Long-term outcomes with IMRT versus 3D-CRT for locally advanced lung cancer: secondary analysis of a randomized clinical trial

The optimal radiotherapy technique for unresectable locally advanced non-small cell lung cancer (LA NSCLC) is controversial. A secondary analysis of the phase 3 randomized clinical trial NRG Oncology-RTOG 0617 compared long-term outcomes with intensity-modulated radiotherapy (IMRT) or 3-dimensional conformal radiotherapy (3D-CRT), both with concurrent carboplatin/paclitaxel chemotherapy for unresectable LA-NSCLC. In this trial, IMRT had a more than 2-fold reduction in severe pneumonitis and less cardiac exposure than 3D-CRT. The lung volume receiving low-dose radiation (lung V5) did not affect survival or severe adverse events, whereas a heart volume receiving 40 Gy (less than 20%) was independently associated with better survival. The authors conclude that this study supports standard use of IMRT for LA NSCLC; the amount of lung tissue receiving low-dose radiation did not impact long-term outcomes, casting doubt on historical lung V5 constraints.