Radiation therapy for chordomas of the base of skull and cervical spine: patterns of failure and outcome after relapse

Skull base chordoma

PURPOSE

Our purpose was to discuss the optimal treatment and outcomes for patients with skull base chordomas.

METHODS

We reviewed the pertinent literature for this study.

RESULTS

Skull base chordomas usually arise in the clivus and are rarely completely resectable. Therefore, most are treated with radiotherapy (RT). Because of the risk of severe late complications, the dose is often limited with conventional photon RT, and the probability of cure is low. Proton RT alone or combined with photon RT (proton/photon RT) offers the advantage of improved dose distribution and the ability to treat the tumor to a higher dose without exceeding normal tissue tolerance. The 10-year local control rate after proton/photon RT is approximately 40% to 50%. The probability of local control is related to minimum tumor dose and dose inhomogeneity.

CONCLUSIONS

Skull base chordoma is a rare neoplasm that is rarely cured after surgery alone or combined with conventional RT. Proton/photon RT offers the advantage of increasing the tumor dose while minimizing the dose to normal tissues, thus reducing the risk of late complications. The optimal treatment may be photon/proton RT alone or combined with a gross total resection, when feasible.

Clinical results of proton beam therapy for skull base chordoma

PURPOSE

To evaluate clinical results of proton beam therapy for patients with skull base chordoma.

METHODS AND MATERIALS

Thirteen patients with skull base chordoma who were treated with proton beams with or without X-rays at the University of Tsukuba between 1989 and 2000 were retrospectively reviewed. A median total tumor dose of 72.0 Gy (range, 63.0-95.0 Gy) was delivered. The patients were followed for a median period of 69.3 months (range, 14.6-123.4 months).

RESULTS

The 5-year local control rate was 46.0%. Cause-specific, overall, and disease-free survival rates at 5 years were 72.2%, 66.7%, and 42.2%, respectively. The local control rate was higher, without statistical significance, for those with preoperative tumors <30 mL. Partial or subtotal tumor removal did not yield better local control rates than for patients who underwent biopsy only as the latest surgery.

CONCLUSION

Proton beam therapy is effective for patients with skull base chordoma, especially for those with small tumors. For a patient with a tumor of <30 mL with no prior treatment, biopsy without tumor removal seems to be appropriate before proton beam therapy.

Medical aspects of the national centre for oncological hadrontherapy (CNAO — Centro nazionale adroterapla oncologica) in Italy

More than 20 hadrontherapy centres are active in the world and about 40,000 patients have been treated, almost 4000 with ions. Physical selectivity and high relative biologic efficiency (RBE) represent the rationale for using ions in the treatment of tumours. The clinical results are very promising and justify the construction of new centres. We present the main characteristics of CNAO (Centro Nazionale Adroterapia Oncologica) and its possible integration in a nationwide network. The Italian project started in 1991 thanks to the activity of the TERA Foundation and was financed by the Italian Government in 2002. The CNAO will be built in Pavia to start clinical activity in 2007. The equipment will include a synchrotron and 3 treatment rooms mainly devoted to carbon ions but able to deliver also protons. The Centre should be able to deliver up to 20,000 fractions / year. The realization of CNAO is part of a more ambitious project to set up an integrated national network. The need of hadrontherapy centres is defined by epidemiological studies based on Italian tumour registries showing that almost 900 patients can be electively treated with protontherapy and about 10,000 could be included in clinical trials. Considering that ions could be used for radioresistant tumours that affect about 25,000 new patients/year, we estimate that 10-15%, i.e. 3000-4000 patients would benefit from ion therapy. The realization of a nationwide network possibly linked to a larger European network will be very helpful in making available hadrontherapy for a large part of the population.

Imatinib mesylate in chordoma

BACKGROUND

To the authors' knowledge, no effective medical therapy currently is available for advanced chordoma. Imatinib mesylate is a tyrosine kinase inhibitor targeting platelet-derived growth factor receptor-beta (PDGFRB), BCR-ABL, and KIT.

