Patient characteristics
A flowchart of the patient selection process is shown in Figure 1. A total of 580 patients who underwent WBRT were analyzed, and 258 patients were excluded for the following reasons: primary brain tumor, 27; prophylactic WBRT for SCLC, 105; hematological malignancy, 21; post-resection of BM, 63; pediatric patient, 20; and unavailable blood data, 22. Finally, 322 patients who underwent pWBRT were included in this study. Two hundred ninety-one patients (90%) had died,14patients were alive, and 17 patients were lost to follow-up. The Patient characteristics are shown in Table1. The median follow-up duration was 4.0 months (interquartile range, 1.6–9.7), and the median age at the first day of WBRT was 66 years (range, 22.4–87.6). The patients with age ≥60 years, of male sex, a KPS ≥70, and with an ECM were 219 (68%), 178 (55%), 166 (52%), and 263 (82%), respectively. The primary cancers were lung, breast, gastrointestinal, gynecological, and other cancers in 210 (65%), 46 (14%), 38 (12%), 9 (3%), and 19 (6%) patients, respectively. The median NLR and serum albumin level before WBRT were 3.6 (range, 0.26–49) and 3.8 (range, 1.9–5.2), respectively. The WBRT treatment plan included a total dose of 30 Gy in 10 fractions for 272 patients (84%), 30 Gy in 12 fractions for 16 patients (5%), and others for 34 patients (11%).
Univariate and multivariate analyses of the OS
Figure 2A presents the Kaplan–Meier survival curves for patients with BM treated with WBRT. The median OS for all patients was 4.0 months (95% confidence interval [CI]: 3.3–4.4 months). Table 2 shows the factors associated with the OS. In the univariate analysis, the factors associated with a shorter OS were male sex (median OS, 3.1 months; 95% CI: 2.3–3.9 months, P<0.01), KPS ≤60 (median OS, 2.4 months; 95% CI: 2.0–3.1 months, P<0.01), not lung cancer (median OS, 3.0 months; 95% CI: 2.0–3.5 months, P<0.01), presence of ECM (median OS, 3.5 months; 95% CI: 2.8–4.2 months, P=0.02 ), NLR ≥5 (median OS, 2.1 months; 95% CI: 1.8–2.5 months, P<0.01), and serum albumin <3.5 (median OS, 2.1 months, 95% CI: 1.7–2.4 months, P<0.01). The Kaplan–Meier curves for these factors are shown in Figures 2B–2F. In the multivariate analysis, the factors associated with a shorter OS were male sex (hazard ratio [HR]: 1.4, 95% CI: 1.1–1.8, P=0.01), KPS ≤60 (HR: 1.7, 95% CI: 1.3–2.2, P=0.01), presence of ECM (HR: 1.6, 95% CI: 1.2–2.2, P<0.01), NLR ≥5 (HR: 1.6, 95% CI: 1.3–2.1, P<0.01), and serum albumin <3.5 (HR: 1.4, 95% CI: 1.0–1.8, P=0.02). Since we aimed to establish a PSS that can be used regardless of primary cancer, the primary site was not included as a factor in the multivariate analysis.
Prognostic scoring system for patients with BM treated with pWBRT
A new PSS was introduced to predict the survival of patients after pWBRT. The PSS was associated with male sex and the presence of ECM, KPS, NLR, and serum albumin, which were independent prognostic factors. A score of one was assigned to male sex, presence of ECM, KPS ≤60, NLR ≥5, and serum albumin <3.5, and a score of zero to female sex, absence of ECM, KPS ≥70, NLR <5, and serum albumin ≥3.5. Since the HR of each variable was almost equivalent, the weights of the assigned scores were set equally among these factors. The Kaplan–Meier survival curve showed that the median duration of OS for 171 patients with PSS score of 0–2 and 151 patients with a score of 3–5 were 7.4 months (95% CI: 5.9–9.2) and 2.1 months (95% CI: 1.7–2.4), respectively, which were significantly different (P<0.01; Figure 2G, Table 3). Lung cancer patients were almost equally included in the good (68.4%) and poor prognosis groups (61.6%).