ESTRO 36 Abstract Book

S173 ESTRO 36 2017 _______________________________________________________________________________________________

time to complete chemoradiation (CRT), and were more likely to receive standard fractionation vs BID or concomitant boost (see table). With a median follow-up of 35.7 months, PBC improved 3yr locoregional control (LRC) [91.6 vs 69.1%], distant metastasis-free survival (DMFS) [88.9 vs 71.6%], and cause-specific survival (CSS) [94.1 vs 80.0%] compared to C225 [all p<0.001— see A-C on figure]. Median time to distant failure (DF) was shorter for the C225 group (7.1 vs 17.2 months, p=0.006). On MVA the use of C225 increased the risk of locoregional failure (LRF) [HR 4.099, 95%CI 1.949-8.621, p<0.001], DF [HR 3.438, 95%CI 1.684-7.016, p=0.001], and cause-specific mortality (CSM) [HR 4.076, 95%CI 1.894-8.771, p<0.001]. On subgroup analysis the use of carboplatin trended toward decreased DF (p=0.100) compared to C225, although the rates of LRF were similar. When including only the C225 patients, UVA showed a strong trend toward increased LRF associated with ≥T3 tumors [p=0.066] and standard fractionation [p=0.100 — see D on figure 1]; additionally, advanced nodal stage (≥N2b-N3) predicted for increased DF [p=0.029] and CSM [p=0.035]. On MVA of this subgroup, standard fractionation [HR 2.994, p=0.09] and ≥T3 tumors [HR 2.633, p=0.056] continued to trend strongly in predicting for LRF as did advanced nodal stage for DF [HR 5.917, p=0.064] and CSM [HR 6.586, p=0.077].

Conclusion Our findings strongly favor use of cisplatin in CRT treatment of locally advanced p16+ OPC. Until results of randomized trials evaluating cisplatin versus cetuximab are available, off-trial use of C225 in this population as an effort to reduce morbidity should be discouraged, especially in patients with advanced tumor and nodal stage disease. In cases where cisplatin is contraindicated, the use of carboplatin as an alternative option may reduce DF compared to C225. When C225 is used, altered fractionation radiotherapy may be beneficial for LRC. OC-0332 Impact of HPV on effect of chemotherapy in SCCHN : results of the GORTEC 2007-01 randomized trial X. Sun 1 , Y. Tao 2 , A. Auperin 3 , C. Sire 4 , L. Martin 5 , C. Khoury 6 , P. Maingon 7 , E. Bardet 8 , M. Lapeyre 9 , Y. Pointreau 10 , N. Ollivier 3 , A. Cornely 2 , O. Casiraghi 11 , J. Bourhis 12 1 CHRU- Besançon and Hôpital du Nord Franche Comté-, radiotherapy, Montbéliard, France 2 Institut Gustave Roussy, Radiation Oncology, Villejuif, France 3 Institut Gustave Roussy, Biostatistics, Villejuif, France 4 CH de Bretagne Sud, radiotherapy, Lorient, France 5 Centre Le Conquerant, radiotherapy, Le Havre, France 6 Centre Saint Louis, radiotherapy, Toulon, France 7 Centre GF Leclerc, radiotherapy, Dijon, France 8 Centre Gauducheau, radiotherapy, Nantes, France 9 Centre Perrin, radiotherapy, Clermont, France 10 Jean Bernard centre - Victor Hugo clinic, radiotherapy, Le Mans, France 11 Institut Gustave Roussy, Pathology, Villejuif, France 12 CHUV, radiation oncology, Lausanne, Switzerland Purpose or Objective Chemo-radiotherapy (CT/RT) and cetuximab-RT (cetux- RT) were established as standard treatments in non- operated locally advanced (LA) SCCHN. The GORTEC 2007- 01 randomized trial was restricted to patients (pts) with no or limited nodal spread (N0-N2a and non palpable N2b). The results showed that the addition of concomitant CT with cetux-RT backbone markedly improved both PFS and LRC ( Bourhis et al ASCO 2016 ) with no significant benefit on overall survival. The impact of p16 expression on the treatment effect of these patients was not available at the time of the first presentation. Material and Methods The 1:1 randomization between cetux-RT (arm A) and cetux-CT/RT (arm B) was done by minimization on centers, N and T stages. Cetuximab was given as a loading dose of 400 mg/m2 followed by weekly 250 mg/m2 during