METHODS

Six patients with advanced chordoma were treated with imatinib mesylate at a dose of 800 mg daily. In all patients, the tumor was found to be positive for PDGFRB, and in four patients PDGFRB was shown to be phosphorylated/expressed.

RESULTS

After a treatment period of > or = 1 year, overt tumor liquefaction was evident on computed tomography (CT) scan in the first patient. In previous months, a decrease in contrast enhancement on magnetic resonance imaging (MRI) and a decrease in glucose uptake on positron emission tomography (PET) were detected. Similar signs on MRI and PET were observed in subsequent patients, who had a shorter treatment period. One of these patients initially was removed from therapy and then was readmitted to therapy because of difficulties with regard to tumor response assessment; 1 month after the reinitiation of therapy, an overt decrease in tumor density was visible on CT scan in this patient. In four of five symptomatic patients, a subjective improvement was observed early in the course of treatment. The first patient died after 17 months, with a sizeable, mostly liquefied mass. Another patient died early, apparently of unrelated causes. The remaining patients were on therapy at the time of last follow-up.

CONCLUSIONS

Imatinib mesylate has been found to have antitumor activity in patients with chordoma. This activity might be mediated by inactivation of PDGFRB. Tumor response manifests through patterns that are similar to those observed in patients with gastrointestinal stromal tumors who respond to molecular-targeted therapy, but evolves more slowly. The benefit to the patient entailed by this pattern of tumor response in chordoma needs to be elucidated, but may be limited in the presence of significant local disease.

Conformal rotation therapy with central axis beam block is a feasible alternative to intensity-modulated radiotherapy for chordomas of the cervical spine

AIMS

Paraspinal tumours, such as chordoma, represent a treatment challenge for oncologists, requiring high dose to the target volume without exceeding the tolerance dose of the spinal cord. Intensity-modulated radiotherapy (IMRT) is helpful in achieving sharp dose gradients and conformation of dose to the target volume. We present a simpler technique--conformal rotation therapy with a central axis beam block (CRT + BB), which can provide similar dose distributions.

MATERIALS AND METHODS

A patient with a cervical chordoma developed postoperative recurrence and was treated with high-dose palliative radiotherapy. Treatment was delivered using CRT + BB, with three fixed beams and three coplanar arcs. A dose of 62 Gy in 31 fractions was delivered to the 100% isodose, giving a maximum spinal cord dose of 49.6 Gy. The patient relapsed 2 years later, and was re-treated using the same technique to a dose of 57 Gy in 30 fractions. Estimates of spinal cord repair rates in primates were used to determine the tolerance dose of the spinal cord for re-treatment. The patient remained well for a further 25 months before developing local recurrence, which was treated with palliative chemotherapy.

RESULTS

Re-treatment plans using CRT + BB and IMRT were compared. Dose-volume histograms show equivalence of dose to the spinal cord, although the IMRT plan delivered a slightly higher dose to tumour and lower dose to surrounding soft tissues.

CONCLUSION

Treatment using CRT + BB requires careful planning and discussion with neurosurgeons before surgery. The normal curvature of the cervical spine must be eliminated if possible, and the patient must be immobilised with the neck horizontal. If these geometric constraints can be satisfied, then CRT + BB can be used as a safe and effective alternative treatment to IMRT for tumours at this site.

Intensity-modulated Stereotactic Radiotherapy of Paraspinal Tumors: A Preliminary Report

OBJECTIVE

Radioresistant paraspinal tumors may benefit from conformal treatment techniques such as intensity-modulated radiotherapy (IMRT). Local tumor control and long-term palliation for both primary and metastatic tumors may be achieved with IMRT while reducing the risk of spinal cord toxicity associated with conventional radiotherapy techniques. In this article, we report our initial clinical experience in treating 16 paraspinal tumors with IMRT in which the planning target volume was 2 mm or greater from the spinal cord.

