Patient reported respiratory symptoms and lung radiation doses 11 years after loco-regional breast cancer radiation therapy in the DBCG RT Nation Study.

Background and purpose: The Danish Patient Association of Late Effects has received numerous inquiries from breast cancer (BC) survivors suspecting that adjuvant radiotherapy (RT) was the reason for respiratory symptoms. This study investigated patient-reported respiratory symptoms after locoregional RT and their association with ipsilateral lung radiation dose. Patient/material and methods: Patient-reported outcomes (PROs) and RT plans from BC patients treated at a single institution over 2008-2016 were collected. PROs included dyspnoea (EORTC QLQ-C30), cough (PRO-CTCAE), smoking and comorbidities. RT dose-volume metrics were registered including ipsilateral mean lung dose (MLD), and volumes receiving 5 Gy (V5) and 20 Gy (V20). Patients were stratified into MLD tertiles ('low', 'intermediate', 'high') and compared. Additionally, responders were dichotomised by dyspnoea and cough scores ('low' vs 'high'), and dose metrics were compared between symptom groups.

Results: Of 1,011 questionnaire distributed, 490 (49%) were completed and analysed. Median age was 65.8 years (interquartile range [IQR] 58.8;73.4), median time from RT to questionnaire was 11.1 years (IQR 8.9;13.2). Overall MLD was 12.9Gy (standard deviation [SD] 2.8). Any degree of dyspnoea was reported by 203 (41%) and any degree cough was reported by 175 (37%). No differences in dyspnoea/cough scores between MLD groups were found. MLD was 13.0Gy (SD 2.7) in the low dyspnoea group and 12.0Gy (SD 3.0) in the high dyspnoea group, (p = 0.04). MLD was 13.0 Gy (SD 2.7) in the low cough group and 12.5Gy (SD 3.1) in the high cough group (p = 0.23). The same pattern was found for V5lung and V20lung.

Interpretation: No associations between lung dose and patient-reported respiratory symptoms were found for node-positive BC patients 11 years after RT.