Radioisotope therapy of cystic craniopharyngomas

Milestones in dosimetry for nuclear medicine therapy

Nuclear Medicine therapy has reached a critical juncture with an unprecedented number of patients being treated and an extensive list of new radiopharmaceuticals under development. Since the early applications of these treatments dosimetry has played a vital role in their development, in both aiding optimisation and enhancing safety and efficacy. To inform the future direction of this field, it is useful to reflect on the scientific and technological advances that have occurred since those early uses. In this review, we explore how dosimetry has evolved over the years and discuss why such initiatives were conceived and the importance of maintaining standards within our practise. Specific milestones and landmark publications are highlighted and a thematic review and significant outcomes during each decade are presented.

Intracavitary radiation therapy for recurrent cystic brain tumors with holmium-166-chico : a pilot study

OBJECTIVE

Intracavitary injection of beta-emitting radiation source for control of cystic tumors has been tried with a benefit of localized internal radiation. The authors treated cystic brain tumor patients with Holmium-166-chitosan complex (Ho-166-chico), composed of a beta-emitting radionuclide Holmium-166 and biodegradable chit polymer, and evaluated the safety and effective measurement for response.

METHODS

Twenty-two patients with recurrent cystic brain tumor and/or located in a deep or eloquent area were enrolled in this pilot study. The cyst volume and wall thickness were determined on CT or MRI to assess radiological response. The activity of Ho-166-chico injected via Ommaya reservoir was prescribed to be 10-25 Gy to the cyst wall in a depth of 4 mm.

RESULTS

There was neither complications related to systemic absorption nor leakage of Ho-166-chico in all 22 patients. But, two cases of oculomotor paresis were observed in patients with recurrent craniopharyngioma. Radiological response was seen in 14 of 20 available follow-up images (70%). Seven patients of 'evident' radiological response experienced more than 25% decrease of both cyst volume and wall thickness. Another 7 patients with 'suggestive' response showed decrease of cyst volume without definitive change of the wall thickness or vice versa. All patients with benign tumors or low grade gliomas experienced symptomatic improvement.

CONCLUSION

Ho-166-chico intracavitary radiation therapy for cystic tumor is a safe method of palliation without serious complications. The determination of both minimal effective dosage and time interval of repeated injection through phase 1 trial could improve the results in the future.

Intracystic irradiation for craniopharyngiomas

Data collected over a 36-year period were used to assess the value of stereotactically applied intracystic colloidal yttrium-90 (YTx) for the treatment of recurrent cystic craniopharyngiomas (CRF's). The article compares data from 95 YTx procedures carried out on 78 patients during the years 1975 and 2011, using a cumulative beta dose of 270 Gy aimed at the inner surface of the cyst wall. After YTx, the initial cyst volumes decreased an average of 74.7 %. In 54 patients, the volume reduction exceeded 80 %. In 32 patients, the cyst disappeared completely within one year. The mean survival rate following YTx was 7.5 years (range 0.7-31 years). The survival rates at 5, 10, 15, 20, 25, and 30 years were 56, 29, 15, 8, 3, and 1 %, respectively. Late complications of YTx were related to the anatomical location of the cyst, either presellar or retrosellar. A presellar, that is, prechiasmatic/suprasellar localization resulted in neuro-ophthalmological complications in 5.1 % of the cases, while internal carotid artery injury accounted for 1.4 % of the complications. The treatment of retrosellar (retrochiasmatic, suprasellar) tumors may cause hypothalamic, fornix, or pontomesencephalothalamic damage, from untoward radiation to the so-called perforating arteries. This complication occurred in 5.2 % of the cases. In the multimodality management of craniopharyngioma cysts, intracavity YTx irradiation is a valuable treatment alternative despite sporadic complications arising in some surgical cases. The formula for the calculation of the dynamics of reduction of CRF's following yttrium-90 colloid brachytherapy was supported by correlating the collected data. The focus was on our minimally invasive YTx following multiple surgeries of cystic CRFs.

Management of cystic craniopharyngiomas with stereotactic endocavitary irradiation using colloidal 186Re: a retrospective study of 48 consecutive patients

OBJECTIVE

We retrospectively reviewed the results of stereotactic endocavitary irradiation with colloidal 186Re in the treatment of cystic craniopharyngiomas.

METHODS

Among 54 consecutive patients included in a 186Re stereotactic endocavitary irradiation procedure, 42 patients (29 male and 13 female; average age, 38.7 years) received therapeutic injection via intracystic catheter introduced under stereotactic conditions. The mean follow-up period was 43 months (range, 8-148 months). Endocavitary irradiation was the primary treatment for 15 patients and an adjuvant treatment for 27 patients. The mean volume before irradiation was 8.07 mm3, and the mean radiation dose was 381 MBq.