METHODS

IMRT was administered by using a linear accelerator mounted with a multileaf collimator. Two immobilization body frames developed at Memorial Sloan-Kettering Cancer Center were used for patients with and without spinal implants. During a 30-month period, 16 patients underwent IMRT for metastatic and primary tumors. Eleven patients were treated for symptomatic recurrences after undergoing surgery and prior external beam radiotherapy, and one patient was treated after undergoing radiotherapy for a metastatic pancreatic gastrinoma with overlapping ports to the spine. Four patients with primary tumors were treated after primary resection that resulted in positive histological margins. Twelve patients were symptomatic with pain, functional radiculopathy, or both. Tumoral doses were determined on the basis of the relative radiosensitivity of tumors. Patients with metastatic tumors were administered a median tumoral dose of 20 Gy in four to five fractions and a spinal cord maximum dose of 6.0 Gy in addition to the full tolerance dose administered in previous radiation treatments. The primary tumors were delivered a median dose of 70 Gy in 33 to 37 fractions and a spinal cord maximum dose of 16 Gy. The median tumoral volume was 7.8 cm3.

RESULTS

Of the 15 patients who underwent radiographic follow-up, 13 demonstrated either no interval growth or a reduction in tumor size in a median follow-up period of 12 months (range, 2–23 mo). Two patients, one with a thoracic chondrosarcoma and one with a chordoma, showed tumor progression 1 year after undergoing IMRT. Pain symptoms improved in 11 of 11 patients, and 4 of 4 patients had significant improvement in their functionally significant radiculopathy and/or plexopathy. Pain relief was durable in all patients except the two with tumor progression. No patient showed signs or symptoms of radiation-induced myelopathy, radiculopathy, or plexopathy, including 12 patients with a median follow-up of 18 months.

CONCLUSION

IMRT was effective for treating pain and improving functional radiculopathy in patients with metastatic and primary tumors. Although long-term tumor control is not established in this study, high-dose tumoral irradiation can be performed without causing radiation myelopathy in more than 1 year of follow-up.

Repeat operations in the management of clival chordomas: palliative surgery

Some chordomas have a very poor prognosis because of their aggressive growth nature, but the efficacy of repeat operations for these cases has not been well documented. This report concerns 3 patients with aggressive chordoma of the clivus, who underwent operations 6 to 12 times over a period of 8 to 17 years because of symptomatic regrowth. Overall mean interval between repeat operations was 18 months with a range from 5 to 57 months and survival times were 9 to19 years after the first surgery. Main symptoms before each operation were diplopia and visual disturbance. Repeat palliative operations by intentional extradural debulking of the tumour to decompress offending neural structures, as well as maximal removal of the tumour, using appropriate skull base approaches, can mitigate progressive symptoms, and may result in better quality and some prolongation of life, although our patients gradually deteriorated neurologically throughout the clinical course.

Acute radiation-induced toxicity of heavy ion radiotherapy delivered with intensity modulated pencil beam scanning in patients with base of skull tumors

PURPOSE

The purpose of this paper is to evaluate acute radiation-induced toxicity of carbon ion therapy.

MATERIAL AND METHODS

From December 1997 to November 2000, 37 patients with chordomas and low-grade chondrosarcomas of the skull base have been treated with carbon ions at the heavy ion synchrotron (SIS) at GSI, Darmstadt. Tumor-conformal application of carbon beams was realized by intensity-controlled raster scanning in combination with pulse-to-pulse energy variation. The treatment planning procedure included a biological plan optimization. We applied a cobalt-Gray equivalent dose of 60GyE. Acute toxicity was assessed according to the common toxicity criteria (CTC).

RESULTS

Acute toxicity included skin reactions ( degrees I+ degrees II) in four patients, mucositis ( degrees I- degrees III) in eight patients, otitis and middle ear effusion in four, sinusitis in four, nausea/weight loss in one and edema of the temporal lobes in one patient. In two patients, preexisting neurological symptoms worsened. We did not observe acute morbidity > degrees III of normal tissues.

CONCLUSION

Scanning beam delivery of heavy charged particles is safe and reliable. No unexpected acute dose limiting toxicity was observed. With regard to toxicity, a substantial improvement compared to passive beam shaping technology is achieved.

