Fracture after radiation therapy for femoral metastasis: incidence, timing and clinical features

Understanding and Managing Fracture Risk in Patients With Cancer: A Literature Review

One of the most important complications of cancer and its treatments is the increased fracture risk. Fractures can have a significant impact on the patient's quality of life and may be associated with morbidity, mortality, and reduced functional status. The present study aims to investigate the mechanisms underlying the increased risk of fractures in cancer patients, the effect of cancer treatments on fracture risk, and strategies to prevent fractures in this population. This is a literature review using the PubMed - National Center for Biotechnology Information (NCBI), Web of Science, Cochrane Library, Scopus, and electronic internet databases. The search was based on the keywords "fracture risk" AND "cancer", NOT ("osteoporosis" OR "osteoporotic"). Inclusion criteria were clinical studies assessing fracture pathogenesis and prevention, along with fracture risk estimation in cancer patients. Non-human studies, pediatric studies, non-English studies, editorials, and study protocols were excluded. After the application of inclusion and exclusion criteria, 146 studies were finally included. Fracture risk is particularly increased in patients with malignancies. This is due to the direct effect of cancer cells on bone metabolism, the existence of cancer-related factors (bone metastases, hypercalcemia, malnutrition, and increased risk of falls), coexisting diseases (osteoporosis, diabetes mellitus, and rheumatoid arthritis), and the side effects of anticancer treatments (chemotherapy, radiotherapy, and hormone therapy). Fracture risk assessment is based on the measurement of bone mineral density (DXA), the use of the Fracture Risk Assessment Tool (FRAX), laboratory tests (measurement of calcium, phosphorus, vitamin D, alkaline phosphatase, parathyroid hormone, and biomarkers of bone metabolism), and imaging methods (X-rays, computed tomography, magnetic resonance imaging, and PET/CT of bones). To reduce fracture risk in cancer patients, lifestyle changes (exercise, smoking cessation) and anti-osteoclastic drugs such as bisphosphonates and denosumab are administered. Fracture risk in cancer patients is influenced by various factors, including the type of cancer, stage of disease, cancer treatments, bone health status, and presence of bone metastases. Overall, fracture risk in cancer patients is multifactorial and requires comprehensive evaluation and management to optimize bone health and quality of life.

Predictive Factors for Failed Nonsurgical Management of Long Bone Metastasis and Myeloma

BACKGROUND

Understanding the risk factors for failing nonsurgical management of metastatic bone disease is necessary to determine those patients who will benefit from prophylactic stabilization; however, standard predictive models do not include several clinically relevant factors. The primary and secondary objectives of this study were to evaluate comprehensive patient- and disease-related factors as potential predictors of failure of radiation therapy alone for long bone lesions and overall survival in metastatic disease and myeloma.

METHODS

All patients who underwent radiation therapy for long bone metastases at our tertiary care institution from May 2011 to February 2020 were retrospectively reviewed. Of 475 lesions, we excluded those with prophylactic fixation or fracture before radiation therapy, and those <0.5 cm on plain radiographs. Outcomes of the 186 lesions were classified as no progression, progression requiring prophylactic fixation, or progression to pathologic fracture. Blinded radiograph review was done by two orthopaedic oncology surgeons and two musculoskeletal radiologists. Demographic, socioeconomic, lesion, cancer severity, and patient-specific risk factors were identified, and potential predictors were analyzed using backwards stepwise regression.

RESULTS

Following radiation therapy, 8.6% lesions underwent prophylactic fixation and 14.0% fractured. Prophylactic fixation was associated with Mirels' score (OR = 1.98, P = 0.025), lesion cortical involvement (OR = 16.96, P = 0.010), and younger patient age (OR = 0.93, P = 0.024). Fracture was associated with lesion cortical involvement (OR = 10.16, P = 0.003) and "low risk" histology (OR = 9.01, P = 0.057). Orthopaedic treatment (either prophylactic surgery or pathologic fracture management) was associated with Mirels' score (OR = 1.62, P = 0.015), lesion cortical involvement (OR = 8.94, P = 0.002), humerus location (OR = 4.19, P = 0.042), and Medicare (OR = 4.12, P = 0.062) or private insurance (OR = 5.69, P = 0.022) compared with Medicaid. ECOG score (OR = 1.28, P = 0.003) was found to be a risk factor for increased mortality after radiotherapy, while "low risk" histology (OR = 0.51, P = 0.029), mixed lesion type (OR = 0.34, P = 0.006), and increased body mass index (OR = 0.95, P = 0.001) were protective factors.

