Percutaneous image-guided ablation of bone metastases: local tumor control in oligometastatic patients

Figures & data

Table 1. Patient demographics and BM characteristics.

Variable	Number	%
Patients
Male	16	34.7
Female	30	65.3
Target BM
Primary tumor
Thyroid	11	22.5
Breast	21	42.9
Lung	8	16.3
Others*	9	18.3
Metastatic status
Single metastasis	31	63.3
2–3 metastases	18	36.7
Visceral metastases
No	44	89.8
Yes	5	10.2
Location
Spine	10	20.4
Pelvic ring	27	55.1
Long bones	2	4.1
Others**	10	20.4
Chronology
Synchronous	16	32.7
Metachronous	33	67.3
Size
≤2 cm	33	67.3
>2 cm	16	32.7
Radiographic feature
Lytic	32	65.3
Blastic	14	28.6
Mixed	3	6.1
Cortical bone disruption
No	27	55.1
Yes	22	44.9
Nearby critical structure
None	11	22.4
Nerves	34	69.4
Vessels	4	8.2
Bowel	2	4.1
Parenchymal organs	1	2
Cartilage	3	6.1
Previous surgery
No	48	98
Yes	1	2
Previous RT
No	43	87.8
Yes	6	12.2
Concomitant chemotherapy
No	29	59.2
Yes	20	40.8
Imaging modality used for follow up
CT	4	8.2
PET-Scan	27	55.1
MRI	18	36.7

*Ribs (4, 8.2%); Scapula (3, 6.1%); Sternum (2; 4.1%); Femur (1, 2%); Clavicle (1, 2%).

**Colorectal (3, 6.1%); Bladder (1, 2%); Uterus (1, 2%); Prostate (2, 4.1%); Pheocromocitoma (2, 4.1%).

N.: Number; %: Percentage; st. dev: standard deviation; CI 95%: Confidence Interval 95%; BM: Bone metastases.

Figure 1. Forty year old female patient with a history of breast cancer; (A, B) the patient was referred for a single, lytic (17 mm) FDG-avid metastasis of L1 (arrows). (C, D) The patient was treated with a single cryoablation probe (white arrows) combined with thermal monitoring and hydro-dissection of the epidural space (black arrow). (E) The procedure was followed by bone consolidation (i.e. vertebroplasty). (F, G) PET-CT follow-up 3 years later showed no FDG uptake in the treated area nor in other visceral or bone sites.

Table 2. Complications.

Patient	Ablation	Sex	Age	Site of metastasis	Primary Tumor	Type of complication	Time to onset* (N°days)	Management	CTCAE V5
Minor Complication
34	CA	F	55	Pelvis	Breast	Pain	Immediate	Analgesics	2
35	CA	M	55	Pelvis	Colorectal	Partial anesthesia of buttock and difficulty urinating	Immediate	Surveillance	2
41	RFA	M	65	Scapula	Lung	Nausea + Pain	Immediate	Antiemetic + Analgesics	2
43	RFA	F	38	Spine	Breast	Pain	Immediate	Analgesics	2
44	RFA	M	31	Scapula	Phaeochromocytoma	Pain	Immediate	Analgesics	2
39	RFA	F	67	Pelvis	Breast	Pain (Sciatalgia)	Immediate	Analgesics	2
40	RFA	F	68	Pelvis	Lung	Pain	Periprocedural (5 days)	Analgesics + Physiotherapy	2
42	RFA	M	31	Pelvis	Phaeochromocytoma	Pain	Immediate	Analgesics	2
Major complications
5	CA	M	63	Scapula	Thyroid	Fracture scapula	Delayed (30 days)	Screw	3
32	CA	F	72	Humerus	Thyroid	Seeding	Delayed (150 days)	Surgery	3

*Time to onset: immediate complications (<24h within ablation), peri-procedural complications (<30 days within ablation), delayed complications (≥30 days).

Figure 2. LPFS in the entire population.

Figure 3. LPFS, BDFS, DFS and OS according to primary tumor.

Table 3. Univariate analysis of factors predicting local recurrence at the treated site.

Variable	N.	N. local failure	OR [CI 95%]	p
Technique
Cryo	37	11	1	p = .75
RFA	12	3	0.79 [0.18; 3.47]
Sex
Male	17	5	1	p = 1
Female	32	9	0.94 [0.26; 3.43]
Age
≤50	10	2	1	p = .64
[50-60]	13	5	2.50 [0.40; 21.30]
>60	26	7	1.47 [0.28; 11.44]
Bone
Spine	10	2	1	p = .84
Pelvic ring	27	8	1.68 [0.32; 12.8]
Long bone	2	1	4.00 [0.12; 140.20]
Others*	10	3	1.71 [0.22; 16.09]
Primary Tumor
Thyroid	11	3	1	p = 1
Breast	21	6	1.07 [0.22; 6.12]
Lung	8	2	0.88 [0.31; 7.14]
Others**	9	3	1.33 [0.19; 9.67]
BM lesions
≤2 cm	16	0	1	p = .002
>2 cm	33	14	Inf
Radiograhic feature
Blastic	14	3	1	p = .875
Lytic	32	10	1.67 [0.41; 8.57]
Mixed	3	1	1.83 [0.07; 27.21]
Cortical Bone disruption
No	27	8	1	p = .86
Yes	22	6	0.89 [0.26; 3.10]
One or more nearby critical structures
None	11	2	1	p = .39
≥1	38	12	2.08 [0.39; 11.12]
Protective measures
No	20	5	1	p = .75
Yes	29	9	1.35 [0.37; 4.86]
Anesthesia
Neuroleptanalgesia	6	3	1	p = .23
General anesthesia	43	11	0.34 [0.06; 1.96]
Additional consolidation
No	39	13	1	p = .17
Yes	10	1	0.22 [0.02; 1.95]
N. metastases at the time of the ablation
<2	31	7	1	p = .23
≥2	18	7	2.18 [0.61; 7.75]
Visceral metastases at the time of the ablation
No	44	13	1	p = .66
Yes	5	1	0.59 [0.06; 5.86]
Chronology
Synchronous	16	6	1	p = .34
Metachronous	33	8	0.53 [0.15 ; 1.93]
Previous Radiotherapy
No	43	12	1	p = .78
Yes	6	2	1.29 [0.21; 8.00]
Concomitant chemotherapy
No	29	9	1	p = .75
Yes	20	5	0.74 [0.20; 2.67]

* Ribs (4, 8.2%); Scapula (3, 6.1%); Sternum (2; 4.1%); Femur (1, 2%); Clavicle (1, 2%).

** Colorectal (3, 6.1%); Bladder (1, 2%); Uterus (1, 2%); Prostate (2, 4.1%); Pheochromocytoma (2, 4.1%).

N.:Number; OR: Odds ratio; CI 95%: Confidence Interval 95%; BM: Bone metastases.