KEY POINTS
- This single-center retrospective cohort included 811 women receiving postoperative breast radiotherapy. Treatment consisted of 50 Gy in 25 fractions, with an additional 10 Gy in five fractions after breast-conserving surgery.
- Radiation pneumonitis occurred in 49 patients (6.04%): 36 grade 1 and 13 grade 2 events, with no grade 3 or higher toxicity. Most cases developed within three months.
- Mean ipsilateral lung dose was the strongest independent factor associated with pneumonitis (odds ratio, 11.14; 95% confidence interval, 5.49–22.57). Chemotherapy exposure and chest-wall, supraclavicular and internal-mammary irradiation also remained significant.
- A mean lung dose threshold of 12.70 Gy produced an area under the curve of 0.964, with 89.8% sensitivity and 96.5% specificity within the study cohort.
- Patients receiving chest-wall, supraclavicular and internal-mammary irradiation had pneumonitis rates of 22.1%, compared with 1.0% without comprehensive irradiation. However, most detected events were asymptomatic grade 1 changes.
CLINICAL TAKEAWAY
Mean lung dose remains the most actionable planning variable, particularly during comprehensive regional nodal irradiation. However, the proposed 12.70 Gy threshold should not be treated as a universal constraint: only 13 clinically symptomatic events occurred, high-risk patients were excluded, external validation was absent and mean-lung-dose model calibration was poor.