ESTRO 36 Abstract Book

S174 ESTRO 36 _______________________________________________________________________________________________

OC-0330 Locoregionally Recurrent Head and Neck Squamous Cell Carcinoma S.Y. Wu 1 1 Taipei Medical University Hospital, No.111- Section 3 Department of Radiation Oncology, Taipei, Chinese Taipei Purpose or Objective For locoregionally recurrent head and neck squamous cell carcinoma (HNSCC), appropriate therapeutic decisions and prognostic factors remain unclear. Material and Methods The enrolled 4,839 patients were categorized into four groups: Group 1 comprised those undergoing chemotherapy (CT) alone; Group 2 comprised those receiving reirradiation (re-RT) alone (total radiation dose ≥ 60 Gy through intensity modulation radiation therapy [IMRT]); Group 3 comprised those receiving concurrent chemoradiotherapy (CCRT) alone (irradiation total dose ≥60 Gy through IMRT); and Group 4 comprised those receiving salvage surgery with or without RT or CT. Results Age ≥ 65 years, Charlson comorbidity index (CCI) score > 6, clinical stage III-IV at first diagnosis, and recurrence- free interval < 1 year were significant independent prognostic risk factors for overall survival as per univariate and multivariate Cox regression analyses. After adjusting, adjusted hazard ratios (aHRs; 95% confidence intervals [CIs]) for overall mortality in recurrent clinical stages I and II were 0.63 (0.45–0.89, p = 0.009), 0.65 (0.52–0.83, p < 0.001), and 0.32 (0.26–0.40, p < 0.001) in Groups 2, 3, and 4, respectively, whereas they were 1.23 (0.99–1.52, p = 0.062), 0.69 (0.60–0.79, p < 0.001), and 0.39 (0.34–0.44, p < 0.001) for Groups 2, 3, and 4, respectively, for overall mortality in recurrent clinical stage III and IV. Conclusion Salvage surgery is the recommended first treatment choice for recurrent oral cavity and pharyngeal cancers. Re-RT alone and CCRT are more suitable for inoperable recurrent stage I-II oral and nonoral cavity recurrent HNSCCs, respectively. OC-0331 Cetuximab versus Platinum-based Chemoradiation in Locally Advanced p16 Positive Oropharyngeal Cancer C. Barney 1 , S. Walston 1 , P. Zamora 1 , N. Nolan 1 , V. Diavolitsis 1 , D. Blakaj 1 , J. Wobb 1 , D. Mitchell 1 , J. Grecula 1 , P. Savvides 2 , A. Bhatt 1 1 The Ohio State University, Radiation Oncology, Columbus- Ohio, USA 2 The University of Arizona Cancer Center at Dignity Health St. Joseph's Hospital, Medical Oncology, Phoenix, USA Purpose or Objective Randomized trials evaluating intensity modulated radiation therapy (IMRT) concurrent with platinum-based chemotherapy (PBC) versus cetuximab (C225) in treating oropharyngeal cancer (OPC) are underway but have yet to report preliminary data. Meanwhile, as a would-be step toward morbidity reduction, the off-trial use of C225 in p16+ patients is increasing in frequency, even in those who could potentially tolerate PBC. The purpose of this study was to retrospectively compare the efficacy of PBC versus C225 concurrent with IMRT in the treatment of locally From 2010 to 2014, 219 patients with stage III-IVB p16+ OPC were treated definitively (n=188, 6996-7000 cGy) or postoperatively (n=31, ≥6600 cGy) with IMRT plus concurrent PBC (n=155, Cisplatin-136 and Carboplatin-19) or weekly C225 (n=64). Log-rank/Kaplan-Meier analysis and Cox Regression modeling were used for univariate and multivariate analysis (MVA) respectively. advanced p16+ OPC. Material and Methods

Results Tumor and patient characteristics were well balanced – PBC patients had increased median follow-up time and 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].