CONCLUSIONS

Radiograph measurements of cortical involvement were the most clinically relevant for determination of metastatic lesion fracture risk; however, predictors of local failure not addressed in Mirels' score should be considered in clinical decisions about prophylactic fixation. Surgery may be underperformed for histologies commonly considered to be "low risk" for local progression after radiation therapy.

What is the incidence and non-union rate of radiation-associated fractures? - A systematic review of the literature

BACKGROUND

Radiation-associated fractures (RAFs) are a challenging complication in oncologic patients, yet their incidence remains unknown and optimal management lacks consensus.

AIM

This review aimed to evaluate the incidence of RAFs in the trunk, pelvis, and extremities as well as non-union rates of surgical and non-surgical treatment.

MATERIALS AND METHODS

A systematic review of PubMed and Embase databases was conducted. The study was registered on PROSPERO (ID: CRD42024513017). Studies were included if they reported RAFs in oncologic populations, had a sample size of at least five patients, and provided extractable data on RAF incidence or number. The STROBE checklist was utilized for evaluation of study quality. For eligible studies, quantitative analyses were conducted to determine weighted incidence of RAF and fracture non-union.

RESULTS

Thirty-five studies comprising 9,980 patients treated with radiation therapy were included. The weighted incidence of RAFs was calculated to be 6.5% across 8,061 patients. The weighted incidence of femoral RAF was 5.2%, while pelvic RAF incidence was 17.1%. Non-union rates after initial treatment varied from 4% to 100%, with an overall weighted incidence of 48%. Treatments included intramedullary nailing, fixation with screws/plate, prosthetic replacement, conservative treatment, and amputation, with varying success rates.

CONCLUSION

This review highlights RAFs as a significant complication of radiation therapy, with a weighted incidence of 6.5% and a non-union rate of 48%. Advanced radiation techniques have reduced RAF occurrences, but non-union remains a challenge, necessitating tailored treatment strategies. Further research is needed to optimize RAF management and improve patient outcomes.

Clinical Outcomes Among Patients Treated With Stereotactic Body Radiation Therapy to Femur Metastases for Oligometastatic Disease Control or Reirradiation: Results From a Large Single-Institution Experience

Purpose

There are limited data regarding outcomes after stereotactic body radiation therapy (SBRT) for femur metastases, which was an exclusion criteria for the Stereotactic Ablative Radiotherapy for the Comprehensive Treatment of Oligometastatic Cancers (SABR-COMET) trial. We aimed to characterize clinical outcomes from a large single institution experience.

Methods and Materials

Forty-eight patients with 53 lesions were consecutively treated with femur SBRT from May 2017 to June 2022. The Kaplan-Meier method and Cox proportional hazard models were used to characterize time-to-event endpoints and associations between baseline factors and clinical outcomes, respectively. Local control and locoregional control were defined as the absence of tumor progression within the radiation treatment field or within the treated femur, respectively.

Results

Most patients had Eastern Cooperative Oncology Group performance status 0 to 1 (90%), prostate (52%) or breast/lung (17%) cancer, and 1 to 3 lesions (100%), including 29 proximal and 5 distal. Fifty-seven percent of the lesions were treated with concurrent systemic therapy. Median planning target volume was 49.1 cc (range, 6.6-387 cc). Planning target volume V100 (%) was 99% (range, 90-100). Fractionation included 18 to 20 Gy/1F, 27 to 30 Gy/3F, and 28.5-40 Gy/5F. Forty-two percent had Mirels score ≥7 and most (94%) did not have extraosseous extension. Acute toxicities included grade 1 fatigue (15%), pain flare (7.5%), nausea (3.8%), and decreased blood counts (1.9%). Late toxicities included fracture (1.9%) at 1.5 years and osteonecrosis (4%) from dose of 40 Gy in 5F and 30 Gy in 5F (after prior 30 Gy/10F). One patient (2%) required fixation postradiation for progressive pain. With median follow-up 19.4 months, 1- and 2-year rates of local control were 94% and 89%, locoregional control was 83% and 67%, progression-free survival were 56% and 25%, and overall survival were 91% and 73%. Fifty percent of local regional recurrence events occurred within 5 cm of gross tumor volume.