Surgical seeding of chordomas

OBJECT

Chordomas have a high propensity for local recurrence and progression, as well as for systemic and cerebrospinal fluid metastasis. The authors identified and analyzed a series of patients with chordomas, focusing on an underrecognized pathological entity-surgical seeding of tumor cells.

METHODS

In a retrospective analysis of 82 patients with chordomas treated over a 10-year period (1990-2000), the authors found six patients (7.3%) in whom surgical seeding had occurred. In five (83%) of these patients the primary tumor was located at the clivus. In one (17%), the tumor was present at the cervical spine. There were two male (33%) and four female patients (67%) whose mean age was 34 years. The seeding sites, which were separate from the primary tumor, were located along the operative route or in the abdomen where fat was removed. The seeding was diagnosed 5 to 15 months (mean 12 months) after surgery. One seeding site was present in five patients, and 17 seeding sites were present in one patient. The involved tissues included mucosa, bone, dura, muscle, and fat. After resection, all seedings were confirmed histologically.

CONCLUSIONS

Seeding of chordomas occurs along the operative route and at distant locations where tissue is harvested. Early diagnosis and aggressive surgery are recommended. Based on the results of this study, the authors suggest that surgical techniques, postoperative radiotherapy, neuroradiological follow-up protocol, and even research on chordomas should be reevaluated.

Combination of photon and proton radiation therapy for chordomas and chondrosarcomas of the skull base: the Centre de Protonthérapie D'Orsay experience

PURPOSE

Prospective analysis of local tumor control, survival, and treatment complications in 44 consecutive patients treated with fractionated photon and proton radiation for a chordoma or chondrosarcoma of the skull base.

METHODS AND MATERIALS

Between December 1995 and December 1998, 45 patients with a median age of 55 years (14-85) were treated using a 201-MeV proton beam at the Centre de Protonthérapie d'Orsay, 34 for a chordoma and 11 for a chondrosarcoma. Irradiation combined high-energy photons and protons. Photons represented two-thirds of the total dose and protons one-third. The median total dose delivered within the gross tumor volume was 67 cobalt Gray equivalent (CGE) (range: 60-70).

RESULTS

With a mean follow-up of 30.5 months (range: 2-56), the 3-year local control rates for chordomas and chondrosarcomas were 83.1% and 90%, respectively, and 3-year overall survival rates were 91% and 90%, respectively. Eight patients (18%) failed locally (7 within the clinical tumor volume and 1 unknown). Four patients died of tumor and 2 others of intercurrent disease. In univariate analysis, young age at time of radiotherapy influenced local control positively (p < 0.03), but not in multivariate analysis. Only 2 patients presented Grade 3 or 4 complications.

CONCLUSION

In skull-base chordomas and chondrosarcomas, the combination of photons with a proton boost of one-third the total dose offers an excellent chance of cure at the price of an acceptable toxicity. These results should be confirmed with a longer follow-up.

Skull base chordomas: overview of disease, management options, and outcome

Cranial base chordomas are locally invasive tumors that, from a midline, clival location, extend in different directions and display various patterns of skull base invasion. Although histologically benign, their invasive nature makes true “oncological” resection virtually impossible to achieve in most cases, despite modern skull base surgical techniques. Moreover, because of the tumor's location and proximity to critical neural and vascular structures, surgery-related morbidity can be significant when an aggressive resection is undertaken. Cytoreductive surgery assumes a critical role in the management of these lesions. The choice of surgical approach and the extent of resection are dependent on several factors: location and extension of the tumor, the surgeon's philosophy and familiarity with a specific approach, and the patient's preexisting clinical status. Proton-beam radiotherapy seems to be effective as an adjunct to surgery in achieving local tumor control. The timing of radiation therapy, however, remains controversial. Gamma knife surgery has been proposed as an adjunctive therapy, but the limited experience and short follow-up periods do not permit formulation of meaningful conclusions at this time. Recurrences are common, although in a subset of patients prolonged disease-free survival is demonstrated.

