Stromal responses to fractionated radiotherapy

Area of Science:

• Oncology
• Radiotherapy
• Cell Biology

Background:

• Landmark trials support hypofractionation in adjuvant whole-breast radiotherapy.
• Understanding radiotherapy's impact on stromal cell biology is crucial.

Purpose of the Study:

• To investigate the effects of fractionated photon radiotherapy on mammary stroma.
• To determine how fractionation parameters influence the cellular microenvironment.

Main Methods:

• Utilized 3-D collagen matrices, fibroblasts, and TGF-β1 to model mammary stroma.
• Exposed samples to 6 MV X-rays with varying daily fraction sizes (90, 180, 360 cGy).
• Assessed collagen matrix stiffness and fibroblast activation.

Main Results:

• Fibroblast activation and matrix stiffness increased over time, with marked changes upon irradiation and growth factor stimulation.
• Increasing fraction size significantly reduced fibroblast proliferation and activation.
• Larger fraction sizes led to a modest, irreversible increase in matrix stiffness and reduced reactive stroma formation.

Conclusions:

• Increasing fraction size reduces fibroblast activation and modestly increases matrix stiffness in 3-D mammary stroma cultures.
• Further in vitro studies are needed to assess net stromal reactivity to radiotherapy.
• Stromal cell microenvironment is a key factor in optimizing radiotherapy fractionation schedules.