Table 3 BMs characteristics in relation to the occurrence of symptomatic radionecrosis stratified for SRS modality

Symptomatic RN (G2-G3)

56

29

27

 Median occurrence time months (range months)

10.3 (1.2–54.8)

6.9 (1.2–32.3)

15.9 (4.9–54.8)

 Median volume cm³ (range cm³)

3.1 (0.04–13.6)

2.7 (0.04–13.6)

3.2 (1.1–13.6)

G2 RN

44

24

20

 Median occurrence time months (range months)

9.9 (1.2–54.8)

7.5 (1.2–32.3)

14.2 (4.9–54.8)

 Median volume cm³* (range cm³)

3.2 (0.04–13.6)

2.5 (0.04–10.0)

4.8 (1.1–13.6)

 Doses delivered

  20 Gy

10

10

0

  24 Gy

34

14

20

G3 RN

12

5

7

 Median occurrence time months (range months)

24.1 (2.5–44.9)

3.9 (2.5–14.6)

35.6 (16.5–44.9)

 Median volume cm³* (range cm³)

2.0 (0.6–13.6)

3.4 (0.6–13.6)

1.9 (1.1–13.6)

 Doses delivered

  20 Gy

1

1

0

  24 Gy

11

4

7

Predictors of symptomatic RN occurrence

 Maximum BM diameter

p << 0.001

HR 2.2 [95% CI 1.6–3.1]

p << 0.001

HR 4.4 [95% CI 2.5–7.8]

p = 0.059

HR 1.8 [95% CI 1.0–3.4]

 Target volume

p << 0.001

HR 1.1 [95% CI 1.0–1.2]

p << 0.001

HR 1.4 [95% CI 1.3–1.5]

p = 0.076

HR 1.1 [95% CI 1.0–1.1]