Stereotactic body radiation therapy for
Non-Spine Bone Metastases
Overview
Advanced cancer frequently leads to bone metastases, with autopsy reports indicating that 70-85% of patients had bone metastases at the time of diagnosis. While conventional palliative radiation therapy has been shown to reduce pain and enhance the quality of life, there is no evidence of an increase in overall survival. Recent advancements in radiation therapy may have the potential to enhance both overall survival and local control rates.
The treatment of oligometastatic disease has seen a recent technological breakthrough in the form of Stereotactic Body Radiation Therapy (SBRT) for bone metastases. Compared to conventional radiation therapy, SBRT can administer substantially higher biologically equivalent doses (BED). The Canadian Association of Radiation Oncologists (CARO) describes SBRT as āthe precise delivery of highly conformal and image-guided hypofractionated external beam radiotherapy, delivered in a single or few fraction(s), to an extracranial body target with doses at least biologically equivalent to a radical course when given over a protracted conventionally fractionated (1.8ā 3.0 Gy/fraction) schedule.ā SBRT enables a shift in the objective of therapy from simply providing relief from pain and symptoms to achieving maximum local tumor control while reducing pain.
Benefits of SBRT for Non-Spine Bone Metastases
One of the primary goals of SBRT is to alleviate pain caused by bone metastases. Studies have shown significant pain reduction in patients treated with SBRT. Research indicates that SBRT achieves high rates of local control, meaning it effectively stops tumor growth in the treated area. Local control rates often exceed 85%. Because SBRT is delivered in fewer sessions, patients can complete their treatment quickly, which is especially beneficial for those with advanced cancer.
Indications for SBRT
As SBRT is still a relatively new field, information on the toxicities and outcomes associated with such treatment is still to be learned. There are three primary reasons for considering SBRT as a treatment option in the case of bone metastases:
Treating a location that has already been subjected to conventional external beam radiation therapy in the past is referred to as retreatment.
In cases of oligometastases where there are five or fewer metastatic sites.
Oligometastatic progression in patients who have metastases that are spread extensively throughout their body but one or two areas may be disproportionately affected. SBRT can focus on these specific areas that are either causing discomfort or showing progression on radiography.
For patients who have bone metastases outside of the spine, SBRT seems to be a viable and secure treatment alternative. Pooling and analyzing data can be difficult due to the inconsistent endpoints across clinical trials. Establishing a consensus on SBRT endpoints is crucial to standardize outcome evaluation reporting and enable comparisons across various trials.
Clinical Endpoints and Evaluation
An international consensus on clinical endpoints has been developed for bone metastases in the context of conventional radiation therapy. Patient-reported pain scores and the quantity of analgesics used are used to determine the response categories. A pain score of 0 out of 10 at the treated site with no concurrent increase in analgesic consumption is the definition of a complete response to treatment, whereas a pain reduction of 2 or more at the treated site without any increase in analgesic consumption or a 25% reduction in analgesics with no increase in pain score or 1 point above the baseline is the definition of a partial response. An increase in pain score of 2 or more above the baseline with a constant analgesic intake or a 25% increase in analgesic consumption with a stable pain score is the definition of pain progression. Responses that do not fall within the definitions mentioned above are considered indeterminate.
The definitions mentioned above cannot be directly applied to patients undergoing SBRT treatment because the indications for SBRT treatment differ from those of conventional radiation therapy. As mentioned before, the potential indications for SBRT differ significantly from those of conventional treatment, with three major indications being considered: need for retreatment, oligometastatic disease, and oligometastatic progression.
If the objective of treatment is to alleviate pain, the evaluation can be performed using the endpoints established by the international consensus. For patients with oligometastatic disease, it is appropriate to use the Response Evaluation Criteria in Solid Tumors (RECIST) criteria to evaluate asymptomatic lesions. Radiological imaging becomes more significant in asymptomatic lesions. According to the RECIST criteria, in bone metastases with soft tissue involvement, response rates should be defined as follows: a complete response is the disappearance of all lesions, a partial response is a decrease in size of ā„30% from baseline, progressive disease is defined as an increase in size of ā„20%, and stable disease is neither a partial response nor progressive disease.
