INTRODUCTION:

Breast cancer is the most common type of cancer¹, with more than 2.2 million cases diagnosed in 2020. About 1 in every 12 women at some point in their lives. It is the first cause of death from cancer among women, and nearly 685,000 women died of it in 2020². The percentage of female breast cancer in Syria is 30%, and it is the most common type of cancer among women³. Breast cancer is most common in women, but it can also affect men.

Breast cancer can occur in any part of the breast, the ducts that carry milk to the nipple are where most breast tumors begin (ductal cancers), some of them start in the glands that produce breast milk (lobular cancers), there are a few less prevalent kinds of breast cancer as well^4,5. There are five stages of breast cancer. The zero stage is when the ductal tumor can be diagnosed by mammography alone. The first stage tends to be a growth and extends out of the ductal; the second stage is a big tumor which spreads to the skin and chest; the third stage tumor extends to lymph nodes and axillary; the fourth stage tumor extends to other organs like the lung or bone; and that's the late stage⁶. Some of the most common cancers, such as breast cancer, have high cure rates when detected early and treated according to best practices. Therefore, early detection and treatment of cancer is needed for better health management^7,8.

The cumulative incidence of cancer therapy-associated cardiovascular toxicities (CTACVT) after adjuvant treatments for breast cancer and other cancers may be as high as 33%, indicating that anticancer therapy may directly lead to heart disease or accelerate disease, or increased risk of cardiovascular disease. These toxic effects may be transient or chronic and induced by different mechanisms that vary with the type of chemotherapy is used⁹. These effects can occur during the treatment or many years after the completion of the treatment as a result of undiagnosed or subclinical dysfunction^10,11.

Anticancer drugs are divided into two types according to their cardiovascular toxicity: Type I drugs such as anthracyclines, anti-metabolic¹², micro-tubule inhibitors, alkylating agents, lead to irreversible cardiovascular disorders⁹. Type II drugs such as HER2 inhibitors, VEGF inhibitors, tyrosine kinase inhibitors, IMiDs, lead to reversible cardiovascular disorders⁹.

Cancer drugs can cause many manifestations of cardiovascular toxicity such as heart failure, left ventricular dysfunction, acute myocarditis, arrhythmias, angina, myocardial infarction, heart failure, cardiomyopathy, myopericarditis, myocardial ischemia, pericardial effusions, perimyocarditis, hypertension, angioedema, venous thromboembolism, stroke…^9,13,14.

Monitoring of cardiovascular toxicity is based on the following indicators: left ventricular ejection fraction (LVEF) which is done by echocardiogram, computerized axial tomography, cardiac catheterization, nuclear stress test, cardiovascular toxicity can also be assessed by cardiopulmonary exercise testing and by testing and measuring cardiac enzymes and proteins¹⁵, natriuretic peptides (ANP, BNP, NT-proBNP)^16,17. The laboratory tests for cardiac proteins and enzymes are among the most important tests to be done to detect cardiovascular toxicity, as troponin and creatine phosphokinase. Cardiac troponin T (cTnT) and troponin I (cTnI) are cardiac regulatory proteins that regulate actin-myosin calcium interactions¹⁸. Outside of the myocardium, cTnI has not been identified. Although skeletal muscle expresses very little cardiac troponin T¹⁸, the current cTnT assay does not detect structural troponin. The detection of cardiac injury by measuring both cTnI and cTnT in serum is a sensitive and specific assay. Levels of cardiac-specific troponins I and T can become increased in the blood within 3 or 4 hours of a myocardial injury and can remain elevated for 10 to 14 days. The normal range for troponin T is < 0.1ng/ml and for troponin I is < 0.03 ng/ml¹⁹. Creatine phosphokinase (CK) is a type of protein, known as an enzyme, is produced by a variety cells and tissues²⁰. It is mostly found in skeletal muscles (CK-MM)²¹ and heart (CK-MB), with lesser amounts in the neuronal tissue (CK-BB)²². The normal range of creatine phosphokinase for men is 55-170U/L and for women it is 30-192 U/L. It can rise in the case of muscle injury, myocarditis or heart attack, and in the case of stroke or brain injury. This test is useful in the case of heart damage, but it is not completely specific²².

