2062 - Hypofractionation Improving Loco-Regional Control for Sequential Chemoradiotherapy in Non-Small Cell Lung Cancer. A Multicenter Long Term Experience.

A. A. Jacinto¹, W. Altei², L. D. F. Morato¹, T. F. Simionatto¹, A. A. D. S. Rovina¹, R. Gadia Sr¹, J. O. Dias³, and G. A. Viani⁴; ¹Barretos Cancer Hospital, Barretos, Brazil, ²Radiation Oncology Department - Barretos Cancer Hospital, Barretos, Brazil, ³Molecular Oncology Research Center - Barretos Cancer Hospital, Barretos, Brazil, ⁴Faculdade de Medicina de Ribeirão Preto- Universidade de São Paulo/USP, Barretos, Brazil

Purpose/Objective(s): Non-small cell Lung Cancer (NSCLC) patients are normally diagnosed with advanced-stage disease. Concomitant chemoradiotherapy (cCRT) is the standard of care for these patients and has shown improved locoregional control (LRC) and overall survival (OS). Many patients not candidates for this modality are submitted to sequential radiotherapy (sCRT), and, in this scenario, hypofractionation is one of the attempts to improve LRC and OS by reducing the impact of accelerated repopulation of the tumor during long treatments.

Aim: Compare the standard cCRT versus sCRT (before and after the implementation of the hypofractination focusing on the impact of LRC. Materials/

Methods: In this retrospective study conducted in two institutions, we compared outcomes and prognostic factors of 205 patients submitted to cCRT with conventional fractionation (CONV-C, 70 patients), sCRT with conventional fractionation (CONV-S, 48 patients), and sCRT with hypofractionation (HYPO-S, 87 patients).
Results: Patients were submitted to CONV-C, CONV-S, and HYPO-S. The PS status of the HYPO-S group was significantly poorer than the other groups (p=0.002). The median FU of the entire group was 20 months. OS, PFS, and distant failure were not significantly different amongst the different groups. The LRC was equivalent for CONV-C (59%) and HYPO-S (67%), but it was lower in the CONV-S (36%) group. On univariate analysis, the treatment group (p=0.001), stage group (p=0.007), and T stage (p=0.025) were associated with improvement in LRC. In the multivariate (HYPO-S vs CONV-S, HR=3.566; HYPO-S vs CONV-C, HR=1.540) and PS status (0 and 1 vs 2-4, HR 2.799) were associated with improvement in LRC. There was no difference in OS between treatment groups. Regarding toxicity, the esophagitis rate was not different between the groups and HYPO-S was associated with a lower rate of grade = or > 2 pneumonitis when compared with CONV-C and CONV-S (7%, 10% and 25%, respectively, p=0.001.
Conclusion: Our data demonstrate the equivalence of LRC with HYPO-S when compared with CONV-C for LA_NSCLC and despite negative selection bias for HYPO-S, no difference on OS was found when compared with CONV-C. Additionally, our data confirm the literature about the safety profile and tolerance of hypofractionation in this scenario. Hypofractionation should be considered an option for LA- NSCLC patients non-eligible for concurrent chemoradiation.