RESULTS

Cystic mean volume after irradiation was 2.6 cm3 (P < 0.001 with initial volume). The retraction of the cyst was complete for 17 patients (44%) and partial for 17 (44%). In partial retraction, cystic volume decreased more than 50% for 12 (3%) patients and less than 25% (13%) for 5. Cystic volume remained the same or increased for 5 (13%) patients. Concerning visual functions, 12 (44.5%) patients improved and 2 worsened, despite tumor control. No endocrinological deterioration occurred. Among 17 patients with preoperative cognitive dysfunction, 10 improved and 6 had no change. One patient showed memory alteration 4 months after stereotactic endocavitary irradiation despite cyst volume reduction. No mortality occurred.

CONCLUSION

186Re stereotactic endocavitary irradiation for the treatment of cystic craniopharyngiomas is a safe and effective procedure with a tumor control rate greater than 70%. This treatment can be used for first-intention treatment of pure cystic craniopharyngiomas or for second-intention treatment of cystic recurrences.

LONG-TERM RESULTS AND LATE COMPLICATIONS AFTER INTRACAVITARY YTTRIUM-90 COLLOID IRRADIATION OF RECURRENT CYSTIC CRANIOPHARYNGIOMAS

OBJECTIVE

Data were analyzed to assess the value of stereotactically applied intracystic colloidal yttrium-90 (YTx) for the treatment of recurrent cystic craniopharyngiomas during a 30-year period.

METHODS

This article compares data from 73 YTx procedures in 60 patients between 1975 and 2006. The cumulative beta dose aimed at the inner surface of the cyst wall was 300 Gy.

RESULTS

After YTx, the initial cyst volumes decreased an average of 79%. In 47, the reduction was more than 80%; in 27 of them, the cyst disappeared completely within 1 year. The mean survival after YTx was 9.4 years (range, 0.7–30 yr). Actuarial survival rates at 5, 10, 15, 20, 25, and 30 years were 81, 61, 45, 18, 2, and 0%, respectively. Late complications of YTx were related to the anatomic localization of the cyst, either presellar and retrosellar, e.g., a presellar (prechiasmatic/suprasellar) localization caused neuro-ophthalmological complications in 5.8% and internal carotid artery injury in 1.6%. The treatment of retrosellar (retrochiasmatic, suprasellar) tumors occasionally induced hypothalamic and/or pontomesencephalothalamic damage obviously by untoward radiation to the so-called perforating arteries. This occurred in 3.2% of these latter patients.

CONCLUSION

Despite sporadic complications, intracavitary YTx irradiation is a valuable treatment alternative for craniopharyngioma cysts, sometimes as part of a multimodality management in these tumors, especially in precarious surgical cases.

Intracavitary therapeutic options in the management of cystic craniopharyngioma

BACKGROUND

Craniopharyngioma remains an entity of controversial management due to its critical anatomical relationships and its well-known recurrence tendency. Total resection, although desirable, is not always accomplished, and it is associated with potentially permanent endocrinological and visual deficits. Consequently, this situation has led to the development of new management strategies seeking lesser morbidity. Because a high percentage of these lesions are cystic, bleomycin and radioactive-emitting sources have been postulated as new therapeutic options with promising results.

DISCUSSION

The information known to date regarding these substances is summarized and we perform a retrospective review of the clinical trials conducted over the past 30 years with special emphasis on outcome, morbidity, and mortality. Two cases from our institution are presented as examples of multimodality management.

CONCLUSION

Overall, these newer options stand out as valid alternatives in the controversial management of these challenging tumors.

Re-evaluation of the dose to the cyst wall in P-32 radiocolloid treatments of cystic brain tumors using the Dose-Point-Kernel and Monte Carlo methods

Intracavity instillation of beta-emitting colloid pharmaceuticals is a common technique used to treat cystic brain tumors. Most of the dosimetric calculations that have been reported in the literature for this problem are based on empirical formulas derived by Loevinger. Concentration of P-32 radiolabeled solution for the delivery of a prescribed dose (200 Gy to the cyst wall) has been published previously using this formalism in what we refer to as a standard nomogram. The calculations using the Loevinger formulas for calculating the P-32 activity necessary to achieve 200 Gy at the cyst wall is re-evaluated and compared to numerically computed results based on full Monte Carlo simulations (EGSnrc) and the dose-point-kernel (DPK) integration method. For cyst diameters greater than 1 cm, the new calculations agree well with previously published results (the standard nomogram) to within a few percents. However, for cyst diameters of less than 1 cm, it is shown that the standard nomogram results underestimate the therapeutic activity by a factor of approximately 3 for very small diameters (approximately 0.2 cm). New tables based on our calculations are presented and the sources of discrepancies are identified. It is concluded that the new set of data based on our calculations should replace the standard nomogram to administer accurately the target dose to the cyst wall for the smaller diameter cysts (< 1 cm).

