Reirradiation with Stereotactic Ablative Radiotherapy in Recurrent Nasopharyngeal Carcinoma

Local recurrence (LR) rates in nasopharyngeal carcinoma (NPC) following definitive radiation (RT) ± chemotherapy (CT) range from 7–15%. A prospective trial comparing endoscopic surgery and re-irradiation in recurrent cases found that surgery improved survival in a carefully chosen group of patients with low-volume mucosal recurrence. However, the fact that the recurrent disease is mostly multifocal and infiltrative in nature makes a limited group of patients suitable for surgery. In this study, we aimed to report our stereotactic ablative radiotherapy (SABR) outcomes in cases diagnosed with recurrent NPC.

The data of 83 patients who underwent SABR in our department between 2007 and 2022 with the diagnosis of local-regional recurrent NPC, which was unresectable or had surgical margin positivity after resection were evaluated retrospectively. The Kaplan-Meier method was used for survival analyses (IBM SPSS v.23).

Patient, tumor, and treatment characteristics are presented in Table 1. The median age was 53 (range, 19-78). The median follow-up was 24 months (range, 3–151 months). The median interval between patients' first and second RT's was 39 months (range, 4–238 months). The initial response evaluation following reirradiation found a complete response in 38%, a partial response in 40%, stable disease in 8%, and progression in 1%. In follow-up, LR developed in 20 patients (24%) and distant metastasis (DM) developed in 14 patients (17%). The most common sites of DM were the lung, bone, and liver. SABR provided 76% local control (LC). The 1- and 2-year overall survival (OS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) rates were 67% and 53%, 65% and 46%, and 62% and 49%, respectively. In univariate analysis, LRFS (60% vs. 34%, p=0.002) and DMFS (63% vs. 31%, p=0.007) rates were higher in patients with recurrent tumor volume ≤36 cc compared to patients with tumor volume >36 cc. Age (≤53 vs. >53 years), gender (male vs. female), interval between RTs (≤2 vs. >2 years), surgery before SBRT (yes vs. no), SBRT dose (≤30 vs. >30 Gy) and device (robotic- vs. linear accelerator-based), and site of recurrence (primary vs. neck recurrence) could not be identified for prognostic significance for OS, LRFS, and DMFS parameters. A notable proportion of patients experienced late toxicity, with 20% exhibiting grade 3 or 4 toxicity and 12% experiencing grade 5 toxicity. Fourteen patients (17%) experienced massive hemorrhage as a result of carotid blow-out syndrome (CBOS); two patients (2%) suffered from cerebrovascular disease as a result of carotid artery stenosis; five patients (6%) experienced brain parenchymal necrosis; three patients (3.5%) had permanent gastrostomies; and three patients (3.5%) had hearing loss. There was no observed disparity in toxicity levels between doses administered consecutively or every other day.

Table 1. Patient, tumor, and treatment characteristics.

Using SABR as a reirradiation method for people with recurrent NPC has shown to be very effective at achieving LC while keeping treatment-related side effects at a level that can be tolerated. There is a positive correlation between a smaller recurring tumor volume and higher levels of local recurrence-free survival (LRFS) and distant metastasis-free survival (DMFS).