Clinical Outcomes of Pain and Quality of Life after Spine Radiosurgery

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Clinical Outcomes of Pain and Quality of Life after Spine Radiosurgery

Gregory J. Gagnon and Fraser C. Henderson

That a rigid spine is essential for the proper functioning of the individual can be inferred from its importance in our phylogenetic development. In fact, vertebrate appearances in the fossil record 500 million years ago coincide with increasing size as well as specializations, such as an endoskeleton, a muscular system, paired lateral appendages, a central nervous system, cephalization, and anatomical equipment supporting a more energetic lifestyle. These specializations are not seen in the invertebrate chordates, which possess a more primitive internal support structure called the notochord.1 These specializations have enabled the over 57,000 species of vertebrates to colonize a great variety of aquatic, terrestrial, and aerial environments, and the success of this subphylum can be further seen by the presence of its members among the largest, fastest, and most migratory of animal species. Laws of recapitulation would therefore assign great importance to the vertebrate axis.

Functionally, the vertebrate axis, a collection of vertebral bones, connective tissue, and muscles, which we call the spine, has a correspondingly broad set of duties, including structural support (i.e., of the head, shoulders, and chest), weight distribution, attachment (of ligaments, tendons, and muscles), maintenance of flexibility (flexions, extensions, and rotations), and protection (of the spinal cord, nerve roots, and thoracic organs), as well as hematopoiesis and mineral storage. In short, the vertebrate axis lies at the center of our morphogenesis, and its functional consequences are wide ranging, enabling an active, mobile lifestyle.²

In the diseased state, particularly in the case of malignant involvement, many of the functions can be compromised, leading to significant physical impairment and poor quality of life. In addition, pain is a common consequence of spinal involvement and a frequent contributor to poor quality of life. The surgical, radiotherapeutic, and systemic therapies typically administered for spinal malignancies are also not without significant functional risks and, despite beneficial intentions, carry the potential to further hamper the proper functioning of the spine. These all ultimately influence the quality of life in myriad ways.

Rationale for Radiosurgery

Malignancies of the spine may be primary or metastatic, but metastatic tumors are far more common. In these patients, with the infrequent exceptions of oligometastases, treatment is largely palliative or prophylactic. Several aspects of spinal metastases are notable: First, spinal metastases are common, with an incidence of at least 100,000,³ and bone pain is commonly associated with these metastases. In fact, bone pain is the most common pain syndrome requiring treatment in cancer patients. Second, patients with bone metastases typically have more severe symptoms than patients with visceral metastases. Third, survival is typically longer in patients with bone-only metastases than patients with visceral metastases (sometimes survival rates of several years can be expected⁴), so symptoms related to malignant involvement and debilitation can slowly gnaw at a reasonable quality of life. For example, survival with bone metastases can be as long as 29.3 months for prostate cancer and 22.6 months for breast cancer,⁵ long enough for patients to suffer severely from inadequately palliated spinal sites or to suffer recurrence from incompletely treated sites. Fourth, patients with bone metastases usually become symptomatic earlier and have symptoms for a longer period of time. Fifth, complications of metastatic involvement are common, occurring in one third of patients; these complications produce high morbidity.⁶

Perhaps most importantly, treatment options for the spine are somewhat limited because of the necessity of preserving its varied functional requirements as well as the dose-limiting radiation tolerance of significant internal or adjacent critical structures. Although radiotherapy, a mainstay in the treatment of both primary and metastatic disease of the spine and spinal cord, has proven effective in controlling tumors, the potential unintended consequences, such as radiation myelitis, limit the achievable doses. At times, this results in decreased efficacy of this treatment, especially in previously irradiated areas.

Stereotactic radiosurgery provides a technology by which spinal lesions can be treated with very high doses of radiation while minimizing exposure of surrounding healthy tissues. This allows for the treatment of lesions at higher doses, safer treatments at similar doses, or both, compared with conventional radiotherapy. Retreatment of recurrent spinal lesions is also possible with radiosurgery. Clearly, the complexities of the spine and of malignant spinal involvement create a need for an individualized and multidisciplinary approach within which we feel the CyberKnife system from Accuray Inc. (Sunnyvale, California) is ideally suited as a therapeutic tool.

Radiosurgical Technique

Table 10.1 is a summary of our guidelines for the treatment of spinal lesions analyzed in this chapter.

Clinical Measures of Response

The evaluation of patients with spinal lesions can be problematic. Most patients who present with such lesions have no neurological deficit⁷ but nonetheless have significant functional impairment, relating to the broad set of functions performed by the intact spinal axis. Thus, it is important to include measures of pain and quality of life in evaluations of these patients.