Radiation necrosis of the brain in acromegaly

Radiotherapy in acromegaly: Long-term brain parenchymal and vascular magnetic resonance changes

BACKGROUND

Radiation therapy (RT) effectiveness on hormonal reduction is proven in acromegaly; however, collateral long-term effects are still undetermined. This transversal neuroimaging study on a large cohort of acromegalic patients aimed to investigate the rate of parenchymal and vascular changes after RT.

MATERIALS AND METHODS

Thirty-six acromegalic patients underwent RT (RT+) after unsuccessful surgery and were compared to RT- acromegalic patients matched for age, gender, adenoma features, clinical and surgical history. All patients underwent magnetic resonance angiography (MRA) to investigate intracranial artery abnormalities and FLAIR sequence to assess white matter changes according to the Wahlund scale.

RESULTS

RT+ acromegalic patients had a higher rate of controlled disease (29/36 vs. 12/36, P<0.001). RT+ acromegalic patients had MRI/MRA evaluation 15.3±9.6 years after RT. RT+ acromegalic patients had a significantly higher Wahlund score than RT- acromegalic patients (6.03±6.41 vs. 2.53±3.66, P=0.006) due to increased white matter signal abnormalities at the level of the temporal lobes, the basal ganglia (insula) and the infratentorial regions, bilaterally. Among RT+ patients one died because of temporo-polar anaplastic astrocytoma, one suffered from a stroke due to right internal carotid artery occlusion, one presented with cystic degeneration of the temporal poles. Long-dated RT (>10 years before MR evaluation) was associated with a higher rate of RT-related white matter changes (P=0.0004).

CONCLUSIONS

RT seems to have created a cohort of patients with brain parenchymal changes whose clinical and cognitive impact is still unknown. These patients might require a prolonged MRI and MRA follow-up to promptly detect delayed RT-related complications and minimize their clinical consequences.

Visual loss despite anticoagulation in radiation-induced optic neuropathy

Radiation therapy to the brain may produce necrosis and loss of function months after completion of the treatment. The case is presented of a 62-year-old man who developed radiation-induced optic neuropathy 2 years after treatment for a glioma of the left temporal lobe, despite being on anticoagulation therapy. Although anticoagulation appears to be beneficial in cerebral radiation necrosis, its usefulness in the treatment of radiation-induced optic neuropathy is unclear.

Stereotactic conformal radiotherapy for pituitary adenomas: technique and preliminary experience

OBJECTIVE

Stereotactic conformal radiotherapy (SCRT) is a high precision technique of fractionated radiotherapy which ensures accurate delivery of radiation with reduction in the volume of normal tissue irradiated as compared to conventional external beam radiotherapy. We describe the technique and preliminary experience of SCRT in patients with residual and recurrent pituitary adenomas.

PATIENTS AND METHODS

Between February 1995 and March 1999, 22 patients (mean age: 45.3, range: 20-67 years) with residual or recurrent pituitary adenomas (13 nonfunctioning, nine secretory) were treated with SCRT. All were immobilized in a relocatable Gill-Thomas-Cosman (GTC) frame and tumour was localized on a postcontrast planning computerized tomography (CT) and MRI scan. The gross tumour volume (GTV) and the critical structures were outlined on contiguous 2-3 mm separated slices. A margin of 5 mm (12 patients) to 10 mm (10 patients) was grown around GTV in three-dimensions (3-D) to generate the planning target volume (PTV). The treatment was delivered by three (five patients) and four (17 patients) maximally separated conformal fixed fields with each field conformed to the shape of the tumour using customized lead alloy blocks (19 patients) or multileaf collimator (three patients). The patients were treated on a 6-MV linear accelerator to a dose of 45 Gy in 25 fractions (18 patients) and 50 Gy in 30 fractions (four patients).

