2695 - A Phase II Trial of Stereotactic Body Radiation Therapy and Fluoroestradiol Positrom Emission Tomography in Patients with Oligoprogressive Estrogen Receptor-Positive Metastatic Breast Cancer
Presenter(s)
J. G. Bazan Jr1, Y. R. Li2, T. Abuali2, R. Nelson3, and J. Mortimer4; 1Department of Radiation Oncology, City of Hope National Medical Center, Duarte, CA, 2City of Hope, Duarte, CA, 3Division of Biostatistics, City of Hope National Medical Center, Duarte, CA, 4Department of Medical Oncology, City of Hope National Medical Center, Duarte, CA
Purpose/Objective(s): The term oligoprogression (OP) refers to a clinical scenario in which patients with diffuse metastatic disease on systemic therapy have a limited number of metastases that have progressed or are new whereas the majority of metastases are stable or improved. OP disease is increasingly being encountered in clinical practice due to improvements in systemic therapy. Treating OP disease with local ablative therapies may therefore prolong the time to more diffuse progression necessitating a change in systemic therapy and may therefore lead to improved overall survival in these patients. Only one study has evaluated the role of SBRT in patients with OP MBC. This trial accrued 47 patients with OP MBC, with 2/3 having triple negative disease. There was no difference in PFS between patients that received SBRT versus those that did not (4.2 months vs. 4.4 months, p=0.2). Whether ablative therapies are beneficial in subtypes of breast cancer that have many effective systemic therapies available, such as ER+ breast cancer, remains an open question and an unmet clinical need.
Materials/Methods: Phase II study for patients with OP ER+ MBC (1-4 new and/or progressing metastatic lesions). Eligible patients will receive stereotactic body radiation therapy (SBRT) to the OP lesions. SBRT will be delivered to each lesion in 3-5 fractions. Each patient’s systemic therapy regimen will be held during study therapy and will resume upon completion of study therapy. Patients will then be restaged at 12 weeks post-SBSRT. Patients that have at least stable disease at that time point will continue on their systemic therapy and then be re-staged 12 weeks later (24 weeks after SBRT). This study will also study the role of ER-targeted positron emission tomography (PET) imaging with 16a-18F-Fluoro-17ß-Fluroestradiol (FES) in the OP ER+ patient population with FES PET scans obtained at baseline, and at each of the 2 follow-up imaging timepoints. A key secondary hypothesis is that the use of FES PET in addition to standard imaging at baseline and in follow-up will help confirm patients have OP disease and will help assess for new lesions on subsequent restaging.
Results: TBD
Conclusion: TBD