Zapatero A et al. (2004) Impact of mean rectal dose on late rectal bleeding after conformal radiotherapy for prostate cancer: Dose-volume effect. Int J Radiat Oncol Biol Phys 59: 1343–1351

Three-dimensional conformal radiotherapy (3D-CRT) aims to increase radiation dose to the target tissue in prostate cancer, but this approach has been associated with a moderate increase in late rectal bleeding. Zapatero et al. have investigated the clinical and dosimetric factors predicting this complication.

Records were retrospectively analyzed for 107 patients with Stage T1c-T3 prostate cancer who had been treated with 3D-CRT. Dose levels were 70.0 Gy (n = 21), 72.0 Gy (n = 57) and 75.6 Gy (n = 29). The primary endpoint was Grade 2 or worse rectal bleeding. Late bleeding was defined as bleeding occurring >120 days after the end of treatment.

The 4-year actuarial incidence of Grade 2 or worse late rectal bleeding was 7.7% ± 2.5%. Rectal volume was significantly lower and mean dose to the rectal volume (Dmean) was significantly higher in patients with rectal bleeding than in those without (median rectal volume 49 cm3 vs 85 cm3, P <0.024; Dmean 57.0 Gy vs 46.0 Gy, P <0.0005). The percentage of rectum receiving >60.0 Gy (Vr60) also correlated with rectal bleeding (P <0.0005). Receiver operating characteristic curve analysis confirmed Vr60 and rectal Dmean as good predictors of late rectal bleeding: the area under the curve was 0.889 and 0.892, respectively.

While data from larger, prospective studies are awaited, the authors have applied new constraints at their center (rectal Dmean 50.0 Gy and Vr60 42 %) as a result of this study.