Fig. 2

Observed (A) and predicted (B) GI toxicity up to 37.5 months post-treatment. GI toxicity was most common at 6 weeks post-treatment but resolved almost completely by 4.5 months (A). No late grade ≥ 2 toxicity GI toxicity was observed. Sixty-five (95.6% [95% CI: 87.6–99.1%]) of sixty-eight evaluable patients had a reduction in rectal NTCP (late grade ≥ 2 toxicity or rectal bleeding) after insertion of the hydrogel spacer with a prescription dose of 82 Gy compared to a prescription of 78 Gy but with no HS (B). The median decrease in NTCP was 11.3%. (95% CI: 9.5–13.0%). The three patients with an increase in rectal NTCP (shown in red) had sub-optimal placement of the spacer at the time of insertion