Table 1.
Patient, tumor, and treatment characteristics.
Table 2.
Dose parameters between the radiotherapy techniques.
Table 3.
Follow-up and 3-year rectal toxicity (Grade ≥2) rate according to the fraction dose when delivering 70 Gy to the prostate with 3DCRT.
Table 4.
Follow-up and 3-year rectal toxicity (Grade ≥2) rate according to the treatment technique employed when delivering high dose (78–80 Gy) at a standard fractionation (2 Gy).
Fig 1.
Risk of late rectal toxicity (Grade ≥2), overall and by symptoms (SOMA-LENT classification).
Table 5.
Parameters impacting on the risk of acute rectal toxicity (Grade ≥2) in the prospective cohort (n = 487).
Fig 2.
Impact of dose escalation on the Grade ≥2 overall rectal toxicity risk.
The patients (n = 491) received either a total dose of 70Gy (n = 277) or 78-80Gy (n = 220), using the same 3D conformal RT technique.
Fig 3.
Impact of hypofractionation on the Grade ≥2 overall rectal toxicity (Fig 3A) and rectal bleeding risks (Fig 3B).
The patients (n = 555) received a total dose of 70 Gy with the same 3D conformal RT technique, at either 2 Gy/fr (n = 272) or 2.5 Gy/fr (n = 283).
Fig 4.
Impact of the radiation technique on the overall rectal toxicity (Grade ≥2) risk when delivering high doses to the prostate.
The patients (n = 401) received a total dose of 78–80 Gy, by means of either 3DCRT (n = 220) or IMRT alone (n = 63), or by combining IMRT and IGRT (n = 128).
Table 6.
Parameters impacting on the 3-year risk of late rectal toxicity (Grade ≥2).
Fig 5.
Nomogram and calibration plot (validation cohort) for the 3-year Grade ≥2 overall late rectal toxicity risk.
3DCRT: 3D conformal radiotherapy, IGRT: image-guided radiotherapy, IMRT: intensity-modulated radiotherapy. To use the nomogram, align a straight edge so that it intersects with each predictor line (RT technique, total dose, or dose per fraction), then read the corresponding "Points" on the first line for each predictor. Add the points of the three predictors in order to calculate the total points. Align your straight edge to the "Total points" line and read the toxicity "Risk" on the last line. For example, a patient treated with IMRT and IGRT (0 points) to a total dose of 80 Gy (65 points) at 2 Gy (0 points) per fraction has a risk of late rectal toxicity of 7% (65 points). Calibration plot to assess the nomogram performance by a nonparametric fit of the predicted probability versus actual observed probability in the validation cohort. The corresponding C-index is 60%.