In Review | Interventional Radiology Programme | Oncology | Palliative Care

This article is a summary and review of a recent study published in Radiology Imaging Cancer. It does not constitute original research, nor is it intended to replace or replicate the original study. Unless otherwise referenced, all information presented remains the intellectual property of the original authors. For full details and context, readers are encouraged to access the original publication and consult the complete disclaimer information.

  

As interventional oncology continues to evolve, there is growing recognition of its role in palliative care—particularly in the management of painful bone metastases. 

The skeletal system is one of the most frequent sites of cancer spread, and when it’s involved, the consequences can be devastating.

Patients with these cancers often experience complications such as high calcium levels, fractures, spinal cord compression, and persistent bone pain. These events can significantly impact physical ability and overall quality of life, making effective symptom control a top priority.

Traditionally, alongside opioid and non-opioid painkillers, external beam radiation therapy has been the go-to treatment for focal bone pain. But even with radiation, many patients don’t achieve full pain relief. In fact, a significant number continue to suffer from moderate to severe pain long after treatment. For them, options become limited, typically relying on strong systemic analgesics, which may bring side effects without always offering adequate comfort.

Over the past decade, we’ve seen image-guided thermal ablation techniques step into this gap. These minimally invasive procedures have become an established approach, especially for patients who aren’t surgical candidates or who haven’t responded well to radiation. Cryoablation, in particular, has emerged as a promising technique. It allows us to see the ablation zone during the procedure, tailor the treatment to the shape and size of the lesion and often results in less discomfort both during and after treatment. Patients can also benefit from shorter hospital stays and faster recovery.

Our final study in this review – the Multicenter Study of Cryoablation for Palliation of Painful Bone Metastases (MOTION) study by Jennings & Prologo et al. was designed to explore these palliative impacts in more depth.

The study was a prospective, multicentre, international trial conducted over 24 weeks to evaluate the safety and efficacy of a single cryoablation session for the palliation of pain in patients with metastatic bone disease, carried out at 11 experienced centres across the United States and France between February 2016 and March 2018. 

Eligible participants were adults (aged 18 years or older) with imaging- or biopsy-confirmed metastatic bone lesions arising from a known non-skeletal primary malignancy. 

Inclusion criteria required that participants were either not candidates for conventional pain therapies—such as radiation or systemic analgesics—or had experienced inadequate relief from these treatments.  Additionally, participants were required to report a worst pain score of at least 4 out of 10 in the preceding 24 hours, as measured by the Brief Pain Inventory–Short Form (BPI-SF). 

Patients were excluded if they had primary bone tumours or if safe treatment of the target lesion would have necessitated the formation of an ice ball within 0.5 cm of critical structures, such as the spinal cord, brain, major abdominal vessels, or other vulnerable neural elements.

 
Let's take a Closer Look 

Each participant underwent cryoablation targeting a single metastatic bone lesion within 14 days of screening. In cases where multiple lesions were present, the most painful was selected as the index lesion for treatment.  

A standardised cryoablation protocol, typically consisting of two freeze-thaw cycles, was followed. In certain cases, an additional cycle was performed at the operator's discretion to optimise tumour coverage and local control. CT was used to guide and monitor the procedure, with imaging obtained at defined intervals during the freezing process.

CT was used to guide and monitor the procedure, with imaging obtained at defined intervals during the freezing process. The duration of freezing was adjusted to ensure maximal safe coverage of the target lesion. Where necessary, thermoprotective measures such as hydrodissection were employed to protect adjacent critical structures. 

Technical success was defined as the successful completion of the ablation procedure aimed at palliation of pain. The primary endpoint was the change in “worst pain in the past 24 hours” at week 8 post-treatment. The Brief Pain Inventory–Short Form (BPI-SF) was used to evaluate improvement, with a clinically meaningful improvement defined as a reduction of at least two points from baseline.  A responder was defined as someone who met this threshold without a substantial increase in opioid use, specifically, no more than a 25% increase in MEDD.

Secondary endpoints included changes in worst and average pain scores, alterations in analgesic use (both opioids and NSAIDs), the need for additional treatments for pain at the index lesion or new sites, changes in quality of life (based on overall BPI-SF scores), and functional status as measured by the Karnofsky performance scale.

