Intra-Operative Electron Boost and Hypofractionated Whole-Breast Irradiation During Breast-conserving Treatment (BCT)

Local Neoplasm Recurrence, Toxicity

Hypofractionated Whole breast irradiation, Hypofractionated Whole breast irradiation long term results, Breast conserving therapy, IORT with electrons in breast cancer, IOERT as anticipated Boost, IOERT and hypofractionated whole breast irradiation

Title: HIOB - Hypofractionated Whole-Breast Irradiation preceded by Intraoperative Radiotherapy with Electrons as anticipated Boost ISIORT- 01 HIOB is defined as hypofractionated WBRT (40,5 Gy in 2,7 Gy per fraction) preceded by an Intraoperative Boost to the tumor bed ( 90 % reference dose of 10 Gy, 11,1 Gy Dmax IOERT). Primary endpoint is the proof of superiority of a new treatment regimen. The HIOB study concept is supposed to test the hypothesis whether such a combined schedule is superior (or iso-effective) towards standard RT in terms of local control and cosmetic outcome. In the vast majority of all publications, annual and 5 year in-breast recurrence rates following BCT showed a clear dependency on patient age within the following boundaries (primary references): Age \> 50: Bartelink (standard): 0,7% (annual) 3,5% (5y) START B (best): 0,4 %(annual) 2,0% (5y) Age 41-50: Bartelink (standard) 1,2% (annual) 6,0% (5y) Whelan (best) 0,72%(annual) 3,6% (5y) Age ≥ 35-40 Bartelink (standard) 2% (annual) 10% (5y) Whelan (best) 0,72% (annual) 3,6% (5y) long these three different age groups, benchmarking will be performed against the best published results following 'Golden Standard'RT, usually defined as conventionally fractionated WBRT with 50 Gy (25 x2) plus external tumor bed boost with 10-16 Gy electrons (5-8x2Gy). Superiority is defined as going below the lower limit of the estimated 5 year local recurrence rate within the respective age group Inferiority is defined as crossing the respective upper limit . Secondary endpoint: Disease free survival Tertiary endpoint: toxicity assessment (acute and late) including long term cosmetic evaluation Study design and statistics: * Prospective multicenter single-armed * Sequential probability ratio test (SPRT) * Separate analysis within three different age groups Estimated Accrual time: strongly dependent on recruitment per year within the respective age group . Due to the statistical estimation of Szenario A and B the study will close after max. Time-period of 10 years in case of A or 6,4 years in case of B.. Principal investigators and study coordinators: UC of Radiotherapy and Radio-Oncology UC of Special Gynecology and Breast Cancer Center Landeskrankenhaus Salzburg, Paracelsus University Clinics

Study population: See Points 4.1 und 4.2 Inclusion/Exclusion criteria of the entire protocol Operation: * Lumpectomy / segmentectomy / tumorectomy with sufficient safety margins (see above). Lymph node assessment must follow a sentinel node concept. * Perioperative antibiotic prophylaxis is mandatory * After IORT, radio-opaque clips have to be fixed at the tumor bed. Histology: R0-Resection is mandatory Chemotherapy: neoadjuvant:allowed adjuvant: allowed. There are no limitations towards special chemotherapeutic schemes and schedules. Radiotherapy: IOERT * IOERT is performed on mobile or fixed linacs * Reference dose: 11 Gy specified as maximum dose, with a minimum target volume dose of 90% encompassing the PTV (i.e. 10 Gy). WBRT * must start within day 36- 56 postoperatively (week 6 - 8 p.o.) in case of adjuvant hormonal treatment (or no further tumor specific medication) * In case of adjuvant chemotherapy, a time - gap between IOERT and WBRT up to 9 months is allowed. * Single reference dose per fraction: 2,7 Gy (ICRU) * Number of fractions: 15, Number of fractions per week: 5 * Total WBRT dose: 40,5 Gy RT of regional lymphatics: exclusion criterion Diagnostics of Local recurrence: * yearly mammographies, * optional breast sonography, MRI * LR has to be histologically confirmed Follow-up screening for detection of metastases (minimum requirements): * Chest X-Ray, optional * abdominal sonography, optional * lab tests incl. tumor markers, optional Assessment of acute toxicity of WBRT according to CTC-toxicity Scoring-systems: Assessment of late toxicity according to LENT-SOMA scoring-systems Assessment of cosmetic outcome according to 5-point- Scoring System (vanLimbergen) starting before WBRT, including photo documentation in standardized positions

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