Surgical seeding of chordomas

Object

Chordomas have a high propensity for local recurrence and progression, as well as for systemic and cerebrospinal fluid metastasis. The authors identified and analyzed a series of patients with chordomas, focusing on an underrecognized entity—surgical seeding.

Methods

In a retrospective analysis of 82 patients with chordomas treated over a 10-year period (1990–2000) the authors found six patients (7.3%) in whom surgical seeding had occurred. In five (83%) of these patients the primary tumor was located at the clivus. In one (17%) the tumor was present in the cervical region. There were two male (33%) and four female patients (67%) with a mean age of 34 years. The seeding sites, which were separate from the primary tumor, were located along the operative route or in the abdomen where fat was removed. The seeding was diagnosed 5 to 15 months after surgery (mean 12 months). One seeding site was present in five patients and 17 seeding sites were present in one patient. The involved tissues included mucosa, bone, dura, muscle, and fat. After resection, all seedings were documented histologically.

Conclusions

Seeding of chordomas occurs along the operative route and at distant locations where fat is harvested. Early diagnosis and aggressive surgical treatment are recommended. Based on the results of this study, it is suggested that surgical techniques, postoperative irradiation, the neuroradiological follow-up protocol, and even research on chordomas should be reevaluated.

Stereotactic radiosurgery and hypofractionated stereotactic radiotherapy for residual or recurrent cranial base and cervical chordomas

Object

In patients with chordomas the lesions often recur. Furthermore, the location of some chordomas within the base of the skull and the cervical spine can prevent complete resection from being achieved. Previous series have shown that stereotactic radiosurgery can be used as a treatment for residual chordomas with good overall results. The authors review their experience in using linear accelerator (LINAC) stereotactic radiosurgery to treat patients with recurrent and/or residual cranial base and cervical chordomas.

Methods

Ten patients with chordomas (eight with cranial base and two with cervical lesions [below C-2]) underwent LINAC stereotactic radiosurgery. The mean patient age was 49 years (range 30–73 years). There were seven men and three women. Three patients had undergone one prior surgery, five had undergone two previous surgeries, and two had undergone three prior operations. The mean radiation dose was 19.4 Gy (range 18–24 Gy), and the maximum intratumoral dose averaged 27 Gy (range 24.1–33.1 Gy). The mean secondary collimator size was 14.4 mm (range 7.5–20 mm). The volume of the tumor treated ranged from 1.1 to 21.5 ml. In five patients a standard frame-based LINAC radiosurgery system was used, whereas in the other five the CyberKnife, a frameless image-guided LINAC radiosurgical system, was used. All patients were available for follow-up review, which averaged 4 years (range 1–9 years). Over the course of follow up, one chordoma (10%) was smaller in size, seven were stable, and two chordomas progressed (one in a patient who underwent reoperation and a second course of stereotactic radiosurgery, and the second in a patient who underwent reoperation alone). There were no new neurological deficits noted following radiosurgery in the eight of 10 patients in whom there was no tumor progression, and no patient developed radiation-induced necrosis.

Conclusions

Stereotactic radiosurgery can be used to treat patients with recurrent or residual chordomas with excellent tumor control rates. Longer follow-up review in larger series is warranted to confirm these findings.

Stereotactic fractionated radiotherapy for chordomas and chondrosarcomas of the skull base

PURPOSE

To investigate the treatment outcome of patients suffering from skull base chordoma or chondrosarcoma after fractionated stereotactic radiotherapy.

METHODS AND MATERIALS

We report 45 patients treated for chordoma or chondrosarcoma with postoperative fractionated stereotactic radiotherapy between 1990 and 1997. Patients had CT and MRI for 3D treatment planning performed under stereotactic guidance. Median dose at isocenter was 66.6 Gy for chordomas and 64.9 Gy for chondrosarcomas. MRI imaging was obtained in intervals after therapy to evaluate local relapse. Survival was calculated according to the Kaplan-Meier method.

