Testing the Drug Atezolizumab or Placebo With Usual Therapy in First-Line HER2-Positive Metastatic Breast Cancer

Inclusion Criteria:

The patient must have signed and dated an Institutional Review Board (IRB)-approved consent form that conforms to federal and institutional guidelines
The trial is open to female and male patients
Patients must be >= 18 years old
Patient must have an Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

Histologically confirmed adenocarcinoma of the breast with locally recurrent, unresectable disease or metastatic disease outside the central nervous system (CNS) confirmed as described below; eligible patients include those with either:

De novo metastatic disease presenting without prior history of HER2-positive breast cancer:

Diagnosis should have been made from a biopsy of a metastatic disease site, but biopsy from the breast primary or involved regional lymph nodes is acceptable if biopsy of the metastatic sites was thought to carry excessive risk for the patient

Locally recurrent or metastatic disease following prior therapy for early breast cancer:

Diagnosis must have been made from the biopsy of the locally recurrent or metastatic disease
There must be an interval of >= 6 months between completion of neoadjuvant/adjuvant HER2-targeted therapy and documentation of locally recurrent or metastatic HER2-positive disease by biopsy
Patients must have measurable disease based on RECIST 1.1, as determined by the site, which has not been irradiated to be eligible

Patients with brain metastases are eligible if they meet ALL the following criteria:

Four or fewer metastatic sites to CNS
Largest unexcised tumor does not exceed 3 cm
No metastases to brain stem, midbrain, pons, medulla or the optic nerves and chiasm
Must have measurable disease outside the CNS, based on RECIST 1.1, as determined by the site, which has not been irradiated
If patient presented with symptoms from CNS metastases, the symptoms must have resolved with initiation of steroids and initial local therapy (surgery, radiation therapy, or both)
Must have been evaluated by Medical Oncologist and plan is to administer trastuzumab, pertuzumab, and a taxane as first-line systemic therapy
May have received administration of trastuzumab OR lapatinib concurrently with radiation therapy for brain metastases. Toxicities related to lapatinib if administered, should be =< grade 1 per the CTCAE v5.0, and the lapatinib must have been completed at least 2 weeks prior to study entry
No history of intracranial hemorrhage or spinal cord hemorrhage
No neurosurgical resection or brain biopsy within 10 days prior to study entry
After study entry and before randomization, send tissue for central HER2 confirmation; a tumor specimen obtained at the time of diagnosis of locally recurrent or metastatic disease must have been determined to be HER2-positive based on local testing according to American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines (Wolff 2018); HER2 status should initially be assessed using an Food and Drug Administration (FDA)-cleared IHC assay; positive is defined as IHC 3+ staining intensity; if HER2 IHC results are equivocal (2+), then HER2 status will be determined using a FDA-cleared HER2 in situ hybridization (ISH) test according to ASCO/CAP guidelines; Note: Once HER2-positive is confirmed on central testing, patients will be randomized to atezolizumab/placebo; randomization within 14 days from study entry will ensure that the Pharmaceutical Management Branch (PMB)-supplied agents will be received at the site for treatment on day 22 of cycle 1
The tumor specimen obtained at the time of diagnosis used for HER2 testing must also have central testing for PD-L1 status; patients will be eligible irrespective of PD-L1 testing result including PD-L1 indeterminant
The tumor specimen obtained at the time of diagnosis used for HER2 and PD-L1 testing should also have central testing for estrogen receptor (ER) and progesterone receptor (PgR) according to current ASCO/CAP guideline recommendations for hormone receptor testing; patients with < 1% ER and PgR staining by IHC will be classified as negative; if enough material for central confirmation of ER and PgR is unavailable, local testing results for ER and PgR may be used for eligibility
Localized palliative radiation therapy to sites of non-measurable disease is allowed for symptom management and may begin prior to study entry and continue following study entry while receiving study therapy
Patients must have imaging of the chest/abdomen/pelvis, preferably with a CT scan, and a bone scan within 5 weeks prior to study entry; (NOTE: if a patient is unable to receive CT contrast, a MRI of the abdomen/pelvis and non-contrast chest CT should be performed; positron emission tomography/computed tomography [PET/CT] is not an acceptable alternative)
MRI of the brain (or contrast CT scan of the brain if patients are unable to undergo MRI) must be obtained in patients with symptoms suggesting possible central nervous system (CNS) metastatic disease; neuroimaging is recommended but not required in asymptomatic patients
Absolute neutrophil count (ANC) must be >= 1200/mm^3 (within 14 days prior to study entry)
Platelet count must be >= 100,000/mm^3 (within 14 days prior to study entry)
Hemoglobin must be >= 8 g/dL (within 14 days prior to study entry)
Total bilirubin must be =< 1.5 x upper limit of normal (ULN) for the lab or direct bilirubin =< ULN for patients with bilirubin levels > 1.5 x ULN (within 14 days prior to study entry)
Aspartate aminotransferase (AST) and alanine aminotransaminase (ALT) must be =< 2.5 x ULN for the lab or =< 5 x ULN for patients with liver metastases (within 14 days prior to study entry)
Serum creatinine =< 1.5 x ULN or measured or calculated creatinine clearance >= 50 mL/min using the Cockcroft-Gault formula for patients with creatinine levels > 1.5 x ULN for the lab (within 14 days prior to study entry)
Patients not receiving anti-coagulant therapy must have prothrombin time (PT) and international normalized ratio (INR) =< 1.5 x ULN within 14 days prior to study entry; for laboratories that do not report an ULN for the INR assay, use =< 1.5 as the value for the ULN; patients receiving anti-coagulants should have a baseline INR assessed, but the value does not affect eligibility
A serum thyroid-stimulating hormone (TSH) and AM (preferably in morning) cortisol must be obtained within 14 days prior to study entry to obtain a baseline value; patients with abnormal TSH or AM cortisol baseline levels should be further evaluated and managed per institutional standards; asymptomatic patients who require initiation or adjustment of medication or are followed without initiating treatment based on endocrinologist's recommendations are eligible
Left ventricular ejection fraction (LVEF) assessment must be performed within 6 weeks prior to study entry; (LVEF assessment performed by echocardiogram is preferred; however, multigated acquisition scan (MUGA) scan may be substituted based on institutional preferences); the LVEF must be >= 50% regardless of the cardiac imaging facility's lower limit of normal
Administration of atezolizumab may have an adverse effect on pregnancy and poses a risk to the human fetus, including embryo-lethality; women of child-bearing potential and men must agree to use adequate contraception (non-hormonal or barrier method of birth control; abstinence) prior to study entry, for the duration of study participation, and for 5 months (150 days) after the last dose of atezolizumab/placebo and 7 months after the last dose of trastuzumab and pertuzumab; should a woman become pregnant or suspect she is pregnant while she or her partner is participating in this study, she should inform her treating physician immediately
Human immunodeficiency virus (HIV)-infected patients on effective anti-retroviral therapy with undetectable viral load within 6 months of study entry are eligible for this trial

