D. Van den Weyngaert

Palliative effectiveness of radiation therapy in the treatment of superior vena cava syndrome.

A study was made of 34 patients concerning the palliation effect of radiation therapy in the treatment of superior vena cava syndrome (SVCS). They were seen between 1986-1993, at the Department of Radiotherapy in Middelheim General Hospital, Belgium, Antwerp. All patients had a syndrome of superior vena cava obstruction secondary to malignancy. The histologic diagnosis delivered an equal distribution of small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC). All patients with a SCLC received chemotherapy as initial treatment, but showed no response, relapse or evolution during treatment. Each treatment began with rapid-high dose irradiation, to continue after re-evaluation with rapid high-dose in cases of poor response or with the conventional fractionation of 2 Gy daily in patients showing good relief of symptoms. The initial rapid-high dose schedules depended on the performance status of the patients. Seventy-six percent of the patients with NSCLC showed good relief of their symptoms. It was very unexpected but the majority of NSCLC patients responded more quickly than SCLC patients, within three days after initiating treatment. In SCLC, 94% of the patients responded up until death. The palliation index defined as the ratio of the symptom-free period on the total survival which is 1 in ideal circumstances, was 0.55 in NSCLC and 0.90 in SCLC. In this last group, death was mainly due to disease progression in distant sites.

The value of treatment portal films in radiotherapy for bronchial carcinoma.

In 1985, thoracic irradiation was performed in 74 patients with lung cancer in our centre. For a total of 182 field set-ups, 142 portal films were taken and compared to the simulator radiograph. In 46 cases (33%), the portal films were at variance with the simulator film. Minimal differences, demanding no further correction were seen in four cases (2.9%). There were no errors due to misplacement of a transparent plastic plate on which the field (with central axis and blocks) is outlined. A slight patient malposition was found on eight portal films (5.6%). In 5.6%, the centre of the plastic plate did not match the field centre. Wrong block position was the most common type of error: 26 cases (18.3%). In 18 of these, the marking of treatment field edges and blocks on the plastic plate was incorrect. The tumour was even partially shielded in 16 of these. In the other eight cases, block placement was erroneous at treatment set-up. Even in the presence of careful simulation and field set-up, portal film remains an indispensable step in the quality control of radiotherapy for lung cancer.

Deep cerebral invasion by basal cell carcinoma of the scalp

We report recurrent basal cell carcinoma of the scalp with deep cerebral invasion in an 82-year-old man. Plain films and CT showed extensive, full thickness, skull destruction at the vertex. Gadolinium-enhanced MRI revealed neoplastic invasion of the meninges and left cerebral hemisphere, down to the lateral ventricle. We postulate that tumour extended into the brain along perivascular spaces of transcerebral vessels. This hypothesis is supported by the cleft-like contrast enhancement on MRI.

886 Palliative effectiveness of radiation therapy in the treatment of superior vena cava syndrome

A study was made of 34 patients concerning the palliation effect of radiation therapy in the treatment of superior vena cava syndrome (SVC3). They were seen between 1986–1993, at the department of Radiotherapy in Middelheim General Hospital Antwerp. All patients had a syndrome of superior vena cava obstruction secondary to malignancy. The histologic diagnosis delivered an equal distribution of small cell carcinoma (SCLC) and non-small cell carcinoma (NSCLC). All patients with a small cell carcinoma received chemotherapy as initial treatment, but they didn’t respond, relapsed or became evolutive during treatment. Each treatment was started with rapid-high dose irradiation, to continue after re-evaluation with rapid high-dose in case of a less good response or with the conventional fractionation of 200 cGy daily in patients with a good relief of symptoms. The initial rapid-high dose schedules depended on the performance status of the patients. Seventysix percent of the patients with non-small cell lung carcinoma showed a good relief of their symptoms. It was very unexpected but the major part of NSCLC responded more quickly than SCLC, within 3 days after initiating treatment. In SCLC, 94% of the patients responded and this until death. The palliation index which is defined as the ratio of the symptom free period on the total survival and should be I in ideal circumstances, was 0.60 in case of NSCLC and 0.95 in case of SCLC. In this last group death was mainly due to disease progression in distant sites.

20 The use of alanine in conformal radiotherapy dosimetry

Dosimetry with alerting is based on the relative and non destructive measurement of stable free radicals produced by radiation. Absorbed dose to the detector is measured as the signal intensity of the central line o1 the eleclron paramagnetic resonance (EPR) powder spectrum o1 alanine. The following experiments prove that solid alanine detectors can be used as reliable transfer dosimeters to check complicated treatment setups in tote for radiothearpy. Experiments have been set-up as a blind test in which neigther the details of irradiation (choice of beam ballistic, beam energy, position of the alanine detector in the phantom, the number of isocenters...) nor the dose administered were previously reported to the read out center. The detector volume (4.8mm diameter, 10 mm length) was outlined on the CT images as target volume and checked with the physical volume of the detector. After irradiation the detectors were returned tot read out using the calibration for Co-60. A) stereotactic treatment: two tests were performed using a water filled head phantom immobilized into a Leksell frame. In a first experiment a single isocenter treatment plan with 5 arcs was performed using a 6 MV photon beam with collimator aperture oi 15 mm and 12 mm resulting in a calculated dose to the detector of 32.5Gy alter evalualing the dosevolume histogram; measured dose wets 32.15 Gy. The experiment was repeated using 8 arcs and a collimator aperture of 40 mm resulting in a more homogeneous dose distribution around the detector: the ratio of specifiedto measured dose was 0,995. B) conlormal treatment: again two experiments had been carried out using the Peacock system ® for intensity modulation of the radiation beam (6 MV ) during treatment. In a first experiment one alanine detector was placed into an Alderson head phantom immobilized with a thermoplast mask and irradiated to 20 Gy yielding a ratio between specified and measured dose of 1.01. A second experiment simulaled a brain stem irradiation: one detector was placed at the location of the brain stem and two more bilaterally in the target volume.The measured dose corresponded within 0.5% with the specified dose at the three locations.