Can elective nodal irradiation be omitted in stage III non-small-cell lung cancer? Analysis of recurrences in a phase II study of induction chemotherapy and involved-field radiotherapy

Purpose: To establish the recurrence patterns when elective mediastinal irradiation was omitted, patients with Stage III non-small-cell lung cancer were treated with sequential chemotherapy (CHT) and involved-field radiotherapy (RT). Methods and Materials: Fifty patients were treated with either two or four cycles of induction CHT, followed by once-daily involved-field RT to 70 Gy, delivered using three-dimensional treatment planning. The contoured gross tumor volume consisted of the pre-CHT tumor volume and nodes with a short-axis diameter of ≥1 cm. Patients were reevaluated at 3 and 6 months after RT using bronchoscopy and chest CT. Elective nodal failure was defined as recurrence in the regional nodes outside the clinical target volume, in the absence of in-field failure. Results: Of 43 patients who received doses ≥50 Gy, 35% were disease free at last follow-up; in-field recurrences developed in 27% (of whom 16% had exclusively in-field recurrences); 18% had distant metastases exclusively. No elective nodal failure was observed. The median actuarial overall survival was 18 months (95% confidence interval 14-22) and the median progression-free survival was 12 months (95% confidence interval 6-18). Conclusion: Omitting elective mediastinal irradiation did not result in isolated nodal failure. Future studies of concurrent CHT and RT for Stage III non-small-cell lung cancer should use involved-field RT to limit toxicity.