Pelvic insufficiency fractures and pelvic bone metastases after neoadjuvant (chemo)radiotherapy for rectal cancer

Figures & data

Table 1. Radiological characteristics of PIFs and pelvic bone metastases at different imaging modalities.

Imaging modality	PIF	Pelvic bone metastases
Plain radiography	Sclerotic band or line	Lytic or sclerotic focal mass-like lesion
CT	Linear fracture line, sclerotic bands, cortical disruption, or periosteal reaction, usually no soft tissue component	Focal lytic lesion with or without soft tissue component
MRI	- T1-weighted hypo-intense fracture line - T2-weighted high signal indicating marrow edema - No restricted diffusion	Focal mass-like lesion: - Low T1-weighted signal - Intermediate to high T2-weighted signal - Restricted diffusion
Bone scintigraphy	H-shaped (‘Honda’ sign) or butterfly pattern	Rounded or pleiomorphic-shaped focal uptake
Other supporting characteristics	- No metastatic disease - Within the radiation field - Preferential sites: sacroiliac joints, supra-acetabular region, and pubic bone (near the symphysis) - Bilateral, symmetrical and fractures that run parallel to the joints	- Other (osseous) metastatic disease - Outside the radiation field - No preferential site in the pelvis

PIF: pelvic insufficiency fracture; CT: computed tomography; MRI: magnetic resonance imaging; DWI: diffusion-weighted imaging.

Figure 1. Flow diagram of patient selection.

Table 2. Baseline characteristics of rectal cancer patients treated with neoadjuvant (C)RT.

	n = 300
Age, mean (range)	63 (36–86)
Gender
Male	182 (60.7%)
Female	118 (39.3%)
Clinical stage
1	64 (21.3%)
2	73 (24.3%)
3	122 (40.7%)
4	26 (8.7%)
Unknown	15 (5.0%)
Radiotherapy dose
50 Gy (25 × 2 Gy)	91 (30.3%)
25 Gy (5 × 5 Gy)	209 (69.7%)

Gy: Gray.

Table 3. Clinical course and treatment of PIFs in patients treated with neoadjuvant (C)RT.

	Patients with PIF n = 32
Mean age (range, years)	68 (47–84)
Gender
Male	9 (28.1%)
Female	23 (71.9%)
Neoadjuvant radiotherapy
Long schedule 50 Gy (25 × 2 Gy)	8 (25%)
Short schedule 25 Gy (5 × 5 Gy)	24 (75%)
Stage when diagnosed with PIF
1	2 (6.3%)
2	9 (28.1%)
3	13 (40.6%)
4	6 (18.8%)
Unknown	2 (6.3%)
Symptoms
Yes	18 (56.3%)
No	12 (37.5%)
Unknown	2 (6.3%)
Median time between symptoms and diagnosis (weeks)	4 (IQR 0–7)
5-year overall survival	63.5%
Median survival (months)	86 (IQR 44–120)

PIF: pelvic insufficiency fracture; Gy: Gray; IQR: interquartile range.

Data availability statement

All data underlying the results are available as part of the article and no additional source data are required.