Results of radiation treatment of cerebellar medulloblastoma

Survival of very young children with medulloblastoma (primitive neuroectodermal tumor of the posterior fossa) treated with craniospinal irradiation

PURPOSE

Very young children with medulloblastoma are considered to have a worse prognosis than older children. As radiotherapy remains an important part of the treatment, the adverse prognosis could be due to inadequate radiation treatment rather than biological factors. We analyzed the published literature to examine the impact of radiotherapy on survival in this group.

METHODS AND MATERIALS

A Medline search was performed and we reviewed studies of treatment of medulloblastoma where radiotherapy was delivered using megavoltage equipment and the minimum follow-up allowed the calculation of 5-year survival rates.

RESULTS

Thirty-nine studies were published between 1979 and 1996 with a treatment including craniospinal irradiation and boost to the posterior fossa. Eleven studies comprising 1366 patients analyzed survival by age at diagnosis. Eight of 11 studies showed a worse 5-year survival for the younger patient group which reached statistical significance in two. There is also a suggestion of a higher proportion of children with metastatic disease at presentation in the very young age group. The usual policy in younger children was to give a lower dose of radiotherapy to the craniospinal axis (CSA) and posterior fossa (PF) with reduction of dose in the range of 15 to 25% compared to standard treatment. As dose reduction to the posterior fossa is associated with worse survival and local recurrence is the predominant site of failure, the major determinant of worse survival in very young children with medulloblastoma may be suboptimal radiotherapy. Protocols including postoperative chemotherapy with delayed, omitted, or only local tumor irradiation do not reach survival rates of protocols with standard radiotherapy, also suggesting a continued importance for irradiation.

CONCLUSION

Very young children with medulloblastoma have a worse prognosis than older children. Inadequate radiation dose and technique to the primary tumor region may be a major contributing factor. Current chemotherapeutic regimes alone are not sufficient to compensate for reduced radiation doses and volumes.

The use of stereotactic radiosurgical boost in the treatment of medulloblastomas

PURPOSE

Starting in 1992, we began using a stereotactic radiosurgical (SRS) boost for the treatment of medulloblastomas. Four patients ranging in age from 7 to 42 years old have since been treated and are the subject of this retrospective study.

METHODS AND MATERIALS

All patients were initially treated with a maximally debulking surgery and external beam radiotherapy, which were then followed by a stereotactic radiosurgical boost using a modified 6 MeV linear accelerator. Radiosurgical boost doses ranged from 4.50 to 10.0 Gy. Target volumes ranged from 1.1 to 8.1 cc. The procedure was well tolerated with minimal acute toxicities.

RESULTS

All four patients are alive without evidence of recurrence (at 8 to 35 months). Acute nausea and vomiting was elicited during the radiosurgical procedure in the first patient treated. We have since begun premedicating patients with antiemetics or treating under general anesthesia. Late complications consisted of panhypopituitarism in one patient, which was thought to be attributable to the previous course of whole-brain radiotherapy. We have not observed any incidence of radionecrosis in this small cohort of patients.

CONCLUSIONS

Our preliminary results with the use of radiosurgery for medulloblastomas are optimistic, and we would like to suggest the inclusion of a radiosurgery boost in future clinical trials for treatment of this disease.

Survival results in adult patients treated for medulloblastoma

The records of all 27 adult patients (age, greater than or equal to 16 years) diagnosed with cerebellar medulloblastoma between 1968 and 1986 were reviewed. Twenty-four patients (89%) were treated with postoperative megavoltage irradiation. Twenty of these patients underwent craniospinal irradiation. Sixteen patients received greater than 5000 cGy to the posterior fossa (range, 2340 to 6600 cGy; median, 5490 cGy). Forty-eight percent of patients also received adjuvant chemotherapy. A 5-year and 10-year actuarial survival rate of 48% was achieved. The use of adjuvant chemotherapy did not improve survival in this series. All relapses occurred within 35 months of diagnosis (median time to relapse, 23.5 months), except one patient who had a recurrence in the posterior fossa at 140 months. The posterior fossa was the most common site of treatment failure and represented 50% of all initial relapses. All survivors had no sequelae, except one in whom leukoencephalopathy developed after craniospinal irradiation and intrathecal methotrexate administration. The survival results obtained in this series compare favorably with other reported modern adult medulloblastoma series.

