Purpose: To evaluate the influence of clinical covariates, particularly pre-chemotherapy gross tumor volume (GTV), post-chemotherapy GTV, on overall survival in the treatment of stage III non-small cell lung cancer (NSCLC).
Methods and materials: We retrospectively analyzed 102 patients who were enrolled on three consecutive clinical trials, which employed the treatment paradigm of two cycles of induction chemotherapy followed by thoracic radiation therapy. The pre-chemotherapy GTV, post-chemotherapy GTV, change in GTV, histology, disease stage, performance status, age, race, treatment with concurrent chemoradiotherapy versus radiotherapy alone were evaluated to determine their impact on overall survival. The log10 of the GTV was used to normalize the data and thereby reduce the impact of exceptionally large values.
Results: Both the log10 of the post-chemotherapy GTV and Eastern Cooperative Oncology Group (ECOG) performance status covariates were highly prognostic for overall survival (p = 0.006 and p = 0.008, respectively). Disease stage (at diagnosis) was also significant (p = 0.048). The log10 pre-chemotherapy GTV covariate was borderline significant (p = 0.067). The strongest prognostic model was the two-covariate model, which contained the log10 post-chemotherapy GTV and ECOG performance status covariates, (model chi2 of 18.67, with p = 0.001 for each covariate).
Conclusions: The log10 post-chemotherapy GTV has significant prognostic survival value when the strategy of induction chemotherapy is employed in the treatment on stage III NSCLC. ECOG performance status and stage were also significant prognostic factors for survival.