MAINSTREAM is a prospective, multicentre, randomised, placebo-controlled, double-blind,
parallel-group, investigator-initiated clinical trial. The study is powered to
demonstrate the difference between the groups in the primary endpoint, which has been
defined as the occurrence of a decrease in LVEF by ≥ 5% assessed by transthoracic
echocardiography (TTE) within 24 months. Approximately 600 patients will be recruited in
three tertiary supraregional Polish oncology centers. Of those patients, after an
estimated dropout, during the single-blinded phase of drug uptitration to the target
dose, 480 will be randomized in a 1:1 ratio into sacubitril/valsartan or matching
placebo.
In brief, patients with histologically confirmed, and phenotypically assessed breast
cancer at an early stage, defined as stages I-III and oligometastatic IV stage, with a
radical treatment plan, which includes surgery and the post- and/or pre-operative
systemic treatment, will be included in the study. The patients must be classified in the
0-2 classes of the Eastern Cooperative Oncology Group. In the baseline echocardiography
analysis, the LVEF must be ≥50% and the patients must be in the sinus rhythm. The
patients who underwent prior therapy with anthracyclines and/or left-sided radiotherapy,
suffered from myocardial infarction within the preceding 3 months prior to the study, or
have symptomatic, clinically relevant heart failure, will be excluded from the study.
Similarly, patients with contraindications, or prone to the adverse effects of the
studied drug, which includes patients with symptomatic hypotension, hyperkalemia defined
as K+ higher than 5.5 mmol/L and estimated glomerular filtration rate (eGFR) <30
mL/min/1.73 m2 on the screening visit, will also be considered ineligible to participate
in this trial. Patients must not have been on treatment with ACE-I/ARB/ARNI at least in
the 36 hours prior to study enrollment. According to the ESC guidelines on
cardio-oncology, the inclusion and exclusion criteria for the trial define the vast
majority of the studied population in the low- or moderate risk of cancer therapy-related
cardiac dysfunction (CTRCD), however, the inclusion of patients at high risk of either
anthracycline- or anti-HER-2-associated CTRCD, such as patients aged ≥80 years, is not
impossible. No very high-risk patients will be considered eligible for enrollment.
After assessment of the inclusion and exclusion criteria, and all examinations, including
the echocardiography assessment, the patients will begin the single-blinded phase of
treatment with sacubitril/valsartan during the screening visit. The MRI study may be
performed according to the availability of the method in each participating facility. The
initial dosing of the drug will be 49/51 mg twice daily, which should be uptitrated to
the target dose of 97/103 mg twice daily at the Run-in-visit scheduled at 6-8 days from
the initial evaluation and drug introduction, tolerance permitting. After further 6-8
days of single-blinded treatment with target dose of sacubitril/valsartan, providing
satisfactory tolerance of the drug, the patients will undergo randomization at the
Randomization visit.
Providing the patient signed informed consent, is fully eligible for randomization, and
underwent the single-blinded study treatment regimen with satisfactory tolerance, the
patient will be randomized with the use of an electronic, centralized randomization
system, blinded to the patient's characteristics, to either interventional group, which
will be administered with sacubitril/valsartan, or the placebo group. The system will
dynamically randomly allocate patients to the two groups in a 1:1 ratio.
After randomization, the patients will follow treatment with either sacubitril/valsartan
or a matching placebo, for a maximum of 24 months. During this period, three study visits
are planned, at 3 months, 12 months, and 24 months from randomization. At each visit, the
patients will be assessed for the medical presentation, undergo laboratory and imaging
studies, and will be assessed for the presence of adverse events. In patients, who will
be unable to tolerate the target dose of the study drug of 97/103 mg twice daily, the
dose can be down-titrated to 49/51 mg twice daily at the investigator's discretion (after
having considered whether there is any other concomitant medication that could act as a
parallel contributor to the lower tolerance of the drug). If the dose of 49/51 mg twice
daily cannot be tolerated, the dose could be temporarily lowered by half for a period of
two weeks. However, if after that period the uptitration of the dose is impossible, the
patients will have to be excluded from further participation in the trial. The physicians
will be strongly encouraged to foster the continuation of the target dose of the study
drug, based on their assessment of the patient's condition.
