Incidental irradiation of the regional lymph nodes during deep inspiration breath-hold radiation therapy in left-sided breast cancer patients: a dosimetric analysis

Abstract

Background Radiotherapy using the deep inspiration breath-hold (DIBH) technique compared with free breathing (FB) can achieve substantial reduction of heart and lung doses in left-sided breast cancer cases. The anatomical organ movement in deep inspiration also cause unintended exposure of locoregional lymph nodes to the irradiation field. Methods From 2017–2020, 148 patients with left-sided breast cancer underwent breast conserving surgery (BCS) or mastectomy (ME) with axillary lymph node staging, followed by adjuvant irradiation in DIBH technique. Neoadjuvant or adjuvant systemic therapy was administered depending on hormone receptor and HER2-status. CT scans in FB and DIBH position with individual coaching and determination of the breathing amplitude during the radiation planning CT were performed for all patients. Intrafractional 3D position monitoring of the patient surface in deep inspiration and gating was performed using Sentinel and Catalyst HD 3D surface scanning systems (C-RAD, Catalyst, C-RAD AB, Uppsala, Sweden). Three-dimensional treatment planning was performed using standard tangential treatment portals (6 or 18 MV). The delineation of ipsilateral locoregional lymph nodes was done on the FB and the DIBH CT-scan according to the RTOG recommendations. Results The mean doses (Dmean) in axillary lymph node (AL) level I, II and III in DIBH were 32.28 Gy (range 2.87–51.7), 20.1 Gy (range 0.44–53.84) and 3.84 Gy (range 0.25–39.23) vs. 34.93 Gy (range 10.52–50.40), 16.40 Gy (range 0.38–52.40) and 3.06 Gy (range 0.21–40.48) in FB (p < 0.0001). Accordingly, in DIBH the Dmean for AL level I were reduced by 7.59%, whereas for AL level II and III increased by 22.56% and 25.49%, respectively. The Dmean for the supraclavicular lymph nodes (SC) in DIBH was 0.82 Gy (range 0.23–4.11), as compared to 0.84 Gy (range 0.22–10.80) with FB (p = 0.002). This results in a mean dose reduction of 2.38% in DIBH. The Dmean for internal mammary lymph nodes (IM) was 12.77 Gy (range 1.45–39.09) in DIBH vs. 11.17 Gy (range 1.34–44.24) in FB (p = 0.005). This yields a mean dose increase of 14.32% in DIBH. Conclusions The DIBH technique may result in changes in the incidental dose exposure of regional lymph node areas.

Does Breast Surgery Type Alter Incidental Axillary Irradiation? A Dosimetric Analysis of the “Sentinel Envahi et Randomisation du Curage” SERC Trial

“…Other data show that the technique has a major impact on the AID. Two studies found deep inspiration breath hold (after either BCS or a mastectomy) to significantly reduce the Dmean dose in the Berg level 1 by around 3 Gy as compared with free-breathing radiotherapy [ 27 , 28 ]. For this reason, it could be suggested that the axillary dose, even if incidental, should be systematically recorded to correlate its relationship with axillary control, especially in the case of ALND omission after positive SLNB, whatever the type of surgery.…”

Optimal fractionation and timing of weekly cone-beam CT in daily surface-guided radiotherapy for breast cancer

“…Radiation therapy (RT) plays an important role in improving the survival rate of patients with breast cancer [ 1 ], and accurate tumour localisation during RT is critical for tumour control and toxicity in healthy tissues [ 2 ]. However, localisation is susceptible to patient setup errors, breast morphological changes, respiration, etc [ 3 ].…”