Position Selection for Postoperative Cervical Cancer Treatment with Volumetric Modulated Arc Therapy: Supine or Prone Position

• Published in: International journal of radiation oncology, biology, physics Vol. 120; no. 2; pp. e725 - e726
• Main Authors: Xiao, N.J., Chen, Z.J.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01-10-2024
• ISSN: 0360-3016
• DOI: 10.1016/j.ijrobp.2024.07.1594

The optimal positioning for postoperative adjuvant radiotherapy in cervical cancer patients, whether prone or supine, is uncertain due to varying degrees of intestinal adhesions and patient discomfort in the prone position. Therefore, our study aimed to explore dosimetric differences and clinical implications associated with the supine and prone positions.
This study retrospectively included patients who underwent postoperative adjuvant radiotherapy for cervical cancer at our institution between 2019.11 and 2022.10. Patients were divided into supine and prone groups. Comparisons were made between the two groups regarding the 95% PTV and irradiation doses to the bowel pouch, sigmoid colon, rectum, bladder, and pelvis. Additionally, hematologic toxicity, weight changes, and bowel toxicity during radiotherapy were compared between the two groups. Finally, posing errors during radiotherapy were compared between the two groups of patients.
A propensity-matching method was employed to match the supine and prone groups at a 1:2 ratio. After matching, there were 44 in the supine position and 88 cases in the prone position. The V15 of the bowel pouch was significantly higher in the prone position compared to the supine position (69.07% vs. 60.13%, p = 0.025). In the supine position, the V35 of the sigmoid colon was higher compared to the prone position (86.46% vs. 77.67%, p = 0.04). Rectal V10, V15, V20, and V25 were all higher in the prone position compared to the supine position (p<0.001 for all comparisons). The prone bladder V15 and V25 were significantly lower than in the supine position (p = 0.041 and p = 0.033, respectively). Pelvic V35, V40, and V45 were all higher in the prone position compared to the supine position (p = 0.012, p = 0.003, and p = 0.001, respectively). During radiotherapy, there were no significant differences between the prone and supine groups in terms of the median neutrophil minimum (p = 0.11) and median leukocyte minimum (p = 0.13). Hemoglobin minimum was similar in both groups (p = 0.39). The median platelet reduction differed insignificantly (p = 0.096). The median highest number of diarrhea episodes and BMI changes showed no significant differences (p = 0.15 and p = 0.30, respectively). Additionally, the supine position demonstrated smaller posing errors compared to the prone position (p = 0.016).
This study compared postoperative radiotherapy for cervical cancer patients in supine and prone positions. It found dosimetric advantages for the prone position regarding colon doses, while the supine position was better for rectum and pelvic doses. However, clinical outcomes like diarrhea, hematologic toxicity, and BMI changes showed no significant differences. Given the supine position's comfort and reproducibility, it's recommended for postoperative radiotherapy in cervical cancer patients.