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SU_11_2108 - Late Toxicities Differed Maximum Tolerated Dose Determined by Acute Toxicities: Reanalysis of a Phase I/II Trial of Dose Escalation in Unresectable Thoracic Esophageal Cancer by Simultaneous Integrated Boost
Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3
Late Toxicities Differed Maximum Tolerated Dose Determined by Acute Toxicities: Reanalysis of a Phase I/II Trial of Dose Escalation in Unresectable Thoracic Esophageal Cancer by Simultaneous Integrated Boost
W. Yu1, X. L. Fu1, X. W. Cai1, W. Feng2, Q. Zhang1, and L. T. Gao1; 1Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China, 2Department of Radiation Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University, Shanghai, China
Purpose/Objective(s): To observe the long-term survival and late adverse events of a phase I/II trial (NCT01843049) of simultaneous integrated boost (SIB) for dose escalation in unresectable thoracic esophageal cancer, in which acute toxicities were well tolerated when dose was escalated up to 70Gy.
Materials/Methods: Patients with esophageal squamous cell carcinoma were treated with escalating radiation dose of 4 levels defined as our previous works (Yu et al. Radiother Oncol 2015). A prescription dose of 62.5-64Gy was delivered to the gross tumor volume, with (Level 3 & 4) or without (Level 1 & 2) a SIB up to 70 Gy for the pre-treatment 50% SUVmax area of the primary tumor. Patients also received 2 cycles of chemotherapy of cisplatin and fluorouracil concurrently and 2 more cycles after radiotherapy.
Results: Dose escalation has been safely achieved up to Level 4 with tolerable acute toxicities as previously reported, so a phase II trial was further performed basing on Level 4. After a median follow-up duration of 21.8 (2.5-61.4) months for all 34 patients and 40.1 (13.4-61.4) months for 17 patients still alive, median overall survival time and progression free survival time were 42.4 and 11.7 months, respectively. Grade III or greater late esophageal toxicities (perforation, fistula or hemorrhage) occurred within 1 patient of Level 1 (n=5), 1 patient of Level 2 (n=10), none of Level 3 (n=5) and 7 patients of Level 4 (n=14), respectively, with median occurrence time of 5.4 months. Five patients of Level 4 finally died of grade V late esophageal toxicities.
Conclusion: Severe late esophageal toxicities might have compromised long-term survival after dose of Level 4 was delivered despite of tolerable acute toxicities. Larger numbers of patients should be enrolled into Level 3 for further assessment of treatment tolerance.
Author Disclosure: W. Yu: None. X. Cai: None. W. Feng: None. Q. Zhang: None.