The impact of myelography on the treatment results for medulloblastoma

Comparative dosimetric, setup margin, and treatment time analysis between ring gantry and C-Arm linear accelerators for VMAT-based craniospinal irradiation plans

PURPOSE

The purpose of this study is to evaluate the dosimetric and treatment delivery characteristics of volumetric modulated arc therapy technique (VMAT)-based craniospinal axis irradiation (CSI) between ring gantry Halcyon (HAL) and C-arm based Novalis Tx (NTx) linear accelerator. Set-up margin and treatment delivery time for both machines were also taken into account.

MATERIALS AND METHODS

Fifteen patients, 4 females and 11 males treated between March 2019 and February 2022 within the age group 4-56 years simulated in the supine position and were planned for multiple isocentre VMAT technique in ring gantry Halcyon and C-Arm Novalis linear accelerator for 6FFF and 6 MV flatten beam energy. The number of isocenters was the same in both the machines, usually three for adult adolescent age group patients and two for pediatric patients. Total on-couch time and the patient positional shift were captured for each isocenter during each session of treatment. Margins were calculated using Herk's formula of margin = 2.5Σ +0.7σ. Dosimetry, on-couch time, and set-up margin were compared between two competing arms.

RESULTS

Ninety-five percent of PTV coverage (P = 0.333), volume receiving 107% (P = 0.676), total MU (P = 0.818) in both the arms were comparable and statically insignificant. Low-dose spillage such as D20% (P = 0.212) and D50% (P = 0.008) was lesser in HAL comparable to NTx. CI and HI were statically insignificant. Out of 26 organs at risk (OAR), only 3 organs showed a statically significant dose difference. The mean and maximum setup margin in any linear direction was 0.45 and 0.53 cm for HAL and 0.37 and 0.56 cm for NTx and, variation was statistically insignificant (0.23 < P < 0.47). On-couch time was 4.0 ± 5.5 min lesser for HAL and the difference in on-couch time between the two arms was statistically different.

CONCLUSION

Even though the majority of the delivery parameters such as gantry speed, dose rate, beam characteristic (flatten or unflatten), MLC width, and speed between the ring gantry HAL and C-arm NTx linear accelerators were distinctly different, they offered no or minimal difference in the dose distribution and in the setup margin. HAL gives a faster treatment time delivery, which could be crucial for some selective cases such as patients receiving treatment under general anesthesia.

A low gradient junction technique of craniospinal irradiation using volumetric-modulated arc therapy and its advantages over the conventional therapy

A technique using volumetric-modulated arc therapy (VMAT) fields for craniospinal irradiation with low dose gradients at the field junction was tested for its sensitivity to positional inaccuracy. It was compared against the conventional three-dimensional (3D) conformal radiotherapy in terms of dose uniformity at the junction. Treatment plans generated for ten patients who received craniospinal irradiation (35Gy in 21 fractions) by VMAT technique at our centre were included in this study. For these patients, 3D conformal radiotherapy plans were also generated in addition to the VMAT treatment plans. Intentional shifting of the cranial field in the superior and then in the inferior directions was done, creating a gap or overlap between the fields. Consequent changes in dose distributions in these two plans to positional inaccuracies were studied. The 3D conformal radiotherapy plans showed large dose variations at the junction due to positional shifts as compared to the VMAT plans. With a 5mm superior shift of the cranial field isocentre creating a gap between the cranial and spinal fields, the magnitudes of under-dosing were 13.9±3.6Gy and 4.8±2.0Gy for 3D conformal radiotherapy and VMAT respectively. When the cranial field was moved by 5mm inferiorly creating an overlap between the fields, overdose to the effects of 10.3±4.0Gy and 4.9±1.3Gy were observed for the 3D conformal radiotherapy plans and VMAT plans respectively. The VMAT technique is insensitive to longitudinal setup errors (1-3mm) in patients because of the existence of low dose gradients at the junction between fields. This is unlike the 3D conformal radiotherapy plans which have steep dose gradients at the field edges and thus are highly sensitive to setup errors. Such an advantage for VMAT circumvents the need for dose feathering often practiced with the 3D conformal radiotherapy technique and makes the technique simpler to follow.

Current treatment of leptomeningeal metastases: systemic chemotherapy, intrathecal chemotherapy and symptom management

Treatment of leptomeningeal metastases is multifaceted and includes symptomatic therapy, intrathecal and systemic chemotherapy, and radiotherapy. As the majority of patients have widespread incurable systemic tumor, treatment is predominantly palliative; however, some patients with leukemia, lymphoma or breast cancer may have prolonged remissions and the possibility of cure.