Participants were allowed to continue necessary systemic pain management and oncologic therapies, but those who received additional targeted treatment to the index lesion were excluded from analysis. The use of opioid analgesics was standardised by converting all doses to a morphine equivalent daily dose (MEDD).

Participants were monitored for six months following treatment. Pain levels, quality of life, performance status, and medication use were assessed at multiple intervals: baseline (day of treatment) and weeks 1, 4, 8, 12, 16, 20, and 24. 

Results: Efficacy, Safety, and Outcomes

Among the 65 participants treated, it is important to note that the follow-up data decreased over time related to either disease progression, withdrawal from the study, or death. Notably, by the end of the study, 28% of the participants had died—primarily from cancer progression. None of the deaths were attributed to the procedure, device, or opioid use.

The researchers recorded that pain relief experienced by the remaining cohort was both rapid and sustained. A meaningful reduction in “worst pain in the past 24 hours” (≥2-point drop on a 10-point scale) was observed from as early as week 1.  Mean pain scores improved by 2.6 points by week 8, and improvements remained significant through week 24. 
 

Opioid use, reported by 73% at baseline, remained stable or decreased over time in the majority of participants, with morphine-equivalent daily doses trending downward from week 4 through week 24. Concurrently, quality of life improved steadily, and functional status was maintained throughout the study. Most participants reported that the overall treatment effect was better than at the previous visit during early follow-up.

The procedure was well-tolerated. Mild to moderate adverse events occurred in 22% of the cases. Three participants, however, experienced serious events, including one case leading to amputation; this was the only complication definitively linked to the procedure.

New Perspectives

Patients with metastatic bone disease often face significant physical limitations, largely driven by unrelenting pain. In this context, pain management becomes not just a clinical priority but a quality-of-life imperative. 

The MOTION study builds on growing evidence that image-guided cryoablation offers effective, fast-acting pain relief in this setting, even where conventional treatments such as radiotherapy or opioids have reached their limits.

Encouragingly, clinically meaningful improvements in pain were observed within the first week and sustained across the 24-week follow-up. By week 8, the average reduction in worst pain score exceeded 2 points, a threshold widely accepted as clinically significant. This benefit was maintained for six months, underscoring the durability of the cytoablative effect.   

Although some patients experienced a transient flare in pain early post-procedure, this was likely linked to inflammatory changes inherent to the cryoablation mechanism rather than true disease progression.

Subgroup analyses showed that neither prior radiation therapy nor tumour size significantly influenced pain outcomes, suggesting broad applicability across different patient groups. Importantly, nearly three-quarters of patients began the study on opioids, yet analgesic requirements remained stable or decreased in most cases following treatment. This points to cryoablation’s potential not just as a pain intervention, but as a means of reducing reliance on medications that can impair function and cognitive clarity.

Preservation of functional status and gradual improvements in quality of life further support the clinical value of cryoablation. Even in a population with a high burden of disease—where new metastases and disease progression were common—patients consistently reported improvements in their pain experience, overall condition, and daily functioning. The safety profile was acceptable, with only a small number of serious adverse events, most of which were resolved. A single major complication, a frostbite-related amputation, highlights the importance of meticulous procedural planning, particularly for extremity lesions, but does not undermine the overall tolerability of the intervention.

Limitations of the study—such as the timing of the primary endpoint and the exclusion of spinal metastases—should guide future research, which could benefit from comparative trials, patient-reported opioid goals, and expanded anatomical coverage. Nonetheless, this trial makes a strong case for considering cryoablation earlier in the treatment algorithm for patients with painful bone metastases, particularly when other options have failed or are unsuitable.

In summary, cryoablation provides a clinically meaningful, opioid-sparing, and well-tolerated treatment option for focal palliation of painful bone metastases. In a landscape where rapid pain control can profoundly affect patient wellbeing, it is an option that deserves serious consideration.

The MOTION STUDY was registered at ClinicalTrials.gov NCT02511678 
 

What the Panel Says
 

 

 

Original Study

Jennings JW, Prologo JD, Garnon J, et al.Cryoablation for Palliation of Painful Bone Metastases: The MOTION Multicenter Study. Radiol Imaging Cancer. 2021 Feb 12;3(2):e200101. doi: 10.1148/rycan.2021200101 

Article Information
 

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