Conclusions

Femur SBRT for oligometastatic disease control in well-selected patients was associated with good outcomes with minimal rates of acute and late toxicity. Patterns of local regional recurrence warrant consideration of larger elective volume coverage. Additional prospective study is needed.

A Patient-Specific Fracture Risk Assessment Tool for Femoral Bone Metastases: Using the Bone Strength (BOS) Score in Clinical Practice

Patients with femoral metastases are at risk of fracturing bones. It is important to prevent fractures in order to maintain mobility and quality of life. The BOne Strength (BOS) score is based on a computed tomography (CT)-based patient-specific finite element (FE) computer model that objectively calculates bone strength. In this pilot study, the added clinical value of the BOS score towards treatment-related decision making was assessed. In December 2019, the BOS score was implemented in four radiotherapy centers. The BOS scores and fracture risks of individual patients were calculated and returned to the physician to assist in treatment decisions. The physicians filled out a questionnaire, which was qualitatively analyzed. A follow-up to identify fractures and/or death was performed after six months. Until June 2021, 42 BOS scores were delivered (20 high, 9 moderate, and 13 low fracture risk). In 48%, the BOS score led to an adaptation of treatment plans. Physicians indicated that the BOS score provided objective insight into fracture risk, was reassuring for physicians and patients, and improved multidisciplinary discussions and shared decision making. In conclusion, the BOS score is an objective tool to assess fracture risk in femoral bone metastases and aids physicians and patients in making a more informed decision regarding the most appropriate treatment.

Management of Long Bones Metastatic Disease: Concepts That We All Know but Not Always Remember

Bones are the third most common site of metastatic disease. Treatment is rarely curative; rather, it seeks to control disease progression and palliate symptoms. Imaging evaluation of a patient with symptoms of metastatic bone disease should begin with plain X-rays. Further imaging consists of a combination of (PET)-CT scan and bone scintigraphy. We recommend performing a biopsy after imaging workup has been conducted. Metastatic bone disease is managed with a combination of systemic treatment, radiotherapy (RT), and surgery. External beam RT (EBRT) is used for pain control and postoperatively after fracture stabilization. Single-fraction and multiple-fractions schemes are equally effective achieving pain control. Adequate assessment of fracture risk should guide the decision to stabilize an impending fracture. Despite low specificity, plain X-rays are the first tool to determine risk of impending fractures. CT scan offers a higher positive predictive value and can add diagnostic value. Surgical management depends on the patient's characteristics, tumor type, and location of fracture/bone stock. Fixation options include plate and screw fixation, intramedullary (IM) nailing, and endoprostheses. Despite widespread use, the need for prophylactic stabilization of the entire femur should be individually analyzed in each patient due to higher complication rates of long stems.

STEREOTACTIC BODY RADIATION THERAPY FOR METASTASES IN LONG BONES

OBJECTIVE

To evaluate the cumulative incidence of fracture and local failure and associated risk factors after stereotactic body radiotherapy (SBRT) for long bone metastases.

MATERIAL AND METHODS

Data from 111 patients with 114 metastases in the femur, humerus and tibia treated with SBRT in 7 international centers between October 2011 and February 2021 were retrospectively reviewed and analyzed using a competing risk regression model.

RESULTS

The median follow-up was 21 months (range 6-91 months). All but one patient had a Karnofsky performance status ≥70. There were 84 femur (73.7%), 26 humerus (22.8%) and 4 tibia (3.5%) metastases from prostate (45 [39.5%]), breast (22 [19.3%]), lung (15 [13.2%]), kidney (13 [11.4%]) and other (19 [16.6%]) malignancies. Oligometastases accounted for 74.8% of metastases and 28.1% were osteolytic. The most common total doses were 30-50 Gy in 5 daily fractions (50.9%). Eight fractures (5 in the femur, 2 in the tibia and 1 in the humerus) were observed with a median time to fracture of 12 months (range 0.8-33 months). In 6/8 patients, fracture was not associated with local failure. The cumulative incidence of fracture was 3.5%, 6.1% and 9.8% at 1, 2 and 3 years, respectively. The cumulative incidence of local failure (9/110 metastases with imaging follow-up) was 5.7%, 7.2% and 13.5% at 1, 2 and 3 years, respectively. On multivariate analysis, extraosseous disease extension was significantly associated with fracture (P=0.001; subhazard ratio [SHR] 10.8; 95% CI 2.8-41.9) and local failure (P=0.02; SHR 7.9; 95% CI 1.4-44.7).