Advantage of protons compared to conventional X-ray or IMRT in the treatment of a pediatric patient with medulloblastoma

PURPOSE

To compare treatment plans from standard photon therapy to intensity modulated X-rays (IMRT) and protons for craniospinal axis irradiation and posterior fossa boost in a patient with medulloblastoma.

METHODS

Proton planning was accomplished using an in-house 3D planning system. IMRT plans were developed using the KonRad treatment planning system with 6-MV photons.

RESULTS

Substantial normal-tissue dose sparing was realized with IMRT and proton treatment of the posterior fossa and spinal column. For example, the dose to 90% of the cochlea was reduced from 101.2% of the prescribed posterior fossa boost dose from conventional X-rays to 33.4% and 2.4% from IMRT and protons, respectively. Dose to 50% of the heart volume was reduced from 72.2% for conventional X-rays to 29.5% for IMRT and 0.5% for protons. Long-term toxicity with emphasis on hearing and endocrine and cardiac function should be substantially improved secondary to nontarget tissue sparing achieved with protons.

CONCLUSION

The present study clearly demonstrates the advantage of conformal radiation methods for the treatment of posterior fossa and spinal column in children with medulloblastoma, when compared to conventional X-rays. Of the two conformal treatment methods evaluated, protons were found to be superior to IMRT.

Systemic chemotherapy, intrathecal chemotherapy, and symptom management in the treatment of leptomeningeal metastasis

Metastasis to the leptomeninges occurs in many common cancers, including leukemia; lung, breast, and gastrointestinal cancers; and tumors of the brain. By way of the flow of cerebrospinal fluid, leptomeningeal metastasis spreads throughout the neuraxis. Consequently, therapy for leptomeningeal metastasis must be directed to the entire central nervous system (CNS). Treatment often consists of involved-field radiotherapy, systemic chemotherapy, and intrathecal chemotherapy. However, because meningeal spread occurs most often in advanced disease, treatment is mainly palliative, except in childhood leukemia, where durable remission has been reported. This article outlines the role of systemic and intrathecal chemotherapy in patients with leptomeningeal metastases. Strategies for symptom management in these patients are also described.

Neoplastic meningitis: diagnosis and treatment considerations

Neoplastic meningitis is an increasingly recognized complication of advanced metastatic cancer and, if left undiagnosed or untreated, is characterized by rapid neurologic deterioration and death. Thus, the diagnosis and treatment of neoplastic meningitis present challenges for the clinical oncologist. The diagnosis of neoplastic meningitis is based on clinical signs and symptoms, laboratory analysis of cerebrospinal fluid to determine cell count and cytology, and analysis of neuroimaging studies for evidence of leptomeningeal or cranial nerve enhancement. Once diagnosed, conventional treatment regimens may include radiotherapy combined with systemic or intrathecal chemotherapy, often with the antimetabolites cytarabine and/or methotrexate. However, the prognosis for neoplastic meningitis secondary to an underlying solid tumor or recurrent leukemia is poor with conventional treatment regimens. Therefore, novel agents for intrathecal administration, including DepoCyttrade mark, mafosfamide, and topotecan, or novel therapeutic approaches, including conjugated monoclonal antibodies and immunotoxins or gene therapy, are currently under investigation. Such new agents and therapeutic approaches will facilitate the development of effective treatment strategies and will ultimately improve the outcome for patients with this devastating disease. This article provides an overview of the approaches to the diagnosis, evaluation, and treatment of neoplastic meningitis.

Metastatic medulloblastoma: the experience of the French Cooperative M7 Group

A retrospective analysis was performed to determine the outcome of children with metastatic medulloblastoma given a standardised treatment programme. Of 68 consecutive patients treated in the French M7 protocol for medulloblastoma, 23 presented with metastatic disease. They were uniformly treated with surgery, and the same protocol of chemotherapy and craniospinal radiotherapy. The 7-year relapse-free survival rate is 43% for metastatic patients compared to 68% for patients with localised disease. Survival did not correlate with age, sex, location of metastases, extent of initial surgery and the dose of radiation therapy on the posterior fossa. Survival did correlate with the dose to the cranial field with a threshold dose of 30 Gy. Patients with metastatic disease have a worse prognosis and require more aggressive therapies at initial presentation. The prognostic impact of the different sites of metastatic disease requires further evaluation in cooperative studies.

Radiation therapy of pineal region tumors: 25 new cases and a review of 208 previously reported cases

PURPOSE

Malignant pineal region tumors are rare neoplasms arising in midline structures of the brain. This report analyzes the influence of histology, tumor location, radiation dose, treatment volume, age and cerebrospinal fluid findings on freedom from relapse, freedom from spinal relapse and survival.

