Taylor J Greenwood, MD, Adam Wallace, MD, Aseem Sharma, MD, Jack Jennings, MD, PhD

Spine is the most common site of osseous metastatic disease and when symptomatic presents with debilitating pain Pain comes from periosteal stretching, inflammation, or tumor-related cytokines; exacerbated by spinal cord or nerve root neural compression or pathologic fracture

First line for symptomatic metastases -NSAIDS -Acetomenophen -Opioids -High doses often required -Drowsiness, altered mental status and limits independence (no driving)

Cytotoxic and Targeted Therapy -Improved survival -Side effects sometimes not tolerated -Pain relief variable, often takes weeks to months

Conventional external beam radiation therapy -Partial (~60%) and complete (23%) palliation rates Stereotactic body radiation therapy -May have better longer lasting pain and tumor control

Spine Instability Neoplastic Score (SINS) Considers: -Location -Bone quality -Alignment -Vertebral compression -Posterior involvement -Higher scores = greater instability -Surgical consultation for scores >7 or neural compression

Transpedicular approach using fluoroscopy or CT guidance Radiofrequency, microwave or cryoablation is used to cause tumor necrosis Vertebral augmentation stabilizes pathologic fractures Effective palliation when analgesics are ineffective or not tolerated Effective after radiation has been exhausted Systemic chemotherapy does not need to be stopped Pain relief often immediate

 CT  Cortical integrity  Posterior vertebral wall  Pedicle medial cortex Tumor may retract, Osseous canal stenosis will not When intact: it is a firm backstop during transpedicular acces

 CT  Cortical integrity  Posterior vertebral wall  Pedicle medial cortex  Imaging guidance for small or posterior lesions

 MRI  Shows full extent of tumor  within the vertebral body  Epidural and foraminal extension

 MRI  Shows full extent of tumor  within the vertebral body  Epidural and foraminal extension  Reveals tumor at adjacent levels Pain cannot be localized to a single level when contiguous levels are involved. MRI changed management to a 2 level procedure ?

L1 pathologic compression fracture from metastatic breast cancer treated with radiofrequency ablation (RFA)  At 1 week: Vertebral body has diffuse edema and hyperemia but ablation zone is non- enhancing.  At 3 months : Thin T2 dark, enhancing rim of granulation tissue and hemorrhagic congestion is seen at ablation zone margin. Ablation zone is nonenhancing T2 hyperintense area. Signal void is from vertebral augmentation cement (*). STIR T1 FS C+ * * BeforeAfter 1 week3 months

L3 metastatic renal cell carcinoma treated with stereotactic radiation followed 10 months later by RFA  Lytic metastasis has central non- enhancement consistent with tumor necrosis centrally and viable tumor peripherally  At 2 months after RFA : Paraspinal muscle inflammation is seen, likely from the percutaneous ablation. There is mild residual hyperemia of the vertebral body and signal void from cement. T2 hyperintense smoothy enhancing margin was stable for > 1 year, therefore likely granulation tissue.  Granulation response can be variable in thickness, smooth contour favors fibrosis T2 T1 FS C+ T2 T1 FS C+ BeforeAfter 2 months

In contrast to the previous example... L1 small cell lung cancer metastasis treated with RFA  Zone of ablation is non enhancing but nodular enhancing soft tissue outside the zone of ablation has increased, indicating residual tumor  Salvage Radiation Therapy resulted in tumor retraction * * T1 FS C+ T2 T1 FS C+ Pre-Tx 2 months

Painful sclerotic hypermetabolic L4 metatastatic non-small cell lung caner treated with cryoablation  CT is useful to see the low attenuation “ice ball” in the paraspinal soft tissues but cannot be seen within the compact cancellous bone of the vertebral body.  CO2 gas in the epidural space injected through the subjacent neuroforamen helped prevent neural injury.  Patient reported complete pain relief

MRI 10 months after cryoablation showed tumor recurrence  Ablation tract and T2 dark rim of hemorrhagic congestion are clearly seen  Nodular enhancement is seen within the ablation zone and in the right psoas muscle  T2 dark enhancing marrow is due to the blastic metastasis Axial T1 FS C+ T2 Sag T1 FS C+ T2

S4 rectal cancer metastasis treated with cryoablation  CT guidance shows the “ice ball” delineating the ablation zone.  At 4 months: MRI and PET/CT correlate with the original ablation zone  Central T1 hypointense, T2 hyperintense coagulation necrosis with T2 hypointense, T1 hyperintense rim of hemorrhagic congestion is seen just like RFA  PET/CT shows no uptake in the ablation zone, but disease progression was seen at contiguous levels Cryoablation Sag T2 Axial T1 FS Pre-C PET/CT * *

Post contrast images show tumor enhancement at S3 and necrosis from ablation at S4 DWI can be helpful adjunct tool in evaluating post treatment changes from tumor.  Particularly if contrast in contraindicated and tumor restricted initially  Coagulation necrosis has rapid diffusion (relatively lower high b value signal and increased ADC)  Metastases often have restricted diffusion DWI ADC S3 No Tx S4 s/p cryoablation T2T1 FS C+

Sacral rectal cancer metastasis 1 month after RFA.  T2 heterogeneous, T1 hyperintensity within the ablation zone: hemorrhage or tumor?  Subtraction images are helpful in differentiating residual tumor from hemorrhage. T1 FS C+ T2 FST1 CTSubtraction

Oligometastatic Ewing’s sarcoma to L4 treated with RFA  Follow up PET/CT 3 weeks after RFA showed residual hypermetabolic lesion  Despite attempted retreatment tumor progression was seen 2 months later  Patients symptoms also returned Baseline 3 weeks later 2 months after 2 nd RFA 2 nd RFA PET/CT can detect residual hypermetabolic disease before symptoms return and helps differentiate tumor from granulation tissue

L5 = RFA treated lesion with marrow fibrosis L4 = viable metastatic disease Tumor Fibrosis T1 T2T1 FS C+ PET/CT

1 month 11 months 3 months 8 months L4 leiomyosarcoma metastasis treated with RFA. Images show gradually increasing enhancement surrounding the ablation cavity. Patient developed recurrent back pain.  PET/CT was performed just prior to biopsy.  Final Pathology: Marrow Fibrosis When clinical and imaging parameters are discordant, percutaneous biopsy should be considered before re-treatement.

 Post Ablation changes evolve over the first several months due to an inflammatory response  Margin of Enhancement:  Thin, smooth = expected treatment change  Thick or increasing enhancement does not always equal tumor  When clinical and imaging parameters are discordant, biopsy should be considered before re-treatment.  PET/CT and DWI are useful in evaluation of residual or recurrent hypermetabolic disease.