Relationship between acute and late normal tissue injury after postoperative radiotherapy in endometrial cancer

To evaluate the relationship between acute and late normal tissue reactions in 317 consecutive endometrial cancer patients treated with surgery and adjuvant radiotherapy (RT).

The data of 317 patients (staging according to the International Federation of Gynecology and Obstetrics) treated with postoperative RT were analyzed. Both low-dose-rate brachytherapy and external beam RT were applied in 247 patients (78%); brachytherapy only in 49 (15%) and external beam irradiation only in 21 (7%). The median follow-up was 7.3 years (range 4-21). The European Organization for Research and Treatment of Cancer, Radiation Therapy Oncology Group system with elements of the late effects of normal tissue, subjective, objective, management, analytic (LENT/SOMA) scale was used to score the RT reactions. The correlation between the occurrence and severity of acute and late bowel and bladder toxicity, as well as the relationship between the severity of acute effects and time to occurrence of late reactions, were assessed using linear and logistic regression analyses.

Of the 317 patients, 268 (85%) experienced acute RT reactions of any grade. Severe acute bowel reactions were observed in 15 patients (5%), urinary bladder complications in 1 patient (0.5%), cutaneous in 1 patient (0.5%), and vaginal in 1 patient (0.5%). Severe acute hematologic toxicity was seen in 3 patients (1%). A total of 158 patients (51%) experienced late RT reactions of any grade. Severe late bowel reactions were observed in 19 patients (6%), urinary bladder in 5 (2%), vaginal in 3 (1%), and bone in 10 (4%). When all toxic events were considered, there was a highly significant correlation between the acute and late bowel reactions (p <0.001), but the acute and late urinary bladder reactions did not correlate (p = 0.64). The grade of acute toxicity was found to predict the grade of late toxicity for the bowel but not for the bladder (p <0.001 and p = 0.47, respectively). The severity of acute bowel and bladder toxicity did not correlate with the time to occurrence of late toxicity in these locations (p = 0.34 and p = 0.47, respectively).

Patients with increased acute bowel toxicity during postoperative RT for endometrial cancer have an increased risk of late bowel injury. A higher grade of acute bowel complications correlated with more severe late events, but was not predictive for its latency time. These findings suggest the possibility of an early indication of patients with an increased risk of late toxicity in whom preventive measures might be attempted.