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Updated: Jun 9, 2026
Stereotactic Radiosurgery for Gynecologic Cancer
Published on: April 17, 2012
18F-Fluorodeoxyglucose-Positron Emission Tomography/Computed Tomography Guided Stereotactic Body Radiation Therapy in
Marcin Kubeczko1,2, Berta Sousa2, Francisco Oliveira3
1Breast Cancer Center, Maria Sklodowska-Curie National Research Institute of Oncology, Gliwice Branch, Gliwice, Upper Silesia, Poland.
Purpose:
Cyclin-dependent kinase (CDK) 4/6 inhibitors have transformed the treatment of hormone receptor-positive/human epidermal growth factor receptor 2-negative metastatic breast cancer, yet resistance remains common. Metabolic response assessed by fluorine 18-labeled deoxyglucose might identify patients at risk of treatment failure earlier than conventional imaging. We evaluated the safety, feasibility, and efficacy of 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (18F-FDG-PET/CT)-guided stereotactic body radiation therapy(SBRT) combined with CDK4/6 inhibitors.
Methods And Materials:
This retrospective study included 29 patients monitored with 18F-FDG-PET/CT, who received SBRT concurrently with CDK4/6 inhibitors treatment or before CDK4/6 inhibitors commencement. Median age was 61 years (IQR, 53-68). Ten patients had de novo disease. The median disease-free interval for patients with recurrent disease was 66.9 months (IQR, 34.5-108.5). The majority of patients (72%) were treated in the first-line setting; 11 received ribociclib, 15 received palbociclib, and 3 received abemaciclib. Fifty-nine radiation treatments were delivered to 70 lesions: 41 before or concomitantly with the first CDK4/6 inhibitors cycle and 18 for oligoprogressive disease. Twenty-six treatments used single-fraction SBRT, and 33 used hypofractionated SBRT.
Results:
Post-SBRT maximum standardized uptake value (SUVmax) reduction was observed in all but one lesion. Metabolic complete response (mCR) occurred in 33 sites (56%), more frequently after single-fraction SBRT than hypofractionated SBRT (P = .03), in smaller lesions (<14 cm3, P = .002), and in lesions with lower SUVmax (<6.3, P = .008). Each unit increase in SUVmax reduced odds of mCR by ∼18% (odds ratio, 0.824; P = .04). Median progression-free survival was 48.2 months; 2-year progression-free survival was 71.5% (95% confidence interval [CI], 50.9-84.6).
Conclusions:
18F-FDG-PET/CT-guided SBRT, particularly single-fraction, added to CDK 4/6 inhibitors, is a valuable treatment modality resulting in substantial rates of mCR. Whether this translates into deferring disease progression requires randomized studies with larger treatment groups. To our knowledge, this study represents the first analysis evaluating 18F-FDG-PET/CT-guided SBRT in combination with CDK4/6 inhibitor-based therapy in patients with metastatic breast cancer.
