IMAGE-GUIDED CRYOABLATION

LIVER METASTASIS — Cryosurgery Procedures

Follow-Up Care after Liver Metastases Cryoablation

Currently, definitions of the appropriate length of follow-up and timing of post-procedure testing and imaging are not well established. Given that the tumors are treated in-situ and not surgically excised, a rigorous follow-up protocol is required. Ongoing surveillance should be carefully planned so as to evaluate the efficacy of treatment as well as to monitor for disease recurrence. A typical follow-up imaging schedule follows, and may be revised at the discretion of the Interventionalist and/or other care team member(s) per institution protocol.

• First scan (MRI or CT) at 24-hours post-ablation or at 7-10 day post-procedure office visit.

• Scan at 1, 3, 6, 9 and 12 months post-procedure.

• Scan at 6 month intervals during the second year post-procedure.

• Yearly scans performed thereafter.

The cryolesion on follow-up CT or MRI should show no evidence of enhancement, and the ablated tumor should show stable size or a decrease in size.

Radiologists who interpret follow-up images in patients who have undergone cryoablation should be very familiar with what constitutes recurrent tumor. In general, rim enhancement is often seen within the first month following cryotherapy treatment, whereas nodular enhancement is considered to be suspicious of recurrent tumor.

In many cases, physicians use CT rather than MRI for follow-up scans because of its lower cost. However, there are some tumors that show up better on MRI, and MRI may then be the better choice for follow-up of these lesions. Also, if a patient underwent MRI-guided ablation, follow-up with MRI scans allows the physician to directly compare follow-up images with the intraprocedural scans to better understand and interpret the findings. For example, if a follow-up scan shows an area of enhancement that would normally be suspicious for residual tumor, comparing it to intraprocedural MR images will ascertain whether or not the enhanced portion was treated during the cryoablation procedure.

It is possible that follow-up protocol will evolve as cryoablation and imaging technology advances.