PATIENTS AND METHODS:

Patients selection:

This study was designed and conducted as a prospective study using 50 newly diagnosed patients [50 women] with breast cancer treated with an alkylating agent (cyclophosphamide) and an anthracin derivative (doxorubicin) over four doses for three months with an interval between one dose and the next 21 days. The patients were treated at the Chemotherapy and Radiotherapy Center at Tishreen University Hospital. Several inclusion and exclusion criteria were used to choose patients. The inclusion criteria was a recent case of breast cancer without having undergone any type of chemotherapy treatment previously. While the exclusion criteria was patients with previous cardiovascular disease records.

We designed a questionnaire to register patients' information (age, weight, smoking, pressure, diabetes, previous diseases, medications).

Biochemical evaluations:

Venous blood was taken from patients before the first chemotherapy dose and after the course of treatment ended (three months after the start of treatment). Laboratory assessments included: 1-Troponin I, which we measured using ELISA (Human Troponin I, Tn-I ELIZA Kit) (Nanjing Pars Biochem CO.,Ltd), Assay range (0.008-0.4ng/ml), where is the normal value within the range (0.01-0.03ng/ml). 2-Creatine Kinase (Ck), which we measured using (Creatine Kinase BioSystems COD 11790,11791)

Statistical analysis:

All data was shown as mean ± standard error of means (SEM). P values lower than 0.05 were defined as statistically significant. The statistical analysis was performed with Paired T student using SPSS Statistics version 20.0. The figures were drawn using Excel.

RESULTS:

The age of patients was between^31-64 years. The weight of patients was between^52-107.

Table 1: Age of patients

	N	Mean	SEM	Std. Deviation
Patients	50	48.46	1.203	8.510

N: number of patients, Mean: mean of ages, SEM: standard error of means

Table 2: Weight of patients

	N	Mean	SEM	Std. Deviation
Patients	50	66.32	1.603	11.338

N: number of patients, Mean: mean of weight, SEM: standard error of means

Effect of chemotherapy on creatine kinase:

There was statistically significant difference when we compared creatine kinase values before starting chemotherapy and after three months of treatment with it (figure 1), p value was < 0.05.

Figure 1. Mean of CK± SEM; (CK) creatine kinase, (Ck0) values of creatine kinase before chemotherapy, (Ck1) values of creatine kinase after three months of chemotherapy, *p=0.005.

Effect of chemotherapy on troponin I:

Three of 50 patients had elevated troponin I to 0.03 ng/ml and six of 50 patients had elevated troponin I more than 0.03ng/ml [0.04ng/ml - 0.07ng/ml]. statistically significant difference was reported when we compared troponin I values before starting chemotherapy and after three months of treatment with it (figure 2), p value was < 0.05.

Figure 2. Mean of T± SEM; (T) Troponin I, (T0) values of troponin I before chemotherapy, (T1) values of troponin I after three months of chemotherapy, *p=0.01.

DISCUSSION:

Chemotherapy is a pharmacological treatment that uses powerful chemicals to kill fast-growing cells in the body. It is an effective approach to treat a variety of cancers. Although it is a useful and consider as a significant method of cancer treatment, some side effects of chemotherapy are mild and curable, while others might lead to serious complications. In women with early-stage breast cancer, advances in treatment have improved disease-free survival and overall survival. However, the adverse cardiovascular consequences associated with adjuvant therapy for breast cancer may negate these improvements.

In our study, we investigated the effects of chemotherapy used to treat women with newly diagnosed breast cancer to assess its toxic effect on the cardiovascular system. We took two measurements of troponin I and creatine kinase (before starting therapy and after completing phase I), and made a paired comparison to recognize any significant differences in these levels after three months of therapy.

Creatine kinase levels significantly decreased after completing phase I of chemotherapy. A study conducted by Bruns et al.²³, matched with our findings. They attributed the low values of creatine kinase after chemotherapy to slow or incomplete activation of the enzyme by sulfhydryl agents, in addition to other factors as drug inhibition or removal of intermediate reaction products by another enzyme. We suggest that low CK activity was associated with other medication like steroids, particularly hydrocortisone (8mg), which was prescribed to the patients after chemotherapy doses to treat nausea and vomiting and other uncomforting chemo-side effects. Low serum creatin kinase activity after three months of chemotherapy was reported by Albert D. Fraser²³, who categorized the patients to ones taking prednisone with the chemotherapy, and patients taking only chemotherapy drugs. After the first period of therapy, he recorded that the CK activity for the prednisone-treated group is considerably lower than in the patients treated with only other chemotherapeutic drugs. We also suggest that the low CK levels could be preceded by CK elevation in the first few days after chemotherapy doses, this elevation is associated with cellular damage, especially skeletal muscle damage. This suggestion was consistent partially with Robert J. Cersosimo et al.²⁴, who found that CK was initially elevated after institution of 5-FU and levamisole. Fractionation of serum CK revealed 100% MM isoenzyme, indicating skeletal muscle damage. Robert J. found a clear association between administration of chemotherapy and CK elevations which began to increase after initiation of chemotherapy and fell dramatically after chemotherapy was discontinued. We believe that our results demonstrate that combination chemotherapy often results in decreased CK activity in many types of cancer. The CK value is not preferred as important biomarkers of cardiotoxicity (such as due to cyclophosphamide and doxorubicin), as long as pathological increase in CK could be hidden by the apparent suppression of CK values in patients who are receiving prednisone with combination chemotherapy.

