Purpose: To identify groups of patients who might benefit from more aggressive systemic or local treatment, based on failure patterns when unresectable NSCLC was treated by radiation therapy (RT) alone.
Methods: From 4 RTOG trials, 1547 patients treated by RT alone were analyzed for patterns of first failure by RPA class defined by prognostic factors, including KPS, weight loss, nodal stage, pleural effusion, age and radiation therapy dose. All patients had NSCLC AJCC Stage II, IIIA, or IIIB, KPS > 50, with no previous RT or chemotherapy. Progressions in the primary (within irradiated fields), thorax (outside irradiated area, but within thorax), brain and distant metastasis other than brain were compared (2-sided) for each failure category by RPA.
Results: The RPA classes were 4 distinct subgroups that had significantly different median survivals of 12.6, 8.3, 6.3 and 3.3 months for Classes I, II, III and IV, respectively, (all groups, p = 0.0002). There were 583, 667, 249 and 48 patients in Classes I, II, III and IV, respectively. Primary failure was seen in 27%, 25%, 21% and 10% for Classes I, II, III, and IV, respectively (I vs. IV, p = 0.014; II vs. IV, p = 0.022). Distant metastasis, including brain metastasis, occurred at significantly higher rates among Classes I and II (58% and 54%) than in Classes III and IV (42% and 27%). A higher rate (58%) of death without an identifiable site of failure was found in Class IV than in Classes I, II and III (27%, 28% and 36%, respectively).
Conclusions: The data suggest that physiologic compromise from the intrathoracic disease in Class IV patients is sufficient to cause death before specific sites of failure became evident. Clinical investigations using treatments directed at specific sites of failure could lead to improved outcome for Class I, II and, possibly, Class III patients. Inclusion of Class IV patients in clinical trials may obscure outcomes.