SBRT in non-spine bone metastases: a literature review

Stereotactic Radiosurgery with Volumetric Modulated Arc Radiotherapy: Final Results of a Multi-arm Phase I Trial (DESTROY-2)

AIMS

To present the final results of a phase I trial on stereotactic radiosurgery (SRS) delivered using volumetric modulated arc therapy (VMAT) in patients with primary or metastatic tumors in different extracranial sites.

MATERIALS AND METHODS

The DESTROY-2 trial, planned as a prospective dose escalation study in oligometastatic (one to five lesions) cancer patients relied on the delivery of a single high dose of radiation utilizing high-precision technology. The primary study endpoint was the definition of the maximum tolerated dose (MTD) of SRS-VMAT. The secondary objectives of the study were the evaluation of safety, efficacy, and long-term outcomes. All patients consecutively observed at our radiotherapy unit matching the inclusion criteria were enrolled. Each enrolled subject was included in a different phase I study arm, depending on the tumor site and the disease stage (lung, liver, bone, other), and sequentially assigned to a particular dose level.

RESULTS

Two hundred twenty seven lesions in 164 consecutive patients (male/female: 97/67, median age: 68 years; range: 29-92) were treated. The main primary tumors were: prostate cancer (60 patients), colorectal cancer (47 patients), and breast cancer (39 patients). The maximum planned dose level was achieved in all study arms, and the MTD was not exceeded. 34 Gy, 32 Gy, 24 Gy, and 24 Gy were established as the single-fraction doses for treating lung, liver, bone, and other extracranial lesions, respectively. The prescribed BED 2Gyα/β:10 to the planning target volume ranged from 26.4 Gy to 149.6 Gy. Twenty-seven patients (16.5%) experienced grade 1-2 and only one grade 3 acute toxicity, which was a pulmonary one. In terms of late toxicity, we registered only 5 toxicity>G2: a G3 gastro-intestinal one, three G3 bone toxicity, and a G3 laryngeal toxicity. The overall response was available for 199 lesions: 107 complete response (53.8%), 50 partial response (25.1%), and 31 stable disease (15.6%), leading to an overall response rate of 94.5%. Progression was registered only in 11 cases (5.5%). The overall response rate in each arm ranged from 88.6% to 96.4%. The overall two-year local control, distant metastasis free survival, disease free survival, and overall survival were 81.7%, 33.0%, 25.4%, and 78.7% respectively.

CONCLUSION

In conclusion, the planned doses of 34 Gy, 32 Gy, 24 Gy, and 24 Gy were successfully administered as single-fractions for the treatment of lung, liver, bone, and other extracranial lesions, respectively, in a prospective SRS dose-escalation trial. No dose-limiting toxicities were registered, and minimal acute and late toxicity were reported. New indications for SRS are currently being studied in oligoprogressive patients receiving targeted drugs or in combination with immunotherapy. The DESTROY-2 trial represents, in our opinion, a credible starting point for future modern radiosurgery trials.

Myonecrosis as a rare side effect of stereotactic body radiotherapy for bone metastases: Report of two cases and a comprehensive literature review

Stereotactic body radiotherapy is a highly effective form of radiation therapy for palliation of bone metastases, but it can also lead to rare but severe side effects, such as myonecrosis. According to the literature, the incidence of myonecrosis after stereotactic body radiotherapy is low and mostly dose dependent. It is crucial to consider the potential impact of immunotherapy and other systemic therapies in the assessment. The course of radiation myonecrosis can vary, and corticosteroids or vascular endothelial growth factor inhibitors may potentially play a role in its treatment. Herein, we report two patients presenting with myonecrosis after stereotactic body radiotherapy for bone metastasis.

External Beam Radiation Therapy for Palliation of Symptomatic Bone Metastases: An ASTRO Clinical Practice Guideline

PURPOSE

This guideline provides evidence-based recommendations for palliative external beam radiation therapy (RT) in symptomatic bone metastases.