Medulloblastoma: I. Clinical, diagnostic, and therapeutic overview

Medulloblastoma, the most common embryonal tumor of the central nervous system, affects both children and adults. It poses a significant therapeutic challenge in that age-dependent differences exist, not only in their pathobiology, but in the efficacy of chemotherapy and radiotherapy. This is particularly the case in very young children, whose still developing nervous system exhibits a low tolerance to radiotherapy. We review the epidemiology, clinical presentation, radiologic features, and current therapeutic concepts relative to this unique neoplasm. Efforts are made to highlight clinical controversies.

Clinical presentation, treatment, and outcome of trilateral retinoblastoma

In this report, three new cases of trilateral retinoblastoma are presented. The clinical presentation, treatment, and outcome of the patients are described and compared with those of 32 cases that have been previously reported in the literature. A positive family history was obtained in 68% of the patients. The mean age at diagnosis of bilateral retinoblastoma was 7.2 months. The mean age at diagnosis of trilateral disease was 39.7 months, resulting in a mean latent interval of 32.6 months. The mean time from diagnosis of trilateral retinoblastoma to death was 6.6 months, and all patients died with spinal metastases. The patients who received no therapy survived an average of 1.3 months after the diagnosis of trilateral disease. The patients who received any form of definitive therapy survived 9.7 months. Five patients who had complete or dramatic response to therapy by computed tomography scans had local intracranial tumor present at autopsy. Therefore, more aggressive local therapy may be warranted.

Medulloblastoma--prognostic factors and outcome of treatment: review of the Mayo Clinic experience

From March 1965 through December 1984, 58 patients (35 male and 23 female patients; median age, 17 years) with posterior fossa (PF) medulloblastoma underwent surgical treatment and postoperative radiation therapy at our institution. Radiation fields were the craniospinal axis in 39 patients, PF plus spinal axis in 12, PF in 6, and whole brain in 1. Median radiation doses were 43 Gy (22 to 60 Gy) to the PF and 34 Gy (6.2 to 50 Gy) to the spinal axis. Overall 5- and 10-year survivals were 50% and 33%, respectively; 5- and 10-year relapse-free survivals were 46% and 32%. Treatment failed in 34 patients (59%): in 18 who had irradiation to the craniospinal axis (13 had received 50 Gy or less to the PF) and in 16 who had a radiation field of less than the craniospinal axis. A statistically significant (P less than 0.05) improvement in 10-year survival was associated with the following prognostic variables: PF dose of 50 Gy or more, whole-brain irradiation, and spinal axis irradiation. In comparison with subtotal resection, total resection was correlated with better 10-year relapse-free survival but not overall survival. All five patients with initial treatment failure only in the spine had received a radiation dose of 30 Gy or less to the spinal axis. The 2-year survival after relapse was 46% with salvage chemotherapy or irradiation in 23 patients and 0% in the 11 patients who received no further treatment (P less than 0.01).

Pediatric neuro-oncology: controversies in current therapy

Current Phase III clinical trials for the treatment of malignant central nervous system (CNS) tumors of childhood are reviewed. Combination neurosurgical, radiation treatment and chemotherapy have improved both the quality and duration of life for the affected children. Controversy exists regarding the appropriate adjunctive chemotherapy for newly diagnosed CNS neoplasms but this is being prospectively studied in controlled trials. Major dilemmas persist regarding the management of low-grade gliomas and recurrent CNS neoplasms. Preliminary data on possibly favourable protocols are cited. Future directions for clinical and basic laboratory investigation are also briefly reviewed.

