External beam radiotherapy in pT4 well-differentiated thyroid cancer: A population-based study of 405 patients
Menée auprès de 405 patients atteints d'un cancer de la thyroïde différencié de stade pT4 (âge médian au diagnostic : 53 ans ; durée médiane de suivi : 14,3 ans), cette étude évalue l'efficacité, du point de vue de la récidive locorégionale, de la survie sans progression et de la survie spécifique, d'un traitement par radiothérapie externe
Purpose/Objective: The benefit of external beam radiotherapy (EBRT) in locally advanced, well- differentiated thyroid cancer (WDTC) is uncertain. The purpose of this study is to evaluate locoregional recurrence (LRR), progression-free survival (PFS) and cause-specific survival (CSS) of patients with pT4 well-differentiated thyroid carcinoma. Materials/Methods: A population-based retrospective review was conducted of consecutive patients with pT4 (American Joint Committee on Cancer 8th edition) WDTC treated provincially between 1985 to 2013. The primary end points were cumulative incidence of locoregional recurrence (LRR) and cause-specific survival (CSS). To account for the competing risks of death from other causes, Fine-Gray's test was used. Cox-proportional hazards model was used for analyzing overall survival (OS). Multivariate models and propensity matching was used to account for the effects of covariates. Results: A total of 405 patients were identified with a median follow up time of 14.3 years for a total of 4209 person-years of follow up. The median age at diagnosis was 53 years (range: 20-87). There were 211 patients (52%) who received EBRT. EBRT receipt was associated with age ≥55 (56% vs 35%, p<0.001), airway involvement (42% vs 8%, p<0.001) and R1/2 resection (81% vs 51% p<0.001). The 10-year outcomes for the non-EBRT group and EBRT group respectively were: LRR 21.6% vs 11.4%, CSS: 84.1% vs 93.1%, and OS: 85.7% vs 67.5%. On multivariate analysis, EBRT was associated with a lower rate of LRR (HR: 0.334, p<0.001), but was not associated with CSS (HR: 1.56, p=0.142) nor OS (HR: 1.216, p=0.335). After propensity score matching, the EBRT cohort had lower rates of LRR relative to the non-EBRT cohort (HR: 0.261, p=0.0003), but there were no differences in CSS or OS. Conclusion: In this large, population-based analysis of patients with pT4 WDTC, EBRT was associated with lower rates of LRR, but no difference in CSS or OS.
International Journal of Radiation Oncology, Biology, Physics 2021