Evaluation of Radiotherapy Dose in Secondary Breast Angiosarcoma: Implications for Pathogenesis

Area of Science:

• Oncology
• Radiation Oncology
• Medical Physics

Background:

• Survivors of early-stage breast cancer (BC) face an elevated risk of developing secondary breast angiosarcoma (AS).
• The precise role of radiotherapy (RT) in the development of secondary breast AS remains unclear.
• Breast angiosarcoma is a rare malignancy primarily affecting the superficial breast tissue.

Purpose of the Study:

• To investigate the radiotherapy (RT) dose absorbed by secondary breast angiosarcoma (AS) in a cohort of breast cancer survivors.
• To determine if secondary breast AS develops in areas of reduced RT dosage.

Main Methods:

• A retrospective analysis of patients diagnosed with secondary breast AS between 2008 and 2017 at Helsinki University Hospital was conducted.
• Angiosarcoma (AS) volumes were delineated using treatment planning systems based on patient records, imaging, and pathology.
• Radiotherapy (RT) plans were recalculated to determine the absorbed dose at the skin surface and within the AS volume.

Main Results:

• Ten patients with a history of RT for breast cancer (BC) were diagnosed with secondary breast AS.
• All identified AS cases occurred within the original planning target volume for BC treatment.
• Calculated RT doses at superficial depths (1-2 mm) ranged from 67% to 104% of the prescribed dose.
• The maximum RT dose within the AS volume varied between 86% and 117% of the prescribed dose.

Conclusions:

• The study indicates that secondary breast AS does not develop in regions receiving a significantly lower RT dose than prescribed.
• The findings suggest that the pathogenesis of secondary breast AS is not linked to underdosed areas within the radiotherapy field.