[Profile of ambulatory radiosurgery with the gamma knife system. 2: Report of clinical experiences]

Stereotactic radiosurgery in the treatment of brain metastases: the current evidence

Chemotherapy has made substantial progress in the therapy of systemic cancer, but the pharmacological efficacy is insufficient in the treatment of brain metastases. Fractionated whole brain radiotherapy (WBRT) has been a standard treatment of brain metastases, but provides limited local tumor control and often unsatisfactory clinical results. Stereotactic radiosurgery using Gamma Knife, Linac or Cyberknife has overcome several of these limitations, which has influenced recent treatment recommendations. This present review summarizes the current literature of single session radiosurgery concerning survival and quality of life, specific responses, tumor volumes and numbers, about potential treatment combinations and radioresistant metastases. Gamma Knife and Linac based radiosurgery provide consistent results with a reproducible local tumor control in both single and multiple brain metastases. Ideally minimum doses of ≥18Gy are applied. Reported local control rates were 90-94% for breast cancer metastases and 81-98% for brain metastases of lung cancer. Local tumor control rates after radiosurgery of otherwise radioresistant brain metastases were 73-90% for melanoma and 83-96% for renal cell cancer. Currently, there is a tendency to treat a larger number of brain metastases in a single radiosurgical session, since numerous studies document high local tumor control after radiosurgical treatment of >3 brain metastases. New remote brain metastases are reported in 33-42% after WBRT and in 39-52% after radiosurgery, but while WBRT is generally applied only once, radiosurgery can be used repeatedly for remote recurrences or new metastases after WBRT. Larger metastases (>8-10cc) should be removed surgically, but for smaller metastases Gamma Knife radiosurgery appears to be equally effective as surgical tumor resection (level I evidence). Radiosurgery avoids the impairments in cognition and quality of life that can be a consequence of WBRT (level I evidence). High local efficacy, preservation of cerebral functions, short hospitalization and the option to continue a systemic chemotherapy are factors in favor of a minimally invasive approach with stereotactic radiosurgery.

Gamma knife radiosurgery for patients with multiple cerebral metastases

Although efficacy of gamma knife radiosurgery has been demonstrated in numerous studies, the policies in patients with multiple metastases seem to be unequivocal. The maintained quality of life, the possibility of short hospitalization and the continuation of a systemic chemotherapy are increasingly important arguments in favor of a minimally invasive radiosurgical approach. These factors are particularly emphasized in patients with a dismal prognosis. The current retrospective analysis was undertaken to summarize the clinical results of radiosurgery in patients with multiple cerebral metastases of various primary cancer. Fractionated whole brain radiotherapy (WBRT) was omitted as prophylactic treatment and applied only in cases with general tumor spread. Clinical data of all consecutive patients (n = 215) who received gamma knife radiosurgery for cerebral metastases between January 2001 and January 2003 at the gamma knife Centers of the Karolinska Hospital and H.M. Queen Sophia Hospital (Sophiahemmet) Stockholm were analyzed retrospectively. 172 patients were treated for multiple metastases (198 treatments). The median prescription dose was 22 Gy (range 14-34 Gy). The Kaplan Meier plot shows a median survival (MST) of 7.8 months for patients with multiple cerebral metastases and 13.7 months for patients with single metastases. There was no relation between survival and number of metastases in patients with multiple metastases. Within this group 11.6% (20/172 patients) developed adverse radiation reactions. Tumor recurrences were documented by FDG-PET in 7 patients (out of 172 patients: 4.1%) after a median latency of 10 months after radiosurgery. In summary, gamma knife radiosurgery provides a highly effective and minimally invasive method to treat patients with multiple cerebral metastases even without prophylactic WBRT. Local control and patient survival in the present series of patients is in accordance with other retrospective series of patients with single and multiple metastases.

Stereotactic radiosurgery for multiple brain metastases from breast carcinoma

BACKGROUND

The current study analyzed the feasibility and outcome of stereotactic radiosurgery (SRS) for treatment of brain metastases from breast carcinoma.

METHODS

During an 8-year period, 151 patients with a combined total of 620 brain metastases from breast carcinoma underwent 197 outpatient SRS procedures. Sixty-three percent of all patients had multiple brain metastases. The median tumor volume was 2.2 cm(3) (range, 0.1-20.9 cm(3)). The mean prescribed tumor dose was 19 +/- 4 grays. Local/distant tumor recurrences were treated with additional radiosurgical therapy for patients with stable systemic disease. All patients were categorized according to the Radiation Therapy Oncology Group classification. Survival time and freedom from local tumor recurrence were analyzed using the Kaplan-Meier method. Prognostic factors were identified using the Cox proportional hazards model.

RESULTS

The overall median survival duration was 10 months after SRS. Ninety-four percent of patients did not experience local brain tumor recurrence after radiosurgery. In addition, 70.2% of patients did not have disease recurrence in the brain. Most patients died of systemically progressing malignancy. A Karnofsky performance score > 70 and recursive partitioning analysis Class I were related to prolonged survival in the univariate and multivariate analyses. Age, whole-brain radiotherapy, surgery, number of metastases, chemotherapy, and latency period from diagnosis of the primary tumor to the development of brain metastases did not reach prognostic relevance in the multivariate model. Patients with RPA I, II, and III survived 34.9, 9.1, and 7.9 months, respectively. There was no treatment related permanent morbidity and mortality. The transient morbidity rate was 17%. Sixteen patients exhibited symptomatic transient complications related to treatment.

CONCLUSIONS

The results of the current study indicate that SRS is a feasible treatment concept for selected patients with multiple brain metastases from breast carcinoma.