Gamma knife radiosurgery for craniopharyngiomas: longterm results in the first Swedish patients

Object. The purpose of this study was to assess the long-term treatment efficacy and morbidity of patients who undergo gamma knife radiosurgery (GKS) for craniopharyngioma.

Methods. Twenty-one consecutive Swedish patients were evaluated retrospectively: 11 children (≤ 15 years) and 10 adults. The time from diagnosis to the most recent follow-up imaging study was 6.3 to 34.3 years (mean 18.2 years, median 16.8 years). Tumor volumes and morbidity from GKS or other treatments were assessed at the time of the most recent imaging study or at the time of a subsequent new treatment. The observation period ranged from 0.5 to 29 years (mean 7.5 years, median 3.5 years). The prescription dose ranged from less than 3 Gy to 25 Gy. The mean tumor volume was 7.8 cm3 (range 0.4–33 cm3).

There were 22 tumors in 21 patients treated with GKS. Five of these tumors were reduced in size, three were unchanged, and 14 increased. Tumor progression correlated with a low dose to the tumor margin. Eleven (85%) of 13 tumors that received a dose of less than 6 Gy to the margin increased in size, whereas only three (33%) of nine tumors that received 6 Gy increased. This difference was statistically significant (p = 0.01). In five of six patients tumors that became smaller after GKS there were no recurrences within a mean follow-up period of 12 years. Nine (82%) of 11 tumors in children ultimately increased after GKS, compared with five (50%) of 10 in adults. In eight patients there was a deterioration of visual function. In all except one this could be related to a volume increase but radiation-induced damage could not be excluded as a factor in any of them. Four patients developed pituitary deficiencies.

Conclusions. Gamma knife radiosurgery is effective in controlling growth of craniopharyngiomas with a minimum dose of 6 Gy. The findings also suggest that other stereotactic techniques, such as cyst aspiration and intracystic treatment, are only of value in reducing tumor volume in preparation for safe GKS.

Cystic craniopharyngioma: long-term results after intracavitary irradiation with stereotactically applied colloidal beta-emitting radioactive sources

OBJECTIVE

Long-term follow-up data were analyzed to assess the value of intracavitary irradiation with stereotactically applied beta-emitting radioisotopes for the treatment of craniopharyngioma cysts.

METHODS

Sixty-two of 70 consecutive patients with predominantly cystic craniopharyngiomas were selected for retrospective analysis. Beta-Emitting isotopes were injected intracystically using a computed tomography-guided and computer-assisted three-dimensional stereotactic treatment planning and application system (cumulative dose to the inner surface of the cyst wall, 200 Gy).

RESULTS

The tumor response rate gained with yttrium-90-labeled silicate (66 of 78 cysts) or phosphorous-32-labeled chromic phosphate (8 of 78 cysts) was 79.5%. Four cysts treated with rhenium-186-labeled sulfate did not respond. Mean survival after intracavitary irradiation was 9.0 +/- 0.9 years (median follow-up, 11.9 yr). In patients with solitary cysts, the mean survival was 12.5 +/- 1.4 years (actuarial 5- and 10-yr survival rates, 80 and 64%, respectively). Six months postoperatively, visual deficits (38 of 62 patients) had improved in 23 patients and were stable in 15 patients. The side effects that occurred 6 to 12 months after treatment with yttrium-90 were complete blindness (three patients), worsening of visual field cuts (one patient), third nerve palsy (one patient), and diabetes insipidus and/or panhypopituitarism (three patients).

CONCLUSIONS

Intracavitary irradiation using yttrium-90 or phosphorous-32 is highly effective in the treatment of cystic craniopharyngiomas. If applied as initial treatment in patients with solitary cysts, it is the only required therapy over a long period.

Phosphorus-32 intracavitary irradiation of cystic craniopharyngiomas: current technique and long-term results

PURPOSE

The management of patients with craniopharyngiomas is often multifaceted and multidisciplinary. The purpose of this study was to examine the results of phosphorus-32 intracavitary irradiation in the treatment of patients with predominately cystic craniopharyngiomas.