RESULTS

All chondrosarcomas had achieved and maintained local control and recurrence-free status at follow-up of 5 years. Local control rate of chordomas was 82% at 2 years and 50% at 5 years. Survival was 97% at 2 years and 82% at 5 years. At maximum follow-up of 8 years local control and survival rate of chordomas was 40% (82%). Clinically significant late toxicity developed in one patient.

CONCLUSIONS

Our results demonstrate the feasibility of fractionated photon beam therapy and its success in the treatment of skull base tumors. Modern 3D treatment techniques provide superior results compared to conventional techniques. The role of high-precision radiotherapy compared to particle beam therapy in the treatment of these tumors is not yet fully clear and further research is needed.

Intrasellar chordomas mimicking pituitary adenoma

OBJECT

Whereas chordomas involving the sellar region are uncommon, largely or entirely intrasellar examples are rare. The goal in this study was to present examples of these rare tumors as a guide to their proper diagnosis and treatment.

METHODS

The authors report three cases in which the chordomas filled the pituitary fossa and presented as nonfunctioning pituitary adenomas. All lesions exhibited the typical histological patterns and immunophenotype of chordoma. One tumor, studied ultrastructurally and subjected to DNA analysis, was shown to have a diploid histogram. The authors present a clinicopathological study of these three cases and review the literature on intrasellar chordomas.

CONCLUSIONS

Although these tumors are easily misdiagnosed and therefore may not receive optimal treatment, aggressive surgical resection can yield a favorable prognosis in lesions with a limited extent.

Intrasellar chordomas mimicking pituitary adenoma

Whereas chordomas involving the sellar region are uncommon, largely or entirely intrasellar chordomas are rare. The authors report three cases in which the chordomas filled the pituitary fossa and presented as nonfunctioning pituitary adenomas. All lesions exhibited the typical histological patterns and immunophenotype of chordoma. One tumor, studied ultrastructurally and subjected to DNA analysis, was shown to have a diploid histogram. The authors present a clinicopathological study of these three cases and review the literature on intrasellar chordomas.

Proton radiation therapy for chordomas and chondrosarcomas of the skull base

OBJECT

Local tumor control, patient survival, and treatment failure outcomes were analyzed to assess treatment efficacy in 58 patients in whom fractionated proton radiation therapy (RT) was administered for skull base chordomas and chondrosarcomas.

METHODS

Between March 1992 and January 1998, a total of 58 patients who could be evaluated were treated for skull base tumors, 33 for chordoma and 25 for chondrosarcoma. Following various surgical procedures, residual tumor was detected in 91% of patients; 59% demonstrated brainstem involvement. Target dosages ranged from 64.8 and 79.2 (mean 70.7) Co Gy equivalent. The range of follow up was 7 to 75 months (mean 33 months). In 10 patients (17%) the treatment failed locally, resulting in local control rates of 92% (23 of 25 patients) for chondrosarcomas and 76% (25 of 33 patients) for chordomas. Tumor volume and brainstem involvement influenced control rates. All tumors with volumes of 25 ml or less remained locally controlled, compared with 56% of tumors larger than 25 ml (p = 0.02); 94% of patients without brainstem involvement did not experience recurrence; in patients with brainstem involvement (and dose reduction because of brainstem tolerance constraints) the authors achieved a tumor control rate of 53% (p = 0.04). Three patients died of their disease, and one died of intercurrent disease. Actuarial 5-year survival rates were 100% for patients with chondrosarcoma and 79% for patients with chordoma. Grade 3 and 4 late toxicities were observed in four patients (7%) and were symptomatic in three (5%).

CONCLUSIONS

High-dose proton RT offers excellent chances of lasting tumor control and survival, with acceptable risks. In this series all small- and medium-sized tumors with no demonstrable brainstem involvement have been controlled; all such patients are alive. Surgical debulking enhanced delivery of full tumoricidal doses, but even patients with large tumors and disease abutting crucial normal structures benefited.

