A rapid phantom technique for checking blocked vertex fields.

A simple phantom technique for quality assurance in beam arrangements involving a vertex field is described. Clinical personnel can quickly check that blocks for the vertex field have been cut to the proper magnification and that the vertex field is in proper registration with accompanying isocentric transverse fields. Errors can be identified rapidly and corrections made with no inconvenience to the patient.

Outcome for children with medulloblastoma treated with radiation and cisplatin, CCNU, and vincristine chemotherapy.

It has previously been reported in a single-institution trial that progression-free survival of children with medulloblastoma treated with radiotherapy and 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), cisplatin, and vincristine chemotherapy during and after radiotherapy was better than the outcome in children treated with radiotherapy alone. To better characterize long-term outcome and duration of disease control, this treatment approach was used for 10 years and expanded to three institutions. Sixty-three children with posterior fossa medulloblastomas were treated with craniospinal local-boost radiotherapy and adjuvant chemotherapy with vincristine weekly during radiotherapy followed by eight 6-week cycles of cisplatin, CCNU, and vincristine. To be eligible for study entry, patients had to be older than 18 months of age at diagnosis and have a subtotal resection, evidence of metastatic disease, and/or brainstem involvement. Patients younger than 5 years of age and without these poor risk factors who received reduced-dose craniospinal radiotherapy (2400 cGy) were also eligible for entry into the study. Sixty-three of 66 eligible patients (95%) were entered and placed on this treatment regimen. Forty-two patients had brainstem involvement, 15 had metastatic disease at the time of diagnosis, and 19 had received a subtotal resection. Progression-free survival for the entire group at 5 years is 85% +/- 6%. Three children have succumbed to a second malignancy, and overall 5-year event-free survival is 83% +/- 6%. Progression-free survival was not adversely affected by younger age at diagnosis, brainstem involvement, or subtotal resection. Five-year actuarial progression-free survival for patients who received reduced-dose radiotherapy was similar to that for patients receiving conventional-dose radiotherapy. Patients with metastatic disease at the time of diagnosis had a 5-year progression-free survival rate of 67% +/- 15%, as compared to 90% +/- 6% for those patients with localized disease at the time of diagnosis (p = 0.037). The authors conclude that overall progression-free survival remains excellent for children with posterior fossa medulloblastomas treated with this drug regimen. Chemotherapy has a definite role in the management of children with medulloblastoma. Further studies are indicated to define which subpopulations of children with medulloblastoma benefit from chemotherapy and what regimens are optimum in increasing disease control and, possibly, in reducing the amount of radiotherapy required.

Failure of hyperfractionated radiotherapy to reduce bone growth arrest in rats.

PURPOSE: Radiotherapy of the craniospinal axis is causing an age dependent growth arrest in children. The purpose of this paper was to examine in an animal model, whether hyperfractionated radiotherapy, given with twice daily fractions in conventional overall treatment time, would cause less growth arrest of the spinal column than a regular treatment schedule. METHODS AND MATERIALS: The time-dose-fraction schedule for the treatment of the craniospinal axis of children with medulloblastomas was used as model for the treatment of the spine in rats. The entire spine of weanling rats received either 3570 cGy in 21 daily fractions of the 170 cGy, 5 times per week over 27 days, or 3630 cGy in 33 fractions of 110 cGy, given twice daily with 6-hr intervals over 21 days. RESULTS: Both fraction schedules were isoeffective and caused a growth inhibition of 9.5%. The growth arrest was complete after 1870-2420 cGy. The alpha/beta ratio for the growing rat vertebrae was 3400 cGy. This result contrasts with the growth sparing effect observed with hyperfractionation of accelerated treatment schedules. CONCLUSION: Growing bone is a fast proliferating tissue. Hyperfractionation with 110 cGy BID compared to 170 cGy given once a day, has no sparing effect on bone growth in rats if given in conventional overall treatment time.

Mediastinoscopy incisional metastasis. A radiotherapeutic approach.

Tumor seeding of the mediastinoscopy tract has been described. Although it is a rare occurrence, it can present the radiation oncologist with a therapeutic dilemma. Two cases of mediastinoscopy scar recurrences are reported. Their response to treatment and a review of previous cases are included.

Glioblastoma oncometry.

A prospective study of 20 patients was conducted to determine changes in the computed tomography appearance of glioblastomas seen at the completion of radiation therapy. An interval CT was obtained after 4000 to 4500 cGy to the whole brain and was compared to a similar baseline study. The tumor volume increased in twelve patients by 13 to 878% (mean 126%) and decreased in seven by 13 to 73% (mean 37%). It remained unchanged in one patient. A broadening or thinning of the enhancing rim frequently accompanied the increased or decreased tumor, respectively. Volume change immediately after whole brain radiotherapy was no prognostic indicator. The volume increase seen in 60% of the patients had implications for treatment planning of the boost field. It translated into a potential field size increase of up to 5.6 cm (mean 3.5 cm) and could contribute to a geographic miss. It is concluded that following whole brain radiation therapy, a repeat CT scan or magnetic resonance imaging, depending on the initial exam, is necessary for optimal planning of the reduced radiation field.

Unresectable gliomas in children: tumor-volume response to radiation therapy.

Serial tumor volume measurements were performed on computed tomographic (CT) scans or magnetic resonance (MR) images of 12 children treated with radiation therapy for high-grade (three children) or low-grade (nine children) astrocytomas of the optic nerve, thalamus, hypothalamus, cerebellar-pontine angle, and pons. Three types of initial tumor response were observed: Tumor volume increased in four children, remained unchanged in one, and decreased immediately after completion of radiation therapy in the others. High-grade tumors regressed maximally within 6 months and low-grade tumors within 10-25 months. All high-grade tumors recurred within 12 months. Three low-grade tumors recurred 3, 6 1/2, and 10 years after diagnosis, respectively. The tumor-volume halving time was 60-78 days for high-grade tumors and 108-330 days for low-grade tumors. The tumor doubling time was 48-60 days for high-grade tumors. The posttreatment increase in tumor volume has implications for radiation treatment planning. It did not indicate a poor prognosis.