Single-Fraction Radiotherapy (SFRT) For Bone Metastases: Patient Selection And Perspectives

Definitive single fraction spine stereotactic radiosurgery for metastatic sarcoma: Simultaneous integrated boost is associated with high tumor control and low vertebral fracture risk

INTRODUCTION

Sarcoma spinal metastases (SSM) are particularly difficult to manage given their poor response rates to chemotherapy and inherent radioresistance. We evaluated outcomes in a cohort of patients with SSM uniformly treated using single-fraction simultaneous-integrated-boost (SIB) spine stereotactic radiosurgery (SSRS).

MATERIALS AND METHODS

A retrospective review was conducted at a single tertiary institution treated with SSRS for SSM between April 2007-April 2023. 16-24 Gy was delivered to the GTV and 16 Gy uniformly to the CTV. Kaplan-Meier analysis was conducted to assess time to progression of disease (PD) with proportionate hazards modelling used to determine hazard ratios (HR) and respective 95 % confidence intervals (CI).

RESULTS

70 patients with 100 lesions underwent SSRS for SSM. Median follow-up was 19.3 months (IQR 7.7-27.8). Median age was 55 years (IQR42-63). Median GTV and CTVs were 14.5 cm3 (IQR 5-32) and 52.7 cm3 (IQR 29.5-87.5) respectively. Median GTV prescription dose and biologically equivalent dose (BED) [α/β = 10] was 24 Gy and 81.6 Gy respectively. 85 lesions received 24 Gy to the GTV. 27 % of patients had Bilsky 1b or greater disease. 16 of 100 lesions recurred representing a crude local failure rate of 16 % with a median time to failure of 10.4 months (IQR 5.7-18) in cases which failed locally. 1-year actuarial local control (LC) was 89 %. Median overall survival (OS) was 15.3 months (IQR 7.7-25) from SSRS. Every 1 Gy increase in GTV absolute minimum dose (DMin) across the range (5.8-25 Gy) was associated with a reduced risk of local failure (HR = 0.871 [95 % CI 0.782-0.97], p = 0.009). 9 % of patients developed vertebral compression fractures at a median of 13 months post SSRS (IQR 7-25).

CONCLUSION

This study represents one of the most homogenously treated and the largest cohorts of patients with SSM treated with single-fraction SSRS. Despite inherent radioresistance, SSRS confers durable and high rates of local control in SSM without unexpected long-term toxicity rates.

An Analysis of Clinical and Systemic Factors Associated with Palliative Radiotherapy Delivery and Completion at the End of Life in Alberta, Canada

Radiotherapy (RT) is often utilized for symptom control at the end of life. Palliative RT (pRT) may not be taken to completion by patients, thus decreasing clinical benefits and adversely impacting resource allocation. We determined rates of incomplete pRT and examined predictors of non-completion using an electronic questionnaire. Methods: A questionnaire was embedded within the RT electronic prescribing system for all five cancer centers of Alberta, Canada, between 2017 and 2020. Prescribing radiation oncologists (ROs) were tasked with completing the questionnaire. Treatment variables were collected for 2040 patients prescribed pRT. Details on pRT courses delivered and completed were used to determine rates of incomplete RT. Electronic medical records of a subset of 367 patients randomly selected from the 2040 patients were then analyzed to examine for association of non-completion of RT with patient, disease, and therapy-related factors. Results: Overall, 10% of patients did not complete pRT. The rate of single fractions prescribed as a proportion of all RT fractions increased from 18% (pre-2017: pre-study era) to 29% (2017-2020: study era) (p < 0.0001). After conducting multivariate analysis on the overall group, multiple lifetime malignancies (OR:0.64) or increasing the number of pRT fractions (OR:0.08-0.17) were associated with non-completion. Being selected for stereotactic RT (OR:3.75) or survival > 30 days post-RT prescription (OR:2.20-5.02) were associated with greater rates of RT completion. The ROs' estimates of life expectancy at the time of RT prescription were not predictive of RT completion. In the multivariate analysis of the 367-patient subset, the presence of hepatic metastases (OR 2.59), survival 30-59 days (OR 6.61) and survival 90+ days (OR 8.18) post-RT prescription were associated with pRT completion. Only increasing pRT fractionation (OR:0.05-0.2) was associated with non-completion. Conclusion: One in ten patients prescribed pRT did not complete their treatment course. Decreasing pRT fractionation and improving prognostication in patients near the end of life may decrease rates of incomplete RT courses.

