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Treating metastatic bone disease takes a multidisciplinary team

Panel discusses whether to curette metastatic lesions, the appropriate femoral stem length and how to determine the pathologic fracture risk.

Issue: February 2006

ByKristy Weber, MD

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Metastatic bone disease is becoming more common as patients with cancer are living longer. Many of these patients seek medical care at community hospitals, and general orthopedic surgeons and those trained in orthopedic oncology manage their skeletal issues. The overall care of these patients requires a multidisciplinary team of health care providers often including a medical oncologist, radiation oncologist, pathologist, radiologist, orthopedic surgeon, physical therapist and chaplain. Multiple factors must be considered in the care of those with metastatic bone disease, including comorbidities, histology of the primary tumor, expected lifespan, activity level and pain.

Surgical considerations involve these factors in addition to the location of the tumor and presence of neurologic symptoms. Occasionally, nonoperative treatment is indicated. In general, stabilizing impending fractures or actual pathologic fractures involves different techniques and concepts than those used for patients with nonpathologic traumatic fractures. Bone infiltrated with cancer is weakened and requires more durable implants or prosthetic devices to last the expected remaining life of the patient. For instance, patients with pathologic femoral neck fractures are treated with prosthetic replacement rather than in situ pinning or plate/screw fixation. Methylmethacrylate is often used in combination with prostheses or intramedullary devices to supplement the fixation.

In this roundtable discussion, orthopedic oncologists discuss specifics of how to manage patients with metastatic bone disease. Further information can be found in the listed references and during the Instructional Course Lecture at the 2006 American Academy of Orthopaedic Surgeons meeting.

Kristy Weber, MD
Moderator

Kristy Weber, MD: When is it appropriate (if ever) to open the cortex and curette a metastatic lesion before stabilizing the extremity?

Valerae O. Lewis, MD: The decision to curette a bone metastasis before stabilizing the extremity depends upon the size of the lesion, amount of bone destruction present, histology of the tumor and whether postoperative radiation is planned. Large lytic lesions with minimal structural bone remaining may benefit from curettage and cementation to augment the structural stability of the construct. Additionally, curettage of the lesion reduces local tumor load and thereby facilitates the anti-tumor effects of postoperative radiation for less radiosensitive tumors such as renal cell carcinoma (RCC). Metastatic RCC will often progress within the bone after surgery, potentially compromising fixation and requiring a salvage procedure. However, the vast majority of metastatic bone lesions do not require open curettage and can be treated with intramedullary fixation or prosthetic reconstruction with postoperative radiation after the wound heals. Maximum recalcification of lytic areas is seen two to three months after radiation. It is important that the radiation oncologist treats the entire length of the fixation device or prosthesis as tumor cells are often displaced to the distal end of the bone with reaming.

R. Lor Randall, MD, FACS: When considering structural integrity for lesions that are refractory to radiation, curettage with cementation and stabilization can significantly decrease local complications of disease progression. Generally, I perform an intralesional curettage for metastatic RCC and thyroid cancer. Both lesions are extremely vascular, so these patients benefit from preoperative embolization. If I’m performing a curettage, then local surgical adjuvants such as liquid nitrogen or phenol can provide increased tumor cell necrosis, although this has not been scientifically proven for bone metastasis. I have recommended percutaneous radiofrequency ablation in conjunction with stabilization in some cases to potentially decrease pain and tumor burden. While I usually perform this procedure myself, at many institutions the interventional radiologist may perform this procedure.

Weber: To reiterate Dr. Randall’s point about preoperative embolization for highly vascular tumors, this should be considered for metastatic RCC, thyroid cancer and occasionally multiple myeloma. This precaution is proven to minimize intraoperative hemorrhage and can potentially be life-saving. Embolization is critical for large lesions in the spine or pelvis where curettage of the tumor will be performed. I generally ask the interventional radiologists to embolize the lesion the day before my planned surgical procedure and admit the patient overnight. Because a dye load is required to visualize the feeding vessels to the tumor, it is important to check the serum creatinine, especially in patients who have previously had a nephrectomy for RCC.

