Local tumor progression after ultrasound-guided percutaneous microwave ablation of stage T1a renal cell carcinoma: risk factors analysis of 171 tumors

Figures & data

Table 1. Baseline characteristics of patients undergoing microwave ablation.

Variable
Gender
Male	122 (75.3%)
Female	40 (24.7%)
Mean age ± (SD) (years)	62.6 ± 14.5 (Range 21–86)
No. of tumors	171
Single	153 (89.5%)
Multiple	18 (10.5%)
Mean tumor diameter ± (SD) (cm)	2.6 ± 0.8 (Range 0.6–4.0)
Tumor size
< 3.0 cm	102 (59.6%)
3.0–4.0 cm	69 (40.4%)
Diagnosis of pathological
Renal clear cell carcinoma	165 (96.5%)
Papillary cell carcinoma	5 (2.9%)
Cystic renal cell carcinoma	1 (0.6%)
Treatment parameter
Median total operative time (minutes)	7.0 (Range 2.5–17)
Mean ablation power (Watts) ± (SD)	50.8 (Range 40–60)
Median follow-up (months)	45.5 (Range 5–125)

Figure 1. (a) US scan during ablation with tumor (thick arrows) adjacent to the bowel (thin arrow) that distance between tumor margin and renal pelvis <5 mm as measured by US. (b) US scan local separation of the liquid (thin arrow) between the tumor (thick arrows) and the bowel during hydrodissection. (c) US scan during ablation antenna was percutaneously inserted into the tumor and placed at the desired location. (d) US scan during ablation the heat-generated hyperechoic water vapor did completely encompass the entire tumor.

Figure 2. Overall survival curve between local tumour progression (LTP) and LTP free patients with renal cell carcinoma (RCC) treated with microwave ablation (MWA). There is no significant difference between the two groups (p = 0.38).

Figure 3. (a) Axial contrast-enhanced T1-weighted fat saturation MR image shows exophytic 2.7 cm clear cell RCC (arrow) located in safe location. (b) Axial contrast-enhanced T1-weighted fat saturation MR image shows no enhancement for nodular areas after US-guided percutaneous MWA. (c) (d) Axial contrast-enhanced T1-weighted fat saturation MR image and Axial contrast-enhanced CT obtained 30 months after MWA. A LTP nodular occurred in the anterior deep part of the ablation area.

Table 2. Univariate analysis of risk factors associated with local tumor progression treated by MWA.

Variable	LTP (n = 5)	No LTP (n = 166)	p Value
Age (year)	56.4 ± 18.6 (Range 27.0–79.0)	62.8 ± 14.4 (Range 21.0–84.0)	0.97
Sex			0.81
Male	4	118
Female	1	39
Pathological diagnosis			0.91
Clear cell	5	160
Papillary cell	0	5
Cysticl cell	0	1
Tumor size (cm)	2.9 ± 0.8 (Range 1.9–3.7)	2.6 ± 0.8 (Range 0.6–4.0)	0.82
Location			0.41
Left	97	2
Right	69	3
Growth pattern			0.29
Convex	3	54
Parenchyma	1	92
Endogeny	1	20
Tumor location			0.02
Distant from bowel or renal pelvis	120	1
Near bowel and near renal pelvis	46	4
Ablation power (W)	50.0 ± 7.1 (Range 40–60)	50.8 ± 3.0 (Range 35–60)	0.56
Ablation time (minute)	6.9 (Range 4.5–11.3)	7.0 (Range 2.5–17.0)	0.91
Survival	68.2 ± 34.0 (Range 37–125)	44.8 ± 28.3 (Range 6–125)	0.96

Table 3. Independent risk factors associated with local tumor progression with Cox Proportional Hazards Model.

Variable	B	SE	Wald	df	Sig	Exp (B)	95.0% CI foi Exp (B)
							Lower	Upper
Age	−.039	.027	2.109	1	.146	.962	.913	1.014
Sex	−.612	1.174	.271	1	.602	.542	.054	5.419
Tumor size	. 213	.610	.122	1	.727	1.237	.375	4.089
Tumor location	2.420	1.193	4. 112	1	.043	11.245	1.084	116.606
Ablation power (w)	.025	.198	−016	1	.90	1.025	.696	1.511
Ablation time (second)	−.001	.004	. 075	1	.785	.999	.992	1.006

Table 4. Local tumor progression cease characteristic after MWA/RFA/LCA of renal malignancies.

Age	Tumor size (cm)	Pathological	Adjacent organs	Tumor location	Quantity of needle	Time of LTP (month)
59	2.7	Clear cell RCC	NC	Safe	1	30
58	3.7	Clear cell RCC	Bowel	Dangerous	2	29
79	3.6	Clear cell RCC	Kidney Pelvis	Dangerous	2	19
27	2.0	Clear cell RCC	Bowel	Dangerous	2	43
59	2.6	Clear cell RCC	Bowel	Dangerous	2	26

Table 5. Local tumor progression studies after MWA/RFA/LCA of renal malignancies for stage of T1a reported since 2007.

Study	No. of patients	Mean tumor median size (cm)	Technique	Follow-up (months)	LTP (%)	RFS
Psutka et al. (2013)	143	3	image-guided P-RFA	77.16 (median)	4. 2	96.1% (5 years)
Thompson et al. (2015)	180	2.1	image-guided P-RFA	60 (median)	2.7	98% (years)
Lucas et al. (2008)	86	2.4	image-guided P-RFA	40 (median)	3.5	93.0 (3 years)
Hae Jin Kim et al. (2016)	51	2.1	CT-guide P-RFA	26	3.9	94.1% (5 years)
Haruyuki Takaki et al. (2010)	51	2.4	CT-guide P-RFA	34.0 (median)	0	98% (5 years)
Thomas D. Atwell (2013)	75	1.9	US-guide P-RFA	38.4 (median)	1.3	93.2% (5 years)
Thompson et al. (2015)	187	2.9	image-guided P-CA	60 (median)	1.6	98% (3 years)
Georgiades et al. (2014)	115	2. 8	CT-guide P-CA	60	3	97% (5 years)
Thomas D. Atwell (2013)	61	2.3	US-guide P-CA	21. 6 (median)	4. 9	95.6% (5 years)
WEI GUAN (2012)	48	3. 1	US-guide P-MWA	17 (median)	4.2	90.4 (3 years)
Klapperich et al. (2017 )	100	2.6	CT-guided P-MWA	17 (median)	1	99% (3 years)
Jie Yu et al. (2014)	41	2.7	US-guide P-MWA	20.3 (median)	0	NS
Present study (2017)	168	2.6	US-guide P-MWA	44 (median)	3.0

Figure 4. (a) Axial contrast-enhanced CT image shows exophytic 2.6 cm clear cell RCC (arrow) located in dangerous location (The edge of the tumor is 0.5 cm from bowel). (b) (c) Axial and sagittal contrast-enhanced CT image shows no enhancement for nodular areas after US-guided percutaneous MWA. (d) sagittal contrast-enhanced CT image obtained 29 months after MWA. A LTP nodular occurred in the above of the ablation area.