Hypofractionated Whole-Breast Irradiation Preceded by Intra-Operative Radiotherapy With Electrons as Anticipated Boost HIOB A New Option in Breast-Conserving Treatment for Operated Breast Cancer Stages I and II

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