The primary endpoint of the study has been defined as the occurrence of a reduction in
LVEF by ≥ 5% assessed by TTE within 24 months. Among the secondary endpoints of the
study, the clinical composite endpoint of death from any cause or hospitalization for
heart failure and its components will be analysed, as well as the wide spectrum of
echocardiographic, electrocardiographic, laboratory, and clinical outcomes, including the
CTRCD resulting in the need to implement treatment consistent with the ESC guidelines on
cardio-oncology. To maintain utmost objectivity, all examinations performed in relation
to the study, including the echocardiographic, electrocardiographic, and magnetic
resonance imaging analyses will be sent using 3D option ImageCom (TOMTEC Imaging Systems
GmbH, Germany) - a multi-modality, vendor-neutral 3D/4D viewer - to the core laboratory
where their results will be analysed by two independent investigators blinded to the
patient's randomization status.
Breast cancer treatment The patients should be treated according to the standard
protocols of the participating centres, with the intention of radical treatment based on
the surgical excision of cancer, with addition of either pre- or post-surgical chemo-
and/or radiotherapy. The choice of the scheme of oncological treatment will be at the
discretion of the treating oncologist and will be performed after analysis of the risk of
recurrence, the potential response to a particular type of treatment, with consideration
of possible drug-related adverse effects, and patient's co-morbidities and preferences.
All decisions, including the scheme of therapy, will be performed in accordance with the
recommendations of the Polish Society of Clinical Oncology.
Pre-operative and post-operative chemotherapy with alkylating drugs, which include
anthracyclines, usually in multi-drug regimens, will begin most commonly, with the
initiation of anthracyclines (4 cycles or 3 cycles of EC). In routine perioperative
treatment, trastuzumab will be administered̨ for 12 months, but shorter regimens (6
months) may be considered in individual situations, however, due to the cardiotoxic
effects of trastuzumab, it will not be routinely given concomitantly with anthracyclines.
As there are currently no data regarding the potential differences in the
pharmacodynamics and pharmacokinetics, and consequently efficacy and safety of
sacubitril/valsartan prophylactic treatment in patients with breast cancer and systemic
therapy, there may be genetic biomarkers defining the disease susceptibility and
prognosis, as well as the response to treatment. For each patient who gives informed
consent to participate in the study, an additional blood sample will be taken at the
first visit. After completion of the study, the subanalysis of the trial will be
attempted based on the genetic profile aiming at defining the genetic pattern
characterizing the response to sacubitril/valsartan for the prevention of cardiotoxicity
caused by anthracyclines and/or anti-HER-2 targeted drugs.
At the screening visit and completion of the study, the patient will undergo TTE, which
according to the recent ESC Guidelines on cardio-oncology has been defined as the
first-line modality in assessment of cardiac function in oncological patients. The
assessment of LVEF with the use of 3D echocardiography will be preferred in all patients,
although in selected cases a two-dimensional LVEF assessment will be accepted. In every
patient, the assessment of global longitudinal strain will be recommended. The
investigator performing the echocardiography will be blinded to the patient's
randomization scheme. All images will be sent to the core laboratory. The quality of life
will be assessed with the 36-Item Short Form Survey (SF-36) questionnaire at the
screening visit and at the completion of the study.
Laboratory tests The details of the blood tests performed during each study visit are
presented in Table 4. All blood samples will be performed at fasting, on the day of the
study visits, and analysed in the local laboratories of the three participating oncology
centres. The blood sample for genetic testing in patients who sign an additional consent
for genetic evaluation will be collected only on the screening visit and stored locally
for the eventual transfer into the biobank of the Maria Sklodowska-Curie Institute -
Oncology Centre (MSCI), Gliwice, Poland for further analyses. High-sensitivity cardiac
troponin (with a preference to measure cardiac troponin T over troponin I due to
previously described variability in the results of the latter), as well as N-terminal
prohormone of brain natriuretic peptide (NT-proBNP), will be assessed using assays at the
local laboratories of the participating oncology centres during study visits and at any
time when deemed necessary by the physician-in-charge, or as supported by the local
treatment protocols established by the participating centres and with reference to the
ESC guidelines on cardio-oncology. The investigators will be blinded to the patients'
randomization results.
Intervention in case of HF development Based on the prior studies, it is estimated that
approximately 20% of patients from the placebo arm and 10% of study drug arm might
develop a certain degree of cardiotoxicity and require introduction of cardioprotective
agents. The diagnosis of CTRCD should be based on the assessment of TTE and/or
high-sensitivity cardiac troponin, as well as NT-proBNP. The intervention in case of
development of either symptomatic, or asymptomatic CTRCD should be in line with current
ESC guidelines on cardio-oncology and may include discontinuation or temporary
interruption of chemotherapy, or continuation of treatment with thorough patient
monitoring, while the study drug/placebo might be terminated or continued, depending on
the severity of CTRCD.