RESULTS

The technique of SCRT has become a part of the routine work of the radiotherapy department. The treatment was well tolerated with minimal acute toxicity. One patient developed transient quadrantanopia 2 weeks after treatment with full recovery after a short course of corticosteroids. One patient had a transient visual deterioration 7 months after treatment due to cystic degeneration of the tumour which fully recovered following surgical decompression. Nine of the 15 patients presenting with visual impairment had improvement after treatment and the visual status remained stable in all others. One patient with acromegaly and one with a prolactinoma achieved normalization of elevated hormonal abnormality four and 10 months after SCRT, respectively. The remaining seven patients with a secretory adenoma had declining hormone levels at last follow-up. Newly initiated hormone replacement therapy was required in five patients. At a median follow-up of 9 months (range 1-44 months), the 1 and 2 year actuarial progression free and overall survival were 100%.

CONCLUSION

Stereotactic conformal radiotherapy is a high precision technique suitable for the treatment of pituitary adenomas requiring radiotherapy. Preliminary results suggest effective tumour control and low toxicity within the range expected for conventional external beam radiotherapy. While the technique is of potential benefit in reducing the volume of normal brain irradiated, the advantages in terms of sustained tumour control and reduced toxicity over conventional radiotherapy need to be demonstrated in long-term prospective studies.

External irradiation of macroinvasive pituitary adenomas with telecobalt: a retrospective study with long-term follow-up in patients irradiated with doses mostly of between 40-45 Gy

PURPOSE

Published dose recommendations for radiotherapy in patients with pituitary macroadenomas vary. Therefore, we retrospectively analyzed the results in our patients from the treatment period 1973-1992.

METHODS AND MATERIALS

From a total of 89 patients with macroinvasive adenomas, 66 received radiation therapy immediately following subtotal surgical removal (combined treatment modality), and 22 were irradiated as primary treatment or after surgical recurrence. Only one patient was reirradiated. The surgical interventions have been performed by the same surgeon. For the majority of patients (79 out of 89) with a mean follow-up of 8.1 years (0.5-19 years) the total tumor dose ranged between 40-45 Gy at a dose per fraction of 1.8-2.25 Gy. All patients had bilateral opposed fields with telecobalt. Eleven patients had an additional arc rotation.

RESULTS

The 10-year progression-free survival for all 89 patients independent of treatment modality was 88.1%. The 10-year progression-free survival for patients treated by surgery and adjuvant radiation therapy (40-45 Gy at 1.8-2.25 Gy, 60 out of 79) was 90.3%, and for radiation therapy alone (40-45 Gy at 1.8-2.25 Gy, 19 out of 79), 100% (p = 0.32). The prognostic factors for progression-free survival were the subtype of adenoma, the presence of visual symptoms at the time of diagnosis, the suprasellar extension, and the initial hormone levels. The presence of infiltration of adenoma cells in the basal dura or in the mucosa of the sinus sphenoidalis do not represent prognostic factors showing the special biological behavior of pituitary adenomas. Signs of x-ray-induced cerebral necrosis have not been observed in any patient. Long-term visual complications developed in four patients. This could be due to scar formation in the treated region, which can compress the optic nerve and provoke disturbance similar to an empty-sella syndrome. The latter occurred prevalently years after treatment, even though surgical methods of sellar plugging were used. The incidence of hypopituitarism after combined treatment modality at time of last follow-up (irradiated between 40-45 Gy at 1.8-2.25 Gy) was low (36%, 21 out of 60).

CONCLUSION

In patients with pituitary macroadenomas, radiotherapy with a total dose of 40-45 Gy at 1.8-2.25 Gy per fraction resulted in a high local tumor control without serious morbidity.

Delayed radiation necrosis of the central nervous system in patients irradiated for pituitary tumours

Four cases of delayed radiation necrosis involving the CNS were found in a group of 46 patients irradiated for pituitary tumours over a six year period. This occurred in three of 11 patients with Cushing's disease representing an incidence of 27% in this group. There were no cases among 11 patients with acromegaly or among seven with prolactinomas. One case (6%) was found in the 17 patients with chromophobe adenomas. Standard doses of radiation were delivered to these patients and the findings support suggestions that the metabolic disturbances of Cushing's disease may reduce tolerance to radiation. Our results and a literature review indicate that if radiotherapy is used to treat Cushing's disease, the total dose should be less than 50 Gy at 2 Gy per day fractionation.

