Pathological fracture after radiotherapy: systematic review of literature

SUMMARY

OBJECTIVE:

To evaluate the epidemiological data and available treatments for fractures secondary to radiotherapy treatment.

METHODS:

Identification of publications on pathological skeletal fractures previously exposed to ionizing radiation.

RESULTS:

The incidence of fractures after irradiation varies from 1.2% to 25% with a consolidation rate of 33% to 75%, being more frequent in the ribs, pelvis, and femur. The time elapsed between irradiation and fracture occurs years after radiotherapy. Risk factors include age above 50 years, female gender, extensive periosteal detachment, circumferential irradiation, tumor size, and anterior thigh location. The etiology is still uncertain, but cellular disappearance, reduction of bone turnover and activity were observed hematopoietic as possible causes of failure of consolidation.

CONCLUSION:

There is no consensus in the literature on the factors related to the development of fractures, with radiation dose, previous tumor size and periosteal detachment being suggested as potential factors.

KEYWORDS:
Fractures, Spontaneous; Fracture Healing; Radiotherapy; Radiation Effects

RESUMO

OBJETIVO:

Avaliar dados epidemiológicos e tratamentos disponíveis para fraturas secundárias ao tratamento radioterápico.

MÉTODOS:

Identificação de publicações sobre as fraturas patológicas ocorridas em esqueleto previamente exposto à radiação ionizante.

RESULTADOS:

A incidência de fraturas após irradiação varia de 1,2% a 25% com taxa de consolidação de 33% a 75%, sendo mais frequente em costelas, pelve e fêmur. O tempo decorrido entre a irradiação e a fratura ocorre anos após a radioterapia. Os fatores de risco incluem idade acima de 50 anos, sexo feminino, descolamento periosteal extenso, irradiação circunferencial, tamanho do tumor e localização anterior na coxa. A etiologia ainda é incerta, mas foram observados desaparecimento celular, redução do turnover ósseo e da atividade hematopoiética como possíveis causas da falha de consolidação.

CONCLUSÃO:

Não há consenso na literatura avaliada sobre os fatores relacionados ao desenvolvimento de fraturas, sendo a dose de radiação, o tamanho prévio do tumor e o descolamento periosteal sugeridos como fatores potenciais.

PALAVRAS-CHAVE:
Fraturas espontâneas; Consolidação da fratura; Radioterapia; Efeitos de radiação

INTRODUCTION

Radiotherapy is a therapeutic technique based on the use of ionizing radiation, commonly used in cancer treatments. It has been applied as adjuvant or isolated therapy for the local control of different types of cancer. Although it is an important therapeutic tool for oncology patients, radiotherapy is not exempt from adverse effects. Ionizing radiation also affects the healthy tissues of the body, which may lead to complications often difficult to solve. Specifically, in the skeletal tissue, it can lead to osteonecrosis, actinic osteitis, pathological fractures, failure of consolidation, and osteomyelitis¹.

Pathologic fractures after the bone is exposed to ionizing radiation, although relatively infrequent², have challenging treatment due to the high rate of complications, especially the failure in consolidation and infection, leading to disastrous functional results³.

The objective of this study is to critically and systematically review the literature available on this topic. The review will focus on epidemiological data, especially risk factors, as well as the treatments available for these fractures.

FIGURE 1
RADIOGRAPHIC IMAGING OF PATHOLOGICAL FRACTURE OF THE RIGHT PROXIMAL HUMERUS IN PATIENTS WITH UNDIFFERENTIATED PLEOMORPHIC SARCOMA AFTER TWO YEARS OF TREATMENT WITH RESECTION AND RADIOTHERAPY.

METHODS

This systematic review was conducted by identifying publications about pathological fractures on skeletons previously exposed to ionizing radiation. We considered relevant randomized prospective clinical trials, meta-analyses, and systematic reviews of the literature. We considered less relevant studies with case series and case reports.

The search began by determining the keywords, after formulating the structured question. The keywords were determined based on the PubMed, Lilacs, and SciELO databases. We included in this systematic review articles published in English, Spanish, and Portuguese. The relevant keywords identified are shown in Table 1.

TABLE 1
KEYWORDS IDENTIFIED IN PORTUGUESE, SPANISH, AND ENGLISH.

Portuguese	Spanish	English [MeSH Terms]
Fraturas espontâneas	Fracturas Espontáneas	Fractures, Spontaneous
Consolidação da fratura	Curación de Fractura	Fracture Healing
Radioterapia	Radioterapia	Radiotherapy
Efeitos de radiação	Efectos de la Radiación	Radiation Effects

After identifying the keywords, they were searched in the PubMed (www.ncbi.nlm.nih.gov/pubmed), Lilacs (lilacs.bvsalud.org), and SciELO (www.scielo.org) databases. The results were classified hierarchically based on the relevance of the study. Finally, after retrieving the publications, the search was expanded with the use of the related citations and see all tools, inside the PubMed database. We also searched for publications in the Ovid Cochrane Database of Systematic Reviews and the Ovid Cochrane Database of Controlled Trials.