METHODS AND MATERIALS

Patient and treatment parameters of 25 cases of pineal region tumors managed at Stanford University are presented, and an additional 208 published cases were reviewed. Univariate and multivariate analysis were performed to delineate parameters predictive of freedom from relapse, freedom from spinal relapse, and survival for all 233 patients.

RESULTS

The 5- and 10-year freedom from relapse for Stanford patients was 63% and 46%, respectively. The 5- and 10-year survival for Stanford patients was 67% and 61%, respectively. The 5- and 10-year freedom from relapse for the total 233 cases was 66% and 61%, respectively. The 5- and 10-year survival for all patients was 74% and 68%, respectively. For the entire group, biopsy confirmed germinoma and non-biopsied tumors had superior freedom from relapse compared to non-germinoma germ cell tumors (p = 0.03, p = 0.005, respectively). Non-biopsied patients had improved survival compared to non-germinoma germ cell tumors (p = 0.004). Pineal parenchymal tumors had worse freedom from relapse compared to non-biopsied patients (p = 0.04). For patients with suprasellar tumors, germinomas were associated with improved freedom from relapse compared to non-germinoma germ cell tumors (p = 0.02). Simultaneous pineal and suprasellar tumors had superior survival compared to solitary tumors of pineal (p = 0.04), suprasellar (p = 0.03), or third ventricle location (p = 0.03). Twenty-two patients (9.4%) developed isolated spinal relapse. Five- and 10-year spinal relapse rates for all patients were 11% and 13%. Survival after spinal relapse was 19%. Pineal parenchymal tumors had lower freedom from spinal relapse compared to non-biopsied patients (p = 0.001). For tumors located in the pineal gland, germinomas and pineal parenchymal tumors had lower freedom from spinal relapse than did non-biopsied patients (p = 0.006, p = 0.004, respectively). Pineal germinomas had lower freedom from spinal relapse than germinomas with suprasellar location (p = 0.04). Univariate and multivariate analysis identified tumor histology as the most significant predictor of freedom from relapse, freedom from spinal relapse and survival.

CONCLUSION

Histologic type had the greatest impact on outcome. Treatment recommendations should be based on assessment of histologic type and extent of disease.

Radiologic determination of the caudal border of the spinal field in cranial spinal irradiation

PURPOSE

The purpose of this paper is to determine the inferior border of the caudal sac which dictates the placement of the lower border of the spinal field in Cranial Spinal Irradiation.

METHODS AND MATERIALS

We have reviewed the pre-treatment craniospinal Magnetic Resonance Imaging studies of 24 evaluable children with seeding central nervous system tumors who were treated at our institution with Cranial Spinal Irradiation since 1988.

RESULTS

The Magnetic Resonance Imaging studies demonstrated significant variation in the terminal location of the caudal sac, ranging from S2 to S4. The most frequent termination was at S2 (12/24). In four patients (4/24), termination was at mid S1 and in eight others (8/24), it was found to be at or below S3. In addition, the presence of spinal metastases may displace the distal limit even further inferiorly.

CONCLUSION

Rather than arbitrarily placing the inferior field edge at S2, we recommend individualizing the required margin for the spinal field which should be determined using sagittal T1-weighted images of the lumbosacral spine. This is particularly important in patients who present with spinal metastases, since tumor may extend the dural sac termination distally.

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).

The treatment and long-term prognosis of children with intracranial tumors: a study of 610 cases, 1950-1981

Six hundred and ten children aged under 16 years with intracranial tumors were referred for radiotherapy between 1950 and 1981: 579 were new cases and 31 had recurrent disease after primary treatment elsewhere. Radiotherapy was completed in 93% of all cases. The actuarial survival rate for all new cases was 53% at 5 years, 46% at 10 years, 40% at 20 years, and 39% at 30 years. The oldest children (10-15 years) had the best survival and the youngest (0-2 years) had the worst survival. Children treated with megavoltage x-ray equipment (1970 to 1981) had a significantly greater survival than those treated with orthovoltage X rays (1950-1969). Overall, a direct correlation was found between survival and maximum radiotherapy dose. Children having a total excision of the tumor prior to radiotherapy showed a greater survival than those treated by a subtotal or partial tumor removal. Children treated by radiotherapy alone had a survival comparable to those treated by sub-total excision and radiotherapy. There is a striking difference in survival expectation depending on initial functional category (I to III). The overall survival rates of 428 children completing treatment for glioma were 49% at 5 years, 43% at 10 years, and 40% at 15 years. The results according to certain specific tumor sites within the cerebral hemispheres are reported. Age is an important prognostic factor in low grade and also high grade astrocytomas, children having longer survivals than adults. Sub-total or partial excision of craniopharyngiomas combined with radical radiotherapy appears to give the best long-term results. Of 73 new cases, the 5-, 10-, and and 15-year survival rates were 92%, 84%, and 79%. Recurrent craniopharyngiomas treated by surgery alone can be salvaged by further conservative surgery and radical radiotherapy. Optic gliomas are slow growing low grade astrocytomas. Survival rates at 5, 10, and 15 years for 20 children with mostly chiasmal lesions were 89%, 89%, and 78%, respectively. In 73 children with brain stem tumors, 17% remained alive for up to 15 years. The risk of CNS seeding from intracranial ependymomas depends on site of origin and grade of malignancy, with 50% incidence occurring in cases with high grade lesions situated in the posterior fossa. Survivals at 5, 10, and 15 years in 51 children were 51%, 40%, and 31%. Adjuvant chemotherapy improves survival.(ABSTRACT TRUNCATED AT 400 WORDS)

