Skeletal metastases can cause severe pain and functional impairment, secondary to direct invasion or osteolysis. Direct palliation of these metastases can reduce the burden of pain. Surgical excision or radiotherapy has been used to target these tumors. In precarious locations, such as the sternum, surgery may lead to significant morbidity. Radiotherapy requires multiple visits, which may be difficult for the severely disabled. Minimally invasive, image-guided procedures are gaining wider acceptance in treating these lesions. Kyphoplasty has been used for vertebral column metastases. Osteoplasty of a metastasis to a flat, non-weight-bearing bone is rarely reported. The author reports the successful palliation of a sternal metastasis with kyphoplasty. Ultrasound imaging was used with fluoroscopy. Reproducibility, by other providers, is imperative with any emerging technique; this will facilitate wider patient access and device innovation. Hopefully, future multicenter trials will validate the efficacy and safety of this technique.
Metastatic non-small cell lung cancer is the leading cause of cancer death among men and women in the United States and worldwide [1,2]. Life expectancy, following diagnosis, is less than 1 year. One recent study, evaluating patients with metastatic non-small cell lung cancer, reported a median survival of 8.9 months; this median survival increased to 11.6 months, with early palliative care . Early palliative care, within 8 weeks of the diagnosis, led to improvements in quality of life and mood .
Early stage metastatic bone disease may remain undetected. Advanced metastases can cause devastating skeletal-related events, such as spinal cord compression or vertebral fractures . Metastases, alone, can be painful and disabling due to direct invasion and osteolysis. Radiation therapy, analgesics, neurolysis, implantable neuromodulatory procedures, and physical therapy have been used to treat painful metastases.
Percutaneous ablative procedures are used to target painful soft tissue tumors. These techniques are being used, with increasing frequency, in primary and metastatic bone tumors . Collectively, these procedures provide an alternative to wide surgical excision and the attendant morbidity. These methods use imaging and specialized access devices. Tumor destruction is afforded by chemical agents (ethyl alcohol or acetic acid) or thermal energy (laser, microwave, ultrasound, cryotherapy, and radiofrequency) . Radiofrequency ablation produces a discrete thermal lesion and has been efficacious in painful skeletal metastases . Discrete vertebral column metastases have been successfully treated with percutaneous spine stabilization . Pain relief following vertebroplasty and kyphoplasty, in pathological and non-pathological vertebral fractures, has been attributed to spinal stabilization [6,7].
The efficacy of cementoplasty procedures in non-weight-bearing bones suggests a mechanism of pain relief, unrelated to bone stabilization . Polymethyl methacrylate (PPMA) cement causes an exothermic reaction, with curing and solidification. Temperatures ranging from 50 to 57°C have been reported at the bone—cement interface during polymerization . Average peak temperatures ranging from 45 to 100°C, depending on the cement, have been reported . Neurolysis occurs at 45°C ; these temperatures result in the destruction of tumor cells and vascular supply . So, pain relief may occur due to several mechanisms: 1) bone stabilization; 2) direct tissue toxicity; 3) neurolysis; and 4) thermal injury [8,9].
Osteoplasty of non-weight-bearing, flat bones is rarely reported . Three recent case reports describe osteoplasty, with or without radiofrequency ablation, of the scapula and sternum [8,11,12]. Cavity creation and targeting with complementary imaging modalities (fluoroscopy and ultrasound) may enhance the safety in non-spinal metastases. The author reports the successful palliation of a sternal metastasis, due to non-small cell lung cancer, using these imaging methods.
A 58-year-old man underwent a right lower lobectomy, for a moderately differentiated squamous cell carcinoma. The margins and mediastinal nodes were negative, but regional nodes (peribronchial) were positive: stage 2B. He received, but did not complete, adjuvant chemotherapy (carboplatin, taxotere, and abraxane). Taxotere caused an allergic reaction and he developed a peripheral neuropathy. Serial computed tomography (CT) scans were negative for disease recurrence.
Approximately 22 months following surgery, he was referred to a pulmonologist for smoking cessation and obstructive airway disease—the patient continued to smoke in the postoperative period. A chest radiograph did not demonstrate any tumor recurrence and pulmonary function improved with bronchodilators. Unfortunately, a bronchoscopy demonstrated tumor recurrence at the bronchial stump and in the right upper lobe. Positron emission tomography scanning demonstrated bilateral, multicentric, and hypermetabolic disease. He was not a candidate for a complete pneumonectomy.
