Patient description: The patient is a 63-year-old man presenting to the Emergency Department with a history of acute urinary retention in the past 2 days. Abdominopelvic CT scan revealed a large prostate and a bladder filled with urine. He is a candidate for urethral catheterization and TURP. Further evaluation revealed: Post-void residual: 71 mL Prostate volume (TRUS): 63 mL Prostate-specific antigen (PSA) level: 3.5 ng/mL His recent blood chemistry (3 days ago) was normal: Hgb: 13.6 g/dl WBC: 133000 /mm3 Plt: 370000 /ml PT: 12 second PTT: 34 second INR: 0.9 Creatinine: 0.5 mg/dl BUN: 10 mg/dl U/A: Color: yellow Appearance: cloudy PH: 5.3 Specific gravity: 1.010 Glc: 100 Nitrite: negative Ketone: none Leukocyte esterase: negative RBC: negative WBC: 2 WBCs/hpf U/C: negative

Clinical trial eligibility criteria: eligible ages (years): 18.0-999.0,  Adenocarcinoma of the Prostate Castration-resistant Prostate Cancer Recurrent Prostate Cancer Stage III Prostate Cancer Stage IV Prostate Cancer The subject has a proven histologic diagnosis of prostate adenocarcinoma, but may have undergone prior surgery and/or radiation. 2. The subject must currently have castration resistant prostate cancer defined as 2 serial rising PSAs with a castrate level of testosterone (<50 ng/dL). 3. A subject with non-metastatic CRPC may not have received prior chemotherapy unless in the neoadjuvant or adjuvant setting > 24 months ago and may not have received prior zoledronic acid or denosumab. 4. A subject with metastatic CRPC must have bone metastases accessible for biopsy by CT guidance. 5. The subject must be willing to undergo sequential biopsy of bone or bone metastases. 6. Subjects must have discontinued additional hormonal (eg bicalutamide, abiraterone, estrogen) therapy prior to the first dose of cabozantinib. No antiandrogen withdrawal period is required. 7. Subjects previously treated on another investigational agent must have a 2-week or more washout before starting cabozantinib, depending on the agent, toxicity profile, and half-life. However, such patients may begin tetracycline dosing after consent is signed. 8. Subjects who are currently on GnRH agonists or antagonist therapy must continue androgen suppression. 9. The subject is ≥18 years old on day of consent. 10. Eastern Cooperative Oncology Group Performance Status (ECOG PS) 0 or 1. 11. Organ and marrow function as follows: 1. ANC ≥1500/mm3 without colony stimulating factor support. 2. Platelets ≥100,000/mm3. 3. Hemoglobin ≥9 g/dL. 4. Total bilirubin ≤1.5 x the upper limit of normal (ULN). For subjects with known Gilbert's disease, bilirubin≤3.0 mg/dL. 5. Serum albumin ≥2.8g/dL. 6. Serum creatinine ≤1.5 x ULN or calculated creatinine clearance >50 mL/min. The Cockcroft and Gault equation should be used: Male: CrCl (mL/min) = (140 age) × wt (kg) / (serum creatinine × 72). 7. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤ 3.0 x ULN. 8. Lipase <2.0 × ULN and no radiologic or clinical evidence of pancreatitis. 9. Serum testosterone level <50 ng/dL. 10. Urine protein/creatinine (UPC) ratio ≤1.0 unless the patient has a neobladder. 11. Serum phosphorus, magnesium, calcium and potassium ≥ lower limit of normal (LLN). 12. The subject is capable of understanding and complying with the protocol requirements and has signed the informed consent document. 13. Sexually active subjects and their partners must agree to use medically accepted barrier methods of contraception (eg, male or female condom) during the course of the study and for 4 months after the last dose of study drug(s), even if oral contraceptives are also used. All subjects of reproductive potential must agree to use both a barrier method and a second method of birth control during the course of the study  The subject has received cytotoxic chemotherapy (including investigational cytotoxic chemotherapy) or biologic agents (eg, cytokines or antibodies) within 3 weeks, or nitrosoureas/ mitomycin C within 6 weeks before the first dose of study treatment. 2. Prior treatment with cabozantinib and other met inhibitors. 3. Prior treatment with a small molecule kinase inhibitor or a hormonal therapy (including investigational kinase inhibitors or hormones) within 14 days or five half-lives of the compound or active metabolites, whichever is longer, or before the first dose of study treatment. 4. The subject has received radiation therapy: 1. to the thoracic cavity or gastrointestinal tract within 3 months of the first dose of study treatment. 2. to bone or brain metastasis within 14 days of the first dose of study treatment. 