Kristine Wiborg Høgsbjerg, Stine Elleberg Petersen, Else Maae, Louise Wichmann Matthiessen, Mette Møller, Maja Vestmø Maraldo, Marie Benzon Mogensen, Mette Holck Nielsen, Camilla Jensenius Skovhus Kronborg, Birgitte Vrou Offersen
Acute side effects after breast cancer radiotherapy were primarily skin-related, higher but transient after PT compared to γRT. Non-skin-related side effects, including respiratory, fatigue, and arm/shoulder morbidity, were comparable between PT and γRT. These prospective data, using modern techniques and moderate hypofractionation, suggest that PT is a feasible and clinically acceptable treatment approach for adjuvant treatment of invasive breast cancer or DCIS, while acknowledging the higher incidence of transient acute skin toxicity.
PURPOSE: Proton therapy (PT) is associated with favorable dosimetric characteristics compared with photon radiotherapy (γRT) in invasive breast cancer; however, clinical evidence on acute toxicity remains limited. This study aims to compare acute treatment-related side effects between moderately hypofractionated PT and γRT in breast cancer.
MATERIALS AND METHODS: The DBCG PROTON Trial - Acute Side Effects was a preplanned sub-study of the national, phase III randomised trial, the DBCG Proton Trial. Patients with invasive breast cancer or DCIS scheduled for adjuvant radiotherapy, who were expected to receive a high cardiac and/or pulmonary dose based on γRT planning CT, were randomised 1:1 to PT or γRT. Acute side effects were prospectively assessed during radiotherapy and up to 6 months post-treatment. Outcomes included skin -related side effects, respiratory symptoms, dysphagia, fatigue, and arm/shoulder side effects.
RESULTS: A total of 167 patients (186 treated breasts) were included (PT 84, γRT 83). Skin-related side effects peaked at week five, with higher grade 2-3 dermatitis (71% PT vs 20% γRT), pruritus (20% vs 5%), and local pain (17% vs 4%) after PT compared to γRT. All skin-related grade 2-3 side effects were transient, resolving to grade 0-1 within 2-4 weeks. Respiratory symptoms, dysphagia, and fatigue were mild and similar between groups. Clinically relevant arm/shoulder morbidity was rare. No treatment discontinuations due to side effects were observed.
CONCLUSION: Acute side effects after breast cancer radiotherapy were primarily skin-related, higher but transient after PT compared to γRT. Non-skin-related side effects, including respiratory, fatigue, and arm/shoulder morbidity, were comparable between PT and γRT. These prospective data, using modern techniques and moderate hypofractionation, suggest that PT is a feasible and clinically acceptable treatment approach for adjuvant treatment of invasive breast cancer or DCIS, while acknowledging the higher incidence of transient acute skin toxicity.