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With improved survival outcomes in breast cancer radiation treatment, the need to further minimize side effects is paramount [1,2]. Although radiation treatment plans are carefully designed to spare normal tissue, the accuracy of the treatment is fundamental to ensure that this is achieved for each individual fraction. This treatment accuracy relies on the stability and reproducibility of patient positioning combined with robust setup verification.

Based on the results of the FAST and FAST forward studies the five-fraction schedule was implemented faster due to COVID-19. These hypofractionation schedules require greater awareness of daily variations in treatment accuracy due to the higher dose per fraction [3-10]. According to Fiagan et al. daily online correction of the positioning inaccuracies might be the main explanation of superior results for ultrahypofractionated radiation therapy in 5 fractions with online IGRT compared to conventionally hypofractionated radiation therapy, using an offline NAL protocol [11]. Furthermore, Junker et al. stated that CBCT frequency in adjuvant breast radiotherapy should not be determined solely based on the magnitude of setup errors during the first three treatment fractions [12].

Rooney et al. provided insight into the clinical, cognitive and environmental factors involved that may influence the routine clinical decision in position verification. Recognition of these factors can improve the quality of individual decisions [13]. And Costin et al. aims to identify factors impacting on patient setup analysis. They also tried to evaluate the role of each verification device, board immobilization and position in influencing positioning errors [14].

Further improvements are described by Chen et al., Cherenkov imaging will enable us to improve treatment delivery accuracy in real-time. The latter could provide daily surface guided radiotherapy (SGRT) and real time treatment delivery quality control for clinical setup patients without adding additional radiation image dose [15]. Although SGRT is complementary to IGRT, reporting both interfractional and intrafractional variations, Laaksoma et al. pointed out that daily orthogonal IGRT was advised due to improved isocenter accuracy [16]. And Le Deroff et al. found that imaging dose could be reduced up to a factor 10 with optimized protocols [17]. 

Finally, the ESTRO-ACROP guideline for positioning, immobilisation and set-up verification for loco-regional photon breast cancer irradiation recommends the following concerning the position verification in breast cancer radiation treatment:

•    Daily 2D-2D or 3D online position verification should be used where feasible
•    2D online/offline position verification is appropriate with consideration of limitations
•    Image matching should consider bony anatomy as well as soft tissue displacement/deformation

1.    Ferlay et al. doi.org/10.1002/ijc.29210.
2.    Breast Cancer Trialists doi.org/10.1016/S0140.
3.    Haviland et al. doi.org/10.1016/S1470-2045(13)70386-3.
4.    The START Trialists’ Group. doi.org/10.1016/S0140.
5.    Whelan et al. doi.org/10.1056/NEJMoa0906260.
6.    Meattini et al. doi.org/10.1016/S1470-2045(21)00539-8.
7.    Krug et al. doi.org/10.1007/s00066-020-01744-3.
8.    Coles et al. doi.org/10.1016/j.clon.2020.03.006.
9.    Murray Brunt et al. doi.org/10.1200/JCO.19.02750.
10.  The FAST Trialists group. doi.org/10.1016/j.radonc.2011.06.026.
11.  Fiagan et al. doi.org/10.1016/j.phro.2022.05.003.
12.  Junker et al. doi.org/10.3390/cancers14174164
13.  Rooney et al. doi: 10.1200/OP.21.00622
14.  Costin et al. doi:10.1016/j.critrevonc.2022.103798
15.  Chen et al. doi: 10.1016/j.tipsro.2022.08.011.
16.  Laaksomaa et al. doi: 10.5603/RPOR.a2022.0097.
17.  Le Deroff et al. doi: 10.1016/j.phro.2022.02.004.