Impact of early tumor reduction on outcome differs by histological subtype in stage III non-small-cell lung cancer treated with definitive radiotherapy.

BACKGROUND: We retrospectively investigated the impact on survival of early tumor reduction during definitive radiotherapy for inoperable stage III non-small cell lung cancer (NSCLC) patients, according to their histological subtypes.
METHODS: Between November 2006 and December 2012, 152 consecutive patients with inoperable stage III NSCLC who underwent definitive radiotherapy were reviewed retrospectively. Forty-one patients were excluded for not satisfying the inclusion criteria. Forty-five (40.5 %) and 48 (43.2 %) patients were diagnosed with squamous cell carcinoma (SQC) and adenocarcinoma (ADC), respectively. The tumor reduction rate (TRR) was defined as follows: TRR = 1-[gross tumor volume (GTV) on computed tomography at shrinking irradiation field planning]/(GTV on computed tomography at the initial treatment planning). The Cox proportional hazard model was used to identify significant prognostic factors for overall survival (OS) and progression-free survival (PFS).
RESULTS: We evaluated 111 patients, with a median follow-up time of 52.2 months in surviving patients. The median TRR was 45.9 %. In all patients, there were significant associations between TRR and PFS (P = 0.036) on multivariate analysis, although TRR had no correlation with OS (P = 0.141). With respect to histological subtype, multivariate analyses revealed that a higher TRR showed significant associations with better OS and PFS in the SQC group (P = 0.013 and 0.040, respectively). In contrast, a higher TRR was associated with poorer OS in the ADC group (P = 0.030); there was no association between TRR and PFS.
CONCLUSION: We found that a higher TRR is a promising prognostic factor for better survival and disease control in SQC patients.