Session Item

In April 2020, the “Fast Forward” study was published showing the efficacy of an extreme hypofractionated radiotherapy scheme, delivering the total dose of radiation in five sessions.  We present the experience in our department with patients treated with this regimen under routine clinical practice conditions, reporting short-term toxicity and efficacy outcomes.

Descriptive observational study of 160 patients diagnosed with breast cancer. From July 2020 to December 2021, we evaluated the results obtained in all patients that were treated with conservative surgery and posteriorly by breast irradiation alone according to the Fast Forward protocol at a total dose of 26 Gy/in five fractions over one week.
Patients were women with invasive or ductal in situ carcinoma of the breast and were treated by Breast-conserving surgery with sentinel lymph node biopsy (SLNB) or Axillary dissection (ALND). Concurrent endocrine therapy or trastuzumab were administred.
The clinical target volume (CTV) encompassed all palpable breast tissue, excluding the rib cage and pectoralis muscle strain. The planning target volume (PTV) that represents setup error and patient breathing was defined as 5 mm expansion around the CTV, but within the patient's external contour.
Patients received 26 Gy in five fractions of 5.2 Gy using the irradiation techniques previously described. A sequential tumour bed radiotherapy boost (10 Gy in five fractions of 2Gy) over lumpectomy cavity was administrated with patient selection based on the discretion of the treating physician. Regarding the follow-up of the patients, clinical examination and acute toxicity were assessed during the treatment, at the completion of treatment, 4 weeks after treatment and subsequently every 6 months for 1 year, using the Common Terminology Criteria for Adverse Events (version 4.0)

Median of age was 64 years (43-83).  82 patients (51.3 %) have been treated for left, 77 (48.1 %) for right and 1 (0.6 %) for bilateral breast cancer. 66 patients had pT1c (41.3 %), and 71.3 % were ductal infiltrative. Tumours were mainly intermediate grade (41.9 %), hormone-sensitive (81.3 %), with low proliferation index (Ki-67 <20%; 51.9 %), HER2 negative (85 %).
Surgical resection margins were mainly negative (99.4 %). A total of 72,5 % and 23.8 % received hormonotherapy and chemotherapy respectively. A minority of patients received an additional tumour boost following WHBI of  10 Gy in five sessions of 2 Gy over a week. The median of PTV volume was 899 cm3 (110-2509 cm3).  
The early toxicity observed was grade I radio dermatitis in 117 patients (73.1 %). 
With a median of follow up of 15 months (3.9-28.77) only one patient has presented local relapse treated with mastectomy.

Extreme hypofractionated scheme on the breast alone, out of a clinical trial, have shown to be feasible, with very low early toxicity. A greater follow-up is necessary to assess long-term toxicity and efficacy.