The investigators propose to evaluate the feasibility, safety, and preliminary efficacy of delivering online, adaptive magnetic resonance imaging (MRI)-guided and gated stereotactic body radiation therapy for patients with recurrent or metastatic ovarian cancer on a novel, integrated Co-60 MRI treatment machine. To best assess this technology, the investigators will focus on patients that have no more than three sites of progressive disease within the central thorax, liver, and/or non-liver abdominopelvis to receive adaptive, MRI-guided and gated SBRT with MRI simulation. Patients will be treated in five fractions over one to two weeks. By adhering to strict normal tissue constraints, expected toxicity will be within the current standard of care but will allow adaptation based on daily anatomic changes. The prescription dose will be determined based on hard normal tissue constraints, and capped at 10Gy per fraction. Although the long term goal will be to achieve improved local control and disease-free survival with reduced toxicity, the present study will be driven by the short term goal of demonstrating the feasibility of this novel treatment approach for recurrent or metastatic ovarian cancer.

Inclusion Criteria:

• Histologically or cytologically confirmed primary disease histology of solid ovarian, fallopian tube, or primary peritoneal tumor categorization.
• Deemed medically fit for stereotactic body radiation therapy by the treating physician.
• At least 18 years old.
• Karnofsky Performance Status ≥ 70
• Completed any systemic therapy (excluding endocrine therapy, which may be ongoing) at least one week prior to planned start of SBRT (two weeks preferred) and must have no plans to initiate systemic therapy for at least one week following end of SBRT (two weeks preferred).
• Able to understand and be willing to sign an IRB approved written informed consent document (or legally authorized representative, if applicable).

Exclusion Criteria:

• Past history of radiotherapy within the projected treatment field of any of the disease sites to be treated by MRI-guided, gated, and/or online adaptive SBRT
• Current central nervous systemic disease.
• Widespread progressive disease, i.e., more than three sites of progressive disease (note that more than three sites of disease are permitted provided there are no more than three sites of progressive disease).
• Actively receiving any investigational agents.
• Presence of uncontrolled intercurrent illness including, but not limited to, ongoing or active infection, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia, or psychiatric illness/social situations that would limit compliance with study requirements.
• Pregnant and/or breastfeeding. Patients of childbearing potential must have a negative pregnancy test within 14 days of study entry.
• Medical contraindication to undergoing MR imaging.