However, the RECIST criteria are not applicable to assess the response of bone metastases without any involvement of soft tissue. Studies in the literature suggest that a more fractionated treatment schedule may be more effective in promoting the recalcification of bone, possibly due to its greater biological efficacy. Likewise, osteolytic lesions can undergo remineralization following palliative radiotherapy, with a gradual increase in median percent density change as the dose and fractionation are increased. The higher biologically effective dose (BED) of SBRT may lead to increased recalcification in patients undergoing this treatment.
For patients with oligometastatic disease, the assessment of local control and prevention of distant metastases could serve as relevant endpoints to evaluate the efficacy of SBRT. Secondary endpoints such as tumor markers like prostate-specific antigen (PSA) in prostate cancer, progression-free survival, and overall survival are also crucial in assessing the outcomes of SBRT.
For patients with oligometastatic progression, distinct endpoints need to be defined. Patients with widespread metastases with oligometastatic progression may experience symptoms or increased size in one to two new areas. If these lesions cause symptoms, the endpoint definitions outlined in the international consensus should be applied. In case the lesions are asymptomatic and have a soft tissue component involved, the RECIST criteria can be used to assess the response. In this patient population, the occurrence of distant metastases becomes a relatively less significant concern as they already have metastases in other parts of the body.
Practical Considerations
When considering SBRT for non-spine bone metastases, several practical aspects need to be addressed:
- Patient Selection: Not all patients are ideal candidates for SBRT. Selection criteria often include the size and location of the metastases, patient’s overall health, and previous treatments.
- Technology and Expertise: Successful SBRT requires advanced technology and skilled professionals. It is typically available in specialized cancer centers with experience in high-precision radiation therapy.
- Multidisciplinary Approach: Treatment planning for SBRT often involves a team of specialists, including radiation oncologists, medical physicists, and radiologists, to ensure the best outcomes.
Future Directions
The field of SBRT is continually evolving, with ongoing research aimed at improving outcomes and reducing side effects. Future studies are likely to focus on:
- Refining Techniques: Enhancing imaging and delivery techniques to further increase precision and reduce side effects.
- Personalized Medicine: Developing personalized treatment plans based on genetic and molecular characteristics of tumors.
- Combination Therapies: Exploring the combination of SBRT with other treatments, such as immunotherapy, to improve efficacy.
Conclusion
SBRT represents a powerful tool in the management of non-spine bone metastases, offering effective pain relief and high local control rates with minimal severe side effects. As research and technology continue to advance, SBRT is poised to become an even more integral part of cancer treatment strategies, providing hope and improved quality of life for patients with metastatic cancer.
Do you have more questions?Ā
How does SBRT compare to other treatment options for non-spine bone metastases, such as surgery or conventional radiation therapy?
SBRT offers a non-invasive alternative to surgery with comparable efficacy and potentially fewer complications. Compared to conventional radiation therapy, SBRT typically requires fewer sessions and can achieve better tumor control.
Are there any specific types of cancer for which SBRT is particularly effective in treating bone metastases?
SBRT is particularly effective for solid tumors that have metastasized to the bones, regardless of the primary cancer type. It has shown promising results in treating metastases from lung, breast, prostate, and other cancers.
What are the potential long-term effects of SBRT on bone health and surrounding tissues?
SBRT minimizes damage to surrounding healthy tissues, reducing the risk of long-term side effects such as radiation-induced fractures or soft tissue injury. Regular follow-up monitoring helps detect any potential late effects early on.
How soon after starting SBRT can patients expect to experience pain relief?
Pain relief can vary from patient to patient but is often experienced within days to weeks after completing SBRT, as the radiation works to shrink the tumor and reduce pressure on surrounding nerves.
Are there any dietary or lifestyle changes patients should make before, during, or after undergoing SBRT?
Maintaining a balanced diet and staying physically active can support overall health during and after SBRT. It’s important to discuss any specific dietary or lifestyle recommendations with your healthcare team.
What factors determine the number of SBRT sessions required for treatment?
