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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.

e15296 Background: The median age of pancreatic ductal adenocarcinomas (PDAC) patients is approximately 70 years. PDAC rarely affects individuals under the age of 40. We investigated clinicopatholo...

199 Background: The median age of pancreatic ductal adenocarcinomas (PDAC) patients is approximately 70 years. We investigated clinical features of PDAC occurring in young patients (< 40 years) in order to determine if any difference exists in comparison to older patients. Methods: We reviewed a single-institution database of 785 patients with pathologically proven PDAC between 2001 and 2012. We examined the clinical features in patients with PDAC below 40 years of age and compared it to those in older patients (≥ 40 years). Results: Of these 785 patients, a total of 10 patients (1.3%) under the age of 40 were identified, with a range of 28 to 37 years. Clinical features in young and older patients have been summarized (table). There are no differences between groups in terms of sex, smoking, tumor location, UICC stage, a family history of PDAC and a family history of any cancer. In the young patients group, three of them were diagnosed with localized diseases, two others with locally advanced diseases, and five others with metastatic diseases. Two of the three patients with localized diseases underwent curative operation. The five patients with metastatic diseases received chemotherapy, and only one patient achieved a partial response treated with FOLFIRINOX regimen. Two of the patients were long-term survivors, having survived over three years. Six of the patients had a family history of other cancers in first-degree relatives. Unexpectedly and most importantly, only one patient had a family history of PDAC. Conclusions: Cases of patients with PDAC below 40 years of age are rare. The clinical features in young patients were generally similar to those in older patients. Almost all young patients had no family history of PDAC, which suggests that hereditary genetic factors have a weak relationship with cases of onset of PDAC at a young age in Japan. [Table: see text]