A Proof-of-principle Study of HBO-SRS for Brain Metastases

Inclusion Criteria * Metastatic brain tumor referred to radiation oncology for treatment * Size of the presenting metastatic lesion up to 5.0 cm diameter * Age \> 18 years * Patients must give informed consent indicating they are aware of the investigational nature of this treatment * Karnofsky Performance Status \> 70% (Zubrod score 0 to 1) * Women of childbearing potential must have a negative serum or urine pregnancy test within 14 days to start of study therapy * CBC and CMP within 30 days to start of study therapy * Chest imaging (Chest Xray or Chest CT) within past 12 months, that does not show any contraindication to hyperbaric therapy (if patient has had any thoracic surgery or other significant event that might have affected the thorax such as trauma, pneumothorax, chest tube insertion, pleurodesis, or thoracentesis and has not had imaging since that event, then the imaging should be repeated). * Neurosurgery Consult Exclusion Criteria * Pregnant women or women of childbearing potential without adequate contraception. Contraception, which can include abstinence, is required since the last menstrual period until completion of SRS. * Evidence of pneumothorax (Untreated pneumothorax risks tension pneumothorax during ascent in HBO chamber) * COPD with C02 retention (Such patients can develop respiratory depression as HBO reduces their hypoxemic drive) * Uncontrolled seizure disorder (Note that patients on adequate antiepileptic medications may receive HBO) * Claustrophobia resistant to medication (Pre-medication with anxiolytics is generally sufficient for almost all anxious patients undergoing HBO treatment) * History of middle ear surgery * Failure to equalize pressure in the middle ear can cause displacement of middle ear structures with consequent hearing loss * To clarify: placement of a tympanostomy tube is not a contraindication to HBO, and in fact may improve tolerability of the procedure * History of bleomycin administration (HBO can exacerbate interstitial pneumonitis in such patients) * Current cis-platinum chemotherapy, i.e. therapeutic levels in the bloodstream at the time of HBO therapy. (HBO can increase cytotoxicity of cis-platinum) * Uncontrolled high blood pressure (HBO can increase systemic vascular resistance) * Unstable angina or myocardial infarction within the previous 3 months (Increased afterload due to HBO can increase myocardial workload) * Cardiac EF ≤ 35% * Pulmonary edema can arise with HBO in certain patients with severe heart failure * In patients with prior history of CHF, subsequent echocardiogram and ECG are required to establish EF\>35% * Treatment with disulfiram (Disulfiram inhibits superoxide dismutase and is not approved for use concomitantly with hyperbaric oxygen therapy) * Active drug/alcohol dependence or abuse * Lack of adequate social support structures, e.g. homelessness * Tumors with potential confounding results on serum marker studies * Small cell (neuroendocrine) carcinomas * Carcinoid tumors