Correlation of dosimetric factors and radiation pneumonitis for non-small-cell lung cancer patients in a recently completed dose escalation study.

PURPOSE: To determine dosimetric factors for lung, lung subregions, and heart that correlate with radiation pneumonitis (Radiation Therapy Oncology Group Grade 3 or more) in the 78 evaluable patients from a Phase I dose escalation study (1991-2003) of three-dimensional conformal radiation therapy (3D-CRT) of non-small-cell lung cancer.

METHODS AND MATERIALS: There were 10 > or = Grade 3 pneumonitis cases within 6 months after treatment. Dose-volume factors analyzed for univariate correlation with > or = Grade 3 pneumonitis were mean dose (MD), effective uniform dose (d(eff)), normal tissue complication probability (NTCP), parallel model f(dam) and V(D) for 5 < or = D < or = 60 Gy for whole, ipsilateral, contralateral, upper and lower halves of the lungs and heart D05, and mean and maximum doses.

RESULTS: The most significant variables (0.005 < p < 0.006) were ipsilateral lung V(D) for D < 20 Gy. Also significant (p < 0.05) for ipsilateral lung were V(D) for D < 50 Gy, MD, f(dam) and d(eff); for total lung V(D) (D < 50 Gy), MD, f(dam), d(eff) and NTCP; for lower lung V(D) (D < 60 Gy), MD, f(dam) and d(eff). All variables for upper and contralateral lung were insignificant, as were heart variables.

CONCLUSIONS: Previously reported correlations between severe pneumonitis and whole lung V13 and with other dose-volume factors of total lung and lower lung are confirmed. The most significant correlations were for (V05-V13) in ipsilateral lung.