Inclusion Criteria:
* Participants that are greater than or equal to 18 years of age
* For U.S. sites, patients can read and understand English or Spanish; for Canadian site, participants can read and understand English or French
* Histology confirmed, or clinical suspicion of, invasive epithelial ovarian, fallopian tube, or peritoneal carcinoma. Must be grade 2 or 3 or high (where high is defined as grade 2/3). All histologies including serous, endometrioid, clear cell sarcoma, or carcinosarcoma histology is acceptable. Mixed histology also acceptable.
* Treatment naïve for this cancer diagnosis
* Planned for neoadjuvant chemotherapy (platinum-based doublet with taxane +/- anti-VEGF antibody) for at least 3 but no more than 5 cycles followed by an interval debulking surgery. \[Note: this study evaluates response while on neoadjuvant treatment. The final collection of specimen and questionnaire is at the time of surgery and immediate post-operative state. Therefore, there are no eligibility criteria related to treatment in the adjuvant setting (e.g., intraperitoneal treatment) and adjuvant therapy should proceed as the physician deems appropriate.\]
* Measurable disease as defined by RECIST 1.1, CT scan (with or without contrast) within 12 weeks of study enrollment.
* Eastern Cooperative Oncology Group (ECOG) performance status of 0,1, or 2
* Able to provide tissue biopsy (core or excisional) sufficient for diagnosis and biomarker analysis, may use outside archival tissue if available.
* If currently using anti-coagulation medication, no contraindication for temporary stoppage of use during the study based on physician judgement
* Willing and able to swallow pills without difficulty
* Un-transfused platelet count \> 100,000 cells/μL
* Willing and able to participate in all required evaluations and procedures in this study protocol (e.g. undergoing treatment, scheduled visits and examinations, serum testing, questionnaires, pill log/diary)
* Absolute neutrophil count \> 1.5 x 109 cells/L
* Hemoglobin \> 9.0 g/dL, may use transfusions and the value can be post-transfusion
* Estimated creatinine clearance of \> 30 mL/min, calculated using the formula Cockcroft-Gault \[(140-age) x Mass (kg)/(72 x creatinine mg/dL)\] x 0.85 for female
* No severe hepatic impairment defined as AST or ALT elevation \< 2.5 x institutional ULN, unless liver metastasis is present \< 5 x ULN
Exclusion Criteria:
* Definite contraindication for either aspirin use or stopping current aspirin use based on physician's clinical judgment
* History of vascular event in the last 12 months (e.g., myocardial infarction or unstable angina, stroke, coronary artery angioplasty or stenting, coronary artery bypass graft, relevant \[serious or significant\] arrhythmias, significant vascular disease, congestive heart failure or vascular interventions).
* History of hypertensive crisis and/ or uncontrolled HTN, systolic blood pressure \> 150 mmHg; diastolic blood pressure \> 90mmHg. Participants must have blood pressure \< 150/90 mmHg taken in a clinic setting by a medical professional within 2 weeks prior to starting study.
* Current or history of ulcers which prohibits aspirin consumption, severe hepatic failure, or acute or chronic renal disease where aspirin use is contraindicated
* History of gastrointestinal or genitourinary bleeding or other bleeding diathesis or coagulopathy within 6 months prior to enrollment of study
* Uncontrolled erosive esophagitis requiring 2 or more treatments
* Other cancer diagnosis in the last 3 years other than non-melanoma skin cancer
* Autoimmune disorder requiring systemic therapy
* Chronic steroid use defined as 3 weeks in the past year or any length of time in the past 30 days.
* Other aspirin or NSAID hypersensitivities or contraindications (e.g. allergy)
* History of bariatric surgery
* Currently pregnant at the Screening visit or planning on becoming pregnant during the study period
* Participant is unable to swallow orally administered medication and patients with gastrointestinal disorders likely to interfere with study medication.
* Metabolism CYP2C9, known G6PD deficient patients
