Olaparib as Adjuvant Treatment in Patients With Germline BRCA Mutated High Risk HER2 Negative Primary Breast Cancer

Olaparib treatment in patients with germline BRCA1/2 mutations and high risk HER2 negative primary breast cancer who have completed definitive local treatment and neoadjuvant or adjuvant chemotherapy

Patients will be randomised in 1:1 ratio to either olaparib or placebo. Randomisation will be stratified by Hormone receptor status (ER and/or PgR positive/HER2 negative versus TNBC), prior neoadjuvant versus adjuvant chemotherapy and prior platinum use for breast cancer. Randomised patients will receive study treatment for up to a maximum of 12 months. All patients will have safety assessments every 2 weeks during the first month, every 4 weeks for the following 5 months and 3 monthly for the remaining 6 months of study treatment plus 30 days after its discontinuation. Following randomisation, all patients will be assessed regularly for signs, symptoms and evidence of disease recurrence by taking medical history, physical examination and mammogram/breast MRI. Efficacy assessments will be performed on a 3 monthly basis during the first 2 years, followed by 6 monthly assessments for years 3, 4 and 5 and annually thereafter. All patients (except those with bilateral mastectomy) will have mammogram / breast MRI annually for 10 years beginning 6 months after randomisation. All randomised patients will have clinical assessment visits for 10 years following their randomisation into the study. Once a patient completes 10 years of clinical assessment they will enter the survival follow up phase of the trial which will continue until approximately 10 years after the last patient is randomised.

Inclusion Criteria: * Histologically confirmed non-metastatic primary invasive adenocarcinoma of the breast that is one of the following phenotypes: 1. Triple negative breast cancer defined as: ER and PgR negative AND HER2 negative (not eligible for anti-HER2 therapy) 2. ER and/or PgR positive, HER2 negative * Documented germline mutation in BRCA1 or BRCA2 that is predicted to be deleterious or suspected deleterious (known or predicted to be detrimental/lead to loss of function). * Completed adequate breast and axilla surgery. * Completed at least 6 cycles neoadjuvant or adjuvant chemotherapy containing anthracyclines, taxanes or the combination of both. Prior platinum as potentially curative treatment for prior cancer (e.g. ovarian) or as adjuvant or neoadjuvant treatment for breast cancer is allowed. * ECOG 0-1. Exclusion criteria: * Any previous treatment with a PARP inhibitor, including olaparib and/or known hypersensitivity to any of the excipients of study treatment. * Patients with second primary malignancy. EXCEPTIONS are: 1. adequately treated non-melanoma skin cancer, curatively treated in situ cancer of the cervix, Ductal Carcinoma in situ (DCIS) of the breast, stage 1 grade 1 endometrial carcinoma 2. other solid tumours and lymphomas (without bone marrow involvement) diagnosed ≥ 5 years prior to randomisation and treated with no evidence of disease recurrence and for whom no more than one line of chemotherapy was applied. * Concomitant use of known strong CYP3A inhibitors (e.g., itraconazole, telithromycin, clarithromycin, protease inhibitors boosted with ritonavir or cobicistat, indinavir, saquinavir, nelfinavir, boceprevir, telaprevir) or moderate CYP3A inhibitors (e.g., ciprofloxacin, erythromycin, diltiazem, fluconazole, verapamil). The required washout period prior to starting study treatment is 2 weeks. Concomitant use of known strong (e.g., phenobarbital, enzalutamide, phenytoin, rifampicin, rifabutin, rifapentine, carbamazepine, nevirapine and St John's Wort) or moderate CYP3A inducers (e.g., bosentan, efavirenz, modafinil). The required washout period prior to starting study treatment is 5 weeks for enzalutamide or phenobarbital and 3 weeks for other agents. * Evidence of metastatic breast cancer