RESULTS

We did not identify in the PubMed, Cochrane, LILACS, and SciELO databases relevant publications that include randomized prospective clinical trials, meta-analyses, and systematic reviews of the literature. All publications retrieved are of lesser importance, including case series and case reports.

We retrieved 38 publications in English, from the PubMed database, in humans^4-25. We did not identify any publications on the subject in the Lilacs and SciELO platforms. Table 2 shows the number of articles retrieved for each combination of keywords.

TABLE 2
FREQUENCY OF RELEVANT PUBLICATIONS FOR THE COMBINATION OF KEYWORDS OBTAINED FROM THE PUBMED DATABASE.

“Fracture Healing”[Mesh]	“Radiation Effects”[Mesh]	12 results
“Fractures, Spontaneous”[Mesh]	“Radiation Effects”[Mesh]	81 results
“Fractures, Spontaneous”[Mesh]	“Radiotherapy”[Mesh]	163 results
“Fractura Healing”[Mesh]	“Radiotherapy”[Mesh]	10 results

TABLE 3
FREQUENCY OF COMPLICATIONS FROM RADIOTHERAPY.

Complication	Frequency
Fractures	1.2% to 25%
Delay of consolidation	>45%
Osteonecrosis	15%
Complications of the operative wound	10% to 28%
Physeal growth disorders	60%

These studies were ranked based on the number of patients included in the study. We also identified nine experimental studies performed on animals.

DISCUSSION

Radiotherapy, despite its important adjuvant effect in the treatment of cancer and even of some noncancerous lesions, is not devoid of complications. In the skeleton, its deleterious effect can lead to fractures, delay of consolidation, osteonecrosis, complications of the operative wound and, when performed on children, physeal growth disorders².

FIGURE 2
RADIOGRAPHIC IMAGING OF ACTINIC OSTEONECROSIS IN THE LEFT HIP BONE OF A PATIENT AFTER RADIOTHERAPY.

EPIDEMIOLOGY

The fractures, despite being relatively infrequent, have high rates of complications. The incidence of fractures after irradiation varies from 1.2% to 25%^26-29. In most publications, the incidence is approximately 3%. However, fractures are difficult to treat. The consolidation ratio ranges from 33% to 75%. When it evolves to a consolidation failure, a secondary infection is often present. Of these, 43% required amputation to resolve the complication.

The fractures can occur in any bone previously irradiated. They are more frequent in the ribs, in patients irradiated for treating breast cancer, on the pelvis, in patients treated for cancer in abdominal and pelvic organs^11,30,31 and in the femurs, and in patients treated for soft tissue sarcomas. Of these fractures, those that have a greater functional impact are the femoral ones, because they require surgical treatment and lead to greater mechanic repercussions.

CHART 1
FREQUENCY OF PUBLICATION AND INCLUSION IN THE STUDY

Several studies seek to relate pathological fractures after radiotherapy and risk factors. After evaluating 89 patients with soft tissue sarcomas of the thigh treated with surgical resection and radiotherapy, Blaes et al.¹ identified as risk factors the periosteal detachment performed at the moment of the tumor resection, the circumferential irradiation of the femur, and tumors located in the anterior compartment of the thigh. Other factors such as age, gender, radiation dose, association with chemotherapy, extension of the irradiation field, and histology showed no association with femoral fractures. An important aspect of the study was the follow-up time. The time elapsed between the irradiation and the fracture was very relevant since the fracture occurs many years after radiotherapy.

Gortzak et al.²⁹, in a study with 22 patients who presented pathologic fracture of the femur from 101 patients treated using the association of surgery and radiotherapy for thigh sarcomas, identified as risk factors age, female gender, tumor location in the anterior compartment of the thigh, the tumor size, dose of radiation used and degree of periosteal detachment.

In their publication, which evaluated risk factors for pathologic fractures, Lin et al.²⁷ observed no relevance of the dose of radiation employed in the treatment to the occurrence of a fracture. The relevant factor observed in their study was the periosteal detachment during the surgical treatment. On the other hand, Holt et al.³², in spite of its small case series, found evidence that a high dose of radiotherapy, defined as between 60 and 66 Gy, was statistically more dangerous as a risk factor that a low dose, defined as 50 Gy.

Therefore, there is no consensus in the literature about which risk factors are really related to the fractures after radiotherapy treatments. Table 4 lists the risk factors observed with greater frequency in the largest series of cases published in the literature.

TABLE 4
RISK FACTORS FOR PATHOLOGIC FRACTURES AFTER RADIOTHERAPY.

Age over 50 years.

Female gender.

Location of the fracture: ribs, pelvis, and femur.

Tumor size: larger size, greater frequency.

Periosteal detachment.

Circumferential femoral irradiation.