During months 23 and 24 postoperatively, he was hospitalized frequently for disease progression and multiple pain complaints. Focal anterior chest wall pain corresponded to a midline sternal metastasis; on CT scan, the lesion measured 2.4 × 1.7 × 0.9 cm and was located at the T2-3 costosternal joints. Cortical disruption, anterior and posterior, was identified (Figure 1A–C). Adjacent manubrial metastases did not disrupt the cortices. The patient was placed on intravenous analgesics, when hospitalized. When home, he was maintained primarily on extended release oxycodone (80 mg) and hydrocodone (60 mg), in divided, daily doses. Apart from his focal chest wall pain, the other painful areas subsided.
Chemotherapy (gemzar, vinorelbine) was started. He received radiation therapy to the sternum, with carboplatin as a radiosensitizer. A total of 3,750 cGy was delivered in a fractionated fashion over 3 weeks (month 24 postoperatively). A few weeks after finishing radiotherapy, he was re-hospitalized.
The anterior chest wall persisted. The author (interventional pain management) was consulted. Upon examination, he was an emaciated and fatigued man with dyspnea. He had rest pain and often awoke from sleep. He braced himself, when coughing. Upon examination, there was pinpoint tenderness over the mid-lower sternum. There was a palpable bony depression. The manubrium, xiphoid, and sternocostal joints were only mildly tender. His baseline pain, on the numerical pain rating scale, was 10/10 and he demonstrated facial grimacing and movement avoidance behaviors.
The author performed a local infiltration over the metastatic lesion with 1% lidocaine and 40 mg of Depo-Medrol. The patient reported a temporary reduction in pain (80%), with an improved capacity to take deep breaths. Due to the unique and focal nature of the lesion, the author explained the risks, benefits, and alternatives of sternal kyphoplasty. The patient understood that this was an off-label use of this technique. The patient signed witnessed informed consent.
General anesthesia was induced. The patient was placed in a supine fashion and the chest wall was prepped in a sterile fashion. The neck was placed in slight extension. Intravenous antibiotics were administered. An anteroposterior fluoroscopic image and direct palpation was used to identify the sternomanubrial joint, sternoxiphoid joint, and the sagittal midline. A lateral fluoroscopic image was used to identify the anterior cavitating margin of the metastasis.
A local skin wheal was followed by a stab incision, 3 cm superior to the lesion. A beveled and styletted trocar was advanced at a 45° inclination using a superior to inferior approach (Figure 2A). The trocars were styletted Kyphon® cannulas, usually KyphExpress® cannulas (11 gauge, 3.8 mm diameter tip; Medtronic, Sunnyvale, CA, USA). An ultrasound probe was placed overlying the tumor, caudal to the incision. A straight array transducer (5–10 MHz) was placed in a lateral (Figure 3A) and axial orientation. The stylet was removed. A balloon was inserted (Figure 2B) and insufflated to approximately 1.5 mL. The balloon was a KyhpExpress® 10/2 inflatable balloon tamp (10 mm in length, max volume of 4 mL, 300 psi maximal inflation pressure). Pressures were less than 200lb/in.2. The balloon was within the margins of the anterior and posterior cortices (Figure 2C). This was verified on fluoroscopy and ultrasonography. Sonography demonstrated a balloon within the anterior and posterior margins of the sternum—on lateral and axial images (Figures 3B,C). Bony cortices are echogenic and appear as thin white lines on sonography.
Radiopaque high viscosity PMMA polymer (KyphX® HV-R™ Bone Cement; Medtronic) was admixed with monomer. Approximately 2.5 minutes elapsed before the consistency was akin to thickened toothpaste. Cannulas filled with cement were advanced serially through the trocar. Approximately 2 mL of cement was delivered, before reaching the anterior and posterior cortical margin. As the trocar was removed, a small tail of cement was noted anterior to the sternum. Fluoroscopy and a postoperative CT scan confirmed adequate fill of the tumor (Figure 4A–C). The patient reported a pain reduction to 0/10, about 1 and 24 hours following the procedure. Except some incisional pain cephalad to the tumor, direct palpation did not reproduce any pain. He was discharged on postoperative day 3. He ultimately succumbed to his disease, about 4 weeks following the procedure. His family reported that the patient was thankful of the pain relief. He did not suffer any adverse problems with the procedure.