Brian McGrath, MD: Most diaphyseal and metaphyseal bone metastasis do not require or benefit from curettage. Violating the remaining cortex around a diaphyseal or metadiaphyseal lesion to place limited amounts of cement adds little to the torque or tensile strength of a statically locked intramedullary device. If the diseased segment of bone approximates the proximal interlocking screws, adding cement to the construct may be beneficial. Limited amounts of host bone should be removed. Additionally, acetabular metastases usually require curettage of the lesion down to healthy host bone when possible. Methylmethacrylate is then used in compression to supplement the cup or cage reconstruction.

Weber: How do you determine the length of femoral stem needed when performing prosthetic reconstruction of the hip for an actual or impending pathologic fracture?

McGrath: The treatment of impending and actual pathologic fractures of the hip is multifaceted. The patient’s life expectancy and general condition are important factors to consider when deciding whether to operate and which procedure to perform. The decision to operate on a patient with metastatic bone disease often requires input from the entire oncologic team, including surgeon, medical oncologist and radiation oncologist.

If the decision is made to operate on a pathologic hip fracture, the length of the femoral stem is dictated by the relative risk of ipsilateral metastasis and subsequent fracture measured against the risks associated with preparing the canal and inserting a long-stemmed device such as increased blood loss, fat embolism, and iatrogenic fracture.

Proximal femoral lesions can involve the femoral head, neck or calcar region. Occasionally (10%) distal disease is also present in the ipsilateral femur. These patients should be treated with longer and relatively narrower diameter femoral stems. Suctioning the femoral canal prior to slow stem insertion with the cement in a more liquid phase probably decreases the incidence of clinically significant embolic events. The long-stemmed component prophylactically stabilizes the remaining femur. It is important that postoperative radiation is directed toward the entire length of the implant rather than just the original lesion location. Reaming the canal through a femoral metastasis displaces tumor cells distally to the tip of the stem, therefore, this area must be treated to avoid the development of a lytic lesion and stress riser at the end of the prosthesis.

Lewis: The decision to use a long-stemmed femoral prosthesis depends on the extent of femoral involvement, stage of disease and histology of the tumor. Generally, for metastatic disease in the proximal femur, I use a mid-length stem (250 mm). I feel this provides the patient prophylactic fixation should he/she develop distal disease. However, if the patient has proven distal diaphyseal disease, I will use a stem that spans the distal defect (300 mm to 350 mm).

If the patient has advanced systemic disease, metastatic lesions confined to the proximal femur, or operative time needs to be minimized, I will use a standard length stem. For these patients, they are not likely to survive long enough to develop additional disease distal to the end of the prosthetic stem.

Along the same line, I will also employ a shorter stem (200 mm) if the patient has significant pulmonary disease, thereby minimizing the pulmonary insult during canal reaming and stem insertion. Technically, it is important to ream slowly when placing a long-stemmed prosthesis to minimize pulmonary insult. I tend to over-ream by 2 mm to facilitate stem insertion and minimize pressurization. You can also consider venting the femur distally (mid-lateral line) to minimize the potential for pulmonary embolus; however, with slow reaming I have not found this necessary.

Randall: I invariably use a 300 mm, long-stemmed, fully cemented femoral component for impending and actual femoral neck and acetabular pathologic fractures due to metastatic disease. We recently published data demonstrating no significant increase in cardiopulmonary complications as compared to conventional length stems when appropriate precautionary steps are undertaken. Patients with metastatic disease are living longer with slowly progressive musculoskeletal involvement. The long-stemmed femoral component prophylactically stabilizes the majority of the femur if noncontiguous bone disease occurs and also facilitates more distal fixation and a stable construct if there is local progression in the proximal femur. Surgeons who intend to use longer femoral stems must carefully introduce the cement in a less viscous state while suctioning with a long laparoscopic-type device or venting. They should also perform careful peri-cementing cardiopulmonary monitoring.

As an aside, there is a misconception in the medical oncology community that bisphosphonate prevent pathologic fractures due to metastatic disease to the point that surveillance of skeletal sites has become unnecessary. We must continue to emphasize to our colleagues that, despite advances in bisphosphonate therapy, vigilant follow-up of bony disease sites is as important as ever to identify progressive disease while elective, prophylactic management is possible.

Weber: What system or set of guidelines (formal or informal) do you use to determine whether or not to prophylactically stabilize a lytic bone metastasis?

Lewis: Although based on a small number of patients, I use the Mirels criteria as a guide to determine whether or not to prophylactically stabilize a lytic bone metastasis. However, I also consider the patient’s overall disease status, comorbidities, functional status (ie, whether they need their upper extremities for ambulation), and the patient’s wishes.

