P015 Motion Management Without Fiducial Tracking Using Cyberknife SBRT for Multiple Lung Metastasis from Breast Cancers

Abstract

Cyber Knife robotic stereotactic radiosurgery is minimally invasive tumor treatment modality that can deliver high precision radiotherapy to any part of the body with minimal exposure to adjacent and surrounding vital organs and is used to treat oligometastasis of the lung from primary breast cancer patients. In the modern high precision treatment delivery, utmost care should be taken for motion management of tumor targets. The Objective of this study was to investigate the accuracy and efficacy of Cyber knife in the treatment of lung metastasis from breast cancer using fuducial free respiratory tracking system using cyberknife stereotactic radiosurgery. We examined toxicity and local control rate with fiducial-free CyberKnife stereotactic body radiation therapy (SBRT) for lung metastases from 20 breast cancer patients. All patients had favorable performance status (ECOG 0–2), oligometastatic disease. Total of 56 Lungs lesions were treated with a prescribed dose of 30–35 Gy delivered in five fractions to the planning target volume (PTV) using the CyberKnife with X-sight lung tracking. A median 30 Gy (IQR, 30–35 Gy) dose was delivered to a median prescription isodose line of 70% (IQR, 65–77%) to 20 patients with a total median follow up of 34 months. The toxicity and local control rates were favourable and 1- and 2-year local control estimates were 87% and 73%, respectively. Two of the five local failures were infield in patients who had received irradiation to the gross tumor volume and remaining 3 were in patients who had received irradiation to clinical target volume. No local failures were identified beyond 21 months of therapy. There was no lung, oesophageal or spinal cord toxicity noted in the above patients. Initial evaluation with fiducial free based respiratory tracking system using five-fraction CyberKnife SBRT is a promising treatment option for lung metastasis from breast cancer patients, demonstrating encouraging local control rates with no toxicity. a dose escalation study for the pheripheral lung metastasis from breast cancers is being planned.