The number of SBRT sessions depends on factors such as tumor size, location, and overall health of the patient. Typically, treatment is completed in one to five sessions, allowing for a quicker recovery compared to conventional radiation therapy.
Can SBRT be used as a standalone treatment, or is it typically combined with other therapies?
SBRT can be used as a standalone treatment or in combination with other therapies such as chemotherapy or surgery, depending on the individual patient’s needs.
How does the cost of SBRT compare to other treatment options, and is it typically covered by insurance?
Costs of SBRT can vary, but it’s often comparable to or less expensive than surgery. Many insurance plans cover SBRT, but it’s essential to check with your provider for specific coverage details.
Are there any limitations or risks associated with undergoing SBRT, especially for elderly or immunocompromised patients?
SBRT is generally well-tolerated, but there may be risks associated with any medical procedure. Elderly or immunocompromised patients may have a higher risk of side effects, so careful monitoring and individualized treatment plans are essential.
How soon after completing SBRT can patients resume normal activities, such as work or exercise?
Patients can typically resume normal activities within a few days to a week after completing SBRT. However, it’s essential to follow the guidance of your healthcare team and avoid strenuous activities that may strain the treated area.
Can SBRT be repeated if cancer recurs in the treated area?
Yes, SBRT can be repeated if cancer recurs in the treated area. However, the decision to repeat SBRT will depend on various factors, including the location and extent of recurrence, the patient’s overall health, and previous treatments.
Are there any clinical trials or research studies investigating new uses or combinations of SBRT for bone metastases?
Yes, there are ongoing clinical trials and research studies exploring new uses and combinations of SBRT for bone metastases. These studies aim to improve treatment outcomes and reduce side effects by refining techniques and exploring novel combinations with other therapies.
What imaging tests are used to monitor the effectiveness of SBRT over time?
Imaging tests such as CT scans, MRIs, or PET scans are commonly used to monitor the effectiveness of SBRT over time. These tests help assess tumor response, detect any recurrence, and evaluate the overall treatment outcome.
Are there any specific precautions patients should take during SBRT treatment to minimize potential side effects?
Patients undergoing SBRT should follow any specific instructions provided by their healthcare team, which may include measures to protect the skin in the treatment area, staying hydrated, and managing any potential side effects such as fatigue or nausea.
How does SBRT affect the overall prognosis for patients with non-spine bone metastases?
SBRT can significantly improve the prognosis for patients with non-spine bone metastases by effectively controlling tumor growth, reducing pain, and improving quality of life. However, individual prognosis may vary depending on factors such as the extent of metastases and overall health.
Can SBRT be used to treat multiple bone metastases simultaneously, or is it typically focused on a single site?
SBRT can be used to treat multiple bone metastases simultaneously, depending on factors such as the size, location, and number of metastases. Treatment planning will consider the individual patient’s condition and goals of therapy.
What is the typical recovery process like after undergoing SBRT?
The recovery process after SBRT is generally quick, with most patients experiencing minimal downtime. Some may experience temporary side effects such as fatigue or mild skin irritation, which usually resolve within a few weeks.
Are there any alternative or complementary therapies that can enhance the effectiveness of SBRT?
Alternative or complementary therapies such as acupuncture, massage therapy, or relaxation techniques may help manage side effects and improve overall well-being during SBRT treatment. However, it’s essential to discuss any complementary therapies with your healthcare team to ensure they are safe and appropriate.
How does SBRT impact quality of life for patients undergoing treatment?
SBRT can significantly improve quality of life for patients by reducing pain, preserving function, and minimizing treatment-related side effects. Many patients experience enhanced mobility and a better overall sense of well-being after SBRT.
Are there any restrictions on travel or mobility during SBRT treatment?
There are typically no restrictions on travel or mobility during SBRT treatment. Patients can continue their usual activities unless otherwise advised by their healthcare team. However, it’s essential to attend all scheduled treatment sessions for optimal outcomes.
I am Vedant Vaksha, Fellowship trained Spine, Sports and Arthroscopic Surgeon at Complete Orthopedics. I take care of patients with ailments of the neck, back, shoulder, knee, elbow and ankle. I personally approve this content and have written most of it myself.
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