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).

Radiation therapy for neoplasms of the brain

The effectiveness and complications of radiation therapy for brain neoplasms are reviewed. While the available data suggest a favorable influence and outcome, randomized studies are needed to further optimize radiation therapy techniques and to integrate new therapeutic modalities.

Medulloblastoma: the Duke University Medical Center experience

We have reviewed the clinical experience in the treatment of medulloblastoma with radiotherapy at Duke University Medical Center. One hundred and twenty-seven patients treated between January 1, 1940 and December 31, 1983 were evaluated. The irradiation technique was reviewed and all irradiation doses were recalculated as minimum tumor doses in Gray (Gy). The mean follow-up was 24.4 years and the median follow-up was 26.5 years. The energy of the treatment machine was known in 102 cases. Sixty patients were treated with orthovoltage equipment and 42 patients were treated with megavoltage equipment. As a gross assessment of the impact of the details of radiotherapy treatment upon outcome, patients were grouped into excellent, good, fair, and poor treatment groups. Patients undergoing cranio-spinal axis (CSA) irradiation and receiving greater than or equal to 52 Gy to the posterior fossa and greater than or equal to 30 Gy to the clinically uninvolved remainder of the CSA were classified as having "excellent" technique. Patients undergoing CSA irradiation and receiving 40 to 52 Gy to the posterior fossa and greater than or equal to 20 Gy to the remainder of the CSA were classified as "good." Patients receiving 20 to 40 Gy to the posterior fossa and greater than or equal to 10 Gy to the spinal axis with or without prophylactic cranial irradiation were designated "fair." Any patient not fulfilling the above minimum criteria was categorized as "poor." The actuarial 5-year survival for the entire population was 33%. The 10-year survival was 21%. In 93 patients for whom records were detailed enough to allow categorization of treatment technique, 5-year actuarial survivals were: Excellent 37% (n = 17), Good 55% (n = 13), Fair 35% (n = 23), Poor 20% (n = 40). A complete surgical resection was not correlated with improved disease-free survival (DFS) in the excellent and good groups, but was correlated with an improved DFS in the fair and poor groups. The posterior fossa accounted for 62% of the failures in the 55 patients completing irradiation where the initial site of failure was known. An examination of patterns of failure in the spinal canal failed to demonstrate a dose response relationship above 10 Gy for spinal canal prophylactic irradiation. No patient developed recurrence beyond their period of risk as defined by "Collins' Law."(ABSTRACT TRUNCATED AT 400 WORDS)

Management of medulloblastoma in children, a multidisciplinary problem

The diagnosis and treatment of the medulloblastoma has made remarkable advances in the 60 years that this tumor has been known. The survival time has increased but the quality of survival leaves much to be desired, according to a survey of the literature and the limited experiences in this study. The psychologic sequelae are particularly striking. This study gives a survey of diagnostic and therapeutic possibilities at this moment and goes further into some problems which are met during this process. A multidisciplinary approach is necessary because of the multitude of problems which are encountered. The problematic factors in the treatment and the course of the disease justify taking the patients into a trial in order to evaluate the different forms of treatment.

Myelography for staging medulloblastoma

Thirty-eight patients with newly diagnosed medulloblastoma were studied with myelography and cerebrospinal fluid (CSF) cytology studies before radiotherapy. Seventeen (45%) patients had evidence of dissemination beyond the posterior fossa. Spinal cord lesions were demonstrated in ten patients (26%). Negative results of CSF cytology studies did not preclude demonstration of cord involvement. Children younger than 5 years were more likely than older patients to have spinal cord involvement at diagnosis. Patients who were truly M-0 did better in terms of absolute survival but not relapse-free survival when compared with patients with dissemination. Myelography and cytology studies are necessary in the evaluation of all newly diagnosed patients with medulloblastoma and may also be indicated for patients with other brain tumors with a known propensity for dissemination.