Stereotactic proton beam therapy of skull base meningiomas.

PURPOSE: To review outcomes for patients with skull base meningiomas treated using the stereotactic proton beam at the National Accelerator Center (NAC), Republic of South Africa. METHODS AND MATERIALS: Since 1993, 27 patients with intracranial meningiomas have been treated stereotactically with protons at NAC. Of those, 23 were located on the skull base, were large or had complex shapes, and were treated with radical intent. Both stereotactic radiotherapy (SRT, 16 or more fractions) and hypofractionated stereotactic radiotherapy (HSRT, 3 fractions) were used. Eighteen patients underwent proton HSRT, while 5 patients were treated with SRT. The mean target volume for the HSRT group was 15.6 cm(3) (range 2.6-63 cm(3)). The mean ICRU reference dose was 20.3 cobalt Gray equivalent (CGyE), and the mean minimum planning target dose was 16.3 CGyE. The mean clinical and radiologic follow-up periods were 40 and 31 months respectively. The mean volume in the SRT group was 43.7 cm(3), with ICRU reference doses ranging from 54 CGyE in 27 fractions to 61.6 CGyE in 16 fractions. RESULTS: In the HSRT group, 16/18 (89%) of patients remained clinically stable or improved, while 2/18 (11%) deteriorated. Radiologic control was achieved in 88% of patients, while 2 patients had a marginal failure. Among the 5 SRT patients, 2 were clinically better, and 3 remained stable. All SRT patients achieved radiologic control. Three patients (13%), 2 of them in the HSRT group, suffered permanent neurologic deficits. Analyzing different dose/fractionation schedules, an alpha/beta value of 3.7 Gy for meningiomas is estimated. CONCLUSION: Proton irradiation is effective and safe in controlling large and complex-shaped skull base meningiomas.

The NAC proton treatment planning system.

A three-dimensional proton treatment planning system called PROXELPLAN has been used at the National Accelerator Centre (NAC) since October 1994. This system is entirely based on the VOXELPLAN planning system, developed at the Deutches Krebsforschungszentrum (DKFZ), Heidelberg, Germany. The VOXELPLAN system provides the treatment planning infrastructure while the proton dose distributions are calculated using a software module that was initially developed at the Royal Marsden Hospital, UK. The proton module has been extensively modified and refined. It uses a rayline-tracing algorithm which is suitable for planning current treatments but is not sufficiently dynamic to accommodate the use of compensators. A sophisticated pencil beam algorithm is currently under development.

Status report of the NAC particle therapy programme.

The 200 MeV cyclotron facility at the National Accelerator Centre has been operational since 1987. Between September 1988 and December 1997 a total of 973 patients (26,916 fields) had been treated on the 66 MeV p+Be isocentric neutron therapy system. Patients are currently being treated according to several protocols, including tumors of the head and neck, salivary gland and breast and soft tissue sarcomas, uterine sarcomas and paranasal sinuses. A multiblade post-collimator trimmer has recently being installed. This device provides improved neutron beam shaping capability. Between September 1993 and December 1997 a total of 243 patients (4008 fields) had been treated (mainly intracranial stereotactic irradiations) on the fixed horizontal 200 MeV proton therapy facility. The facility incorporates an innovative automatic patient positioning system. Two new fixed beam lines for proton therapy are presently being designed (horizontal and 30 degrees to the vertical) for an existing unused treatment vault. Spot scanning systems will be developed for both beam lines.

The neutron therapy clinical programme at the National Accelerator Centre (NAC).

A total of 721 patients were treated in the neutron therapy programme at NAC from February 1989-March 1995 with a p(66)/Be isocentric unit. The preliminary results showed: 3-year local control and survival probabilities of 57 and 79% respectively for advanced salivary gland tumours; increased local control for twice-daily neutron therapy for advanced head and neck cancer compared with photon therapy; local control rates of 68 and 83% for locally advanced breast cancer treated with 17 and 19 Gy respectively; complete response rates of 67% for macroscopic residual soft tissue sarcomas and those with irresectable disease of less than 10 cm; complete response rate of 56% for macroscopic residual uterine sarcoma with a median follow up of 38 months; 2-year local control rate and survival of 44 and 38% respectively for advanced squamous carcinoma of the maxillary antrum; complete response rate of 38% for advanced osteosarcomas and chondrosarcomas.

The role of adjuvant treatment in endometrial cancer.

PURPOSE: Divergent opinions exist on the value of adjuvant treatment in endometrial cancer. This paper aims at clarifying the indications for adjuvant radiotherapy by reviewing the literature and presenting own data. METHODS: For endometrial cancer 5-year survival data are analysed with respect to the value of adjuvant radiotherapy and/or chemo-/hormone therapy. RESULTS: Adjuvant radiotherapy in FIGO stage I and II tumors reduces pelvic recurrence rates from 15 to 20% to 1 to 5%. In high risk stage I patients the 5-year survival rate is increased by 30 to 40% using pre-operative high dose endocavitary brachytherapy or postoperative external beam therapy. In stage II disease the 5-year survival rate is increased to 60 to 80% when applying 50 to 60 Gy post surgery. In stage III and IV tumors primary radiotherapy results in 5-year survival rates of 16 to 40%. CONCLUSIONS: In stage I and II endometrial cancer primary treatment consists of surgery followed by radiotherapy in eligible cases. In stage III and IV tumors primary radiotherapy is generally advocated. No properly randomized trials are available to date on the value of adjuvant treatment. There is a great demand for such trials in order to confirm the available data. According to the extent of the disease and the discrimination of certain risk groups these trials should include external beam pelvic irradiation, brachytherapy, para-aortic irradiation as well as systemic chemo-or hormone therapy.