MRI-guided laser thermal ablation for T1a renal cell carcinoma (RCC): A 4-year experience with longitudinal follow-up of patients
Juan C. Camacho1,2, Nima Kokabi1, Tracy E. Powell2, and Sherif G. Nour1,2

1Radiology and Imaging Sciences, Emory University School of Medicine, Atlanta, GA, United States, 2Interventional MRI Program, Emory University Hospital, Atlanta, GA, United States


The objective of this study is to present outcomes of MRI-guided laser ablation for early stage renal cell carcinomas and to describe associated prognostic factors in a consecutive cohort of patients with relative long-term longitudinal follow-up. A prospective cohort of patients presenting with pathology-confirmed RCC underwent MRI-guided biopsy and subsequent laser ablation. Twenty-four consecutive patients presenting with 35 RCC were recruited. Follow-up MRI imaging was obtained in all cases with a median follow-up period of 20 months. Of the different analyzed prognostic factors, R.E.N.A.L nephrometry score was the only one predicting the incidence of complications.

Background and purpose

Incidence of small renal cell carcinomas (RCC) continues to rise, finding likely related to the widespread use of imaging [1]. And although multiple curative strategies are available [2], it is well known that most incidentally found lesions measure less than 4 cm and correspond to stage Ia neoplasms [3]. Of these, surgical management results in >95% recurrence-free survival at 5 years [2] and now, ablative therapies have proved to be effective and are now accepted as state of the art therapy with a recurrence-free survival >90% at 5 years [4-6]. Multiple image guidance and thermal ablative techniques are available, however, experience with MRI-guided laser ablation is limited. Therefore, the objective of this study is to present the outcomes of MRI-guided laser ablation for early stage renal cell carcinomas and to describe associated prognostic factors in a consecutive cohort of patients with relative long-term longitudinal follow-up.

Materials and Methods

Retrospective analysis of a consecutive cohort was performed following IRB approval and verifying HIPAA compliance. The study cohort consisted of consecutive patients with RCC who underwent percutaneous MRI-guided laser ablation with curative intent between January 2012 and October 2015. Imaging follow-up and pathology results were available for all cases. R.E.N.A.L. nephrometry score was applied retrospectively on pre-procedural diagnostic MR imaging to all tumors. All ablations were performed in a 1.5 T interventional MRI suite (MAGNETOM Espree, Siemens Healthcare, Erlangen, German). Initial image adqusition included multiplanar localizing TSE T2W and GRE T1W contrast-enhanced images. Under real-time MR fluoroscopy, a 16-gauge MR compatible co-axial puncture needle (Invivo, Gainesville, FL) and an 18-gauge MR-compatible core needle biopsy gun (Invivo, Gainesville, FL) were advanced into the lesion, and samples were obtained. Then, and under real-time MR fluoroscopy, a 1.5-cm-active tip diode laser fiber (Medtronic, Minneapolis, Minnesota) was introduced within an internally cooled catheter through a 14G introducing sheath. A test laser dose was applied followed by an ablative dose. Real time heat maps were obtained to monitor progress. All renal masses were treated in a single session with the patient under general anesthesia. Follow-up imaging with MRI was performed at 1, 3, 6, and 12 months after ablation, and yearly thereafter to evaluate technical success, tumor recurrence and complication incidence. R.E.N.A.L. scores were analyzed to determine the association of the score with the abovementioned outcomes. Statistical analyses were performed using SPSS software v20.0 (IBM, Armonk, NY). Numerical differences and outcomes analysis between groups were assessed using Chi-square to compare proportions of categorical variables and t-test to compare the mean of two continuous variable samples (p < 0.05).


Twenty-four consecutive patients (11 males (45.8%); 13 females (54.1%)) were recruited who presented with 35 suspicious lesions; mean age was 62,5 years (Median age 66; SD 15,6). All patients had pathologically confirmed RCC with pathology results distributed among lesions as: clear cell carcinoma (60%), papillary RCC (14.2%), chromophobe RCC (5.7%) and oncocytic neoplasm (11.4%). Follow-up MRI imaging was obtained in all cases with a median follow-up period of 20 months. Mean tumor size was 1.75 cm (median 1.6 cm, SD 0.7 cm, range 0.7-3.4 cm) and 22.8% (8/35) lesions measured < 2 cm. Mean nephrometry score was 5.8 (Median 6, SD 1.3). Nephrometry score was >8 in 14.2% (5/35) of lesions and <8 in 85.8% (30/35). No recurrences have been observed. Overall complication rate was 11.4% (all hematomas not requiring additional interventions). Technical success was achieved in all lesions. Nephrometry score >8 were associated with increased risk of complications (p <0.001). Age, gender, metastatic disease at presentation and histology of the lesion were not identified as prognostic factors for technical success, recurrence or complications associated to the procedure (p > 0.05).


In this cohort of consecutive patients, MRI-guided laser ablation of T1a renal cell carcinomas is a safe and effective treatment. The R.E.N.A.L nephrometry score is the only prognostic factor predicting the incidence of complications.


No financial support was received for this clinical study. The location of the study, the facilities and the study subjects were recruited at Emory University Affiliated Hospitals, Atlanta, Georgia, US.


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[6] Camacho JC, Kokabi N, Xing M, Master V, Pattaras J, Mittal P, Kim HS. R.E.N.A.L. Nephrometry score predicts early tumor recurrence and complications after percutaneous ablation: a 5-year experience. J Vasc Interv Radiol. 2015 May; 26(5): 686-93.


Figure 1. a) TSE T2W demonstrates heterogeneous signal in the lesion within the posterior interpolar region (Arrow, Nephrometry score 7a). b) GRE T1W demonstrates a corresponding area of high signal intensity (arrow) c) TSE T2W demonstrates decreased signal intensity compatible with hemorrhagic necrosis and post-ablation changes (arrow). d) Contrast enhanced GRE T1W confirms technical success. e) Isolated MRI fluoroscopy image confirms adequate placement of the laser probe within the lesion.

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)