Systematic Review of Tumor Segmentation Strategies for Bone Metastases

Purpose: To investigate the segmentation approaches for bone metastases in differentiating benign from malignant bone lesions and characterizing malignant bone lesions. Method: The literature search was conducted in Scopus, PubMed, IEEE and MedLine, and Web of Science electronic databases following the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). A total of 77 original articles, 24 review articles, and 1 comparison paper published between January 2010 and March 2022 were included in the review. Results: The results showed that most studies used neural network-based approaches (58.44%) and CT-based imaging (50.65%) out of 77 original articles. However, the review highlights the lack of a gold standard for tumor boundaries and the need for manual correction of the segmentation output, which largely explains the absence of clinical translation studies. Moreover, only 19 studies (24.67%) specifically mentioned the feasibility of their proposed methods for use in clinical practice. Conclusion: Development of tumor segmentation techniques that combine anatomical information and metabolic activities is encouraging despite not having an optimal tumor segmentation method for all applications or can compensate for all the difficulties built into data limitations.

SEOR SBRT-SG stereotactic body radiation therapy consensus guidelines for non-spine bone metastasis

The use of stereotactic body radiation therapy (SBRT) to treat non-spine bone metastases (NSBM) is becoming increasingly common in clinical practice. The clinical advantages of SBRT include good pain control and high local control rates, although only limited data are available. The Spanish Society of Radiation Oncology (SEOR) SBRT group recently convened a task force of experts in the field to address key questions related to SBRT for NSBM, including treatment indications, planning, techniques, and dose fractionation. The task force reviewed the available literature to develop evidence-based recommendations for the safe application of NSBM SBRT and to standardize and optimize SBRT processes. The present document provides a comprehensive analysis of the available data, including ongoing clinical trials and controversies, providing clinically applicable recommendations.

Advances in radiotherapy in bone metastases in the context of new target therapies and ablative alternatives: A critical review

In patients with bone metastases (BM), radiotherapy (RT) is used to alleviate symptoms, reduce the risk of fracture, and improve quality of life (QoL). However, with the emergence of concepts like oligometastases, minimal invasive surgery, ablative therapies such as stereotactic ablative RT (SABR), radiosurgery (SRS), thermal ablation, and new systemic anticancer therapies, there have been a paradigm shift in the multidisciplinary approach to BM with the aim of preserving mobility and function survival. Despite guidelines on using single-dose RT in uncomplicated BM, its use remains relatively low. In uncomplicated BM, single-fraction RT produces similar overall and complete response rates to RT with multiple fractions, although it is associated with a higher retreatment rate of 20% versus 8%. Complicated BM can be characterised as the presence of impending or existing pathologic fracture, a major soft tissue component, existing spinal cord or cauda equina compression and neuropathic pain. The rate of complicated BM is around 35%. Unfortunately, there is a lack of prospective trials on RT in complicated BM and the best dose/fractionation regimen is not yet established. There are contradictory outcomes in studies reporting BM pain control rates and time to pain reduction when comparing SABR with Conventional RT. While some studies showed that SABR produces a faster reduction in pain and higher pain control rates than conventional RT, other studies did not show differences. Moreover, the local control rate for BM treated with SABR is higher than 80% in most studies, and the rate of grade 3 or 4 toxicity is very low. The use of SABR may be preferred in three circumstances: reirradiation, oligometastatic disease, and radioresistant tumours. Local ablative therapies like SABR can delay change or use of systemic therapy, preserve patients' Qol, and improve disease-free survival, progression-free survival and overall survival. Moreover, despite the potential benefit of SABR in oligometastatic disease, there is a need to establish the optial indication, RT dose fractionation, prognostic factors and optimal timing in combination with systemic therapies for SABR. This review evaluates the role of RT in BM considering these recent treatment advances. We consider the definition of complicated BM, use of single and multiple fractions RT for both complicated and uncomplicated BM, reirradiation, new treatment paradigms including local ablative treatments, oligometastatic disease, systemic therapy, physical activity and rehabilitation.

Image-Guided High-Intensity Focused Ultrasound, A Novel Application for Interventional Nuclear Medicine?

Image-guided high-intensity focused ultrasound (HIFU) has been increasingly used in medicine over the past few decades, and several systems for such have become commercially available. HIFU has passed regulatory approval around the world for the ablation of various solid tumors, the treatment of neurologic diseases, and the palliative management of bone metastases. The mechanical and thermal effects of focused ultrasound provide a possibility for histotripsy, supportive radiation therapy, and targeted drug delivery. The integration of imaging modalities into HIFU systems allows for precise temperature monitoring and accurate treatment planning, increasing the safety and efficiency of treatment. Preclinical and clinical results have demonstrated the potential of image-guided HIFU to reduce adverse effects and increase the quality of life postoperatively. Interventional nuclear image-guided HIFU is an attractive noninvasive option for the future.

