Phase I dose escalation trial using stereotactic body radiation therapy (SBRT) for partial breast irradiation (PBI).

1057 Background: To evaluate tolerability of escalating doses of 5 fraction SBRT PBI in treating early stage breast cancer after partial mastectomy on a phase I dose escalation trial. The primary objective was to escalate the PBI dose utilizing a robotic stereotactic radiation system treating the lumpectomy cavity without exceeding the maximum tolerated dose (MTD). Methods: Eligible patients included DCIS or invasive ductal histologies, AJCC stage 0-II with tumor size < 3cm, and margins ≥ 2mm. Prior to simulation 3-4 four gold fiducials were placed around the lumpectomy cavity for real-time respiratory tracking. Dose limiting toxicity (DLT) equaled grade ≥ 3 toxicity by CTCAE deemed definitely related to treatment for: skin, bone (fracture), pulmonary, neurological (intercostal or brachial plexus nerves) or any grade 4/ 5 toxicity definitely attributed to therapy. Both patients and physicians completed baseline and subsequent cosmesis questionnaires using a four point scale – excellent, good, fair, poor. ...