METHODS

The ASTRO convened a task force to address 5 key questions regarding palliative RT in symptomatic bone metastases. Based on a systematic review by the Agency for Health Research and Quality, recommendations using predefined consensus-building methodology were established; evidence quality and recommendation strength were also assessed.

RESULTS

For palliative RT for symptomatic bone metastases, RT is recommended for managing pain from bone metastases and spine metastases with or without spinal cord or cauda equina compression. Regarding other modalities with RT, for patients with spine metastases causing spinal cord or cauda equina compression, surgery and postoperative RT are conditionally recommended over RT alone. Furthermore, dexamethasone is recommended for spine metastases with spinal cord or cauda equina compression. Patients with nonspine bone metastases requiring surgery are recommended postoperative RT. Symptomatic bone metastases treated with conventional RT are recommended 800 cGy in 1 fraction (800 cGy/1 fx), 2000 cGy/5 fx, 2400 cGy/6 fx, or 3000 cGy/10 fx. Spinal cord or cauda equina compression in patients who are ineligible for surgery and receiving conventional RT are recommended 800 cGy/1 fx, 1600 cGy/2 fx, 2000 cGy/5 fx, or 3000 cGy/10 fx. Symptomatic bone metastases in selected patients with good performance status without surgery or neurologic symptoms/signs are conditionally recommended stereotactic body RT over conventional palliative RT. Spine bone metastases reirradiated with conventional RT are recommended 800 cGy/1 fx, 2000 cGy/5 fx, 2400 cGy/6 fx, or 2000 cGy/8 fx; nonspine bone metastases reirradiated with conventional RT are recommended 800 cGy/1 fx, 2000 cGy/5 fx, or 2400 cGy/6 fx. Determination of an optimal RT approach/regimen requires whole person assessment, including prognosis, previous RT dose if applicable, risks to normal tissues, quality of life, cost implications, and patient goals and values. Relatedly, for patient-centered optimization of treatment-related toxicities and quality of life, shared decision making is recommended.

CONCLUSIONS

Based on published data, the ASTRO task force's recommendations inform best clinical practices on palliative RT for symptomatic bone metastases.

Practice and principles of stereotactic body radiation therapy for spine and non-spine bone metastases

Radiotherapy is the dominant treatment modality for painful spine and non-spine bone metastases (NSBM). Historically, this was achieved with conventional low dose external beam radiotherapy, however, stereotactic body radiotherapy (SBRT) is increasingly applied for these indications. Meta-analyses and randomized clinical trials have demonstrated improved pain response and more durable tumor control with SBRT for spine metastases. However, in the setting of NSBM, there is limited evidence supporting global adoption and large scale randomized clinical trials are in need. SBRT is technically demanding requiring careful consideration of organ at risk tolerance, and strict adherence to technical requirements including immobilization, simulation, contouring and image-guidance procedures. Additional considerations include follow up practices after SBRT, with appropriate imaging playing a critical role in response assessment. Finally, there is renewed research into promising new technologies that may further refine the use of SBRT in both spinal and NSBM in the years to come.

Evaluation of the clinical feasibility of cone-beam computed tomography guided online adaption for simulation-free palliative radiotherapy

Background and purpose

Simulation-free radiotherapy, where diagnostic imaging is used for treatment planning, improves accessibility of radiotherapy for eligible palliative patients. Combining this pathway with online adaptive radiotherapy (oART) may improve accuracy of treatment, expanding the number of eligible patients. This study evaluated the adaptive process duration, plan dose volume histogram (DVH) metrics and geometric accuracy of a commercial cone-beam computed tomography (CBCT)-guided oART system for simulation-free, palliative radiotherapy.

Materials and methods

Ten previously treated palliative cases were used to compare system-generated contours against clinician contours in a test environment with Dice Similarity Coefficient (DSC). Twenty simulation-free palliative patients were treated clinically using CBCT-guided oART. Analysis of oART clinical treatment data included; evaluation of the geometric accuracy of system-generated synthetic CT relative to session CBCT anatomy using a Likert scale, comparison of adaptive plan dose distributions to unadapted, using DVH metrics and recording the duration of key steps in the oART workflow.