Technical advances in radiotherapy of head and neck tumors

Future teletherapy in head and neck sites will include treatment of additional aggressive base-of-skull tumors, acoustic neuromas, and external ear canal tumors. In addition, protocols are being developed to take advantage of the enhanced precision of stereotaxic and conformal teletherapy to deliver concomitant boosts to gross or residual disease after surgery. These field-in-field boosts permit accelerated, hyperfractionated radiotherapy to be delivered to tumor, while maintaing or decreasing dose to surrounding normal tissues. The improved results of aggressive, accelerated fractionation schedules may be realized with acceptable morbidities through the use of more focused irradiation.

Proton therapy for tumors of the skull base

Charged particle beams are ideal for treating skull base and cervical spine tumors: dose can be focused in the target, while achieving significant sparing of the brain, brain stem, cervical cord, and optic nerves and chiasm. For skull base tumors, 10-year local control rates with combined proton-photon therapy are highest for chondrosarcomas, intermediate for male chordomas, and lowest for female chordomas (94%, 65%, and 42%, respectively). For cervical spine tumors, 10-year local control rates are not significantly different for chordomas and chondrosarcomas (54% and 48%, respectively), nor is there any difference in local control between males and females. Observed treatment-related morbidity has been judged acceptable, in view of the major morbidity and mortality which accompany uncontrolled tumor growth.

Management of skull base chordoma

Two management modal-ities appear to be important in treating skull base chordomas: surgery and radiation therapy. Radical resection of lesions of the distal sacrum (S3-S5) and coccyx may be curative, as total removal is often achieved. In contrast, complete resection of chordomas of the base of the skull is rarely successful because of the inability to achieve a true complete surgical resection. On the other hand, treatment of skull base chordomas by radiation therapy alone is often difficult owing to the large size of the lesion and the dose limitation imposed by the sensitivity of the adjacent structures. Local relapse is the predominant type of treatment failure of skull base chordoma. Skull base surgery and radiation therapy have significantly improved over the last 20 years. The following papers review the most significant recent analyses of therapeutic options in treating skull base chordomas. It seems that the combination of aggressive surgery followed by combined proton-photon radiation therapy offers the best chance of long-term local control to patients harboring cranial chordomas.

Stereotactic radiosurgery for chordoma and chondrosarcoma: further experiences

PURPOSE

Skull base chordomas and chondrosarcomas pose management challenges owing to their critical location, locally aggressive nature, and high recurrence rate despite multimodality treatment. We used stereotactic radiosurgery as primary or adjuvant therapy to achieve safe and effective therapeutic irradiation.

METHODS AND MATERIALS

At an average of 4 years (range 1-7), we evaluated 15 patients (nine with chordomas and six with chondrosarcomas) who had gamma-knife radiosurgery as an adjunct (13 patients) or as an alternative to microsurgical resection (two patients). Patient age varied from 7 to 70 years (mean 38). There was a distinct male preponderance (2:1). Thirteen patients had undergone between one and four resections. Using conformal radiosurgical planning, a maximum tumor dose of 24-40 Gy (mean 36) and a tumor margin dose of 12-20 Gy (mean 18) was given to a mean tumor volume of 4.6 ml.

RESULTS

Eight patients showed clinical improvement, three remained stable, and four died. Two of the four patients who died had tumor progression remote from the radiosurgery volume; two patients died of unrelated disorders. Among 11 surviving patients, follow-up imaging showed a reduction in tumor size in five, no further tumor growth in five, and an increase in the size of the tumor in one. The patient with further tumor growth after radiosurgery subsequently underwent repeat resection.

CONCLUSION

Despite the formidable management challenge posed by these neoplasms, our long-term evaluation has shown that radiosurgery is a safe and effective treatment for patients with small volume tumors.

