Purpose: To analyze rectal bleeding prognostic factors associated with prostate brachytherapy (PB) or in combination with external-beam radiation therapy (EBRT) and to examine dosimetric indications associated with rectal bleeding.
Materials and methods: The study included 296 patients followed up for >36 months (median, 48 months). PB was performed alone in 252 patients and in combination with EBRT in 44 patients. PB combined with EBRT is indicated for patients with a Gleason score >6. The prescribed dose was 144 Gy for monotherapy and 110 Gy for PB + EBRT (44-46 Gy).
Results: Although 9.1% who received monotherapy had 2.3% grade 2 rectal bleeding, 36.3% who received combined therapy had 15.9% grade 2 rectal bleeding. Combined therapy was associated with higher incidence of rectal bleeding (P = 0.0049) and higher percentage of grade 2 bleeding (P = 0.0005). Multivariate analysis revealed that R-150 was the only significant factor for rectal bleeding, and modified Radiation Therapy Oncology Group (RTOG) grade in monotherapy and biologically equivalent dose (BED) were significant for combined therapy. Moreover, grade 2 rectal bleeding increased significantly at D90 > 130 Gy.
Conclusion: Although R-150 was the significant prognostic factor for rectal bleeding and modified RTOG rectal toxicity grade, BED was the significant prognostic factor for modified RTOG rectal toxicity grade.