Results

Auto-generated contours achieved a DSC of higher than 0.85, excluding the stomach which was attributed to CBCT image quality issues. Synthetic CT was locally aligned to CBCT anatomy for approximately 80% of fractions, with the remaining suboptimal yet clinically acceptable. Adaptive plans achieved a median CTV V95% of 99.5%, compared to 95.6% for unadapted. The median overall oART process duration was found to be 13.2 mins, with contour editing being the most time-intensive adaptive step.

Conclusions

The CBCT-guided oART system utilising a simulation-free planning approach was found to be sufficiently accurate for clinical implementation, this may further streamline and improve care for palliative patients.

Current and potential treatment of colorectal cancer metastasis to bone

BACKGROUND

Colorectal cancer (CRC) with subsequent bone metastasis is associated with a poor prognosis compared with patients who do not develop bone metastasis. However, metastasis in bone is rare, contrasted with more common locations such as the liver and lungs. As a result, the treatment methods targeting CRC bone lesions are limited. This review aims to compile information regarding current and potential medical and surgical treatment methods for colorectal cancer with specific regard to bone metastasis.

METHODS

A computer-based literature review of animal- and human-based studies was conducted using multiple database searches. Case reports were excluded.

RESULTS

Preliminary findings demonstrate that treatments specifically targeting bone metastasis due to colorectal cancer are categorized by local vs. systemic treatment. The primary goals are the alleviation of skeletal-related events and improvement in quality of life. Current options include: chemotherapy, radiation, monoclonal antibodies, and surgery. Emerging options include intratumoral mellitin, MRgFUS, and bone microenvironment targeting.

CONCLUSION

Treatment of CRC metastasis to bone is necessary to slow down metastatic progression, alleviate symptoms, and improve quality of life. With a possible rise in bone metastasis due to increased overall CRC survival rates, more clinical trials should be performed to address this growing concern.

The Role of Post-Operative Radiotherapy for Non-Spine Bone Metastases (NSBMs)

Non-spine bone metastases (NSBMs) can cause significant morbidity and deterioration in the quality of life of cancer patients. This paper reviews the role of post-operative radiotherapy (PORT) in the management of NSBMs and provides suggestions for clinical practice based on the best available evidence. We identified six retrospective studies and several reviews that examined PORT for NSBMs. These studies suggest that PORT reduces local recurrence rates and provides effective pain relief. Based on the literature, PORT was typically delivered as 20 Gy in 5 fractions or 30 Gy in 10 fractions within 5 weeks of surgery. Complete coverage of the surgical hardware is an important consideration when designing an appropriate radiation plan and leads to improved local control. Furthermore, the integration of PORT in a multidisciplinary team with input from radiation oncologists and orthopedic surgeons is beneficial. A multimodal approach including PORT should be considered for an NSBM that requires surgery. However, phase III studies are needed to answer many remaining questions and optimize the management of NSBMs.

Management of pain in patients with bone metastases

Cancer-induced bone pain (CIBP) has a considerable impact on patients’ quality of life as well as physical and mental health. At present, patients with CIBP are managed according to the three-step analgesic therapy algorithm proposed by the World Health Organization. Opioids are commonly used as the first-line treatment for moderate-to-severe cancer pain but are limited due to addiction, nausea, vomiting and other gastrointestinal side effects. Moreover, opioids have a limited analgesic effect in some patients. In order to optimize the management of CIBP, we must first identify the underlying mechanisms. In some patients, surgery, or surgery combined with radiotherapy or radiofrequency ablation is the first step in the management of CIBP. Various clinical studies have shown that anti-nerve growth factor (NGF) antibodies, bisphosphonates, or RANKL inhibitors can reduce the incidence and improve the management of cancer pain. Herein, we review the mechanisms of cancer pain and potential therapeutic strategies to provide insights for optimizing the management of CIBP.