METHODS AND MATERIALS

Thirty patients with cystic craniopharyngiomas underwent phosphorus-32 intracavitary irradiation at our center between 1981 and 1993. The median patient age was 26 years (range, 3-70 years). Thirteen patients had intracavitary irradiation as the primary surgery for their cystic tumors, whereas 17 patients had adjuvant intracavitary irradiation after microsurgical resection, fractionated radiotherapy, or both. Patients in the adjuvant treatment group were more likely to have preoperative anterior pituitary insufficiency (p = 0.008 Fischer exact test) and diabetes insipidus (p = 0.003 Fischer exact test). The median follow-up was 37 months (mean, 46 months, range, 7-116 months).

RESULTS

Phosphorus-32 intracavitary irradiation resulted in cyst regression in 28 of 32 treated cysts (88%). Ten patients (33%) have had tumor progression requiring further surgical intervention. Three patients (10%) died: two of tumor progression, and one of unrelated causes. Visual acuity and fields improved or remained stable in 63% of the patients. Fifteen patients had residual anterior pituitary function before intracavitary irradiation and 10 (67%) retained their preoperative endocrine status. New-onset diabetes insipidus occurred in 3 of 17 patients (18%) who had normal posterior pituitary function preoperatively. Fourteen of 20 adult patients (70%) continued to perform at their preoperative functional level; 3 of 5 pediatric patients who were age appropriate at the time of treatment continued to develop normally. No difference was noted between primary and adjuvant treatment patients with respect to cyst control, visual deterioration, or endocrine preservation after phosphorus-32 intracavitary irradiation.

CONCLUSION

The goals of craniopharyngioma management should be tumor control with preservation of visual, endocrine, and cognitive function. Phosphorus-32 intracavitary irradiation is an important option that enhances the likelihood of achieving these goals in patients with primarily cystic craniopharyngiomas.

Gamma knife surgery for craniopharyngioma

We present our results of Gamma Knife surgery for craniopharyngioma in nine patients. The current status of surgery, radiation therapy, intracavitary instillation of radionucleides and Gamma Knife surgery in the management of craniopharyngiomas is discussed.

Intracavitary brachytherapy of cystic craniopharyngiomas

Visual function, endocrinological status, and radiological outcome are reported in 31 patients harboring a cystic craniopharyngioma, who underwent 35 intracavitary brachytherapy procedures with yttrium-90. In 26 of these patients intracavitary brachytherapy was the primary treatment. The follow-up period ranged from 2 to 80 months (41 +/- 22 months, mean +/- standard deviation). Five patients died from tumor-related causes. Endocrine recovery was modest. Prior to brachytherapy, visual acuity was diminished in 38 eyes and field defects were present in 46. Funduscopy before treatment revealed optic atrophy in 47% of the eyes. Visual acuity improved in 29% of the eyes studied, remained stable in 13%, and deteriorated in 58%. Visual field defects improved in 28% of the eyes studied, remained stable in 20%, and deteriorated in 52%. The possible causes for deterioration in visual function are discussed. Complete resolution of 10 cysts was noted. In 12 patients the size of the cyst decreased; however, in three of these patients new cyst formation took place. The cyst size stabilized in six cases and increased in three. Although there is still a substantial degree of visual function deterioration following intracavitary brachytherapy, morbidity is otherwise low, making this treatment modality a reasonable alternative to craniotomy.

Pathological changes in cystic craniopharyngiomas following intracavital 90yttrium treatment

Radiosurgery, using 90Y injected directly into the cavity of cystic craniopharyngiomas produces remarkable reduction of tumour size and diminishes cyst fluid production. The authors have studied the histology of biopsy and autopsy material obtained from seven patients presented with cystic craniopharyngiomas. Histological examination was carried out before and after 90Y silicate implantation. As an effect of 90Y irradiation, histology of samples taken from the cyst wall revealed that the lining epithelial cell layer became destroyed and the cyst wall shrunk. Large amount of collagen fibres with focal hyaline degeneration was present. Proliferation of intimal cells and subendothelial connective tissue narrowing small vessel lumina also occurred. Considering that fibrotic tissue is more susceptible to shrink, the fibrosis induced by irradiation together with destruction of the squamous epithelium and vascular changes, might explain the reduction of the cyst volume and diminished fluid secretion after 90Y treatment.

Visual outcome in cystic craniopharyngiomas treated with intracavitary phosphorus-32

Seven patients with cystic craniopharyngiomas were treated with stereotactic instillation of radioactive phosphorus-32 (32P). Five patients had been previously treated with various combinations of surgery and external beam irradiation, whereas two had the 32P instillation at a primary therapy. Visual acuity improved in 13 eyes and remained stable in 1. Visual fields normalized in three patients, improved in two, and remained stable in two. Two patients received single treatments with 32P, whereas five required multiple instillations for recurrent cyst expansion.

