1. Introduction
Around the world, cancer is the top reason of death. During the past two decades, the annual incidence of breast cancer has doubled or tripled in Asia [
1]. In Taiwan, breast cancer is also the most common cancer among females with increasing prevalence and incidence [
2,
3,
4]. The etiology of breast cancer remains unsettled, which is attributable to genetic, hormonal, or reproductive factors [
5]. Although the standard treatments for breast cancer patients include radiotherapy, chemotherapy, and target therapy [
6], many patients still seek for help with complementary and alternative medicine. In Taiwan, adult cancer patients who used traditional Chinese medicine (TCM) had a lower cancer mortality rate than those without using TCM (adjusted hazard ratio (HR) = 0.69). Chinese herbal medicine (CHM) and acupuncture are the most common alternative choices [
7,
8,
9,
10]. TCM elicits a protective effect against breast cancer; accordingly, consumption of Chinese herbs can reduce the incidence of invasive breast cancer [
11]. In Taiwan, a large proportion of patients receive CHM and Western medicine concurrently against breast cancer [
12].
Since the inflammatory signals can trigger the formation of a tumor microenvironment, several cancers arise from chronic inflammation [
13]. Being a CHM, San-Huang-Xie-Xin-Tang (SHXXT) is composed of three herbal medicines,
Rhizoma Rhei,
Radix Scutellaria, and
Rhizoma Coptidis at a ratio of 2:1:1 or 1:1:1 [
14]. It serves as a possible therapeutic choice for hepatitis C virus (HCV) infection [
15], hypertension [
16,
17,
18], septic shock [
19], neuronal damage [
20], gastrointestinal (GI) disorders [
21,
22], acute lung injury [
23], and cardiomyocyte injury [
24]. SHXXT can decrease COX2 and NF-κB induction to suppress the replication of HCV [
15]. Through the expression of COX2, ROCK-II, and PDE5, SHXXT ameliorated U46619-induced systemic and pulmonary arterial blood hypertension [
18]. Mediating by the formation of iNOs, COX2, and PGE2, SHXXT can prevent hypotension in LPS-treated rats [
19]. In the neuroblastoma SH-SY5Y cells, SHXXT can prevent the formation of ROS and inflammatory response against neurotoxicity [
20]. In experimentally induced GI motility dysfunction mice, SHXXT is a novel prokinetic agent to alleviate GI motility dysfunction in a dose-dependent manner [
21]. In
Helicobacter pylori infection, SHXXT can induce the anti-inflammatory effect through inhibiting the activation of NF-κB, the production of iNOS, COX-2, and IL-8 in human gastric epithelial AGS cells [
22]. In addition, SHXXT attenuates inflammatory responses by decreasing the expression of IL-1β, iNOS, and TNF-α in lipopolysaccharide-induced rat lung injury [
23]. It can protect rats’ cardiomyocyte against apoptosis through eNOs and MAPK pathways after ischemia-reperfusion injury [
24]. Besides, series studies have demonstrated that SHXXT has immunomodulatory, neuroprotective, and a potent anti-cancer effect [
25,
26,
27,
28]. Since, up till now, no studies have elucidated the relevance of SHXXT for breast cancers in detail, this population-based study aimed to investigate the effect of SHXXT and its constituents on breast cancer patients by analyzing the Taiwan National Health Insurance Research Database (NHIRD). Beside the impact of single constituent or compounds on cancer mortality rate, the study also clarified the dose–relationship effect based on the stratification of cumulative days of CHM use and the annual average CHM dose.
2. Materials and Methods
2.1. Data Source
From March 1995 till now, the Taiwan national health insurance (NHI) program has covered 99.6% of residents. All medical records reimbursed by the NHI were included in the NHIRD, in which the registry of beneficiaries, ambulatory and inpatient care claims data, and the registry of catastrophic illness were the source of the database. In the study, study subjects were recruited from the ambulatory and inpatient claims data liked with the registry of Catastrophic Illness during 2000 to 2010 and followed to the end of 2011.
