Local dose-effect relations for lung perfusion post stereotactic body radiotherapy

Area of Science:

• Radiation oncology
• Pulmonary imaging
• Medical physics

Background:

• Stereotactic body radiotherapy (SBRT) is an effective treatment for lung cancer.
• Lung perfusion reduction is a potential side effect of SBRT.
• Understanding the dose-effect relationship is crucial for optimizing treatment and minimizing toxicity.

Purpose of the Study:

• To model the local dose-effect relationship for lung perfusion reduction in lung cancer patients treated with SBRT.
• To quantify the impact of radiation dose on lung perfusion.
• To establish a predictive model for lung toxicity.

Main Methods:

• Forty-two lung cancer patients treated with SBRT (3x18 Gy) were included.
• Single-photon emission computed-tomography (SPECT) was used to measure lung perfusion pre-SBRT and at 4 and 15 months post-SBRT.
• The dose-perfusion reduction relationship was modeled using logistic and linear-maximum models.

Main Results:

• The logistic model best described the dose-perfusion reduction relationship at 4 months post-SBRT.
• A maximum perfusion reduction of 42.6% was observed at doses >100 Gy.
• This maximum effect significantly increased to 65.2% at 15 months post-SBRT.

Conclusions:

• A 3-parameter logistic model accurately describes the local dose-effect relationship for SBRT-induced lung perfusion reduction.
• The relationship approaches a plateau at doses >100 Gy, with 90% of maximum reduction occurring at 78 Gy normalized total dose (NTD).
• Lung perfusion reduction continues to increase beyond 4 months post-SBRT, with a notable increase observed at 15 months.