Single-Center Preliminary Experience Treating Endometrial Cancer Patients with Fiducial Markers

Area of Science:

• Radiation Oncology
• Gynecologic Oncology

Background:

• Post-operative endometrial cancer patients often require adjuvant radiotherapy to the vaginal cuff.
• Accurate targeting is crucial to maximize dose delivery while minimizing toxicity to surrounding organs.

Purpose of the Study:

• To evaluate the feasibility and effectiveness of daily image-guided radiotherapy (IGRT) using implanted fiducial markers (FMs) for vaginal cuff treatment.
• To assess the role of FMs in guiding radiotherapy for post-surgery endometrial cancer patients.

Main Methods:

• Five patients with vaginal cuff cancer received external beam radiotherapy with a stereotactic boost, guided by three implanted gold FMs.
• Image guidance involved real-time 2D kV monitoring of FMs and analysis of CBCT scans for image registration and organ segmentation (rectum, bladder, vaginal cuff).
• Fiducial marker position and image similarity (Dice index) were analyzed to assess treatment accuracy and reproducibility.

Main Results:

• All patients completed radiotherapy with good tolerance and no significant toxicity.
• Fiducial markers remained stable throughout treatment, with only two patients showing intrafractional shifts > 5 mm.
• High Dice similarity coefficient (DSC) of 0.90 indicated strong performance in bladder segmentation, though rectal variability impacted delivery quality.
• Target coverage was maintained with a 10 mm CTV-to-PTV margin.

Conclusions:

• Daily IGRT with CBCT and FMs is a feasible approach for treating post-operative gynecological cancers.
• This technique shows promise for enabling SBRT, allowing for margin reduction and optimized dose delivery.
• Further studies with larger cohorts are needed to confirm these preliminary findings and explore adaptive strategies.