A prospective phase I comparison of toxicity and cosmesis outcomes of single-fraction IORT and hypofractionated radiotherapy with IORT boost in early-stage breast cancer


Radiation therapy is proven to reduce local recurrence in patients with early-stage breast cancer. To reduce toxicity, treatment time, and improve accuracy, intraoperative radiation therapy was used as definitive treatment or as a boost. The study’s objective was to compare the short-term toxicity and cosmesis of single-fraction (SF) IORT and hypofractionated radiotherapy with IORT boost (HfB) given as definitive treatment.

Methods and materials

Between March 2011 and December 2013, 57 patients aged 45e 91 years and 24 patients aged 43e83 years (total n 5 81) with Stage 0eII were treated with SF or HfB (Mobetron, IntraOp Medical, Sunnyvale, CA). For SF treatment, 21 Gy was delivered using 4.5e6 cm applicators with electron energies from 6 to 12 MeV. For HfB, an intraoperative boost of 10 Gy was delivered using 4e7 cm applicators with energies from 4 to 12 MeV followed by whole-breast radiation with 40.5 Gy over 15 fractions. Toxicity was assessed at 2 weeks, 6 months, and 12 months per Radiation Therapy Oncology Group acute skin toxicity criteria and cosmesis.


At 12 months, SF and HfB were well tolerated by all patients with no Grade 3þ toxicity.
At 1 year, Grade-2 toxicity was resolved. Ninety-eight percent of SF patients and ninety percent of
HfB patients had 0e1 grade toxicity. In the SF and HfB groups, 100% of patients had excellent or
good cosmesis at 12-month followup interval. The SF exhibited a more favorable cosmesis with a
higher percentage of excellent scores compared with HfB (80.4% vs. 45%; p 5 0.0033).


After breast conservation surgery, SF or HfB may be an option for patients with early-stage breast cancer compared to conventional external beam radiotherapy.  2017 American Brachytherapy Society.