Radiation dose escalation is limited by the high incidence of pulmonary and esophageal toxicity, leading to calls for the omission of elective nodal irradiation (ENI) and the willingness to use involved-field irradiation (IFI) in patients with nonsmall cell lung cancer (NSCLC).

A total of 200 eligible patients with inoperable stage III NSCLC were treated with concurrent chemoradiotherapy and randomized into either an IFI or ENI arm. A total of 4 to 6 cycles of cisplatin-based chemotherapy were delivered, and concurrent radiotherapy was started after the second cycle of chemotherapy. Three-dimensional conformal radiotherapy was delivered in once-daily fractions of 1.8 to 2 Gy to 68 to 74 Gy for IFI or 60 to 64 Gy for ENI.

Patients in the IFI arm achieved better overall response rate (90% vs. 79%, P = 0.032) and better 5-years local control rate (51% vs.36%, P = 0.032) than those in the ENI arm. The radiation pneumonitis rate in patients with IFI was lower than in patients with ENI (17% vs. 29%, P = 0.044), and similar trends appeared in the radiation esophagitis, myelosuppression, and radiation pericarditis between 2 study arms, although not significantly. The 1-, 2-, and 5-year survival rates were 60.4%, 25.6%, and 18.3% for the ENI arm and 69.9%, 39.4%, and 25.1% for the IFI arm, respectively. Only the 2-year survival rates were statistically significant (P = 0.048).

IFI arm achieved better overall response and local control than ENI arm, and it allowed a dose of 68 to 74 Gy to be safely administered to patients with inoperable stage III NSCLC. Outcome improvement can be expected by conformal IFI combined with chemotherapy for stage III NSCLC.