analysis was performed, which revealed that the PHEREXA study was the source of heterogeneity. The cause of heterogeneity might be the short follow-up time of only 9 months. There was no statistically significant difference in the incidence of grade ≥ 3 AEs (febrile neutropenia) between the 2 groups [RR = 1.09, 95% CI (0.94,1.28), P = .26]. The incidences of grade ≥ 3 AEs (diarrhea and anemia) were significantly higher in the group with pertuzumab [RR = 2.36, 95% CI (1.98,2.81), P < .01], [RR = 1.43, 95% CI (1.17,1.75),