The most important result of the present study was troponin I elevation induced by an alkylating agent (cyclophosphamide) and an anthracin derivative (doxorubicin), which refers to cardiotoxicity that occurred in 18% of treated patients observed during the first three months after the completion of phase 1 chemotherapy. An increase in troponin I levels was observed in three patients to 0.03ng/ml and in six patients up to 0.03ng/ml [0.04ng/ml - 0.07ng/ml] this increase was statistically significant. Our results correlate with findings in a previous study by J. Melissa et al.²⁵ which showed increases in high-sensitive cardiac troponin-I (hs-cTnI), three months after chemotherapy in patients treated with an anthracycline-based regimen. We suggest that significant cardiac damage leads to troponin release from the troponin complex. Our results also correlate with the study by E. Tzolos et al.²⁶, who found that plasma (hs-cTnI) concentrations showed an increase after the completion of chemotherapy as biochemical evidence of myocardial injury. In our study 18% of treated patients had elevated troponin I levels, this percentage consistent with the study by S. Kilickap et al¹⁷, who found the percentage of patients with positive troponin values ranges from 15 to 34%, indicating irreversible myocardial cell injury in patients treated with cardiotoxic chemotherapy. K. Hiromitsu et al.²⁷ looked for more reliable value than the absolute value of troponin T, as long as TnT baseline have great interindividual variability. In his study the highest level of troponin was not significantly higher in patients with cardiotoxicity than without, while the (hs-TnT) increment and hs-TnT integration value above baseline were significantly greater in patients with cardiotoxicity. We should finally clear that the sampling protocol used in different studies is not homogeneous. It is important to note that the increase of troponin concentrations was detected at different intervals after administration of chemotherapy in various studies indicating that it may be necessary to collect several blood samples to demonstrate the possible increase of it as reliable marker.

In summary, TnI could be better biomarker than CK in determining the early subclinical phase of the cardiomyopathy, before its clinical onset occurs. It could help to develop optimal protocol of administration of anthracycline chemotherapy to ensure oncological efficacy with minimizing cardiac injury.

Our study has some limitations. First of all, it was not possible to create a placebo cohort in this study. It was also possible to study other criteria that reveal cardiovascular toxicity, but we were satisfied with studying creatine kinase and troponin, considering troponin as one of the most important indicators that help in detecting cardiovascular toxicity early. Our study was not sufficient to evaluate TnI concentrations that have been associated with the development of long-term cardiac toxicity, but it is useful for early diagnosis of cardiac damage within a short period of treatment and that requires further investigation for early detection and treatment.

List of Abbreviations:

CTACVT: cancer therapy-associated cardiovascular toxicities

HER2: human epidermal growth factor receptor 2

VEGF: Vascular endothelial growth factor

IMiDs: Immunomodulatory imide drugs

LVEF: left ventricular ejection fraction

ANP: atrial natriuretic peptide

BNP: Brain natriuretic peptide

NT-proBNP: N-terminal pro b-type natriuretic peptide

cTnT: Cardiac troponin T

TnT: troponin T

cTnI: Cardiac troponin I

TnI: troponin I

CK: Creatine phosphokinase

CK-MM: isoenzymes of Creatine phosphokinase (skeletal muscle)

CK-MB: isoenzymes of Creatine phosphokinase (heart)

CK-BB: isoenzymes of Creatine phosphokinase (brain)

ELISA: enzyme-linked immunosorbent assay

SEM: standard error of means

hs-cTnI: high-sensitive cardiac troponin-I

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Received on 25.10.2021 Modified on 11.12.2021

Research J. Pharm. and Tech. 2022; 15(8):3429-3433.

DOI: 10.52711/0974-360X.2022.00574