Sigmoid dose using 3D imaging in cervical-cancer brachytherapy

Area of Science:

• Oncology
• Radiation Oncology
• Medical Physics

Background:

• Cervical cancer treatment often involves brachytherapy, which can pose risks to adjacent organs like the sigmoid.
• Three-dimensional (3D) planning allows for detailed evaluation of organ-at-risk doses.

Purpose of the Study:

• To assess the sigmoid's proximity and dose variations during cervical cancer brachytherapy using 3D planning.
• To identify predictors of sigmoid dose and analyze associated complications.

Main Methods:

• A study of 50 cervical cancer patients treated with low-dose-rate (LDR) or high-dose-rate (HDR) brachytherapy over 36 months.
• Analysis included sigmoid-to-tandem distance, sigmoid/rectum/bladder doses (D0.1 cc, D2 cc), and toxicity.
• 3D imaging was used to evaluate sigmoid proximity and dose-volume parameters.

Main Results:

• Higher sigmoid D0.1 cc doses were observed with HDR (84 Gy) compared to LDR (71.1 Gy) brachytherapy (p=0.02).
• Sigmoid proximity to the tandem significantly correlated with sigmoid dose (p<0.0001).
• HDR treatment showed substantial inter-fraction variation in sigmoid-to-tandem distance (40% CV), necessitating dose adjustments in 20% of fractions. No grade 3-4 sigmoid toxicity was reported after a median 31-month follow-up.

Conclusions:

• 3D imaging confirms the sigmoid is often near the tandem in cervical cancer brachytherapy.
• Significant variations in sigmoid-to-tandem distance between fractions highlight the need for individualized dose-volume assessments for each treatment session.