5-year results of accelerated partial breast irradiation (APBI) with SBRT (stereotactic body radiation therapy) and exactrac adaptive gating (Novalis®) for very early breast cancer patients: was it all worth it?

Clin Transl Oncol. 2021 Nov;23(11):2358-2367. doi: 10.1007/s12094-021-02636-3. Epub 2021 May 27.

Abstract

Purpose: To explore the feasibility of image-guided and respiratory-gated Stereotactic Body Radiation Therapy (SBRT) for Accelerated Partial Breast Irradiation (APBI) in patients with very early breast cancer.

Material and methods: Selected patients with early breast carcinoma after breast-conserving surgery were enrolled in this phase II trial. A fiducial marker was percutaneously placed close to surgical bed and five external fiducials were set on the skin. A CT scan for planning was acquired at free breathing. The treatment was planned and DVH were assessed according to international recommendations. Prescription dose was 30 Gy in five consecutive fractions of 6 Gy. A 6MV monoenergetic LINAC (linear accelerator) that combines stereoscopic X-ray imaging system and ExacTrac Adaptive Gating technique was used. PTV (planning target volume) intrafraction motion was controlled and PTV was irradiated in a selected gated area of the respiratory cycle. Shifts for a correct, gated set-up were calculated and automatically applied.

Results: Between April 2013 and October 2015, a total of 23 patients were included. The median tumor size was 12 mm. The mean PTV volume was 114 cc. The mean ipsilateral lung V9 Gy was 2.2% and for left-sided breast cancers, the volume of the heart receiving 1.5 Gy was 11.5%. Maximum skin dose was 30.8 Gy. Acute toxicity was grade1 in all the patients and 100% experienced excellent/good breast cosmesis outcomes. With a median follow-up of 66 months (range 8-99 months) local-relapse-free-survival reaches 100%. One patient developed a second breast cancer outside the treated quadrant after 25.1 months.

Conclusion: APBI with SBRT and ExacTrac Adaptive Gating System was feasible. The acute and late toxicities were almost null and cosmesis was excellent. We also found that the margins of 5 mm applied from CTV to PTV were sufficient to compensate for geometric uncertainties.

Keywords: Breast cancer; Gating; Partial breast irradiation; SBRT.

Publication types

  • Clinical Trial, Phase II

MeSH terms

  • Breast Neoplasms / diagnostic imaging
  • Breast Neoplasms / pathology
  • Breast Neoplasms / radiotherapy*
  • Breast Neoplasms / surgery
  • Carcinoma, Ductal, Breast / diagnostic imaging
  • Carcinoma, Ductal, Breast / pathology
  • Carcinoma, Ductal, Breast / radiotherapy*
  • Carcinoma, Ductal, Breast / surgery
  • Disease-Free Survival
  • Dose Fractionation, Radiation
  • Feasibility Studies
  • Female
  • Fiducial Markers
  • Heart / radiation effects
  • Humans
  • Lung / radiation effects
  • Mastectomy, Segmental
  • Middle Aged
  • Organ Motion
  • Organs at Risk / radiation effects
  • Postoperative Care / methods
  • Prospective Studies
  • Radiosurgery / instrumentation
  • Radiosurgery / methods*
  • Respiration
  • Skin / radiation effects
  • Time Factors
  • Tomography, X-Ray Computed
  • Tumor Burden