Biomechanical Properties of Metastatically Involved Osteolytic Bone

PURPOSE OF REVIEW

Skeletal metastasis involves the uncoupling of physiologic bone remodeling resulting in abnormal bone turnover and radical changes in bony architecture, density, and quality. Bone strength assessment and fracture risk prediction are critical in clinical treatment decision-making. This review focuses on bone tissue and structural mechanisms altered by osteolytic metastasis and the resulting changes to its material and mechanical behavior.

RECENT FINDINGS

Both organic and mineral phases of bone tissue are altered by osteolytic metastatic disease, with diminished bone quality evident at multiple length-scales. The mechanical performance of bone with osteolytic lesions is influenced by a combination of tissue-level and structural changes. This review considers the effects of osteolytic metastasis on bone biomechanics demonstrating its negative impact at tissue and structural levels. Future studies need to assess the cumulative impact of cancer treatments on metastatically involved bone quality, and its utility in directing multimodal treatment planning.

SBRT in non-spine bone metastases: a literature review

Stereotactic Body Radiotherapy (SBRT) is a technique for delivering high doses of radiation to tumors while preserving the normal tissues located around this area. Bone metastases are frequent in cancer patients. They can be distressingly painful or may cause pathological fractures. Radiation therapy is a fundamental aspect of treatment for bone metastases. The objective of this study is to analyze the literature on non-spine bone metastasis treated with SBRT, including immobilization, volume delineation, dose and fractionation, local control, side effects, and assessment of response after treatment. Full-text articles written in English language and published in the last 10 years were included in this review and were accessible on PubMed and MEDLINE. We examined 78 articles. A total of 40 studies were included in this review. Most were retrospective studies. The articles included were evaluated for content and validation. The immobilization systems and imaging tests used for tumor delimitation were variable between studies. The use of CTV (Clinical Target Volume) has not been defined. Doses and fractions were variable from 15 to 24 Gy/1 fraction to 24-50 Gy in 3-5 fractions, with local control being around 90% with a low rate of side effects. We review state of the art in SBRT non-spine metastases. SBRT can result in better local control and pain management in non-spine bone metastases patients. We need more research in volume delineation determining whether or not to use CTV and the role of MRI in volume contouring, optimal doses, and fractionation according to histology and a reliable response assessment tool. Studies that compare SBRT to conventional radiotherapy in local control and pain control are needed.

Phase 2 Clinical Trial of Stereotactic Body Radiation Therapy for Painful Nonspine Bone Metastases

PURPOSE

The present multicenter, single-arm, phase 2 study aimed to prospectively evaluate the palliative efficacy of stereotactic body radiation therapy (SBRT) in patients with painful nonspine bone metastases.

METHODS AND MATERIALS

Patients with painful (≥2 points on a 0-to-10 scale) nonspine bone metastases from a solid tumor were enrolled. The prescribed dose was 35 Gy in 5 fractions. The primary endpoint was overall pain response rate (complete response [CR] and partial response [PR]) as measured per the International Consensus on Palliative Radiotherapy Endpoints guideline 6 months after SBRT.

RESULTS

Forty-one osseous lesions in 38 patients were registered between June 2018 and June 2019. All lesions satisfied the inclusion criteria, and the patients completed the protocol treatment. Patients most commonly had lung cancer (22%), followed by prostate cancer, uterus cancer, and renal cell carcinoma (15%, 15%, and 12%, respectively). Bone metastases were most commonly located in coxal bones (56%). The median duration of follow-up after registration was 8 months (range, 1-19 months). Among evaluable lesions at 3 and 6 months after SBRT, the 3- and 6-month pain response rates were 78% and 75%, respectively. The local control rate at 6 months was 92%. Seven patients (17%) experienced bone fracture after irradiation, and 3 patients (7%) experienced grade 2 limb edema. One patient had regrowth of coxal bone metastases, and the tumor penetrated the sigmoid colon. Soft tissue abscess around the tumor and osteonecrosis of coxal bones were confirmed. The patient died of infection 4 months after SBRT and was determined to be a possible treatment-related death.

CONCLUSIONS

This prospective clinical trial showed that SBRT for nonspine bone metastases was effective in terms of pain palliation. These findings warrant a larger randomized controlled trial to compare SBRT with conventional radiation therapy. Additionally, operation history should be considered as a risk factor for edema.