Management of primary or recurring grossly cystic craniopharyngiomas by means of draining systems. Topic review and 6 case reports

In primary or relapsing grossly cystic craniopharyngiomas most of the problems related to the neoplastic mass may be, even if temporarily, improved by reducing volume of the cyst. A major surgical approach is unjustified when the aim is only to empty the cyst contents. Drainage of the cyst cavity by means of derivative techniques may be as effective and less invasive; in combined management plans that such tumours often require, they are, therefore, useful complementary procedures that can achieve long-lasting relief of symptoms, provided that the cyst is unilocular. Technical features and indications for such methods, with special regard to the techniques of sump drainage and of tube ventriculocystostomy, are discussed on the basis of the few reported series and of 6 personal cases. Usually only palliative aims are achieved, waiting for more definitive treatment; in a few selected cases, however, they may be quite effective.

Treatment of craniopharyngiomas--the stereotactic approach in a ten to twenty-three years' perspective. I. Surgical, radiological and ophthalmological aspects

A multi-modality treatment programme, where stereotactic methods were used preferentially, gave results in a consecutive series of craniopharyngiomas, not inferior to those reported after microsurgical removal. Fourty-two patients with a follow-up range of 10-23 years are reported.

Stereotaxic intracavitary irradiation for cystic craniopharyngiomas

Stereotaxic intracavitary irradiation with instillation of phosphorus-32 (32P) colloidal chromic phosphate was performed in nine patients with cystic craniopharyngiomas. Serial neurological, ophthalmological, neuroendocrinological, and radiological examinations were performed before and after treatment. Dosimetry was determined based on a computerized tomography (CT) estimation of tumor volume, and was calculated to provide a tumoricidal dose (200 to 300 Gy) to the cyst wall. The follow-up period ranged from 14 to 45 months (mean 27 months). After treatment, all nine patients showed improvement of symptoms and radiological evidence of cyst regression. Because of an expanding solid component producing recurrent symptoms, one patient required a craniotomy 14 months after isotope instillation. Three of five patients with impaired visual acuity before surgery had significant improvement in acuity after treatment. Preoperative visual field defects in eight patients improved in four after 32P therapy. Of seven patients with preoperative endocrine abnormalities, one individual showed almost complete normalization and another had improvement in endocrine function. Patients who exhibited residual neuroendocrine function before isotope instillation developed no significant deterioration in endocrine status during the follow-up period. The findings suggest that stereotaxic intracavitary irradiation is a safe and effective treatment which should be considered as the initial surgery for cystic craniopharyngiomas.

Further experiences in the treatment of cystic craniopharyngeomas with yttrium 90 silicate colloid

20 patients suffering from cystic craniopharyngioma were treated with intracavitary irradiation on 25 occasions. The beta emitting radionuclide 90Y silicate colloid was instilled into the cyst or cystic part of the tumour. 17 patients on 22 occasions underwent follow-up CT and ophthalmological examinations 1 to 144 (average: 34) months after the intracavitary radioisotope therapy. An 23 occasions there was an average of 82 to 90% volume decrease of the craniopharyngioma cysts. On two occasions the volume has remained unchanged and the result of the 90Y therapy cannot be evaluated yet. The neuroophthalmological prognosis was good only when a relatively intact optic disc was seen; when the disc was atrophic the visual deterioration proved to be irreversible. Pathologically, it is the fibrotic tissue that is responsible for the shrinkage of the cyst.

Comparison of computerized tomographic and radionuclide methods in determining intracranial cystic tumor volumes

The dosimetry of radioactive phosphorus (32P) for intracavitary treatment of cystic brain tumors is dependent upon accurate determination of the cyst volume. The authors have used both high-resolution computerized tomography (CT) scanning and an isotope dilution technique with technetium-99m (99mTc) sulfur colloid to determine cyst volumes in an experimental model and in six patients with intracerebral cystic tumors. In six separate comparisons using an experimental phantom "cyst," no significant differences between CT and 99mTc values were detected. In six patients with cystic neoplasms varying from 3 to 6.7 ml in volume, the percent differences between values obtained by CT and isotope dilution ranged from -17.26% to +13.13%. In individual patients, these differences proved to be of little significance for planning dosimetry. In both experimental and clinical trials comparing isotope dilution and CT measurement techniques, the CT technique using the standard software of the scanner and 5-mm thick slices proved to be a highly accurate method of determining cyst volume. The authors now base dosimetric calculations for intracavitary radiation with 32P on CT technique alone.