Table 3 Univariable and multivariable cox regression analysis of potential factors of grade 2 or higher rectal bleeding.

Patient and treatment parameters

 Age (> 70)

1.456 (0.628–3.374)

0.381

 Diabetes (yes)

1.843 (0.769–4.416)

0.171

 Hypertension (yes)

0.893 (0.407–1.956)

0.777

 Cerebrovascular disease (yes)

1.185 (0.279–5.027)

0.818

 Cardiovascular disease (yes)

2.662 (1.111–6.377)

0.028

2.732 (1.060–7.038)

0.037

 Antithrombotic medication (yes)

1.683 (0.764–3.708)

0.196

 RT volume (Whole pelvis)

0.765 (0.347–1.685)

0.506

 ADT (yes)

0.739 (0.335–1.627)

0.452

DVH parameters

 CTV-prostate (cc, continuous)

1.004 (0.986–1.023)

0.657

 Rectal wall V₂₅ (%, continuous)

1.004 (0.974–1.035)

0.803

 Rectal wall V₅₀ (%, continuous)

1.032 (0.976–1.091)

0.269

 Rectal wall V₆₀ (%, continuous)

1.110 (0.995–1.238)

0.061

 Rectal wall V₆₅ (%, continuous)

1.171 (1.032–1.329)

0.014

1.158 (1.017–1.318)

0.027

 Rectal wall V₇₀ (%, continuous)

1.170 (0.987–1.386)

0.070

 Rectal wall D_max (Gy, continuous)

1.169 (0.734–1.863)

0.511

 Rectal wall V₂₅ (> 50%)

0.997 (0.416–2.394)

0.995

 Rectal wall V₅₀ (> 20%)

1.333 (0.588–3.021)

0.491

 Rectal wall V₆₀ (> 15%)

2.173 (0.936–5.045)

0.071

 Rectal wall V₆₅ (> 10%)

1.275 (0.579–2.811)

0.546

 Rectal wall V₇₀ (> 7%)

2.995 (0.705–12.718)

0.137

 Rectal wall D_max (> 74 Gy)

1.579 (0.213–11.680)

0.655

First post-RT endoscopic findings

 Congested mucosa (≥ G2)

1.595 (0.622–4.091)

0.332

 Telangiectasia (≥ G2)

2.050 (0.802–5.239)

0.134

 Ulceration (≥ G1)

0.752 (0.176–3.219)

0.701

 VRS (≥ 2)

2.399 (0.885–6.502)

0.086

 VRS (≥ 3)

2.326 (0.994–5.442)

0.052

2.573 (1.091–6.069)

0.031