Particle beam therapy (hadrontherapy): basis for interest and clinical experience

The particle or hadron beams deployed in radiotherapy (protons, neutrons and helium, carbon, oxygen and neon ions) have physical and radiobiological characteristics which differ from those of conventional radiotherapy beams (photons) and which offer a number of theoretical advantages over conventional radiotherapy. After briefly describing the properties of hadron beams in comparison to photons, this review discusses the indications for hadrontherapy and analyses accumulated experience on the use of this modality to treat mainly neoplastic lesions, as published by the relatively few hadrontherapy centres operating around the world. The analysis indicates that for selected patients and tumours (particularly uveal melanomas and base of skull/spinal chordomas and chondrosarcomas), hadrontherapy produces greater disease-free survival. The advantages of hadrontherapy are most promisingly realised when used in conjunction with modern patient positioning, radiation delivery and focusing techniques (e.g. on-line imaging, three-dimensional conformal radiotherapy) developed to improve the efficacy of photon therapy. Although the construction and running costs of hadrontherapy units are considerably greater than those of conventional facilities, a comprehensive analysis that considers all the costs, particularly those resulting from the failure of less effective conventional radiotherapy, might indicate that hadrontherapy could be cost effective. In conclusion, the growing interest in this form of treatment seems to be fully justified by the results obtained to date, although more efficacy and dosing studies are required.

Brainstem tolerance to conformal radiotherapy of skull base tumors

PURPOSE

The aim of this study was to analyze the long-term incidence of brainstem toxicity in patients treated for skull base tumors with high dose conformal radiotherapy.

METHODS AND MATERIALS

Between 1974 and 1995, 367 patients with chordomas (n = 195) and chondrosarcomas (n = 172) of the base of skull have been treated with combined megavoltage photon and 160 MeV proton radiotherapy. Following 3D treatment planning with delineation of target volumes and critical nontarget structures dose distributions and dose-volume histograms were calculated. Radiotherapy was given an 1.8 Gy or CGE (=Cobalt Gray Equivalent) dose per fraction, with prescribed target doses ranging from 63 CGE to 79.2 CGE (mean = 67.8 CGE). Doses to the brainstem surface were limited to < or = 64 CGE and to the brainstem center to < or = 53 CGE.

RESULTS

Follow-up time ranged from 6 months to 21.4 years (mean = 42.5 months). Brainstem toxicity was observed in 17 of 367 patients attributable to treatment, resulting in death of three patients. Actuarial rates of 5 and 10-year high-grade toxicity-free survival were 94 and 88%, respectively. Increased risk of brainstem toxicity was significantly associated with maximum dose to brainstem, volume of brainstem receiving > or = 50 CGE, > or = 55 CGE, and > or = 60 CGE, number of surgical procedures, and prevalence of diabetes or high blood pressure. Multivariate analysis identified three independent factors as important prognosticators: number of surgical procedures (p < 0.001), volume of the brainstem receiving 60 CGE (p < 0.001), and prevalence of diabetes (p < 0.01).

CONCLUSIONS

Tolerance of brainstem to fractionated radiotherapy appears to be a steep function of tissue volume included in high dose regions rather than the maximum dose of brainstem alone. In addition, presence of predisposing factors as well as extent of surgical manipulation can significantly lower brainstem tolerance in the individual patient.

Endoscopic transsphenoidal resection of a large chordoma in the posterior fossa

The authors report their encouraging experience using an endoscopic technique for transsphenoidal surgery in a patient with a large chordoma in the posterior fossa. The patient was a 40-year-old man with a 2-year history of progressive ataxia, a memory disorder, and emotional instability. A magnetic resonance (MR) image of the brain revealed a midline posterior fossa mass measuring 4 cm in diameter located between the clivus and the brainstem. The basilar artery and its bifurcation were encased by the tumor, which also distorted the brainstem. The patient had been treated at another hospital for obstructive hydrocephalus with a ventriculoperitoneal shunt and he received fractionated external-beam radiation treatment, although no histological diagnosis was ever made. The authors achieved a subtotal resection of the tumor through the patient's nostril using an endoscopic transsphenoidal technique. The portion of the tumor located behind the basilar artery was not resected to protect the brainstem perforating arteries. The patient showed dramatic improvement of his symptoms postoperatively. Residual tumor located behind the basilar artery was treated by stereotactic gamma knife surgery. This is the first reported case of a large posterior fossa chordoma treated by an endoscopic transsphenoidal technique.