Radiation-induced optic neuropathy: a magnetic resonance imaging study

Optic neuropathy induced by radiation is an infrequent cause of delayed visual loss that may at times be difficult to differentiate from compression of the visual pathways by recurrent neoplasm. The authors describe six patients with this disorder who experienced loss of vision 6 to 36 months after neurological surgery and radiation therapy. Of the six patients in the series, two had a pituitary adenoma and one each had a metastatic melanoma, multiple myeloma, craniopharyngioma, and lymphoepithelioma. Visual acuity in the affected eyes ranged from 20/25 to no light perception. Magnetic resonance (MR) imaging showed sellar and parasellar recurrence of both pituitary adenomas, but the intrinsic lesions of the optic nerves and optic chiasm induced by radiation were enhanced after gadolinium-diethylenetriaminepenta-acetic acid (DTPA) administration and were clearly distinguishable from the suprasellar compression of tumor. Repeated MR imaging showed spontaneous resolution of gadolinium-DTPA enhancement of the optic nerve in a patient who was initially suspected of harboring recurrence of a metastatic malignant melanoma as the cause of visual loss. The authors found the presumptive diagnosis of radiation-induced optic neuropathy facilitated by MR imaging with gadolinium-DTPA. This neuro-imaging procedure may help avert exploratory surgery in some patients with recurrent neoplasm in whom the etiology of visual loss is uncertain.

The long-term side effects of radiation therapy for benign brain tumors in adults

Radiation therapy plays an integral part in managing intracranial tumors. While the risk:benefit ratio is considered acceptable for treating malignant tumors, risks of long-term complications of radiotherapy need thorough assessment in adults treated for benign tumors. Many previously reported delayed complications of radiotherapy can be attributed to inappropriate treatment or to the sensitivity of a developing child's brain to radiation. Medical records, radiological studies, autopsy findings, and follow-up information were reviewed for 58 adult patients (31 men and 27 women) treated between 1958 and 1987 with radiotherapy for benign intracranial tumors. Patient ages at the time of irradiation ranged from 21 to 87 years (mean 47.7 years). The pathology included 46 pituitary adenomas, five meningiomas, four glomus jugulare tumors, two pineal area tumors, and one craniopharyngioma. Average radiation dosage was 4984 cGy (range 3100 to 7012 cGy), given in an average of 27.2 fractions (range 15 to 45 fractions), over a period averaging 46.6 days. The follow-up period ranged from 3 to 31 years (mean 8.1 years). Findings related to tumor recurrence or surgery were excluded. Twenty-two patients had complications considered to be delayed side effects of radiotherapy. Two patients had visual deterioration developing 3 and 6 years after treatment; six had pituitary dysfunction; and 17 had varying degrees of parenchymal changes of the brain, occurring mostly in the temporal lobes and relating to the frequent presentation of pituitary tumors (two of these also had pituitary dysfunction). One clival tumor with the radiographic appearance of a meningioma, developed 30 years post-irradiation for acromegaly. This study unveils considerable delayed sequelae of radiotherapy in a series of adult patients receiving what is considered "safe" treatment for benign brain tumors.

