Treatment outcome of single or hypofractionated single-isocentric stereotactic irradiation (STI) using a linear accelerator for intracranial arteriovenous malformation

Visualization of the corticospinal tract pathway using magnetic resonance axonography and magnetoencephalography for stereotactic irradiation planning of arteriovenous malformations

Corticospinal tract (CST) information using anisotropic diffusion-weighted imaging and magnetoencephalography were integrated into radiosurgical planning for two patients with deeply seated arteriovenous malformation. The volume of CST receiving >10 Gy, >15 Gy, and maximum dose of CST could be reduced when plans were created with the aid of CST information compared with plans without the information. The results indicate that the use of CST information might reduce the risk of post-radiosurgical motor disturbance resulting from radiation necrosis.

Hypofractionated stereotactic radiotherapy alone without whole-brain irradiation for patients with solitary and oligo brain metastasis using noninvasive fixation of the skull

PURPOSE

To evaluate the efficacy and toxicity of hypofractionated stereotactic radiotherapy (HSRT) using noninvasive fixation of the skull on solitary or oligo brain metastatic patients as an alternative to stereotactic radiosurgery (SRS) using invasive fixation.

PATIENTS AND METHODS

The subjects were 87 patients who had 4 or fewer brain metastases (50 solitary, 37 oligometastases). Treatment was conducted on 159 metastases by using a linac-based stereotactic system. The median isocentric dose was 35 Gy in 4 fractions. Whole-brain irradiation was not applied as an initial treatment. For the salvage treatment of metachronous brain metastases, repeat HSRT or whole-brain irradiation was applied.

RESULTS

The actuarial 1-year local tumor control rate was 81%. Treatment-related complications were observed in 4 patients in the early period (<3 months) and in 2 patients in the late period. The median survival period was 8.7 months. Metachronous brain metastases occurred in 30 patients, and none of the 18 patients who were eligible for salvage HSRT refused to receive it again.

CONCLUSIONS

Hypofractionated stereotactic radiotherapy achieved tumor control and survival equivalent to those of SRS reported in the literature. The results suggested that HSRT could be an alternative for solitary or oligo brain metastatic patients with less toxicity and less invasiveness compared to SRS.

Repeat linear accelerator radiosurgery for cerebral arteriovenous malformations

PURPOSE

To evaluate repeat radiosurgery (RS2) for cerebral arteriovenous malformations (AVMs) after failure of initial radiosurgery (RS1).

METHODS AND MATERIALS

Between 1986 and 2000, 41 patients underwent RS2. Nine patients were not assessable: seven had insufficient follow-up (RS2 in 1999 and 2000) and two had no recent control angiography data. Thus, 32 (78%) of 41 patients were assessed. Most lesions (29 [90%] of 32) were supratentorial: 22 (69%) on the left, 8 (25%) on the right, and 2 on the midline (6%). The patients had Spetzler-Martin Grade 1-5 (median Grade 3). The symptoms before RS1 included hemorrhage in 20 (63%), epilepsy in 10 (31%), progressive neurologic deficits in 2 (6%), and headaches in 6 (19%). Five patients had two or more symptoms. Twenty-two patients (69%) had received other treatment before RS1, including neurosurgery in 3 patients (9%) and one to six embolizations in 19 patients. At RS1, the median largest nidus dimension was 2.7 cm (range 0.8-5). The median volume was 2.7 cm(3) (range 1.2-9.9). The median time from RS1 to RS2 was 52 months (range 12-126). Between RS1 and RS2, 7 (22%) of 32 patients experienced bleeding. The same irradiation technique was used for RS1 and RS2, except for 2 patients who underwent RS2 at another institution. Circular 15-MV X-ray minibeams (range 6-20 mm) and coronal arcs were used. RS1 was monoisocentric in 75% of cases and multiisocentric in 25%. At RS2, the median largest nidus dimension was 3 cm (range 1.4-5). The median volume was 4.2 cm(3) (range 0.8-13.4). RS2 was monocentric in 72% of cases and multiisocentric in 28%. After RS2, the median follow-up was 19.5 months (range 0-79; mean 25.3).

RESULTS

After RS2, the obliteration rate was 59.3% (19 of 32). The median time to arteriographic obliteration was 21 months (range 12-96). The survival rate was 97% (31 of 32). Five of the 13 patients with a nonobliterated nidus experienced complications; 3 had bleeding (9%) and 2 without prior neurologic deficits developed partially regressive neurologic deficits. One patient with a previously existing deficit developed an additional new partially regressive neurologic deficit after an episode of bleeding. Thus, 3 (9%) of 32 patients had neurologic complications. Moderate-grade parenchymal changes at MRI increased after RS2 (88.2% vs. 57.7% after RS1; p = 0.10, not significant). However, necrosis-like changes did not significantly increase. After RS1 failure, salvage may be attempted by embolization, neurosurgery, or RS2. RS2 should be considered after the second successive annual angiogram if reduction of the nidus is <25%.

CONCLUSION

The results after RS2 are encouraging. A multidisciplinary approach is mandatory to reduce the initial failure rate and to choose the modality and timing of salvage treatment.

Three-dimensional conformal radiotherapy for astrocytic tumors involving the eloquent area in children and young adults

PURPOSE

Although a gross total removal of astrocytic tumors offers a favorable prognosis, it is often difficult to achieve in the eloquent area of the brain. This study was conducted to investigate the possible gain of three-dimensional conformal radiotherapy (3DCRT) for astrocytic tumors located in the eloquent area in children and young adults.

MATERIALS AND METHODS

Twenty patients with astrocytic tumors received the radiotherapy. The median age was 17 years, ranging from 4 to 30 years. Fourteen low-grade tumors (seven pilocytic and seven diffuse), and six high-grade tumors (five anaplastic, one malignant pilocytic) were included. Tumors were located at the thalamus/hypothalamus in 12 cases, optic tract in one case, and the deep cerebral/cerebellar hemisphere in seven cases. A specific fixation device was used for 3DCRT. Forty-six Gy for low-grade tumors and 54 Gy for high-grade astrocytomas with 1.8-2.0 Gy per fraction were in principle employed as the standard regimen. Nominal radiotherapy fields ranged from 2.0 x 2.0 to 15.0 x 11.0 cm2. The median follow-up period was 42 months, ranging from 3 to 108 months.

RESULTS

The actuarial survival rate at 5 years was 68% +/- 13% for all patients. The actuarial survival rate for low-grade glioma was 79% +/- 14% at 5 years and 50% +/- 20% at 3 years for high-grade glioma. The actual progression-free survival rate was 83% +/- 11% at 5 years for low-grade glioma and 50% +/- 20% for high-grade glioma. A complete response was obtained in three (21%) of 14 patients with low-grade astrocytic tumors. Two patients with low-grade tumors and four of six with high-grade tumors died due to tumor progression with infield relapse but not marginal relapse. Twelve survivors with low-grade tumors showed no signs of relapse and no neurological, hormonal, or cognitive deterioration after radiotherapy and were able to attend their school or continue with a full-time job.

CONCLUSIONS

3DCRT is safe and effective for low-grade astrocytic tumors located in the eloquent area in children and young adults.

Fractionated stereotactic radiotherapy: a short review

Currently, optimally precise delivery of intracranial radiotherapy is possible with stereotactic radiosurgery and fractionated stereotactic radiotherapy. We present in this article a review of the underlying basic physical and radiobiological principles of fractionated stereotactic radiotherapy and review the clinical experience for ateriovenus malformations, pituitary adenomas, mengiomas, vestibular schwanomas, low grade astrocytomas, malignant gliomas, and brain metastases.