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PQA 07 - Head and Neck Cancer, Lung Cancer/Thoracic Malignancies, and Nursing and Supportive Care
3534 - Radiotherapy for Early T-Stage Nasopharyngeal Carcinoma: A Prospective Observational Study on the Safety of Petrous Apex-Sparing Irradiation and Dosimetry Benefits of Cochlear
Deqing Liu, - Department of Radiation Oncology, Chongqing University Cancer Hospital & Chongqing Cancer Institute & Cancer Hospital, Chongqing, Chong Qing
D. Liu1, L. Huang2, X. Zhang3, Y. Bai4, S. Li5, Y. Luo6, C. Wang7, X. Shu8, B. Long8, M. Hu8, J. Yan6, Y. Xie9, Y. Wu10, M. L. K. Chua11, and Y. Wang5; 1Radiation Oncology Centre, Chongqing University Cancer Hospital, Chongqing, China, 2Department of Radiation Oncology,Chongqing University Cancer Hospital, Chongqing, China, 3Radiation Oncology Center, Chongqing University Cancer Hospital, Chongqing, China, 4Chongqing University Cancer Hospital, chongqing, China, 5Radiation Physics Center, Chongqing University Cancer Hospital, Chongqing, China, 6Department of Radiation Center, Chongqing University Cancer Hospital & Chongqing Cancer Institute & Chongqing Cancer Hospital, Chongqing, China, 7Department of Radiation Oncology, Chongqing University Cancer Hospital & Chongqing Cancer Institute & Cancer Hospital, Chongqing, China, 8Radiation Oncology Center,Chongqing University Cancer Hospital, Chongqing, China, 9Department of Radiation Oncology, Chongqing University Cancer Hospital, Chongqing, China, 10College of Medicine, Chongqing University, Chongqing, China, 11Duke-NUS, Graduate Medical School, Singapore, Singapore
Purpose/Objective(s):
The delineation of the Clinical Target Volume (CTV) in nasopharyngeal carcinoma (NPC) critically impacts therapeutic efficacy and toxicity, necessitating robust evidence-based refinement. However, Current studies frequently prioritize breadth over incremental evidence-based refinement. This study aimed to evaluate the safety of omitting prophylactic irradiation to the petrous apex in T1-2 stage NPC and to quantify the consequent reduction in cochlear dose.
Materials/Methods:
A prospective observational cohort study was conducted, enrolling consecutive patients with newly diagnosed T1-2NanyM0 NPC. Patients were allocated into two groups based on the attending physician’s delineation practice: Group A (petrous apex-sparing, n=51) and Group B (prophylactic irradiation, n=184).For Group A, if the primary gross tumor volume (GTVp) >3 mm from the petrous apex, the high-risk CTV1 was trimmed to exclude it, while the low-risk CTV2 covered only the cortical bone. If GTVp was adjacent (=3mm), the CTV1 included the cortical bone and CTV2 covered approximately one-third of the petrous apex. In Group B, CTV1 covered one-third to half of the ipsilateral petrous apex, and CTV2 encompassed nearly the entire structure bilaterally. The primary endpoint was local failure-free survival (LFS) and cochlea dosimetry.
This study was registered in chictr.org.cn (number ChiCTR2500113975).
Results:
From July 2020 to June 2022. With a median follow-up of 53.0 months, Group A demonstrated a significant reduction in cochlea radiation exposure. The median Dmean to the cochlea was approximately 22 Gy versus 39 Gy in Group B (p<0.001). Median Dmax was about 28 Gy versus 49 Gy (p<0.001). No local recurrence occurred at the petrous apex was observed in either group. The 5-year LFS was 95.7% in Group A versus 96.8% in Group B (HR, 1.88; 95% CI, 0.34-10.26; p=0.460). No significant differences were observed in 5-year regional failure-free survival, distant metastasis-free survival, or overall survival between the two groups.
Conclusion:
For T1-2 NPC, omitting prophylactic irradiation to the petrous apex is safe, with no increased risk of local recurrence and significantly reduces the radiation dose to the cochlea, which may translate to reduced ototoxicity and improved hearing preservation.