Results of radiotherapy in the treatment of acromegaly: lack of ophthalmologic complications

Between 1956 and 1988, 25 patients were treated with radiotherapy for acromegaly. Acromegalic features were present in 24 (96%), visual field deficits in 4 (16%), and suprasellar extension was present in 7 patients (28%). The median growth hormone level was 40.2 ng/ml (range: 13.8-105) in 15 patients. Initial therapy consisted of radiotherapy alone (19 patients) or surgery followed at some interval by radiation (6 patients). The radiation therapy was administered with megavoltage equipment in 23 (92%) patients and orthovoltage equipment in 2 patients. The median total dose was 46 Gy (range: 24-53.44 Gy) with 21 patients receiving at least 45 Gy. With a median follow-up of 53 months (range: 18-205), 2 of the 19 patients treated with radiotherapy alone have required surgery for symptomatic recurrences. Both are alive and in remission at 69 and 158 months following craniotomy. Thus, the success of radiotherapy as a primary modality in this series is 17/19 (89%). None of the six patients treated postoperatively have recurred. At the time of last follow-up the visual fields remained normal and visual acuity stable in the 21 patients with no pre-existing visual deficits. The four patients with prior visual field deficits improved with therapy. There were no cases of radiation optic neuropathy, brain necrosis or second intracranial malignancies. Seven patients (28%) had evidence of hypopituitarism attributed to the radiotherapy. Growth hormone levels after radiotherapy showed a median of 5.4 ng/ml (range: 3.2-40.0) in 15 patients. Eleven of 15 patients (73%) had growth hormone levels less than 10 ng/ml. Radiation use in acromegaly remains a safe and effective modality assuming careful attention is paid to technique, total dose, and fraction size.

Results of transsphenoidal microsurgery for growth hormone-secreting pituitary adenoma in a series of 214 patients

Of 214 patients with acromegaly who underwent transsphenoidal microsurgical resection of a pituitary adenoma, 54% had growth hormone (GH) levels below 5 ng/ml and 74% had levels less than 10 ng/ml immediately after surgery. Among the 174 patients who could be contacted for long-term follow-up review (average duration 76 months), most recent GH determinations were available for 165. Of these 165 patients, 131 (79.4%) have a GH level less than 5 ng/ml and 153 (92.7%) have a level below 10 ng/ml; these represent 75.3% and 87.9%, respectively, of the total 174 patients reviewed. Fifty-two patients received postoperative radiation therapy. Nine patients underwent reoperation. There were five cases of tumor recurrence following an apparent surgical cure (4.3%), nine new instances of anterior pituitary hypofunction (5%), and five failures of multimodality therapy (2.3%). There were no perioperative deaths, five cases of cerebrospinal fluid leak requiring surgical repair (2.2%), and four cases of postoperative meningitis (1.8%). Permanent diabetes insipidus did not occur. Two of 52 patients who were irradiated postoperatively had severe complications; 23 (54.8%) of 42 patients who were available for follow-up evaluation had developed panhypopituitarism; and eight (19%) of 42 had normal pituitary function an average of 44 months postirradiation.

Absence of irradiation induced ischaemic temporal lobe damage in patients with pituitary tumours

This study was undertaken to confirm the belief that modern day external beam radiotherapy for patients with pituitary tumours should not be associated with any ischaemic temporal lobe damage. Using the oxygen-15 steady state inhalation technique and positron emission tomography regional temporal lobe blood flow, oxygen extraction fraction and oxygen utilisation were measured in 10 normal volunteers and 11 patients with pituitary tumours treated by irradiation. The patients were studied between 1 and 10.9 years after radiotherapy. We found that temporal lobe oxygen utilisation in the irradiated group (mean 2.11 +/- 0.23 ml of O2/100 ml tissue/min) did not differ from the normal group (mean 2.13 +/- 0.26 ml of O2/100 ml tissue/min). This suggests that total doses of between 35 and 56 Gy, delivered in fractions of less than 2 Gy, can be given to a pituitary tumour without demonstrable damage to normal temporal lobe.

Radiation optic neuropathy

Following surgery for pituitary adenoma, radiation therapy is an accepted treatment in reducing tumor recurrence. However, a potential therapeutic complication is delayed radionecrosis of perisellar neural structures, including the optic nerves and chiasm. This particular cause of visual loss, radiation optic neuropathy (RON), has not been emphasized in the ophthalmologic literature. Four cases of RON seen in the past five years are reported. Diagnostic criteria include: (1) acute visual loss (monocular or binocular), (2) visual field defects indicating optic nerve or chiasmal dysfunction, (3) absence of optic disc edema, (4) onset usually within three years of therapy (peak: 1-1 1/2 years), and (5) no computed tomographic evidence of visual pathway compression. Pathologic findings, differential diagnosis and therapy will be discussed in outlining the clinical profile of RON.

