Frequency and Significance of Body Weight Loss During Immunochemotherapy in Patients with Advanced Non-Small Cell Lung Cancer

<b>Background:</b> Limited data are available on the frequency and significance of body weight loss during cancer therapy. This study investigated the frequency of patients who experienced body weight loss during immune checkpoint inhibitor (ICI) plus chemotherapy for advanced non-small cell lung cancer (NSCLC) and the impact of weight loss on treatment outcomes. <b>Methods:</b> Using the clinical data of 370 patients with NSCLC who received a combination of ICI and chemotherapy at 13 institutions, this study investigated the frequency of body weight loss > 5% during treatment and determined the impact of body weight loss on patient outcomes. <b>Results:</b> Of the 370 included patients, 141 (38.1%) lost more than 5% of their body weight during ICI plus chemotherapy (WL group). The 2-month landmark analysis showed that patients who experienced body weight loss of >5% during treatment had worse overall survival (OS) and progression-free survival (PFS) than those who did not (OS 14.0 and 31.1 months in the WL non-WL groups, respectively, <i>p</i> < 0.001; PFS 6.8 and 10.9 months in the WL non-WL groups, respectively, <i>p</i> = 0.002). Furthermore, a negative impact of body weight loss on survival was observed even in those who had obesity (body mass index [BMI] ≥ 25.0) at the start of therapy (OS 12.8 and 25.4 months in the WL non-WL groups, respectively, <i>p</i> < 0.001; PFS 5.7 and 10.7 months in the WL non-WL groups, respectively, <i>p</i> = 0.038). <b>Conclusions:</b> In conclusion, weight loss of >5% during ICI plus chemotherapy negatively influenced patient outcomes. Further and broader studies should investigate the role of nutritional status, specifically weight change and nutritional support, in responsiveness to ICI plus chemotherapy.