Study of Effectiveness of Lovastatin to Prevent Radiation-Induced Rectal Injury

Inclusion Criteria: * Histologically or cytologically confirmed diagnosis of adenocarcinoma of the prostate * Planned treatment with radiation therapy to include external beam and/or brachytherapy with curative intent (total dose ≥60 Gy). A portion of the rectum must receive at least 60 Gy. * Age at least 18 years * Karnofsky Performance Status (KPS) ≥ 70 * No history of prior radiotherapy to the prostate or rectum * History of prior malignancy, if likely to live at least 4 years, is acceptable. * No evidence of distant metastases * Patients may be taking an HMG-coA-reductase inhibitor, but to be eligible, they must be able to be changed to lovastatin 20 mg/day, with the permission of their prescribing physician. * Creatine kinase \< 5 times upper normal limit * Sufficient renal function defined as calculated creatinine clearance ≥ 30ml/min * transaminases \< 3 times upper normal limit Exclusion Criteria: * Planned abdomino-perineal resection after radiotherapy * Contraindication to an HMG-coA-reductase inhibitor * Major medical or psychiatric illness, which in the investigator's opinion, would prevent completion of treatment and would interfere with follow-up. * Currently taking an inhibitor of cytochrome P450 3A4 * Active liver or muscle disease