The prognostic value of weight loss during radiotherapy among patients with nasopharyngeal carcinoma: a large-scale cohort study.

Background: We aim to investigate the prognostic value of weight loss during radiotherapy (RT) among patients with nasopharyngeal carcinoma (NPC).

Methods: A total of 1149 NPC patients who received radical RT were retrospectively analyzed. Patients' weight were measured at initiation of RT (W) and every week during RT (W). Percentage of weight loss (PWL) at 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th week of RT (RT-PWL) were calculated using the following equation: (W -W)/W × 100%. The optimal threshold of RT-PWL was determined by recursive partitioning analyses (RPAs). Our endpoints included disease-free survival (DFS), overall survival (OS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRRFS).

Results: The median RT-PWLs were 0, 0, 1.5, 2.9, 4.1, 5.5, 6.6% at 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th week of RT, respectively. RT-PWL optimal threshold with respect to DFS was 5.3% based on RPAs. Therefore, a consistent threshold of 5% (<5% vs > ≥5%) was selected to classify NPC patients into low RT-PWL and high RT-PWL groups for survival analysis. Compared to high RT-PWL (≥5%), patients with low RT-PWL (< 5%) had significantly better ten-year DFS (61.2% vs 78.8%; P < 0.001), OS (70.1% vs 86.6%; P < 0.001), and DMFS (80.2% vs 88.5%; P = 0.007). However, no difference was observed between LRRFS groups (91.7% vs 94.3%; P = 0.173). In multivariate analysis, high RT-PWL was an independent risk factor for DFS (HR, 1.56; 95%CI, 1.19-2.03; P = 0.001), OS (HR, 1.54; 95%CI, 1.11-2.15; P = 0.011), and DMFS (HR, 1.47; 95%CI, 1.03-2.10; P = 0.033) in patients with NPC. In addition, treatment strategy, plasma Epstein-Barr virus DNA, and N stage were associated with weight loss.

Conclusions: High RT-PWL was significantly associated with decreased DFS, OS, and DMFS for NPC patients. Clinicians should continuously inform patients on the health impact of minimizing RT-PWL under 5% during radiotherapy.