Treatment of CNS tumours with conventional radiotherapy: the importance of dose & volume factors in tumour control & CNS radiation tolerance

Improved localisation of central nervous system (CNS) tumours resulting from newer diagnostic imaging techniques may allow the therapeutic irradiation of smaller volumes than currently practiced with the possibility of less normal tissue injury and/or the use of higher radiation doses. The influence of radiation dose and volume on the control rates for various types of CNS tumour and on the radiation tolerance of CNS tissue is imperfectly understood. Available data on these fundamental issues in the radiation treatment of CNS tumours is reviewed.

Medulloblastoma: staging and treatment outcome

Fifty-two newly diagnosed patients with medulloblastoma were prospectively staged with myelography. Fifty also had at least one CSF cytology study. Twenty-four patients (46%) had evidence of dissemination beyond the posterior fossa at diagnosis. Patients under age 5 years were more likely to have dissemination at diagnosis than older patients (61% vs 38%). The 5-year disease-free survival for 45 patients diagnosed at least 1 year ago and treated with craniospinal irradiation was 62.6%. Overall 5-year survival for this group was 76.7%. Patients without evidence of dissemination at diagnosis had a 5-year disease-free survival of 73.3% compared to 49.1% for patients with M1-3 disease. Eighteen patients relapsed, 16 within 3 years of diagnosis. Eight patients had recurrent tumor in the posterior fossa, eight in the supratentorial compartment, seven in the cord, and five had systemic metastasis. Patients with initial cord involvement were more likely to develop systemic metastasis (4/12) than patients without initial cord involvement (1/33).

Medulloblastoma at the joint center for radiation therapy between 1968 and 1984. The influence of radiation dose on the patterns of failure and survival

In order to assess the efficacy of high-dose irradiation to the posterior fossa and low-dose irradiation to the spinal axis, we reviewed the results of 60 patients with biopsy-proven medulloblastoma treated at the Joint Center for Radiation Therapy (JCRT) between 1968 and 1984. The 5- and 10-year actuarial survival rates for all patients were 68% and 44%, respectively. The median time to recurrence was 19 months. Extent of surgery, age, and radiation dose to the posterior fossa all were of prognostic value. Complete or subtotal gross resection appeared to be a favorable prognostic indicator compared with biopsy only (P less than 0.05), with a 69% versus 40% actuarial survival rate at 5 years, respectively. Infants 2 years of age or less had a diminished 5-year actuarial survival rate of 48% (P less than 0.05) compared with older age groups. The posterior fossa was the predominant site of recurrence and accounted for 78% of all failures. Local control in the posterior fossa was dose dependent. Seventy-nine percent of the tumors that received 5000 cGy or greater were controlled versus only 33% of the tumors that received less than 5000 cGy (P less than 0.02). There were no supratentorial failures, and there was only one isolated spinal cord failure. There were no solitary spinal failures in 24 patients who received a median dose of only 2400 cGy to the spinal axis. We concluded that low-dose irradiation to the spine and whole brain may be indicated with maintenance of a posterior fossa dose of greater than 5000 cGy.

Long-term results of a pilot study of low dose cranial-spinal irradiation for cerebellar medulloblastoma