Exclusion Criteria:

Patients with brain metastases are excluded if they meet ANY of the following criteria:

Symptoms from brain metastases have not resolved prior to study entry
Five or more clearly identified foci of metastases to the brain
Largest unexcised tumor exceeds 3 cm
Spinal cord metastases
Medical Oncologist plans to employ HER2-directed tyrosine kinase inhibitor as component of systemic therapy
Metastatic disease limited to CNS
Leptomeningeal carcinomatosis
History of systemic anti-cancer therapy (e.g., chemotherapy, targeted therapy) for metastatic breast cancer (MBC) except as described in inclusion criteria
History of exposure to cumulative doses of doxorubicin greater than 360 mg per square meter of body-surface area or its equivalent
Prior treatment with mTOR inhibitors or CDK 4/6 inhibitors in combination with endocrine therapy for treatment of metastatic disease
Prior treatment with CD137 agonists or immune checkpoint-blockade therapies, including anti-CD40, anti-CTLA-4, anti-PD-1, and anti-PD-L1 therapeutic antibodies
History of non-breast malignancies (except for in situ cancers treated only by local excision and basal cell and squamous cell carcinomas of the skin) within 5 years prior to study entry
Uncontrolled hypertension defined as sustained systolic blood pressure (BP) > 150 mmHg or diastolic BP > 90 mmHg; (patients with initial BP elevations are eligible if initiation or adjustment of BP medication lowers pressure to meet entry criteria)
History of asymptomatic LVEF decline to < 40% during or after prior HER2-targeted therapy even if the current LVEF is >= 50%

Cardiac disease (history of and/or active disease) that would preclude the use of the drugs included in the treatment regimens; this includes but is not confined to:

Active cardiac disease

Angina pectoris that requires the current use of anti-anginal medication;
Ventricular arrhythmias except for benign premature ventricular contractions;
Supraventricular and nodal arrhythmias requiring a pacemaker or not controlled with medication;
Conduction abnormality requiring a pacemaker;
Valvular disease with documented compromise in cardiac function; or
Symptomatic pericarditis

History of cardiac disease

Prior myocardial infarction documented by elevated cardiac enzymes or persistent regional wall abnormalities on assessment of left ventricular (LV) function;
History of documented congestive heart failure (CHF) defined as symptomatic heart failure with an LVEF < 40%; or
Documented cardiomyopathy
Nervous system disorder (paresthesia, peripheral motor neuropathy, or peripheral sensory neuropathy) >= grade 2, per the CTCAE v 5.0
History of severe allergic, anaphylactic, or other hypersensitivity reactions to pertuzumab or trastuzumab or to any of its excipients, as well as any chimeric or humanized antibodies or fusion proteins
Known hypersensitivity to biopharmaceuticals produced in Chinese hamster ovary cells or other recombinant antibodies
Known allergy or hypersensitivity to the components of the atezolizumab formulation or to any of the study drugs or excipients, (e.g., Cremophor EL, polysorbate 80)

History or risk of autoimmune disease, including, but not limited to, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, vascular thrombosis associated with antiphospholipid syndrome, Wegener's granulomatosis, Sjogren's syndrome, Bell's palsy, Guillain-Barre syndrome, multiple sclerosis, autoimmune thyroid disease, vasculitis, or glomerulonephritis

Patients with a history of autoimmune hypothyroidism on a stable dose of thyroid replacement hormone may be eligible
Patients with controlled type 1 diabetes mellitus on a stable insulin regimen may be eligible

Patients with eczema, psoriasis, lichen simplex chronicus of vitiligo with dermatologic manifestations only (e.g., patients with psoriatic arthritis would be excluded) are permitted provided that they meet the following conditions:

Patients with psoriasis must have a baseline ophthalmologic exam to rule out ocular manifestations
Rash must cover less than 10% of body surface area (BSA)
Disease is well controlled at baseline and only requiring low-potency topical steroids (e.g., hydrocortisone 2.5%, hydrocortisone butyrate 0.1%, fluocinolone 0.01%, desonide 0.05%, alclometasone dipropionate 0.05%)
No acute exacerbations of underlying conditions within the last 12 months (not requiring psoralen plus ultraviolet A radiation [PUVA], methotrexate, retinoids, biologic agents, oral calcineurin inhibitors; high potency or oral steroids)
Treatment with systemic immunomodulatory medications (including but not limited to interferons, IL-2) within 4 weeks or 5 half-lives of the drug, whichever is longer, prior to study entry
Treatment with systemic immunosuppressive medications (including but not limited to prednisone, cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis [anti-TNF] factor agents) within 14 days prior to study entry or anticipation of need for systemic immunosuppressive medications during the study; Note: Intranasal and inhaled corticosteroids or systemic corticosteroids at doses that do not exceed 10 mg/day of prednisone or an equivalent corticosteroid are allowed
Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 2 weeks prior to study entry
Active hepatitis B virus (HBV) infection, defined as having a positive hepatitis B surface antigen (HBsAg) test at screening; patients with a past or resolved HBV infection, defined as having a negative HBsAg test and a positive total hepatitis B core antibody (HBcAb) test at screening, are eligible for the study if active HBV infection is ruled out on the basis of HBV deoxyribonucleic acid (DNA) viral load per local guidelines
Active hepatitis C virus (HCV) infection, defined as having a positive HCV antibody test at screening confirmed by a polymerase chain reaction (PCR) positive for HCV ribonucleic acid (RNA)
Patients with clinically active tuberculosis
Severe infection within 4 weeks prior to study entry, including but not limited to hospitalization for complications of infection, bacteremia, or severe pneumonia
Prior allogeneic stem cell or solid organ transplantation
Symptomatic peripheral ischemia
History of idiopathic pulmonary fibrosis, organizing pneumonia (e.g., bronchiolitis obliterans), drug-induced pneumonitis, idiopathic pneumonitis, or evidence of active pneumonitis or >= grade 1 pulmonary fibrosis, per the CTCAE v5.0, on screening chest CT scan
Administration of a live, attenuated vaccine within 4 weeks pr