2.2. Study Design and Cohort
This study aimed to evaluate the association between breast cancer mortality rate and the use of CHM, including SHXXT or one of its constituents (Rhizoma Coptidis, Rhizoma Rhei, or Radix Scutellaria). From the Registry for Catastrophic Illness database, 79,510 female patients who were newly diagnosed with breast cancer (International Classification of Disease, Ninth Revision, Clinical Modification (ICD-9-CM) = 174) during 2000–2010 were enrolled. The ICD-9-CM codes were identified by Chinese medicine physicians. The index date was the date of new diagnosis with breast cancer. They were followed up until the end of December 2011, death, or withdrawn from the insurance within a year of the follow-up period. Subjects younger than 18 years old or incomplete data were excluded from the analysis (n = 273). Subjects who withdraw from the insurance within a year of the follow-up period were also excluded (n = 51). A patient who took SHXXT or one of the constituents for more than 30 days was set as a CHM user (n = 5505). A patient without using CHM, acupuncture, or manipulative records was identified as a non-CHM user (n = 10,153). Subsequently, in order to match the two populations equally, the CHM user and the non-CHM user identified 5387 breast cancer patients in each group randomly frequency matched with distributions of age, and index year at 1 to 1 ratio. Age was set into three categories (18 to 39 years, 40 to 59 years, and more than 60 years). Gender was categorized as male and female. Urbanization was set into four levels (1, highest, 2, 3 and 4, lowest). The Charlson Comorbidity Index (CCI) score was divided into three groups (0, 1, and 2 or higher). Besides, treatment (radiotherapy, chemotherapy, breast cancer surgery) and drugs which patients received within half a year after the new diagnosis of breast cancer were included and followed up to the end of the study.
2.3. Study Outcome
All-cause mortality was set as the study outcome, in which date of death was obtained from the major illness certificate. The follow-up time was estimated in person-years, continued until the end of December 2011 or the death of the patient, whichever occurred first.
2.4. Statistical Analysis
The CHM user and the non-CHM user were compared in terms of demographic characteristics, CCI score, treatment, and drugs. To exam the categorical variables of the baseline characteristics, chi-square test was used. Otherwise, to exam continuous variables, t test was used. The survival probability between CHM group and non-CHM group were plotted by the Kaplan–Meier method and estimated by the Log-rank test, respectively. To calculate the HRs and 95% confidence intervals (CI) for the breast cancer mortality rate, the Cox proportional hazard model was utilized. SAS statistical software (version 9.4) was used to analyze all the database in the study with a two-tailed significance level of 0.05.
4. Discussion
This retrospective, large-scale, population-based cohort study is not only the first Taiwanese study to investigate the cancer mortality rate among breast cancer patients who received SHXXT or its constituents but also the first study in the Asian population. The use of SHXXT or its constituents reduced the breast cancer mortality rate by 59%. Notably, the protective effect of SHXXT and its constituents on breast cancer increased with the cumulative days and annual average dose. Moreover, the mortality rate was lower in breast cancer patients who used the SHXXT compound than those who only used one of its constituents.
Series studies have reported that extracts of SHXXT constituents have anti-cancer effects. According to the gene set enrichment analysis by Cheng et al., SHXXT can exert anti-proliferative effects on breast cancer HepG2 cells through regulating p53 signaling [
26]. The decoction SHXXT typically contains
Rhizoma Rhei,
Radix Scutellaria, and
Rhizoma Coptidis at ratios of 2:1:1 or 1:1:1. Notably, the anti-proliferative effects of SHXXT are mainly conferred by
Rhizoma Coptidis. The major component of
Rhizoma Coptidis is berberine; it can induce human breast cancer cell apoptosis by upregulating TNF-α and interferon-β in a time- or dose-dependent manner [
29,
30]. Chou and their colleagues reported that berberine induces cytotoxicity in breast cancer cells through reactive oxygen species, dysregulation of redox regulation, centrosomal structure, electron transport, cell signaling, protein folding, proteolysis, and protein trafficking [
31]. Berberine decreases cell viability by inhibiting the Ras/MAPK and PI3K pathways, by suppressing activation of growth factor receptors (Her2/neu, EGF receptor, and VEGF receptor), by increasing apoptosis-related molecules (Smac/DIABLO, caspases, and Bax), tumor suppressor genes (p53, Clip/p21, Klip/p27, and Rb) [
32], and over-expression of HDAC1 [
33], prohibitin [
34], serine/threonine protein phosphatase 2A [
35,
36], and by blockade of Bcl-2 expression. In addition, berberine can increase the amount of E-cadherin and suppress activation of the Wnt/ β-catenin pathway to modulate tumor cell migration and metastasis [
37]. Apart from berberine, coptisine is an isoquinoline alkaloid extract of
Rhizoma Coptidis, from which can emerge the anti-metastasis effect. Through down-regulating MMP-9 and increasing TIMP-1, coptisine can suppress adhesion, migration, and invasion of MDA-MB-231 breast cancer cells [
38]. Hence,
Rhizoma Coptidis inhibits the breast cancer cell proliferation and metastasis based on these two important components.