Quality assurance in stereotactic space. A system test for verifying the accuracy of aim in radiosurgery

A detailed quality assurance (QA) program is essential for high precision single dose irradiations. The accuracy of stereotactic radiosurgery is limited by the errors of each step in the chain for optimal treatment beginning with the diagnostic imaging and target localization leading to the dose planning and ending up with the treatment of the patient. Two main goals were followed on the way to finding a concept for a suitable and sufficient quality assurance routine. First, the chain of items in terms of a complete patient simulation should be followed and second, the stereotactic MR image data should be verified against a reference in our case stereotactic radiographic projection images. Target point verifications were performed using the so-called, unknown target method based on MRI, CT, and stereotactic projection images. A marked radiochromic film, embedded between inserts of the phantom is fixed parallel to either the xy or the xz plane of the stereotactic coordinate system. After imaging and planning, the phantom is adjusted and irradiated. At the end, the film, dyed by the radiation field around the premarked cross, is evaluated. The measured distance between the unit center point (shadow) and the localization of the marked film leads to the deviation to be minimized. This is referred to as the displacement vector. The results, evaluating 170 system tests within 5 years. show that the mean displacement vector of the complete system is 0.48 mm +/-0.23 mm (mean+/- sd). Factors having a significant influence on the overall accuracy are associated with MRI parameters. Test results based on axial images (xy plane; 0.42 mm +/- 0.24 mm) are significantly superior to coronal images (xz plane; x = 0.60 mm +/- 0.02 mm). Further on, the 3D-mpr sequence (0.40 mm +/- 0.19 mm) is significantly superior to the T1 weighted SE sequences (0.66 mm +/- 0.24 mm). Given the high mechanical accuracy of the Leksell gamma knife, the most sensitive technical factor having an influence on the overall precision of radiosurgery is the MRI study. However, using the appropriate imaging sequences and parameters the dislocation error inferred by MRI can be kept very low and restricted to the rare patient inherent distortion factors. With these precautions in mind, MRI is recommended as the imaging method of choice in radiosurgery.

Diagnostic accuracy of MRI compared to CCT in patients with brain metastases

OBJECTIVES

In patients with extracranial neoplasms, the occurrence and number of brain metastases (BM) are critical for further diagnostic approaches and therapeutic strategies and the patient's prognosis. Although widely accepted, there is surprisingly little evidence in the literature that MRI is superior to CCT. Therefore, in patients with solitary BM according to diagnostic contrast-enhanced computed tomography (CCT), we investigated, what additional information could be gained by contrast-enhanced magnetic resonance imaging (MRI).

METHODS/RESULTS

Among 55 patients with solitary BM according to CCT, 17 had multiple BM on MRI (31%) and 38 had solitary BM in both. Based on a presumed binomial distribution of our data, we calculated a rate of at least 19% of patients with solitary BM on CCT, in which MRI would show multiple lesions (p = 0.05). The two main characteristics for BM missed by CCT were the smaller diameter, which averages 2 cm less than in BM identified with both modalities, and a preferential frontotemporal location.

CONCLUSION

MRI is indeed superior to CCT in the diagnosis of BM the essential reasons besides detection of smaller lesions being a better soft tissue contrast, significantly stronger enhancement with paramagnetic contrast agents, the lack of bone artifacts, fewer partial volume effects, and direct imaging in three different planes. Therefore, MRI is indispensable in the diagnostic workup of patients with BM for choosing the optimum therapeutic approach, especially with regard to the decision whether to operate or to primarily irradiate the patient's metastases.

Surgery and radiotherapy compared with gamma knife radiosurgery in the treatment of solitary cerebral metastases of small diameter

OBJECT

The aim of this retrospective study was to compare treatment results of surgery plus whole-brain radiation therapy (WBRT) with gamma knife radiosurgery alone as the primary treatment for solitary cerebral metastases suitable for radiosurgical treatment.

METHODS

Patients who had a single circumscribed tumor that was 3.5 cm or smaller in diameter were included. Treatment results were compared between microsurgery plus WBRT (52 patients, median tumor dose 50 Gy) and radiosurgery alone (56 patients, median prescribed tumor dose 22 Gy). In case of local/distant tumor recurrence in the radiosurgery group, additional radiosurgical treatment was administered in patients with stable systemic disease. Survival time was analyzed using the Kaplan-Meier method, and prognostic factors were obtained from the Cox model. The patient groups did not differ in terms of age, gender, pretreatment Karnofsky Performance Scale (KPS) score, duration of symptoms, tumor location, histological findings, status of the primary tumor, time to metastasis, and cause of death. Patients who suffered from larger lesions underwent surgery (p < 0.01). The 1-year survival rate (median survival) was 53% (68 weeks) in the surgical group and 43% (35 weeks) in the radiosurgical group (p = 0.19). The 1-year local tumor control rates after surgery and radiosurgery were 75% and 83%, respectively (p = 0.49), and the 1-year neurological death rates in these groups were 37% and 39% (p = 0.8). Shorter overall survival time in the radiosurgery group was related to higher systemic death rates. A pretreatment KPS score of less than 70 was a predictor of unfavorable survival. Perioperative morbidity and mortality rates were 7.7% and 1.6% in the resection group, and 8.9% and 1.2% in the radiosurgery group, respectively. Four patients presented with transient radiogenic complications after radiosurgery.

CONCLUSIONS

Radiosurgery alone can result in local tumor control rates as good as those for surgery plus WBRT in selected patients. Radiosurgery should not be routinely combined with radiotherapy.