CONCLUSION

SBRT for metastases in long bones achieved high rates of durable local metastasis control without an increased risk of fracture. Similar to spine SBRT, patients with extraosseous disease extension are at higher risk of local failure and fracture.

The effect of variations in CT scan protocol on femoral finite element failure load assessment using phantomless calibration

Recently, it was shown that fracture risk assessment in patients with femoral bone metastases using Finite Element (FE) modeling can be performed using a calibration phantom or air-fat-muscle calibration and that non-patient-specific calibration was less favorable. The purpose of this study was to investigate if phantomless calibration can be used instead of phantom calibration when different CT protocols are used. Differences in effect of CT protocols on Hounsfield units (HU), calculated bone mineral density (BMD) and FE failure loads between phantom and two methods of phantomless calibrations were studied. Five human cadaver lower limbs were scanned atop a calibration phantom according to a standard scanning protocol and seven additional commonly deviating protocols including current, peak kilovoltage (kVp), slice thickness, rotation time, field of view, reconstruction kernel, and reconstruction algorithm. The HUs of the scans were calibrated to BMD (in mg/cm³) using the calibration phantom as well as using air-fat-muscle and non-patient-specific calibration, resulting in three models for each scan. FE models were created, and failure loads were calculated by simulating an axial load on the femur. HU, calculated BMD and failure load of all protocols were compared between the three calibration methods. The different protocols showed little variation in HU, BMD and failure load. However, compared to phantom calibration, changing the kVp resulted in a relatively large decrease of approximately 10% in mean HU and BMD of the trabecular and cortical region of interest (ROI), resulting in a 13.8% and 13.4% lower failure load when air-fat-muscle and non-patient-specific calibrations were used, respectively. In conclusion, while we observed significant correlations between air-fat-muscle calibration and phantom calibration as well as between non-patient-specific calibration and phantom calibration, our sample size was too small to prove that either of these calibration approaches was superior. Further studies are necessary to test whether air-fat-muscle or non-patient-specific calibration could replace phantom calibration in case of different scanning protocols.

Custom design and biomechanical clinical trials of 3D-printed polyether ether ketone femoral shaft prosthesis

During the surgical resection and reconstruction of a pathological femoral fracture, the removal of the femoral tumor leaves a large bone defect. Thus, it is necessary to reconstruct the defect and perform internal fixation. Polyether ether ketone (PEEK) has been widely used in spinal fusion and cranioplasty given its excellent biomechanical properties, biocompatibility, and stability. The typical design method of femoral prosthesis is based on the contralateral mirror image model (M-model), and we propose a novel method for designing femoral prosthesis, which is based on the cross section and centerline of the mirrored femur (C-model). In this study, the femoral shaft prostheses based on two models were manufactured using fused deposition modeling technology, and we use mechanical test and finite element analysis (FEA) to reveal the differences in mechanical properties of the two models. The mechanical results showed that the maximum loading force and yield strength were increased by 3% and 6% in the C-model prosthesis compared with the M-model prosthesis, respectively. In FEA, the results indicate that the C-model prosthesis could reduce the stress concentration by 5.4%-10.9% compared to the M-model prosthesis. Finally, the 3D-printed PEEK femoral shaft prosthesis based on C-model was implanted, no early complications occurred. Postoperative radiological examination indicated that the prosthesis and the femoral osteotomy end were closely matched and fixed well.

Skeletal Related Events are Rare After Radiation Treatment for Metastatic Disease of the Femur

BACKGROUND

Pain is a common presenting symptom in patients with metastatic disease to the femur (MDF), and it is often difficult to differentiate pain from the tumor itself versus pain from an impending pathologic fracture. Radiation therapy (RT) is commonly used in the management of pain secondary to MDF but is not adequate in isolation when the underlying bone is structurally compromised.