Study on the Correlation between Pain and Cytokine Expression in the Peripheral Blood of Patients with Bone Metastasis of Malignant Cancer Treated Using External Radiation Therapy

The incidence of cancer is increasing worldwide on a yearly basis, with the number of patients with bone metastases also increasing annually. Events associated with bone metastases can seriously affect patient quality of life, through pain, hypercalcemia, bone marrow regeneration disorders, and spinal cord compression. In this nonrandomized controlled clinical trial study, we focused on the relationship between bone metastasis, pain, and cytokines before and after radiotherapy. We hypothesized that radiotherapy alters the cytokine profile of the local bone environment. Combined with the analgesic effects of radiotherapy, certain cytokines may be very sensitive to radiation. External radiation therapy is commonly used to treat cancer patients with bone metastases and can effectively relieve metastasis-related pain, although its underlying mechanisms have not been fully elucidated. For this case-control study, we recruited 30 cancer patients with bone metastasis and 30 healthy individuals. Peripheral venous blood from healthy individuals was collected. The clinical characteristics and peripheral venous blood were collected from patients one week before and one week after radiotherapy. The preradiotherapy and postradiotherapy pain scores, quality of life (QOL), and blood cytokine profiles of the patients to that of the controls were collected to identify pain-related cytokines. Finally, the pain score and the quality of life score improved significantly after radiotherapy. Moreover, the preradiotherapy and postradiotherapy blood cytokine profiles of the patients showed significant differences, indicating that the analgesic effect of radiotherapy against bone metastases is mediated via altered cytokine production. Furthermore, some cytokines were more sensitive to radiotherapy. The levels of MIP-1δ, MCP-2, TIMP-1, RANTES, IGFBP3, and TNF-α showed significant differences in the pairwise comparative analysis and may therefore mediate pain associated with bone metastasis.

In situ real time dosimetric studies for spine stereotactic body radiation therapy in a cadaver implanted with carbon fiber and titanium instrumentation

OBJECTIVE

To compare the dosimetric accuracy of post-operative SBRT in a carbon-fiber versus titanium instrumented spine using cadaveric model METHODS: In situ cadaveric implantation of titanium and carbon fiber instrumentation and dosimeter chips in a thoracic spine. The cadaver underwent SBRT and dose of RT was calculated, measured, and then compared. The sensors were placed in positions to provide data on dosimetry near the screws (within 1 cm) as well as between the screws. The differences between calculated and measured doses were reported as in percentage.

RESULTS

There was a significant difference in the dosimetry from calculated versus measured values near the screws of carbon fiber compared to titanium (P = 0.0057) with a mean percentage difference of only 2.93 for CF and a much higher value of 19.32 for titanium near the screws. There was also greater variability in the percent difference for the two screw types, with differences ranging from -16.54% to 35.20% near titanium screws and -3.37% to 1.66% near CF screws.

CONCLUSION

More accurate dosimetry and RT delivery with carbon fiber screws compared to traditional titanium screws may have implications on optimal radiation delivery as well as complication avoidance. This may be due to reduced scatter and thus lower variability in radiation delivery with VMAT technique.

Radiotherapy of bone metastases

We present the update of the recommendations of the French society of oncological radiotherapy on bone metastases. This is a common treatment in the management of patients with cancer. It is a relatively simple treatment with proven efficacy in reducing pain or managing spinal cord compression. More complex treatments by stereotaxis can be proposed for oligometastatic patients or in case of reirradiation. In this context, increased vigilance should be given to the risks to the spinal cord.

Evaluation of the impact of teaching on delineation variation during a virtual stereotactic ablative radiotherapy contouring workshop

Introduction:

Variation in delineation of target volumes/organs at risk (OARs) is well recognised in radiotherapy and may be reduced by several methods including teaching. We evaluated the impact of teaching on contouring variation for thoracic/pelvic stereotactic ablative radiotherapy (SABR) during a virtual contouring workshop.

Materials and methods:

Target volume/OAR contours produced by workshop participants for three cases were evaluated against reference contours using DICE similarity coefficient (DSC) and line domain error (LDE) metrics. Pre- and post-workshop DSC results were compared using Wilcoxon signed ranks test to determine the impact of teaching during the workshop.

