Cryoprobe Isotherms: A Caveat and Review

Multipoint Thermal Sensors Associated with Improved Oncologic Outcomes Following Cryoablation

INTRODUCTION

Cryoablation (CA) is a minimally invasive modality for the management of small renal cortical neoplasms (RCN). Effective ablation is dependent on achieving target temperatures during CA that result in tumor cell death. We investigated long-term oncologic outcomes following CA using multipoint thermal sensors (MTS), which allow precise temperature determination at four points along the needle.

METHODS

We performed a retrospective review of 20 patients with <4 cm RCN who underwent de novo CA from 2005 to 2009. In 11 procedures, MTS needles were deployed with the goal of obtaining -20°C at the tumor margin, while 9 were done without MTS. Patient demographics, tumor characteristics, and CA procedure data were retrieved and analyzed. Follow-up CT or MRI was used to assess recurrence status.

RESULTS

With a mean follow-up of 45 months, none of the 11 patients experienced a recurrence in the MTS group, compared with 4 of 9 (44.4%) patients in the non-MTS group (p = 0.026). Of the biopsy-confirmed renal cancers, none of the 6 in the MTS group, compared with 3 of 6 (50%) in the non-MTS group, recurred (p = 0.182). Age, tumor size, surgical approach, tumor histopathology, grade, follow-up time, and skin-to-tumor distance were similar between the MTS and non-MTS groups. The MTS group was also associated with increased total length of freeze (p = 0.041), procedure time (p = 0.020), cryoprobe utilization (p = 0.049), and a greater ratio of cryoprobes used per cm diameter of tumor (p = 0.003).

CONCLUSIONS

In this small renal mass pilot study, the use of MTS needles to monitor temperature and guide cryoneedle deployment was associated with improved oncologic outcomes.