DCE-MRI assessment of response to neoadjuvant SABR in early stage breast cancer: Comparisons of single versus three fraction schemes and two different imaging time delays post-SABR

Matthew Mouawad; Heather Biernaski; Muriel Brackstone; Michael Lock; Brian Yaremko; Olga Shmuilovich; Anat Kornecki; Ilanit Ben Nachum; Giulio Muscedere; Kalan Lynn; Frank S Prato; R Terry Thompson; Stewart Gaede; Neil Gelman

doi:10.1016/j.ctro.2019.12.004

DCE-MRI assessment of response to neoadjuvant SABR in early stage breast cancer: Comparisons of single versus three fraction schemes and two different imaging time delays post-SABR

Clin Transl Radiat Oncol. 2019 Dec 25:21:25-31. doi: 10.1016/j.ctro.2019.12.004. eCollection 2020 Mar.

Authors

Matthew Mouawad¹, Heather Biernaski², Muriel Brackstone^{1

2

3

4}, Michael Lock^{3

5}, Brian Yaremko^{3

5}, Olga Shmuilovich^{2

4

6}, Anat Kornecki^{2

4

6}, Ilanit Ben Nachum^{2

4

6}, Giulio Muscedere^{2

4

6}, Kalan Lynn^{2

3

4}, Frank S Prato^{1

2

4

6}, R Terry Thompson^{1

2}, Stewart Gaede^{1

2

3

5}, Neil Gelman^{1

2

6}

Affiliations

¹ Medical Biophysics, Western University, London, Ontario, Canada.
² Lawson Health Research Institute, London, Ontario, Canada.
³ London Health Sciences Centre, London, Ontario, Canada.
⁴ St. Joseph's Health Care, London, Ontario, Canada.
⁵ Department of Oncology, Western University, London, Ontario, Canada.
⁶ Department of Medical Imaging, Western University, London, Ontario, Canada.

Abstract

Purpose: To determine the effect of dose fractionation and time delay post-neoadjuvant stereotactic ablative radiotherapy (SABR) on dynamic contrast-enhanced (DCE)-MRI parameters in early stage breast cancer patients.

Materials and methods: DCE-MRI was acquired in 17 patients pre- and post-SABR. Five patients were imaged 6-7 days post-21 Gy/1fraction (group 1), six 16-19 days post-21 Gy/1fraction (group 2), and six 16-18 days post-30 Gy/3 fractions every other day (group 3). DCE-MRI scans were performed using half the clinical dose of contrast agent. Changes in the surrounding tissue were quantified using a signal-enhancement threshold metric that characterizes changes in signal-enhancement volume (SEV). Tumour response was quantified using K^trans and v_e (Tofts model) pre- and post-SABR. Significance was assessed using a Wilcoxin signed-rank test.

Results: All group 1 and 4/6 group 2 patients' SEV increased post-SABR. All group 3 patients' SEV decreased. The mean K^trans increased for group 1 by 76% (p = 0.043) while group 2 and 3 decreased 15% (p = 0.028) and 34% (p = 0.028), respectively. For v_e, there was no significant change in Group 1 (p = 0.35). Groups 2 showed an increase of 24% (p = 0.043), and Group 3 trended toward an increase (23%, p = 0.08).

Conclusion: Kinetic parameters measured 2.5 weeks post-SABR in both single fraction and three fraction groups were indicative of response but only the single fraction protocol led to enhancement in the surrounding tissue. Our results also suggest that DCE-MRI one-week post-SABR may be too early for response assessment, at least for single fraction SABR, whereas 2.5 weeks appears sufficiently long to minimize confounding acute effects.

Keywords: Breast cancer; DCE-MRI; Response assessment; SABR; Tofts model.