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e18007 Background: Concurrent chemoradiotherapy (CCRT) with cisplatin (CDDP) is a standard treatment for locally advanced head and neck cancer (LAHNC) in the definitive setting. Three cycles of 100 mg/m2 CDDP for every three weeks (Q3W) are now recommended but compliance with CCRT is relatively low due to its severe toxicity. Therefore, the potential de-escalation strategies for LAHNC have been discussed to decrease the therapeutic toxicity. Methods: Patients with LAHNC who underwent definitive CCRT with CDDP between 2012 and 2018 at The Cancer Institute Hospital of Japanese Foundation for Cancer Research were analyzed. Patients were classified into two groups based on the planned CDDP dose: (A) 100 mg/m2 and (B) 80 mg/m2 Q3W for three times. One-to-one propensity score matching was performed to minimize bias between two groups. After patients in two groups were matched by using propensity score, the overall survival (OS), recurrence-free survival (RFS), local recurrence-free survival (LRFS), and metastatic recurrence-free survival (MRFS) were analyzed by the Kaplan-Meier method with the Cox proportional hazards model. The follow-up term was set as two years to evaluate the early survival benefit. The dose and density of CDDP and the objective adverse events were also assessed. Results: A total of 304 patients were included with the median age of 62 (Interquartile range [IQR]: 54-67) years. Among them, 249 patients (82%) were male. Patients were treated with 100 mg/m2 CDDP (n = 145) and 80 mg/m2 CDDP (n = 159) regimens. After the propensity score matching, 119 patients were included in each group, respectively. There were no significant differences in baseline characteristics between two propensity-matched cohorts. The median follow-up time was 24 months in each group. Two-year OS was 93.0% (95% confidence interval [CI]: 88.4-97.8) in group A and 94.9% (91.0-99.0) in group B. Two-year RFS was 86.5% (80.6-92.9) in group A and 83.1% (76.6-90.1) in group B, respectively. No significant difference was observed in OS (Hazard ratio [HR] = 1.42, 95% CI: 0.49-4.08, p = 0.52), RFS (HR = 0.81, 95% CI: 0.42-1.57, p = 0.54), LRFS (HR = 0.57, 95% CI: 0.24-1.36, p = 0.20), and MFS (HR = 1.32, 95% CI: 0.52-3.35, p = 0.56). The median cumulative dose of CDDP was significantly higher in group A (300 mg, interquartile range [IQR]: 240-300) than in group B (240 mg, IQR:160-240) but the frequency of hematological, hepatic, renal, electrolytic, and grade 3-5 any adverse events was not significantly different between two groups. Conclusions: Our study showed no survival difference at 2-year follow-up between 100 mg/m2 and 80 mg/m2 CDDP regimens of definitive CCRT for LAHNC. This result could support the tide of the de-escalation strategy in head and neck cancer treatment. Longer follow-up is necessary and further prospective trials comparing CDDP dosage are warranted.

