Add-Aspirin: the effects of aspirin on disease recurrence and survival after primary therapy in common non-metastatic solid tumours.

INTERVENTION: 1. Randomised blinded phase: Participants will be randomly assigned to 100mg aspirin, 300mg aspirin or matched placebo. All tablets will be enteric‐coated to be taken daily for at least five years 2. Run‐in feasibility phase: During the feasibility phase of the study, all participants will take open label 100mg aspirin daily for a run‐in period of approximately 8 weeks prior to randomisation CONDITION: Cancer ; Cancer PRIMARY OUTCOME: Overall survival ; INCLUSION CRITERIA: Common INCLUSION CRITERIA: 1. Written informed consent 2. WHO performance status 0, 1 or 2 3. Previous or current participants of other primary treatment trials if agreed in advance between trials 4. No clinical or radiological evidence of residual or distant disease Breast cohort INCLUSION CRITERIA: 1. Men or women with histologically confirmed invasive breast cancer 2. Undergone complete primary invasive tumour excision with clear margins 3. Surgical staging of the axilla must have been undertaken by sentinel node biopsy, axillary sampling or dissection 4. In those patients with a positive sentinel node biopsy: 4.1. If 1, 2 or 3 nodes are positive, subsequent management of the axilla (with surgery, radiotherapy or no further intervention) should be completed prior to registration 4.2. If 4 or more nodes are involved, patients must have undergone completion axillary node dissection 5. Radiotherapy (RT): 5.1. Patients who h