Results:

Of 50 workshop participants, paired pre- and post-workshop contours were available for 21 (42%), 20 (40%) and 22 (44%) participants for primary lung cancer, pelvic bone metastasis and pelvic node metastasis cases, respectively. Statistically significant improvements post-workshop in median DSC and LDE results were observed for 6 (50%) and 7 (58%) of 12 structures, respectively, although the magnitude of DSC/LDE improvement was modest in most cases. An increase in median DSC post-workshop ≥0·05 was only observed for GTVbone, IGTVlung and SacralPlex, and reduction in median LDE > 1 mm was only observed for GTVbone, CTVbone and SacralPlex. Post-workshop, median DSC values were >0·7 for 75% of structures. For 92% of the structures, post-workshop contours were considered to be acceptable or within acceptable variation following review by the workshop faculty.

Conclusions:

This study has demonstrated that virtual SABR contouring training is feasible and was associated with some improvements in contouring variation for multiple target volumes/OARs.

Stereotactic Body Radiotherapy for Prostate Cancer: Where, When, and Who? A Bibliometric Analysis

OBJECTIVES

To provide an overview of the achievements and future research with stereotactic body radiotherapy (SBRT) in prostate cancer.

METHODS

SBRT publications for prostate cancer were retrieved from the Web of Science and Dimension database. Bibliometric analyses were performed using VOSviewer and Prism graph. Analysis of variance test was used to compare the publication, citation, and the mean citation between specialty journals. Network maps were produced to identify authors' and countries' collaboration clusters.

RESULTS

Between 2006 and 2020, 574 publications fulfilling the inclusion criteria were identified, and a significant growth trend in publication (P<0.0001) and citation (P=0.001) number was recognized over the period. The United States was the most productive country with 253 (44.2%) articles. The RED Journal had the highest number of publications (14%) and citations (19%). Urology journals published (P=0.01) and cited significantly less than radiation oncology journals (P=0.01). All open access and non-open access number of publications increased over time, with a significant difference between non-open access and open access journals (P<0.0001). Two author clusters were identified, in the United States with the collaboration of Canadian and British authors, and in Italy with the participation of European authors.

CONCLUSION

The number of publications and citations on SBRT for prostate cancer has grown linearly in the last decades. The United States is the leading country in this research field, and the use of SBRT in oligometastatic disease, reirradiation, and salvage seems to be hot topics in this research field.

Prognostic Factors Influencing Survival and a Treatment Pattern Analysis of Conventional Palliative Radiotherapy for Patients with Bone Metastases

BACKGROUND

Treatment indication for bone metastases is influenced by patient prognosis. Single-fraction radiotherapy (SFRT) was proven equally effective as multiple fractionation regimens (MFRT) but continues to be underused.

OBJECTIVE

Primary objectives: (a) to identify prognostic factors for overall survival and (b) to analyze treatment patterns of palliative radiotherapy (proportion of SFRT indication and predictive factors of radiotherapy regimen) for bone metastases.

METHODS

582 patients with bone metastases who underwent conventional radiotherapy between January 1st 2014-31 December 2017 were analyzed. The Cox proportional hazard model was used to identify predictors of overall survival. For the treatment pattern analysis, 677 radiotherapy courses were evaluated. The logistic regression model was used to identify potential predictors of radiotherapy regimen.

RESULTS

The 3-year overall survival was 15%. Prognostic factors associated with poor overall survival were multiple bone metastases [hazard ratio (HR = 5.4)], poor performance status (HR = 1.5) and brain metastases (HR = 1.37). SFRT prescription increased from 41% in 2017 to 51% in 2017. Predictors of SFRT prescription were a poor performance status [odds ratio (OR = 0.55)], lung (OR = 0.49) and urologic primaries (OR = 0.33) and the half-body lower site of irradiation (OR = 0.59). Spinal metastases were more likely to receive MFRT (OR = 2.09).

CONCLUSIONS

Based on the prognostic factors we identified, a selection protocol for patients candidates for palliative radiotherapy to bone metastases could be established, in order to further increase SFRT prescription in our institution.