6502 Background: The standard treatment for post-operative high-risk patients (pts) with locally advanced squamous cell carcinoma of the head and neck (LA-SCCHN) is chemoradiotherapy with 3-weekly cisplatin (CDDP) (100 mg/m2, q3wk, 66 Gy/33Fr; 3-weekly CDDP+RT). However, one concern with 3-weekly CDDP+RT is insufficient CDDP compliance due to high-dose-related toxicities. Weekly CDDP+RT (40 mg/m2, qwk, 66 Gy/33Fr; weekly CDDP+RT) is an alternative regimen with better compliance. Here, we conducted a phase II/III trial of weekly CDDP+RT in post-operative high-risk LA-SCCHN. Methods: This is a multi-institutional randomized phase II/III trial to confirm the non-inferiority of weekly CDDP+RT (Arm B) compared with 3-weekly CDDP+RT (Arm A). The trial enrolled pts aged 20-75 years with post-operative high-risk features (microscopically positive margin and/or extranodal extension) and ECOG-PS 0-1. Pts were randomized in a 1:1 ratio to Arm A or Arm B. Primary endpoint of phase II was the proportion of treatment completion and that of phase III was overall survival (OS). A non-inferiority margin of hazard ratio (HR) was set at 1.32. Results: Between Oct 2012 and Dec 2018, 261 pts were enrolled (Arm A 132 pts, Arm B 129 pts). At the planned second interim analysis in phase III with 76/161 events, the Data and Safety Monitoring Committee recommended terminating the trial and publishing the results because the statistical boundary for OS non-inferiority had met the pre-specified stop criteria. With a median follow-up of 2.2 years in all randomized pts, 3-year OS was 59.1% in Arm A and 71.6% in Arm B with a HR of 0.69 (99.1% CI, 0.374-1.273 [ < 1.32], one-sided p for non-inferiority = 0.00272 < 0.00433). 3-year RFS was 53.0% in Arm A and 64.5% in Arm B with a HR of 0.71 (95% CI, 0.48-1.06). Regarding acute adverse events, neutropenia (≥ grade 3), increased creatinine (≥ grade 2), hearing impairment (≥ grade 2) and mucositis (≥ grade 2) occurred in 48.8%, 8.5%, 7.8% and 55.0% in Arm A and 35.3%, 5.7%, 2.5% and 59.0% in Arm B, respectively. For compliance, median total dose of CDDP was 280 mg/m2 (IQR, 250-299) in Arm A and 239 mg/m2 (IQR, 199-277) in Arm B. Total radiation dose was 66 Gy (IQR, 66-66) in both arms. Proportion of treatment completion was 93.2% in Arm A and 86.8% in Arm B. Conclusions: Weekly CDDP+RT is non-inferior to 3-weekly CDDP+RT for post-operative high-risk LA-SCCHN pts and has a favorable toxicity profile. Weekly CDDP+RT should be considered the new standard treatment option for these pts. Clinical trial information: 000009125 .

e18067Background: Concurrent chemoradiotherapy (CRT) with single agent cisplatin for patients with head and neck cancers (HNC) have been used as the standard treatment for a long time. Although rec...

e17006 Background: CCRT is a standard therapy for locally advanced head and neck cancer patients, but some patients have intolerance to high dose density of CDDP. Predictive factors for CDDP discontinuation need to be investigated for making appropriate treatment decisions. Methods: We retrospectively analyzed nonmetastatic head and neck cancer patients treated with CCRT with CDDP (80 mg/m2 per 3 weeks) from November 2005 to April 2012 in our institute. Radiation therapy was performed as three-dimensional radiotherapy or intensity-modified radiotherapy (IMRT). Results: A total of 164 patients received CCRT, of which 89 (54 %) were Stage IV;. Primary sites were as follows; oral cavity 7, oropharynx 52, hypopharynx 53, larynx 14, nasopharynx 30, paranasal sinus/nasal cavity 3, and unknown primary 5. IMRT was performed to 54 (33 %) patients. Median follow-up time was 19 months (range 1-69 months); 1-year overall survival (OS) and progression free survival (PFS) were 90 % and 78 %. Non-Stage IV; and high creatinine clearance (>70 ml/min) were associated with longer OS in Cox proportional hazard model. As for CDDP treatment, 75 (46 %) patients completed 3 cycles of CDDP, 69 (42 %) patients received 2 cycles, and 20 (12 %) patients received only 1 cycle. The main reasons for CDDP discontinuation were infection (24 patients) and renal dysfunction (18 patients). In logistic regression analysis, male sex, younger age (< 61 years) and high body mass index (BMI) (>25) were associated with 3 cycles completion of CDDP statistically significantly (p = .002, odds ratio 6.622; p = .006, odds ratio 2.602; p = .035, odds ratio 2.655, respectively). Conclusions: In CCRT to head and neck cancer patients, infection and renal dysfunction were the main reasons for CDDP discontinuation. Sex, age and BMI could be predictive of CDDP completion/discontinuation.