QUESTIONS/ PURPOSES

The purposes of this study were to determine 1) the incidence of skeletal related events (SREs) following RT to the femur, 2) the frequency and implications of orthopedic evaluation prior to RT, and 3) the frequency of patients presenting with a pathologic fracture.

METHODS

A retrospective, single-institution review of 86 patients with MDF treated with RT from 2005 to 2018 was performed. Patient demographics, primary cancer type, pathologic fracture, orthopedic interventions, and RT details were assessed. Patients were followed to evaluate the occurrence of skeletal related events of the femur until death or time of last recorded clinical follow-up.

RESULTS

In our cohort of 86 patients, the mean RT dose was 22.3 Gy (8-55.8 Gy) delivered over 6.5 fractions (1-31 fractions). Fifteen patients (17%) received RT less than one month, 30 (35%) less than three months, and 49 (57%) less than six months prior to death. Prior to RT, 42 patients (48.9%) had an orthopedic evaluation, 16 of which (38.1% of those evaluated) received prophylactic stabilization with an intramedullary nail (IMN). Ten patients (11.6%) presented with a pathologic fracture. Following RT, five patients (5.8%) had at least one SRE. Three patients sustained a pathologic fracture, three required repeat RT, and three required further surgical intervention.

CONCLUSION

Metastatic disease of bone is a common condition that affects many cancer patients. In our institution's series of MDF treated with RT, we only found one patient who sustained a pathologic fracture after RT treatment with an unrecognized impending fracture. As only half of the patients were referred for an orthopedic evaluation prior to RT, continued education of medical and radiation oncologists regarding the signs and symptoms of impending pathologic fracture is warranted.Level of Evidence: IV.

High rate of fracture in long-bone metastasis: Proposal for an improved Mirels predictive score

INTRODUCTION

Pathologic fracture is the most feared complication in long-bone metastasis. Various radiographic tools are available for identifying at-risk patients and guide preventive treatment. The Mirels score is the most frequently studied and widely used, but has been criticized, many patients not being operated on until the actual fracture stage. We therefore conducted a French national multicenter prospective study: (1) to determine the proportion of patients operated on at fracture stage versus preventively; (2) to compare Mirels score between the two; and (3) to identify factors for operation at fracture stage according to Mirels score and other epidemiological, clinical and biological criteria.

HYPOTHESIS

Simple discriminatory items can be identified to as to complete the Mirels score and enhance its predictive capacity.

MATERIAL AND METHODS

A non-controlled multicenter prospective study included 245 patients operated on for non-revelatory long-bone metastasis, comparing patients operated on for fracture versus preventively according to body-mass index (BMI), ASA score, Katagiri score items and the 4 Mirels items.

RESULTS

One hundred and twenty-six patients (51.4%) were operated on at fracture stage: 106 (84.1%) showed high risk on Mirels score (score>8), and 15 (11.9%) moderate risk (score=8). On multivariate analysis, 4 independent factors emerged: in increasing order, advanced age (OR=1.03; 95%CI 1.01-1.06), VAS pain score>6 (OR=1.47; 95%CI 1.02-2.11), WHO grade>2 (OR=2.74; 95%CI 1.22-6.15), and upper-limb location (OR=5.26; 95%CI 2.13-12.84).

DISCUSSION

The present study confirmed that more than half of patients with long-bone metastasis are operated on at actual fracture stage, in agreement with the literature. Several studies highlighted the weakness of the Mirels score as a predictive instrument. Comparison between preventive and fracture-stage surgery showed that upper-limb location, intense pain, advanced age and impaired functional status were associated with fracture-stage surgery, and should be taken into account alongside the original Mirels criteria. This improved scoring instrument remains to be validated in a prospective study.

LEVEL OF EVIDENCE

IV, prospective cohort study without control group.