Metastatic skeletal disease places an enormous burden on patients, secondary to pain, functional impairment, and worsening quality of life. Aggressive surgical treatment may result in morbidity and a delayed recovery. Apart from radiation and ablative therapies, pain treatment for skeletal metastases is typically nonspecific. External beam radiation therapy is the current standard of care for skeletal metastases, but may fail to relieve pain in 20–30% of patients . Radiation therapy over the sternum is hampered by the proximity to thoracic viscera. Cardiac complications due to mediastinal radiation can be devastating . Patients may develop acute pneumonitis and esophageal problems [14,15].
Minimally invasive procedures have been safe and efficacious in several clinical studies . A recent systematic review provided a strong recommendation (moderate evidence) for safety and efficacy of vertebral augmentation in metastatic spine disease . A variety of access devices and lytic agents (chemical and thermal) have been embraced by the interventional radiology community to help this unfortunate patient population . Recently, Arthrocare® Cavity SpineWand® (ArthroCare Corporation, Austin, TX, USA) has received 510K Food and Drug Administration (FDA) approval to ablate malignant lesions in the vertebral body . These techniques are target specific and avoid the concomitant soft tissue injury associated with radiation therapy.
The sternum is only 2–3 cm in depth. A shallow angular trajectory is necessary to accommodate the trocar and subsequent balloon distension. This provides a greater margin of safety with respect to tumor fill and avoidance of extravasation. Fluoroscopy permits trajectory planning and direct visualization of the trocar, balloon, and cement at all times. PMMA has several advantages compared with other neurolytic techniques. This cement is radiopaque and viscous. PMMA can be delivered in a controlled fashion and stopped at the earliest sign of extravasation. Image guidance facilitates instrument, balloon, and cement placement. A precise bone cavity can be created with a balloon and the balloon delimits the margins of the cavity. Despite cost and fluoroscopy time, sternal kyphoplasty (balloon-assisted cementoplasty) has a few advantages over cementoplasty. The balloon is a three-dimensional, radiopaque, and roughly spherical structure with a measurable volume and diameter. This is relevant in gauging depth, width, and volume under fluoroscopy. The outer boundaries of the inflated balloon delimit the size of the bone void. This is necessary to predict cement spread and volume. With slow insufflation, one can visualize the balloon perimeter expanding toward the cortex; this may help avoid or recognize sternal cortical breach. Radiopaque contrast allows visualization of the outer spherical margins of the balloon under fluoroscopy. Contrast echogenicity allows visualization of the balloon, in relation to the surrounding soft and bony tissues, with sonography. The sternum is proximate to several vital soft tissue structures and this patient had a cavitating lesion. Kyphoplasty permits cavity creation and may reduce the risk of cement extravasation. Collectively, these factors influenced the author's decision to use kyphoplasty.
Fluoroscopy and sonography are complementary: 1) visualization in different geometric planes (sagittal vs axial) and 2) visualization of different structures (bone vs soft tissues). Ultrasound clearly identified the cortical margins and the proximity to the thoracic soft tissues. Fluoroscopy clearly visualized the sternum on an anteroposterior and lateral projection. This collectively facilitated all steps in the procedure: 1) localization; 2) skin entry point; 3) trocar advancement; 4) trocar stabilization; 5) balloon insufflation; and 6) cement delivery. Combining these imaging modalities with minimally invasive access devices may enhance the safety, targeting, and efficacy of these procedures.
Although this patient had multiple metastases, the size of this osteolytic lesion relative to the sternum and the invasion of the cortex caused great pain. The constant, repetitive movement of the rib cage due to respiration was painful. Opioid therapy was effective in treating other lesions and pain, but not this sternal metastasis. Radiation therapy was unsuccessful—possibly due to persistent inflammation. The profound relief following sternal kyphoplasty in this patient is consistent with outcomes following kyphoplasty for spinal metastases and ablative procedures for skeletal metastases. Osteoplasty of other flat bones has resulted in profound pain relief [8,11,12]. These cases have been performed outside the United States.
Given the tragic consequences of skeletal metastases, direct palliation with kyphoplasty adds to treatment armamentarium. This report adds to the body of literature supporting the role of direct palliation, in complement or in lieu to surgical or radiation therapy.
Balloon kyphoplasty, utilizing fluoroscopy and sonography, may be a useful option in the treatment of painful metastases to non-weight-bearing bones. This therapy should be considered when treating patients with painful skeletal metastases.
The author would like to thank Erik Dickson, RT, Mary Hatch, NP, and Louis Dubois, MD.
- radiation therapy
- disabled persons
- neoplasm metastasis
- surgical procedures, operative
- palliative care
- metastasis to the lung
- lung cancer stage iv
- devices, medical
- functional impairment