ETIOLOGY

Some studies have tried to explain the reason why fractures in irradiated bones have greater consolidation difficulty. These studies are experimental and use animals, particularly rats.

In an experimental study after femoral exposure, radiotherapy at a dose of 18 Gy and fracture in rats, Nicholls et al.³³ observed the evolution toward consolidation failure when examining the femurs in micro-CT. The images showed an absence of callus formation, with a production deficiency of the osteoid and chondroid matrix. However, they did not evaluate the cellularity of the sample.

In a classical publication on the topic, Maeda et al.³⁴ demonstrated, in an experimental study in rats, the histological evolution of an irradiated bone, not fractured. Over the first two weeks, there is a disappearance of bone cells, a reduction of bone turnover and of hematopoietic activity, without biomechanical repercussion. Between six and 18 weeks, histological changes are maintained, with a gradual increase in bone resorption, reduced cortical thickness, and increased bone porosity. After 18 weeks, they observed the gradual improvement of bone porosity and of the number of osteocytes, and increased periosteal bone formation, leading the bone tissue to the physiological state.

By evaluating the effectiveness of the use of amifostine for preventing the death of osteocytes in rat jaws irradiated and fractured, Donneys et al.³⁵ observed a decreased number of osteocytes in the fracture and increased gaps in the matrix. These findings demonstrate that the cell death of osteocytes at the site of irradiation where the fracture is located is greater than when the fracture occurs in non-irradiated bones. This same study showed an inability of the bone tissue to produce a new matrix after the fracture in a bone exposed to ionizing radiation.

Generally, we classify failures of consolidation as vascular and avascular. This differentiation indicates the presence or absence of biological stimulus to bone consolidation. The studies on the subject demonstrate the biological effect of ionizing radiation on normal bones, showing the death of osteocytes and the tissue inability to regenerate, perhaps due to cell deficiency at the fracture site. The scientific literature lacks data on vascularization of the fracture site in irradiated bone tissue, because the typical fracture is repopulated by cells from neovascularization, and this detail needs more in-depth studies.

TREATMENT OF PATHOLOGIC FRACTURES AFTER RADIOTHERAPY

Some publications address the prevention of fractures after radiotherapy, especially in cases that include thigh tumors. In their study assessing risk factors for pathologic femoral fractures after treatments for thigh sarcomas, Gortzak et al.²⁹ suggest intramedullary nailing for patients who meet the criteria for risk of fracture.

In a publication with 22 patients victims of a pathologic fracture after radiotherapy, Sternheim et al.³ demonstrated a high degree of failure after femoral intramedullary nailing. They reported 86% of complications, of which 82% were failures of consolidation. Of the 22 patients, five presented failure of synthesis material after pseudoarthrosis and two had infected pseudoarthrosis.

Primary arthroplasty as a treatment for pathologic fractures after radiotherapy is defended for injuries on some specific locations. Kim et al.² published 36 patients with femoral fractures. Of these, 30 were diaphyseal fractures and 06 trochanteric fractures. Of the 36 fractures, 6 were treated with primary arthroplasty and 30 with osteosynthesis. The patients submitted to osteosynthesis had more complications and need for reoperation with greater frequency than those submitted to arthroplasty. The authors suggest further investigation of primary arthroplasty as a treatment for pathologic femoral fractures after radiotherapy.

In view of the high rate of complication of the treatment of fractures after radiotherapy, some authors suggest the introduction of factors that can collaborate with the consolidation. Duffy et al.³⁶ treated 17 patients with 18 femoral fractures after radiotherapy, with vascularized fibular graft associated with an autologous graft. They reported consolidation in 16 patients in an average time of 9.4 months. These results were not replicated in other studies².

In an experimental study on rats, Nicholls et al.³⁷ assessed the effectiveness of the morphogenetic protein 7 (BMP7, OP-1) in the consolidation of fractures after radiotherapy. They did not observe the effectiveness of the protein in the consolidation of fractures.

In another study on rats, Donneys et al.³⁵ demonstrated that Amifostine is effective to prevent the death of osteocytes at the site of fracture of femurs exposed to ionizing radiation. This is a drug developed to prevent febrile neutropenia in patients undergoing chemotherapy treatment because it seems to have a cytoprotective activity. There are no studies proving its effectiveness in human bone tissue.

This systematic review could not determine a safe and effective therapeutic method for pathologic fractures secondary to radiotherapy.

CONCLUSION

There are studies in the literature relevant to the topic. All publications relating to the subject consist of case reports and case series, or experimental trials on rats.

Due to the absence of relevant studies, there is no consensus in the literature evaluated on factors related to the development of fractures. The dose of radiation, previous size of the tumor, and the periosteal detachment are suggested as potential factors.

The treatment is difficult and with high rates of non-consolidation.

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Publication Dates

• Publication in this collection
  22 July 2019
• Date of issue
  June 2019

History

• Received
  13 Jan 2019
• Accepted
  09 Feb 2019