Radiation-induced changes to bone composition extend beyond periosteal bone

BACKGROUND

Cancer patients receiving radiotherapy for soft tissue sarcomas are often at risk of post-irradiation (post-RTx) bone fragility fractures, but our understanding of factors controlling radiation-induced bone injury is limited. Previous studies have evaluated post-RTx changes to cortical bone composition in the periosteum of irradiated tibiae, but have not evaluated effects of irradiation in deeper tissues, such as endosteal or mid-cortical bone, and whether there are differential spatial effects of irradiation. In this study, we hypothesize that post-RTx changes to cortical bone composition are greater in endosteal compared to mid-cortical or periosteal bone.

METHODS

A pre-clinical mouse model of limited field hindlimb irradiation was used to evaluate spatial and temporal post-RTx changes to the metaphyseal cortex of irradiated tibiae. Irradiation was delivered unilaterally to the hindlimbs of 12-wk old female BALB/cJ mice as 4 consecutive daily doses of 5 Gy each. RTx and non-RTx tibiae were obtained at 0, 2, 4, 8, and 12 wks post-RTx (n = 9 mice/group/time). Raman spectroscopy was used to evaluate spatial and temporal post-RTx changes to cortical bone composition in age-matched RTx and non-RTx groups.

RESULTS

Significant early spatial differences in mineral/matrix and collagen crosslink ratios were found between endosteal and periosteal or mid-cortical bone at 2-wks post-RTx. Although spatial differences were transient, mineral/matrix ratios significantly decreased and collagen crosslink ratios significantly increased with post-RTx time throughout the entire tibial metaphyseal cortex.

CONCLUSIONS

Irradiation negatively impacts the composition of cortical bone in a spatially-dependent manner starting as early as 2-wks post-RTx. Long-term progressive post-RTx changes across all cortical bone sites may eventually contribute to the increased risk of post-RTx bone fragility fractures.

Effects of ex vivo ionizing radiation on collagen structure and whole-bone mechanical properties of mouse vertebrae

Bone can become brittle when exposed to ionizing radiation across a wide range of clinically relevant doses that span from radiotherapy (accumulative 50 Gy) to sterilization (~35,000 Gy). While irradiation-induced embrittlement has been attributed to changes in the collagen molecular structure, the relative role of collagen fragmentation versus non-enzymatic collagen crosslinking remains unclear. To better understand the effects of radiation on the bone material without cellular activity, we conducted an ex vivo x-ray radiation experiment on excised mouse lumbar vertebrae. Spinal tissue from twenty-week old, female, C57BL/6J mice were randomly assigned to a single x-ray radiation dose of either 0 (control), 50, 1000, 17,000, or 35,000 Gy. Measurements were made for collagen fragmentation, non-enzymatic collagen crosslinking, and both monotonic and cyclic-loading compressive mechanical properties. We found that the group differences for mechanical properties were more consistent with those for collagen fragmentation than for non-enzymatic collagen crosslinking. Monotonic strength at 17,000 and 35,000 Gy was lower than that of the control by 50% and 73% respectively, (p < 0.001) but at 50 and 1000 Gy was not different than the control. Consistent with those trends, collagen fragmentation only occurred at 17,000 and 35,000 Gy. By contrast, non-enzymatic collagen crosslinking was greater than control for all radiation doses (p < 0.001). All results were consistent both for monotonic and cyclic loading conditions. We conclude that the reductions in bone compressive monotonic strength and fatigue life due to ex vivo ionizing radiation are more likely caused by fragmentation of the collagen backbone than any increases in non-enzymatic collagen crosslinks.

Surgical Approach to Bone Metastases

PURPOSE OF REVIEW

The purpose of this review was to examine the recent changes in the surgical treatment of bone metastases and how the treatment paradigm has shifted with the improvement of adjuvant therapies. How surgery fits into the local and systemic treatment was reviewed for bone metastases in different areas.

RECENT FINDINGS

The more common use of targeted chemotherapies and focused high-dose radiation have altered the treatment paradigm of bone metastases. Overall changes in the surgical treatment of bone metastases have been driven by an increased multidisciplinary approach to metastatic cancer and the awareness that one type of surgery does not work for all patients. The individual patient treatment goals dictate the surgical procedures used to achieve these goals. Advancements in adjuvant therapy-like radiation and more targeted chemotherapies have allowed for less invasive surgical approaches and therefore faster recoveries and reduced surgical morbidity for patients.