Accelerated partial breast irradiation with external beam radiotherapy : First results of the German phase 2 trial.
OBJECTIVE
To evaluate the feasibility and efficacy of external beam three-dimensional (3D) conformal accelerated partial breast irradiation (APBI) for selected patients with early breast cancer.


METHODS
Between 2011 and 2016, 72 patients were recruited for this prospective phase 2 trial. Patients were eligible for APBI if they had histologically confirmed breast cancer or pure ductal carcinoma in situ (DCIS), a tumor diameter ≤3 cm, clear resection margins ≥2 mm, no axillary lymph node involvement, no distant metastases, tumor bed clips, and were aged ≥50 years. Patients were excluded if mammography showed a multicentric invasive growth pattern, or if they had residual diffuse microcalcifications postoperatively, an extensive intraductal component, or vessel invasion. Patients received 3D conformal external beam APBI with a total dose of 38 Gy in 10 fractions in 1-2 weeks. The trial had been registered at the German Clinical Trials Register, DRKS-ID: DRKS00004417.


RESULTS
Median follow-up was 25.5 months (range 1-61 months). Local control was maintained in 71 of 72 patients. The 3‑year local recurrence rate was 2.1% (95% confidence interval, CI: 0-6.1%). Early toxicity (grade 1 radiodermatitis) was seen in 34.7% (25/72). Late side effects ≥ grade 3 did not occur. Cosmetic results were rated as excellent/good in 96.7% (59/61).


CONCLUSIONS
APBI with external beam radiotherapy techniques is feasible with low toxicity and, according to the results of the present and other studies, on the way to becoming a standard treatment option for a selected subgroup of patients.
Department of Radiation Oncology, University Hospital Erlangen, Universitätsstraße 27, 91054, Erlangen, Germany. oliver.ott@uk-erlangen.de.
Oliver J
OJ
Ott
Department of Radiation Oncology, University Hospital Erlangen, Universitätsstraße 27, 91054, Erlangen, Germany.
Vratislav
V
Strnad
Department of Radiation Oncology, University Hospital Erlangen, Universitätsstraße 27, 91054, Erlangen, Germany.
Wilhelm
W
Stillkrieg
Dept. of Medical Informatics, Biometry and Epidemiology, University Erlangen-Nuremberg, Erlangen, Germany.
Wolfgang
W
Uter
Dept. of Gynecology, University Hospital Erlangen, Erlangen, Germany.
Matthias W
MW
Beckmann
Department of Radiation Oncology, University Hospital Erlangen, Universitätsstraße 27, 91054, Erlangen, Germany.
Rainer
R
Fietkau
D000368:Aged; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000628:therapy*; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D005858:Germany; D006801:Humans; D008137:Longitudinal Studies; D015412:Mastectomy, Segmental / Q000379:methods*; D008875:Middle Aged; D059351:Organ Sparing Treatments / Q000379:methods; D058958:Organs at Risk / Q000528:radiation effects*; D000069473:Radiation Dose Hypofractionation; D011835:Radiation Protection / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D015996:Survival Rate; D016896:Treatment Outcome
Breast cancer; Breast conserving surgery; Radiotherapy; Survival; Toxicity