gms | German Medical Science

Background: After breast conserving surgery postoperative radiotherapy of the whole breast is standard. Intraoperative radiation is an innovative technique with potential to optimize radiotherapy further with respect to efficacy and quality of life. At present IORT of the breast is used as boost with following percutaneous radiotherapy, as only treatment (partial breast irradiation, PBI) in selected patients (studies) or at contraindications against percutaneous radiotherapy. IORT offers high biological effectiveness at favourable cosmetics and patient comfort. Different IORT systems are applied in which the application of electrons offers advantageous aspects. We report about experiences with the mobile linear accelerator NOVAC 7 under practical, dosimetric and radiation protection points of view.

Patients and method: Over all 125 IORT´s were carried out since 2004. Because of breast cancer first 15 patients were irradiated intraoperatively in cooperation with breast surgeons till now. Before treatment the wound edges were approximated by the surgeon. IORT as boost (8-10 Gy related to 90% isodose) was applicated 12 times followed of percutaneous irradiation (45-50,4 Gy). Only IORT as PBI was carried out with 18-20 Gy due to individual aspects (multi-morbidity,axillary pre-irradiation) 3 times. The specific aspects of this first and till now only NOVAC 7 used in Germany are represented regarding radiation protection according to StrlSchV, dosimetric aspects as well as the quality assurance according to DIN particularly under consideration of the high dose per pulse.

Results: The additional needed time is 30 minutes with short pure irradiation time of approx. 1 minute. NOVAC 7 is a mobile dedicated linac, whose radiating head can be moved electrically by an articulated arm. The radiation tubes (4-10 cm) can be placed directly to the tumor bed in cooperation with the breast surgeon and then the tube is being connected to the radiating head. Different electron energies (3-9 MeV) are available guaranteing a homogeneous dose distribution. After a follow-up of 28 (18-61) weeks we saw no relapse.

Conclusion: The feasibility of radiotherapy with NOVAC 7 is easy. We got profound knowledges of dosimetry, calibration and beam characteristics of this linac. Homogeneous dose distribution, a short pure irradiation time and the defined penetration depth are advisable. Till now the experiences are promising but longer follow-up data of ongoing randomised studies are needed.