Dosimetry and acute radiation enteritis comparison between prone and supine position in IMRT for gynecological cancers

Purpose: To probe the differences of dosimetry and acute radiation enteritis between prone and supine position in gynecological cancer patients treated with intensity-modulate radiotherapy (IMRT).

Methods: Gynecologic tumor patients who received IMRT from January 2020 to July 2021 were analyzed. 60 patients were enrolled and divided into the supine or prone position group according to different radiotherapy positions, including 34 patients in prone position and 26 patients in supine position. The dose-volume histogram of organs at risk (OARs) and the incidence of acute radiation enteritis were compared between the two groups. Multivariate logistic regression analysis was conducted to show the clinical characteristics and dose volume metrics to the association of acute radiation enteritis.

Results: The percentage of volume receiving 5 Gy, 10 Gy, 15 Gy, 20 Gy, 30 Gy, 40 Gy, and 45 Gy doses for the small intestine were 79.0%, 67.4%, 59.6%, 44.3%, 17.0%, 8.9%, and 6.0%, respectively in the prone group, which were lower than those in the supine group (P < 0.05). The mean radiation dose (D_mean ) of the small intestine exposure in prone group was decreased (P < 0.001). Compared with the supine group, the prone group who suffered from acute radiation enteritis were much less. The probability of indigestion, nausea, vomiting, diarrhea, and abdominal pain in the prone position were 35.29%, 29.41%, 17.65%, 38.24%, and 5.88%, respectively. The differences in indigestion, nausea, and diarrhea between the two groups were statistically significant (P = 0.012, P = 0.029, and P = 0.041). Multivariate logistic regression analysis was shown that prone position was found to be protective against indigestion (P = 0.002), nausea (P = 0.013), vomiting (P = 0.035), and abdominal pain (P = 0.021).

Conclusion: Prone position in IMRT for gynecological cancers could significantly reduce radiation dose to the small bowel and colon, which would decrease the occurrence and severity of acute intestinal side effects possibly.