Between May 1974 and March 1983, 44 children with histologically verified cerebellar medulloblastoma were seen for post-operative cranial-spinal irradiation following attempted total tumor removal. Six patients were excluded from review because they received all or part of their treatment at another institution (3 patients) or did not complete the planned course of irradiation (3 patients). All of the 38 remaining patients were treated by a previously described technique on a 4 MeV Linear Accelerator with 55 Gy delivered to the primary tumor site. Prior to December 1978, 19 consecutive children (Group A) had spinal prophylactic doses of 30-40 Gy and brain prophylactic doses of 40-50 Gy. After the date, 25 Gy was given to the cranial-spinal axis of 19 consecutive children (Group B). This lower dose was arbitrarily selected with the hope of reducing morbidity in treated survivors and achieving the same tumor control. Risk factors that define good and poor prognosis were evaluated for each group, and there were no differences noted. Myelography and CSF cytology were not routinely performed. Follow-up for the 38 patients ranges from 20 months to 124 months. For the low risk patients, survival (12/15 or 80%) was independent of cranial-spinal radiation dose (Group A 6/8, Group B 6/7). For the high risk patients survival was poor (9/23 or 39%), not dependent on cranial-spinal radiation dose (Group A 5/11, Group B 4/12), and associated with failure at the primary site (10/14), often with CSF seeding (8/10). The other 4 failures include 2 who had moved outside the United States (details of failure are unknown), 1 with supratentorial, CSF seeding and distant metastases, and 1 with distant metastasis only. There were no isolated spinal failures. This pilot study shows that the prophylactic radiation dose to the cranial-spinal axis can be decreased to 25 Gy without jeopardizing control rate and survival in patients with medulloblastoma.

Recent developments in pediatric neuro-oncology

Although brain tumors represent the second most common malignancy in childhood, there are only 1200 to 1500 children diagnosed with brain tumors each year in the US. Approximately 50% of these children are treated at university or cancer treatment centers. Thus, therapeutic trials by default rather than design have been restricted to small numbers of patients. Information on histopathologic groupings, incidence of various tumor types according to age, general treatment trends and survival statistics are available from the Surveillance, Epidemiology, and End Results (SEER) registries of the National Cancer Institute. Although survivals in brain tumor cancers are worse than in other forms of childhood cancer, treatment advances in surgery, radiation and chemotherapy have significantly improved survivals in at least one brain tumor of childhood, medulloblastoma. Ironically, this treatment may have significant long-term adverse effects on intellect, endocrine function, and on the development of second malignancies. Prompt recognition of these delayed effects is of clinical importance, as some effects are amenable to treatment and others may be prevented by careful monitoring of drug and radiation administration.

Impact of improved local control on survival

Estimates of the gain in survival, if all local failures were eliminated, indicate that many more patients could be cured provided the efficacy of treatment of the primary and regional disease were substantially improved. The expected gain in survival is assumed to be the gain in local control, less the loss due to distant metastases and intercurrent disease among the new local control subjects. The observed incidence of DM among local failure patients may be higher than among local control patients; this excess in incidence of DM is assumed to result from metastases established secondary to the persistent or recurring tumor. A powerful argument that higher local control rates would result in more cured patients is the high incidence of long-term survivors after salvage surgery for local failures. Examples of higher survival associated with more effective local therapy are presented from the literature for medulloblastoma, ependymoma, carcinoma of the oral cavity-oropharynx, carcinoma of the urinary bladder, carcinoma of the prostate and carcinoma of the rectum. For Stage I-II cancer of the breast, the reduction of an already low local failure rate by combining surgery and radiation has a very small impact. For tumors, such as, early stage breast cancer, where the possible decrease in local failure is small and the loss due to DM is high, a demonstrable gain in survival is not likely. The potential increase in number of survivors among the U.S. cancer population, if the primary-regional disease were regularly treated successfully, indicates large gains for patients with cancer of the uterine cervix, oral cavity-oropharynx, ovary, colo-rectum, non-oat cell cancer of lung, prostate cancer, and bladder cancer. These provide powerful bases for aggressive investigation of new approaches to improvement of local-regional therapies.

Medulloblastomas: a review of modern management with a report on 75 cases

The authors summarize the 8-year experience of a tertiary medical center with 75 cases of medulloblastoma in Saudi Arabia. A discussion of the evolution of modern management of this difficult problem ensues. As 5-year survival statistics approach 80% in some institutions, attention is being focused on the long-term effects of modern therapy and the quality of life led by these children.

