Stereotactic Radiosurgery vs Whole Brain Radiotherapy in Breast Cancer With Brain Oligometastasis

AIMS AND OBJECTIVES To assess the impact of SRS on overall survival, brain tumour recurrence and radiation toxicity with oligometastatic brain metastasis as compared to patients who receive WBRT.

Primary End Point: Overall Survival (OS) Secondary End Points: Progression Free Survival (PFS) Toxic Effects of Radiation Quality of Life DETAILED RESEARCH METHODOLOGY Study Setting: Department of Radiotherapy and Oncology, Post Graduate Institute of Medical Education and Research, Chandigarh Study Design: Prospective hospital based study

Inclusion criteria:

• Age >=18 years
• Willing to provide informed consent
• Histologically confirmed malignancy with metastatic disease detected on imaging.
• ECOG performance status 0-1
• 1 to 5 brain metastases, each with a maximum diameter of no more than 3.5 cm on contrast enhanced magnetic resonance imaging(MRI) scans.

Exclusion criteria

• Serious medical comorbidities
• ECOG >= 2
• Prior Brain Radiotherapy
• >5 brain metastasis
• Maximum diameter >4cm on MRI

Randomisation and Treatment:

Prior to randomization, a complete history and physical examination by the treating radiation oncologist will be done. Histologically confirmation of malignancy is required, with metastatic disease detected on imaging. Prior to randomization, the patients will be stratified based on number of brain metastases (single vs 2-3), extent of extracranial disease (active vs stable). Extracranial disease will be considered to be stable when the tumor had been clinically controlled for 6 months or longer prior to the detection of brain metastases. After informed consent, eligible patients will be randomised in two arms.

Arm 1:

The WBRT dosage schedule will be 30 Gy in 10 fractions over 2 weeks. For Arm 1, Treatment planning is to be done using CT simulation or conventional simulation (fluoroscopy). Simple beam arrangements, such as parallel opposed beams, will be favoured wherever possible.

Arm 2:

All patients in Arm 2 will undergo planning CT simulation with 1mm slice thickness. For all lesions, the gross tumor volume (GTV) will be defined as the visible tumor on CT and/or MRI imaging. A Planning Target Volume (PTV) margin of 2-5 mm will be added. Organs at risk visible in the planning CT scan will be contoured. The doses will be prescribed to approximately 100% isodose level and 95% of the PTV should receive 95% of the prescription dose. Metastases with a maximum diameter of up to 2 cm will be treated with doses of 22 to 25 Gy and those larger than 2 cm will be treated with doses of 18 to 20 Gy.

Follow up:

Clinical evaluations and MRI scans will be done 1 and 3 months after treatment and every 3 months thereafter. In cases in which a recurrence will be detected, further treatment can be administered. The size of the treated lesions will be measured in 3 dimensions, and this size, the development of new brain metastases, and the development of leukoencephalopathy associated with radiological findings (according to the National Cancer Institute's Common Toxicity Criteria version 4.0319) will be scored based on serial MRI scans. Overall survival will be measured as time until death from any cause, and progression-free survival as time to either progression or death, whichever occurs first. Lesion response will be evaluated in this study using the international criteria proposed by the Response Evaluation Criteria in Solid Tumors (RECIST) Committee20. At each visit, functional status and neurologic toxic effects will be scored. Systemic functional status will be evaluated by using the KPS score. Neurologic function will be evaluated according to the criteria listed21.

Statistical analysis:

This study will aim to detect an improvement in overall survival. The study will therefore be designed with 80% power. It is estimated that the median survival of the control group after randomization in this study will be 9 months. In order to detect a 6-month improvement in median survival from 9 months to 15 months with SRS, a total of 93 patients will be needed. Assuming a 5% rate of loss to follow up, a total of 98 patients will be accrued. The study projects accrual over 48 months with 12 months of additional follow-up. Survival will be calculated using the Kaplan-Meier method with differences compared using the stratified log-rank test. A Cox multivariable regression analysis will be used to determine baseline factors predictive of survival. Differences in rates of grade 2 or higher toxicity between groups will be tested using the Fisher's Exact Test. Differences in progression free survival will be tested using the stratified log-rank test.

Novelty of study: This trial aims to assess the impact of SRS on overall survival, PFS, radiation toxicity and quality of life as compared to WBRT in oligometastatic brain disease in breast cancer patients. It may lead to better understanding of role of SRS in oligometastatic paradigm.