Changes in intracranial pressure associated with delayed cerebral radionecrosis

Continuous recording of intracranial pressure (ICP) from one lateral ventricle in a case of histologically proven delayed temporal radionecrosis due to previous irradiation of the pituitary gland for the treatment of an adiposity of the Cushing type has revealed the occurrence of B-waves and ramplike waves despite the absence of raised intracranial pressure. Ventriculo-atrial shunting failed to relieve the severe psychic symptomatology, which was due to direct tissue damage. These observations indicate that B-waves may have a neurogenic origin.

Tolerance of the mature human central nervous system to photon irradiation

Tolerance of mature human brain to photon irradiation is described. Isoeffect curves have been derived for tolerance of large and small volumes of brain, by examination of doses determined empirically and in clinical use. These have been compared with isoeffect curves of thoracic myelitis, optic nerve and chiasm damage, and brain necrosis. The results show that the best-fitting Ellis-type equations, when five fractions per week are used, have low exponents for overall treatment time and high exponents for the number of increments (N), and are similar to published data on rat myelitis. Of the equations used to test the relationship between total dose and number of increments, the power curve was the best fit. Mean values of exponents for N derived for brain and spinal cord tolerance were 0.4 or more. These were similar to values obtained for optic nerve and chiasm damage, though the data are more limited for this complication. Brain necrosis is observed at slightly higher doses probably because of a difference in the end-point observed rather than because of any fundamental difference in tissue response. Evidence is presented to suggest that some repopulation may occur in widely spaced schedules. The use of the Ellis equation derived from connective-tissue data is inappropriate for central nervous system tissue, and its use may lead to a substantial risk of overdosage. A plea is made for adequate documentation of treatment details when human data are reported. The importance of dose per fraction is emphasized.

The morphologic effects of radiation administered therapeutically for intracranial gliomas: a postmortem study of 25 cases

To investigate the pathologic consequences of therapeutic radiation, this morphologic study evaluated the brains of 25 patients with intracranial gliomas treated both with and without this form of therapy. Although beneficial effects such as the retardation of tumor growth were evident in these studies, among the seventeen patients who received from 5000--6000 rads for malignant gliomas, four developed "late delayed" radiation necrosis. The strong predilection of this tissue response for the white matter adjacent to the neoplasm suggests a local sensitivity which may have been engendered or enhanced by cerebral edema. A fifth case disclosed focal demyelination in the mid-brain suggesting "early delayed" radiation necrosis, and an additional case had distinctive foci of necrosis within the brain stem. Changes of diffuse cerebral edema were noted in many of the radiated brains. It is concluded that radiation therapy in commonly employed dosages for malignant gliomas carries a risk of injury to surrounding cerebral tissues.

Cranial nerve damage in patients after alpha (heavy)-particle radiation to the pituitary

The records of 161 patients were reviewed to determine if radiation damage had occurred following cranial irradiation. All of these patients had received alpha-particle radiation to their pituitary glands during the period when this form of therapy was given for diabetic retinopathy. Extraocular muscle palsy developed in 11 of these patients, iridoplegia in six, and fifth nerve damage in six. All of the palsies developed within a short period following their irradiation, and a definite dose relationship was present. The dose rate was approximately 100 rads/min for all cases. Fractionation varied but it is known for all cases. The estimated doses to the third, fourth, fifth, and sixth cranial nerves was calculated at a saggital plane 13 to 15 mm from the pituitary by using computer-drawn dosimetry charts for the respective aperture size. The energetic alpha particles were produced by the 184-in synchrocyclotron at Berkeley, Calif. A dose relationship for radiation palsies was apparent.

