Dosimetric Evaluation of Organs at Risk From SAVE Protocol

Area of Science:

• Radiation Oncology
• Gynecologic Oncology
• Clinical Trial Research

Background:

• Endometrial cancer treatment often involves adjuvant vaginal cuff brachytherapy (VCB).
• Optimizing VCB techniques is crucial for minimizing toxicity to surrounding organs at risk (OARs).
• Evaluating novel fractionation schemes is essential for improving patient outcomes.

Purpose of the Study:

• To compare the dosimetric characteristics of a short-course VCB regimen with standard of care (SOC) VCB in early endometrial cancer patients.
• To assess radiation doses delivered to OARs, including the rectum, bladder, sigmoid, small bowel, and urethra.
• To evaluate the potential for reduced toxicity with the experimental short-course VCB.

Main Methods:

• A prospective, phase 3, multi-institutional randomized trial (SAVE trial) involving 108 patients.
• Patients were randomized to an experimental short-course arm (11 Gy x 2 fractions) or SOC arms (7 Gy x 3, 5-5.5 Gy x 4, or 6 Gy x 5 fractions).
• Doses to contoured OARs were compared, and absolute doses were converted to 2 Gy equivalent doses (EQD2).

Main Results:

• The experimental short-course VCB demonstrated significantly lower EQD2 doses to the rectum, bladder, sigmoid, and urethra compared to 7 Gy x 3 and 5-5.5 Gy x 4 SOC schemes.
• No significant difference in OAR doses was observed between the experimental arm and the 6 Gy x 5 SOC scheme.
• Small bowel doses were not statistically different across any of the compared arms.
• The 7 Gy x 3 fractionation scheme resulted in the highest EQD2 doses to OARs.

Conclusions:

• Experimental short-course VCB (11 Gy x 2 fx) delivers a comparable biologically effective dose to SOC VCB.
• This approach reduces or maintains EQD2 doses to critical OARs, potentially leading to fewer acute and late adverse effects.
• Short-course VCB shows promise for improving the therapeutic ratio in early endometrial cancer management.