Purpose: We studied symptomatic radiation pneumonitis (RP) and changes in pulmonary function tests (PFTs) after loco-regional radiotherapy (LRRT) with V20 lung constraints in breast cancer (BC).
Patients and methods: Sixty-four women underwent PFTs before and 5 months after 3D planned LRRT for BC. The incidentally irradiated ipsilateral lung V20 was minimised to <30%. Patients were monitored for symptoms of RP 1, 4 and 7 months after radiotherapy (RT) and data on covariates were collected prospectively. The outcome was compared with previous treatment series.
Results: Pneumonitis was less frequent with the applied constraint, that is, four mild and one moderate case, than in our previous report (p < 0·001). In multivariate analyses, neither dosimetric data nor covariates appeared to influence mean changes in vital capacity [-0·11L, standard error of the mean (SEM) 0·03] or diffusing capacity of the lung for carbon monoxide (DLCO) (-0·20 mmol/kPa/min, SEM 0·01), except for pre-RT chemotherapy, which diminished the change in DLCO 5 months post-RT.
Conclusions: The used constraint and 3D planning lowered the rate of RP and short-term changes in PFTs compared with our previous treatment series. Pre-RT chemotherapy affects DLCO baseline levels. Rates of side effects should be continuously studied when new target definitions or therapies are introduced in LRRT of BC.
Keywords: breast cancer; dose–volume histogram; loco-regional radiotherapy; pulmonary function; radiation pneumonitis; radiotherapy.