Late post-irradiation necrosis of the brain

Three examples of late post-irradiation brain necrosis are reported. In two cases operation was performed on account of the space-occupying effects of the lesions, and in the third case the lesion was found post-mortem. The aetiology and pathology of the condition are discussed. Our findings in the three cases described are contrasted with those in 29 patients who had been submitted to similar doses of irradiation, but had not developed necrosis. The literature on pathogenesis is briefly reviewed.

Delayed radiation necrosis of the brain

The cases of six patients are presented to delineate the clinical profile of delayed radiation necrosis of the brain. In five the diagnosis was verified histologically. Symptoms most often begin 9 months to 2 years after radiotherapy. Progressive visual impairment and dementia are common following perisellar irradiation, while hemispheric signs predominate following irradiation of the cerebrum. Cerebrospinal fluid protein may be elevated. Focal delta slowing is usually present on electroencephalography. The necrotic brain may appear on radionuclide brain scan as an area of abnormal uptake and also act as an avascular space-occupying lesion. With computerized tomography, radiation necrosis appears as an intracerebral area with diminished absorption coefficient that is often enhanced with intravenous contrast medium. The syndrome may be sufficiently characteristic to eliminate the need for surgical exploration and biopsy in some cases. Cumulative experience suggests that the risk-to-benefit ratio of radiotherapy becomes increasingly unfavorable for most patients with benign intracranial neoplasms when the standard brain tumor dose of 5000 to 7000 rads is fractionated at greater than 200 rads per day.

Efficacy of cryohypophysectomy in the treatment of acromegaly. Evaluation of 54 cases

Between 1963 and 1974, 54 patients with acromegaly (28 men and 26 women) ranging in age from 23 to 61 years were evaluated. Each patient underwent thorough preperative neurological, roentgenographic, and endocrinological surveys; most demonstrated mild-to-severe abnormalities in growth hormone immunoassay and oral glucose tolerance. Of those who underwent stereotaxic cryohypophysectomy, approximately 80% were considered to have a beneficial result. The efficacy of this form of therapy was judged on the basis of: 1) significant overall clinical improvement and regression of acromegalic features; 2) improvement in the glucose tolerance curve; and 3) a fall of serum growth hormone below 10 ng/ml. Complications including rhinorrhea, meningitis, and hemorrhage occurred in only a small number of cases. A comparison is made between this technique and other, including craniotomy, radiotherapy, and transnasal transsphenoidal hypophysectomy. The efficacy, low morbidity, and the ease with which the procedure may be performed make this our treatment of choice when dealing with growth-hormone-producing pituitary adenomas with no suprasellar extension.

Radiation necrosis of the brain. Neuroradiological considerations with computed tomography

In cases with radiation necrosis of the brain, conventional neuroradiological examinations usually demonstrate only an avascular mass lesion impossible to differentiate from intracerebral tumor or hemorrhage. Computed tomography, performed in addition to angiography in three cases, consistently demonstrated the radiation necrosis as a low density area exhibiting enhancement following infusion of contrast medium. The importance of recognizing radiation necrosis as a differential diagnosis to brain neoplasm is emphasized.

Cerebral radiation necrosis simulating a brain tumor. Case report

✓ Two years after undergoing irradiation for a malignant ethmoid tumor, a 50-year-old man developed signs of increased intracranial pressure, an expanding right frontal lobe mass, and tentorial herniation. Operation revealed a mass that grossly appeared to be a glioma, but microscopically proved to be radiation necrosis of the brain.

[Post-irradiation cervical myelopathy simulating spinal cord tumor]

Os autores relatam um caso de paciente de 25 anos, masculino, submetido a radioterapia cervical por carcinoma indiferenciado do rinofaringe com metástases ganglionares. Seis meses depois desenvolveu tetraparesia progressiva com exames liquórico e mielográfico compatíveis com diagnóstico de tumor intramedular. O exame histopatológico revelou aspecto característico da mielopatia após irradiação.

Stereotactic treatment of acromegaly

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