Results of radiation treatment of medulloblastoma in adults

From 1961 to 1982, 20 adults (greater than 16 years of age) were treated with radiation therapy following surgery for medulloblastoma. All patients received neuro-axis irradiation. Five patients received adjuvant chemotherapy. A 5- and 10-year survival rate of 78 and 55%, respectively, were achieved. Treatment failures were mainly a result of local recurrences, but also of metastases. One patient died of acute myeloid leukemia. One patient developed paraplegia. The survival rate was better in males (2 deaths out of 14) than in females (5 deaths out of 6). All the survivors are free of deficit or sequelae, except the patient with paraplegia.

The value of surveillance testing in childhood brain tumors

Follow-up procedures in children with brain tumors are designed to confirm tumor response to initial therapy, identify recurrence or progression at the time of potential secondary treatment, and establish the patterns of failure. Serial use of neurologic examinations and computerized tomography scans are outlined for all tumor types. Tumors capable of subarachnoid metastasis (medulloblastoma, ependymomas, pineal/suprasellar germ cell tumors, and pineoblastoma) require periodic assessment of the neuraxis by cerebrospinal fluid (CSF) cytology and myelography to establish the frequency of subclinical meningeal seeding in study settings. Serial analysis of specific biochemical markers for medulloblastoma (CSF polyamines) and germ cell tumors (serum and CSF alpha-fetoprotein and beta-human chorionic gonadotropin) are suggested. Serial evoked potentials in brain stem gliomas are recommended.

The argument for a combined cancer consortium research data base

Epidemiologic data that were obtained through the SEER registry (Surveillance Epidemiology End Results Program) are presented. Survival statistics for five major brain tumor types in childhood are presented for the years 1968 through 1979. Further survival statistics are compared in patients treated in community hospitals versus university hospitals. The lack of uniform reporting, absence of pathologic conformation, and limited number of patients seen throughout the country are emphasized. There is a need for the establishment of a data base composed of the member institutions of the childhood cancer consortiums. This data base would address questions of patterns of failure, benefits of surgical and clinical staging, and the value of a new putative pathologic grading system. Additionally, the opportunity to collect these patients should permit identification of long-term treatment effects. Identification of early morbidity may lead to modification of treatment programs. A data base containing treatment and diagnostic parameters would allow significant cross-correlations and would lead to the design of future studies that are based upon accurate data.

Medulloblastoma. Results of a sequential combined treatment

Actuarial progression-free survival rate at 5 years of a series of 34 patients with medulloblastoma treated by combined surgery, radiotherapy, and chemotherapy was 71%. No relapses were observed in 14 patients followed for more than 5 years. Treatment consisted of a short postoperative course of vincristine (VCR) and intrathecal (IT) methotrexate (MTX) followed by irradiation to the entire cranio spinal axis. Maintenance chemotherapy (CCNU, VCR, and IT MTX) was then continued to encompass 2 years from surgery. Failure occurred in nine patients: four had local recurrence, four dissemination within the central nervous system, and one widespread skeletal metastases. Poor prognostic factors such as presence of malignant cells in the cerebrospinal fluid, non-radical surgery, young age, and radiation doses less than 50 Gy to the tumor bed, did not adversely affect the outcome of patients in this series. Long-term sequelae from the treatment program could be observed in all patients, and in 58% they were severe enough to interfere with normal, active life.

A modified radiotherapy technique in the treatment of medulloblastoma

Craniospinal irradiation is a standard treatment technique in patients who receive surgery for medulloblastoma. In most centers megavoltage photon irradiation is used, resulting in significant irradiation exposure to critical organs. In order to overcome this difficulty, we recently modified the technique applied in our center, by using high energy electrons (20 MeV) for irradiation of the spinal cord. The reliability of this technique was checked by performing dosimetry in a specially constructed wax phantom. Attention was focused upon dose variations at the junction of fields. Furthermore, the influence of vertebrae on the absorbed dose distribution of high energy electrons is presented. This technique seems to be safe and reliable in selected patients (children and teenagers).