A Study of Trastuzumab Emtansine (Kadcyla) Plus Pertuzumab (Perjeta) Following Anthracyclines in Comparison With Trastuzumab (Herceptin) Plus Pertuzumab and a Taxane Following Anthracyclines as Adjuvant Therapy in Participants With Operable HER2-Positive Primary Breast Cancer

Inclusion Criteria:

   - Eastern Cooperative Oncology Group (ECOG) performance status less than or equal to
   (
   - Non-metastatic histologically confirmed primary invasive breast carcinoma that was
   operable

   - HER2-positive breast cancer

   - Known hormone receptor status of the primary tumor

   - Adequately excised: participants must have undergone either breast-conserving surgery
   or mastectomy/nipple- or skin-sparing mastectomy

   - Pathological tumor-node-metastasis staging (Union for International Cancer
   Control-American Joint Committee on Cancer [UICC/AJCC] 7th edition): eligible
   participants must have either:

Node-positive disease (pN more than or equal to [>/=] 1), any tumor size except T0, and any
hormonal receptor status; or Node-negative disease (pN0) with pathologic tumor size >2.0
centimeters by standard local assessment and negative for estrogen receptor (ER) and
progesterone receptor (PR) determined by a central pathology laboratory

   - Participants with synchronous bilateral invasive disease are eligible only if both
   lesions are HER2-positive

   - No more than 9 weeks (63 days) may elapse between definitive breast surgery (or the
   last surgery if additional resection required for breast cancer) and randomization

   - Baseline left ventricular ejection fraction (LVEF) >/=55% measured by echocardiogram
   (ECHO; preferred) or multiple-gated acquisition (MUGA) scans

   - Documentation on hepatitis B virus (HBV) and hepatitis C virus (HCV) serology is
   required

   - Female participants of childbearing potential must be willing to use one highly
   effective form of non-hormonal contraception or two effective forms of non-hormonal
   contraception. For male participants with partners of childbearing potential, one
   highly effective form of contraception or two effective forms of contraception must be
   used. Contraception must continue for the duration of study treatment and for 6 months
   after the last dose of study treatment

Exclusion Criteria:

   - History of any prior (ipsilateral and/or contralateral) invasive breast carcinoma

   - History of non-breast malignancies within the 5 years prior to randomization, except
   for carcinoma in situ (CIS) of the cervix, CIS of the colon, melanoma in situ, and
   basal cell and squamous cell carcinomas of the skin

   - Any clinical T4 tumor as defined by tumor-node-metastasis classification in UICC/AJCC
   7th edition, including inflammatory breast cancer

   - For the currently diagnosed breast cancer, any previous systemic anti-cancer treatment
   (for example, neoadjuvant or adjuvant), including but not limited to, chemotherapy,
   anti-HER2 therapy (for example, trastuzumab, trastuzumab emtansine, pertuzumab,
   lapatinib, neratinib, or other tyrosine kinase inhibitors), hormonal therapy, OR
   anti-cancer radiation therapy (RT) (intra-operative radiotherapy as a boost at the
   time of primary surgery is acceptable)

   - Previous therapy with anthracyclines, taxanes, or HER2-targeted therapy for any
   malignancy

   - History of DCIS and/or lobular CIS (LCIS) that was treated with any form of systemic
   chemotherapy, hormonal therapy, or RT to the ipsilateral breast where invasive cancer
   subsequently developed. Participants who had their DCIS/LCIS treated with surgery only
   and/or contralateral DCIS treated with radiation are allowed to enter the study

   - Participants with contraindication to RT while adjuvant RT is clinically indicated

   - Concurrent anti-cancer treatment in another investigational trial

   - Cardiopulmonary dysfunction as defined by protocol: angina pectoris requiring
   anti-anginal medication, serious cardiac arrhythmia not controlled by adequate
   medication, severe conduction abnormality, or clinically significant valvular disease,
   significant symptoms (Grade >/=2) relating to left ventricular dysfunction, cardiac
   arrhythmia, or cardiac ischemia, myocardial infarction within 12 months prior to
   randomization, uncontrolled hypertension, evidence of transmural infarction on
   electrocardiogram (ECG), requirement for oxygen therapy

   - Other concurrent serious diseases that may interfere with planned treatment, including
   severe pulmonary conditions/illness, uncontrolled infections, uncontrolled diabetes,
   or known infection with HIV

   - Any known active liver disease. For participants who are known carriers of HBV/HCV,
   active hepatitis B/C infection must be ruled out per local guidelines

   - Inadequate hematologic, renal or liver function

   - Pregnant or lactating women

   - Hypersensitivity to any of the study medications or any of the ingredients or
   excipients of these medications, including hypersensitivity to benzyl alcohol

   - Chronic immunosuppressive therapies, including systemic corticosteroids