In addition to
Rhizoma Coptidis,
Radix Scutellaria is another constituent of SHXXT, which also has an anti-cancer effect due to its containing Oroxylin A and numerous flavonoids such as wogonin and baicalin [
39]. Being a major component of
Radix Scutellaria, Oroxylin A inhibits the binding activity of hexokinase-II (HK-II) with mitochondria in a SIRT3-dependent manner to suppress glycolysis and induce mitochondrial cytotoxicity in human breast cancer cell lines [
40]. Another component of
Radix Scutellaria, wogonin, inhibits breast cancer cells invasion by downregulating ERK1/2 and PKC-δ [
41]. Through decreasing both endogenous and PMA-induced MMP-9 expression, wogonin could inhibit tumor invasion and metastasis [
42]. Wogonin also could induce cell differentiation, impair cell apoptosis, and activate both antioxidant and anti-angiogenesis activity against breast cancer formation [
43,
44,
45,
46].
Moreover, the other constituent of SHXXT,
Rhizoma Rhei, exerts a high estrogenic potency, of which chrysophanol 1-O-β-D-glucopyranoside, aloe emodin, and rhapontigenin are the main isolated compounds. Most breast cancer cells are estrogen receptor- (ER)/progesterone receptor (PR)-positive, with human epidermal growth factor receptor 2 (HER2)-negative (69%), and almost half of postmenopausal patients have ER-positive breast cancer cells [
47,
48]. Since estrogen can stimulate ER-positive breast cancer cell to proliferate, a selective ER modulator that blocks the binding of estrogen to ER is effective to treat ER-positive breast cancer [
49,
50]. Through regulating the expression of ER,
Rhizoma Rhei can modulate the proliferation of breast cancer MCF-7 cell in a concentration-dependent manner [
51]. Chrysophanol 1-O-β-D-glucopyranoside mediates mitochondria-dependent apoptosis, whereas aloe emodin and rhapontigenin activate the caspase-8 pathway to induce mitochondria-independent apoptosis. Therefore,
Rhizoma Rhei components could help hormone replacement therapy and chemoprevention against breast cancer owing to their potent estrogenic and inhibitory activities [
52].
Since three constituents of SHXXT all have an important anti-cancer effect, the cancer mortality rate influence of the SHXXT component is supposed to be superior to that of a single constituent. Around the world, the major causes of morbidity and mortality are tumor invasion and metastasis. To halt the breast cancer mortality, the main objective is to inhibit cancer invasion and metastasis. Since extracts of three SHXXT constituents not only have anti-proliferative and anti-angiogenesis effects but also exert anti-invasive and anti-metastatic impacts on breast cancer, the multi-component nature of medicinal herbs makes them particularly suitable to treat complex disease through synergistic activity [
53]. Therefore, SHXXT is more effective than its individual components in terms of reducing mortality in breast cancer patients.
The strength of the study is that the study traced a large sample size of patients for a long period by using NHIRD. NHIRD is good for assessing survival rates, herb–drug interactions, and the cost-effectiveness of drug treatments. In addition, the study analyzed the specific ascertainment of numerous outcome events, the identification of an exposure–response relationship, and the comparison of different average annual doses. Besides, the data contained in an administrative database rather than data collected in a hospital-based study helped to avoid selection bias.
However, several limitations are retained in the study. First, this retrospective observational study could only analyze the data contained in NHIRD. Since the de-identified data are released for public research and the NHIRD is a claims-based database, no additional clinical information is available, e.g., histology subtype, gene change, and cancer staging [
54,
55,
56]. Second, some possible confounders such as lifestyle practices, physical activity, dietary intake, and genetic factors are unavailable. Besides, the exposure–response relationship is only expressed in terms of cumulative days of CHM use; the actual adherence could not be ascertained. In addition, patients directly purchasing CHM or herbs from herbal pharmacies or health food stores cannot be identified in the NHI program. Only CHM prescribed by licensed doctors can be reimbursed; hence, the frequency of the CHM use might have been under-estimated. However, a large portion of patients would likely prefer to purchase CHM in the NHI system because of the comprehensive coverage and lower cost of CHM prescriptions. Finally, randomized controlled trials should be arranged in the future due to the more powerful statistical significance.