EPID-based in vivo dosimetry for stereotactic body radiotherapy of non-small cell lung tumors: Initial clinical experience.

PURPOSE: EPID-based in vivo dosimetry (IVD) has been implemented for stereotactic body radiotherapy treatments of non-small cell lung cancer to check both isocenter dose and the treatment reproducibility comparing EPID portal images. METHODS: 15 patients with lung tumors of small dimensions and treated with volumetric modulated arc therapy were enrolled for this initial experience. IVD tests supplied ratios R between in vivo reconstructed and planned isocenter doses. Moreover a γ-like analysis between daily EPID portal images and a reference one, in terms of percentage of points with γ-value smaller than 1, Pγ<1, and mean γ-values, γmean, using a local 3%-3mm criteria, was adopted to check the treatment reproducibility. Tolerance levels of 5% for R ratio, Pγ<1 higher than 90% and γmean lower than 0.67 were adopted. RESULTS: A total of 160 EPID images, two images for each therapy session, were acquired during the treatment of the 15 patients. The overall mean of the R ratios was equal to 1.005±0.014 (1 SD), with 96.9% of tests within±5%. The 2D image γ-like analysis showed an overall γmean of 0.39±0.12 with 96.1% of tests within the tolerance level, and an average Pγ<1 value equal to 96.4±3.6% with 95.4% of tests with Pγ<1>90%. Paradigmatic discrepancies were observed in three patients: a set-up error and a patient morphological change were identified thanks to CBCT image analysis whereas the third discrepancy was not fully justified. CONCLUSIONS: This procedure can provide improved patient safety as well as a first step to integrate IVD and CBCT dose recalculation.

Linear accelerator and Greitz-Bergstrom's head fixation system in radiosurgery of single cerebral metastases. A report of 86 cases.

Between 1984 and 1991 86 patients with single cerebral metastases underwent linear accelerator radiosurgery using the atraumatic and reproducible Greitz-Bergström head-fixation device. Routine one-month follow-up documented disappearance of the tumour in 16 patients, with resolution of the oedema and ventricular shift. Shrinkage of the metastasis occurred in 51 patients. In 9 patients the tumour remained stable, in 7 there was progression of tumour size. Among the patients showing shrinkage of the tumour or unchanged tumour volume, repeated radiosurgery resulted in disappearance of the metastasis in 5 and further shrinkage in 28. In 14 patients routine stereotactic CT follow-up study led to the detection of a new metastasis, again treated with excellent results. Local recurrence occurred in 2 patients and radiation necrosis in the target area in 5 patients. Radiosurgery thus proves to be an appropriate alternative to surgery. The versatility of our non-invasive and painless method permits CT staging (which we consider essential) without hospitalization of the patient.

Combined radiation and drugs: the effect of intra-arterial chemotherapy followed by radiotherapy in head and neck cancer.

This study was designed to ascertain whether a prior reduction of tumor size by drugs could affect the final outcome of tumors treated with radiation. 142 patients with head and neck cancer (oropharynx, maxillary antrum and intra-oral) were randomized for the study. In 72 cases, irradiation was preceded by a continuous intra-arterial infusion of 3-5 mg/day methotrexate to a total dose of 90-120 mg; the other 70 patients were treated with radiotherapy alone. Chemotherapy, given prior to radiotherapy, caused a shift in the tumor stage (i.e. a reduction in tumor size) in more than one third of the cases. The overall 5-year survival was 43% in the combined treatment group and 25% in the group treated with radiation alone (statistical difference: p less than .05). However, when analysed separately the difference was statistically significant only in oral cavity tumors (5-year survival of 54% in the combined modality group vs. 27% in the control group), although local control rates after both single and combined modalities were not statistically different from those of oropharynx and maxillary antrum tumors. In these last lesions, however, the dissemination of disease was more frequent; therefore, the lack of improvement of cure rate with the combined modality in these cases seems to be related to both the higher tendency of these tumors to disseminate and the low effectiveness of intra-arterial chemotherapy in controlling distant metastases. Mild and transient local and systemic toxicities were observed during chemotherapy infusion, but no radiosensitising effect on normal skin and mucosa was seen during radiotherapy in patients who had received pre-irradiation chemotherapy.