Cynthia Cabatan-Awang

Prospective Study of Stereotactic Radiosurgery Without Whole Brain Radiotherapy in Patients with Four or Less Brain Metastases: Incidence of Intracranial Progression and Salvage Radiotherapy

This prospective study was conducted to evaluate the treatment outcome after stereotactic radiosurgery (SRS) alone with special attention to its influence on intracranial freedom from progression (FFP), local control, time to whole brain radiotherapy (WBRT), and survival. Forty-one patients with brain metastases who met the inclusion criteria were enrolled in this prospective cohort and treated by SRS alone between January 1998 and September 2001. The overall local control rate was 76%. The one year actuarial intracranial FFP was 33%. Ten patients (24%) had relapse at treated site. Twenty-three patients (56%) had intracranial progression with a median time of 4.25 months (1–24.6). Salvage radiotherapy was given in 21 patients (51%). Only 12 (29%) patients required WBRT with the median time to WBRT after SRS of 4.85 months. Nine patients (22%) underwent additional SRS at the median time of 5 months after the first procedure. The median survival was 10 months. At the time of follow up, 16 patients (39%) were still alive with a range of 6–31 months. This prospective study suggests that the omission of WBRT in the initial treatment of patients with SRS for four or less brain metastases may allow up to 70% of patients to avoid WBRT.

Initial clinical results of stereotactic radiotherapy for the treatment of craniopharyngiomas.

The efficacy and toxicity of stereotactic radiotherapy (SRT) for the treatment of craniopharyngioma has been retrospectively evaluated in 16 patients. The median tumor diameter was 2.8 cm (range 1.5–6.1) and the median tumor volume was 7.7 cc (range 0.7–62.8). SRT was delivered to a single isocenter using a dedicated 6 MV linear accelerator to patients immobilized with a relocatable stereotactic head frame. The three-year actuarial overall survival was 93% and the rate of survival free of any imaging evidence of progressive disease was 75%. The three-year actuarial survival rates free of solid tumor growth or cyst enlargement were 94% and 81% respectively. Our results suggest that SRT is a safe and effective treatment approach for patients with craniopharyngioma. Long-term follow-up is required to determine whether the normal tissue-sparing inherent with SRT results in reduction of the neurocognitive effects of conventional radiotherapy for craniopharyngioma. SRT can be delivered to craniopharyngioma that may be difficult to treat with stereotactic radiosurgery due to proximity of the optic chiasm. Further clinical experience is necessary to determine the clinical utility of beam shaping in the setting of SRT.

Radiosurgery and stereotactic radiation therapy of skull base meningiomas: proposal of a grading system.

Objective: The development of a grading system to guide treatment selection, and predict treatment difficulty and outcome of skull base meningiomas infiltrating the cavernous sinus which are managed by stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT), based on an 8-year experience with stereotactic radiation of skull base meningiomas. Methods: T1 gadoliniun-enhanced magnetic resonance imaging (MRI) of 40 patients with skull base meningiomas, with or without prior surgery, who underwent radiosurgery or stereotactic radiation therapy from 1991 to 1998 at the UCLA Medical Center were reviewed, and the result of treatment was related to the tumor grade. Grade was based on tumor infiltration of the cavernous sinus and extension into adjacent structures. Treatment was performed with a linac-based system. The dose prescribed to the periphery of the tumor for SRS patients (n = 34) ranged from 12 to 22 Gy, and the maximum dose delivered to the tumor ranged from 24 to 46 Gy. SRT (n = 6). Treatment was planned using a single isocenter, usually prescribed to the 90% isodose volume, bringing the fractionation scheme to the maximal tolerance of the optic apparatus. The periphery dose ranged from 24 to 46 Gy with a maximum dose of 45 to 51 Gy. Clinical and MRI follow-up was performed every six months for the first 3 years and every year thereafter. Results: Grade I meningiomas were restricted to the cavernous sinus (n = 12). Grade II cavernous sinus meningiomas extended to the clivus and/or the petrous bone, without compression of the brainstem (n = 9). Grade III meningiomas had superior and/or anterior extension with compression of the optic nerve or tract (n = 9). Grade IV tumors compressed the brain stem (n = 8), and Grade V were bilateral lesions (n = 2). Tumor control rates were 90% for Grade I, 86% for Grade II, 86% for Grade III, 42% for Grade IV and no control for tumors Grade V. Complications were not related to tumor grade. Conclusion: This grading system correlated with outcome and difficulty in planning radiosurgery. Failure of treatment was more likely to occur in patients with higher Grade tumors.