3. to any other site(s) within 28 days of the first dose of study treatment. 5. The subject has received radionuclide treatment within 6 weeks of the first dose of study treatment. 6. The subject has received any other type of investigational agent within 28 days before the first dose of study treatment. 7. The subject has not recovered to baseline or CTCAE ≤ Grade 1 from toxicity due to all prior therapies except alopecia and other non-clinically significant AEs. 8. The subject has a primary brain tumor. 9. The subject has active brain metastases or epidural disease (Note: Subjects with brain metastases previously treated with whole brain radiation or radiosurgery or subjects with epidural disease previously treated with radiation or surgery who are asymptomatic and do not require steroid treatment for at least 2 weeks before starting study treatment are eligible. Neurosurgical resection of brain metastases or brain biopsy is permitted if completed at least 3 months before starting study treatment. Baseline brain scans are not required to confirm eligibility.) 10. The subject has prothrombin time (PT)/ International Normalized Ratio (INR) or partial thromboplastin time (PTT) test results at screening ≥ 1.3 x the laboratory ULN. 11. The subject requires concomitant treatment, in therapeutic doses, with anticoagulants such as warfarin or warfarin-related agents, heparin, thrombin or Factor Xa inhibitors, or antiplatelet agents (eg, clopidogrel). Low dose aspirin (≤ 81 mg/day), low-dose warfarin (≤ 1 mg/day), and prophylactic low molecular weight heparin (LMWH) are permitted. 12. The subject requires chronic concomitant treatment of strong CYP3A4 inducers (e.g., dexamethasone, phenytoin, carbamazepine, rifampin, rifabutin, rifapentin, phenobarbital, and St. John's Wort). Because the lists of these agents are constantly changing, it is important to regularly consult a frequently-updated list such as http://medicine.iupui.edu/clinpharm/ddis/table.asp; medical reference texts such as the Physicians' Desk Reference may also provide this information. As part of the enrollment/informed consent procedures, the patient will be counseled on the risk of interactions with other agents, and what to do if new medications need to be prescribed or if the patient is considering a new over-the-counter medicine or herbal product. 13. The subject has experienced any of the following: 1. clinically-significant gastrointestinal bleeding within 6 months before the first dose of study treatment. 2. hemoptysis of ≥0.5 teaspoon (2.5 mL) of red blood within 3 months before the first dose of study treatment. 3. any other signs indicative of pulmonary hemorrhage within 3 months before the first dose of study treatment. 14. The subject has radiographic evidence of cavitating pulmonary lesion(s). 15. The subject has tumor in contact with, invading or encasing major blood vessels. 16. The subject has evidence of tumor invading the GI tract (esophagus, stomach, small or large bowel, rectum or anus), or any evidence of endotracheal or endobronchial tumor within 28 days before the first dose of cabozantinib. 17. The subject has uncontrolled, significant intercurrent or recent illness including, but not limited to, the following conditions: a. Cardiovascular disorders including: i. Congestive heart failure (CHF): New York Heart Association (NYHA) Class III (moderate) or Class IV (severe) at the time of screening. ii. Concurrent uncontrolled hypertension defined as sustained BP > 140 mm Hg systolic, or > 90 mm Hg diastolic despite optimal antihypertensive treatment within 7 days before the first dose of study treatment. iii. Any history of congenital long QT syndrome. iv. Any of the following within 6 months before the first dose of study treatment unstable angina pectoris clinically-significant cardiac arrhythmias stroke (including TIA, or other ischemic event) myocardial infarction thromboembolic event requiring therapeutic anticoagulation (Note: subjects with a venous filter (e.g. vena cava filter) are not eligible for this study) b. Gastrointestinal disorders particularly those associated with a high risk of perforation or fistula formation including: i. Any of the following within 28 days before the first dose of study treatment intra-abdominal tumor/metastases invading GI mucosa active peptic ulcer disease inflammatory bowel disease (including ulcerative colitis and Crohn's disease), diverticulitis, cholecystitis, symptomatic cholangitis or appendicitis malabsorption syndrome ii. Any of the following within 6 months before the first dose of study treatment