Painful, lytic lesions that destroy the cortex and are >2.5 cm in the extremities require prophylactic stabilization, especially for those in the lower extremities. For asymptomatic, concentric lesions that are >2.5 cm without significant cortical loss, protected weight-bearing and external beam radiation are good treatment options. However, if these lesions are symptomatic, I discuss with the patient their risk of fracture with physiologic loading and give them the option of protected weight-bearing and radiation vs. prophylactic stabilization. For large, asymptomatic lesions in the peritrochanteric area, I often recommend operative stabilization due to the high stresses that are transmitted through this anatomic area with normal walking.

Randall: The Mirels system is a very good starting point. However, this method does not address the patient’s functional demands, their anticipated lifespan and their baseline osteoporosis risk. For more active patients with a better prognosis, I may recommend surgical intervention for a borderline score. Postmenopausal women with bone metastasis are at higher risk due to potential decreased bone density in addition to the lytic lesion, and I may recommend treatment for a borderline score.

McGrath: The Mirels classification system is easy to use and quite effective in predicting the relative risk of an impending pathologic fracture of the lower extremity. This system is a refinement of Harrington’s original classification and adds the functional parameters of pain and lesion location. Harrington’s system, although a landmark in its day, underestimates smaller lesions in the femoral calcar and less geographic lesions.

Weber: Recent biomechanical research has concentrated on the ability of quantitative computed tomography (qCT) and other noninvasive radiographic methods to measure the structural rigidity of cross-sectional areas of bones containing lytic defects. The goal was to accurately predict the load-bearing capacity of the bone and relative fracture risk. This was the first study to investigate the effect of defects in trabecular bone as opposed to cortical bone. The results indicate that the structural behavior of the trabecular section of bone is determined by its weakest cross-section. Ideally these algorithms will be used in the clinical setting to measure the risk of pathologic fracture and monitor the response of bone metastasis to systemic or local treatment.

Weber: Should prosthetic reconstructions for metastatic bone disease be cemented or uncemented?

Randall: Press fit (uncemented) components rely upon the generation of hoop stresses to facilitate fixation. In my opinion, hoop stress should be minimized in metastatic bone disease; it is a nemesis. Furthermore, adjuvant radiation therapy inhibits bone ingrowth. The available clinical and experimental data on the effect of bisphosphonates on periprosthetic bony ingrowth is inconclusive and is somewhat controversial. I strongly recommend cementing all prosthetic reconstructions in patients with metastatic bone disease.

Lewis: Unlike joint reconstruction in the non-oncologic patient population, prosthetic stems in patients with metastatic bone disease should be cemented. Cemented prostheses offer the benefits of immediate weight-bearing, and the cement augments the weakened pathologic bone. Immediate weight-bearing and restoration of function is the goal for this patient population with a limited lifespan. In addition, postoperative radiation is used in this patient population, which inhibits bone ingrowth and potentially compromises the stability of the construct.

McGrath: All prosthetic reconstructions for metastatic disease should be cemented. The principle of pressfit or porous ingrowth is completely lost on weakened and diseased bones. In this group of relatively immunocompromised patients, the use of antibiotic-impregnated cement has distinct theoretical advantages.

Weber: The comments in this round table are from experienced orthopedic oncologists who routinely treat patients with metastatic bone disease. However, much of the information we use to guide treatment of these patients is based on personal or collected experience. Questions of whether to curette metastatic lesions, what length femoral stem to use and how to determine the likelihood of pathologic fractures will be answered more definitively by well-designed, prospective, large, single institution or multi-institutional studies that are currently not available. These studies can provide Level 1 evidence that is needed to better standardize the care of patients with metastatic bone disease.

Dr. Randall receives an unrestricted research grant from Biomet.

For more information:

• Weber KL, Lewis VO, Randall RL, Lee AK, Springfield D. An approach to the management of the patient with metastatic bone disease. Instructional Course Lecture. 2004;53:663-76.
• Mirels H. Metastatic disease in long bones: A proposed scoring system for diagnosing impending pathologic fractures. Clin Orthop Rel Res. 1989;249:256-64.
• Hong J, Cabe GD, Tedrow JR, Hipp JA, Snyder BD: Failure of trabecular bone with simulated lytic defects can be predicted non-invasively by structural analysis. J Orthop Res. 2004;22:479-486.