Hypofractionated Stereotactic Radiotherapy for Recurrent Malignant Gliomas

Objective: The results of hypofractionated stereotactic radiotherapy (SRT) for the treatment of unselected patients with malignant glioma recurrent after conventional therapy were analyzed. Materials and Methods: Between January 1997 and March 1999, 21 patients with recurrent malignant glioma received SRT at UCLA. All patients received prior conventional radiotherapy (median 6000 cGy). The interval from initial diagnosis to SRT varied from 3 to 99 months (median 11). Tumor volume ranged from 4.5 to 33.7 cc (median 12). Fifteen patients had glioblastoma multiforme and 3 had anaplastic astrocytoma with an oligodendroglial component. Two patients with prior low-grade astrocytoma and one with an unbiopsied brainstem tumor did not have pathological confirmation of tumor grade at time of relapse. Five patients had multifocal recurrences and 11 had imaging evidence of indistinct tumor. Twelve patients had progressive disease after receiving salvage chemotherapy. Patients received 4–6 daily fractions of 400 to 600 cGy. Median total SRT dose was 2500 cGy. Follow-up ranged from 1 to 20 months and no patients were lost. Results: The actuarial median and one-year survival were 6.7 months and 15%, respectively. Fifteen patients died of progressive glioma and one of a pulmonary embolus. Sixteen patients relapsed after SRT: 11 local, 4 local plus distant, one marginal. All patients with distant relapse also had local failure at some time. The median time to local relapse for the 14 patients with an initial component of local failure was 5 months. There were trends to superior survival for those with an initial diagnosis of nonglioblastoma and those with frontal/occipital lobe recurrences. No patient developed documented radionecrosis. Two patients underwent operation following SRT. Histopathological analysis of the operative specimen revealed malignant glioma. Conclusions: The authors conclude that hypofractionated SRT is a feasible, safe alternative for patients with recurrent malignant glioma. Local failure represents the overwhelming pattern of relapse after SRT, regardless of the clinical or imaging characteristics of patients with recurrent tumor. Improving the outcome for this group of patients may require a multimodality approach of SRT plus concurrent chemotherapy.

Stereotactic Radiosurgery of Cerebral Arteriovenous Malformations: Appearance of Perinidal T2 Hyperintensity Signal as a Predictor of Favorable Treatment Response

The purpose of this study was to analyze the significance of perinidal T2 hyperintensity appearance after radiosurgery of arteriovenous malformations (AVMs), as a predictor of treatment response. Our initial experience with linear accelerator (LINAC) radiosurgery at University of California, Los Angeles, between 1990 and 1997 involved treatment of 129 patients affected by cerebral AVMs. Based upon availability of neuroimaging follow-up, 48 patients with 50 AVMs were selected for review. Forty (80%) of the AVMs underwent complete obliteration or significant reduction on follow-up MRI, on average 20 months after radiosurgery. Thirteen (72%) of 18 obliterated AVMs were associated with perinidal T2 hyperintensity signal, on average 18 months (6–49) after radiosurgery. Ten (20%) of 50 AVMs (average volume 23.1 cm3, ranging 7.5–46.5) were unchanged. Furthermore, only 3 AVMs in this group showed reversible T2 signal changes. In patients with complete nidal obliteration, appearance of T2 hyperintensity signal achieves 72% sensitivity in predicting successful treatment response.

Reproducibility of Frame Positioning for Fractionated Stereotactic Radiosurgery

Fractionated stereotactic radiation therapy is a useful new approach for treating a number of intracranial neoplasms including meningiomas, pituitary adenomas, craniopharyngiomas, and recurrent gliomas. For the majority of these we employ a conventional fractionation scheme of 180 cGy per fraction for 25 to 30 fractions, using a modified Gill–Thomas–Cosman (GTC) relocatable frame to accommodate fractionated delivery. The GTC system uses a custom acrylic dental appliance to set the frame position and an occipital plate and Velcro straps fix the head in place. Daily reproducibility is evaluated through use of a “depth helmet,” a plastic hemispherical shell containing 25 holes at regularly spaced intervals. The depth helmet attaches to the GTC frame and the distance from the shell to the patients head is recorded at each of the 25 positions. This paper describes a new simplified approach to the quantitative assessment of day-to-day variability in head fixation using the depth helmet measurements. This approach avoids the need to try and decide on the relative merit of 25 numerical differences at each fitting and provides a straightforward mathematical and conceptual framework for the description of fit and clinical decision making. The mathematical analysis and computer program we have developed uses all 25 measurements to provide a single three-dimensional displacement vector as well as displacement values in the three principal patient dimensions. Measurements at each of the 25 depth helmet positions are automatically separated into three principal axes corresponding to the patients left/right (x), anterior/posterior (y), and superior/inferior (z) using the spherical relations: x = r sin(Φ) cos(θ), y = r sin(Φ) sin(θ), z = r cos(Φ), where θ and Φ are the polar and azimuthal angles respectively and ris the distance from the center of the depth helmet to the surface of the patients head. For each patient, a set of initial measurements is taken at the CT scanner with the patient in the treatment (supine) position. Because treatment planning is based on the CT scan, this serves as the baseline from which subsequent deviations are recorded. In an analysis of our first 30 patients representing over 750 fractions, the mean RMS deviation, that is, the mean three-dimensional displacement from baseline, was 0.468 ± 0.296 mm. Among individual patients the range was 0.169 mm to 1.438 mm. A closer analysis suggests that in-plane (AP/PA-lateral) deviations occur randomly. Deviations along the superior/inferior direction are greater than those in-plane, and in several patients a small shift along this axis, possibly due to a loosening or stretching of the Velcro straps, has been noted over time. We have found our method to be a useful indicator of day-to-day reproducibility, allowing ready identification and correction of three-dimensional shifts relative to the patient axes. Based on our initial analysis, we can now define quantitative limits of acceptability in repositioning for subsequent fractionated delivery.

Preliminary Novalis Experience in the Treatment of Skull Base Chordomas with StereotacticRadiosurgery and Stereotactic Radiotherapy

Purpose: The treatment of chordomas is challenging. The role of radiation therapy in addition to surgery is well established. Different techniques have been applied aiming to improve tumor local contr