Is there a different dose-effect relation between the primary tumor and involved lymph nodes in locally advanced non-small-cell lung cancer? A hypothesis-generating study

Purpose: It is unknown whether the dose-response relation of the primary tumor in NSCLC is different from that of the involved lymph nodes (LN). As the recurrence rate is much lower in LN, we hypothesized that LN need a lower radiation dose.Material and methods: A retrospective analysis of prospective data was performed on patients with locally advanced NSCLC treated with (chemo)radiotherapy. The impact of EQD(2,T) prescription dose on relapse was analyzed using Cox regression modeling correcting for baseline diameter.Results: From 2006 to 2010, 75 consecutive patients were included, resulting in 142 lymph nodes in the analysis. Any relapse (locoregional/distant) occurred in 58 patients (77%), while involved nodal relapse (INR) was observed in 13% of patients. No dose-response relationship was observed for INR (p=.22). Primary tumor progression was seen in 40% of patients together with a significant dose-response relationship (p=.033). Baseline nodal diameter was not associated with INR (p=.76), while primary tumor diameter was a highly significant predictor for relapse (p=.0031).Conclusions: These results suggest that LN control may be achieved at lower radiation doses than needed for the primary tumor. Prospective dose de-escalation studies on LN are warranted to decrease the incidence of severe esophagitis without compromising local tumor control.