A total of 83 elderly patients were enrolled and treated after six cycles of induction therapy. 62 patients (32 cases in observation group and 30 cases in R2+GM-CSF group) achieved CR after first-line induction therapy and 21 patients (12 cases in observation group and 9 cases in R2+GM-CSF group) achieved above PR after first-line induction therapy, then received second-line therapy. The patients were ineligible for HSCT, had a response above PR, and entered this retrospective cohort study of receiving R2+GM-CSF (new R2) group as maintenance therapy or observation, by the patients’ intention. All patients provided signed the consent. Thirty-nine patients received R2+GM-CSF and 44 patients received observation. Most of the 83 patients with high-risk B cell lymphoma were newly diagnosed (75 cases, 90.4%) and the main pathological type was DLBCL (70 cases, 84.3%; germinal center B-cell (GCB) 9 cases, Non-GCB 61 cases). Additionally, the majority of patients were elderly with good physical status and were at the advanced stage of lymphoma at the time of diagnosis. Although the number of patients who achieved CR before maintenance therapy was higher in the R2+GM-CSF group (61.5% vs. 47.7%), there was no significant difference between the two groups (P = 0.208). Table 1 shows the patients’ baseline characteristics. The mean age, sex, disease isotype, lactate dehydrogenase (LDH) level, beta-2 microglobulin (beta2-MG) level and metaphase cytogenetics showed no significant differences between the two treatment groups. Furthermore, Ann Arbor stage, IPI score, and Eastern Cooperative Oncology Group (ECOG) score at diagnosis also showed no significant differences. All the details are presented in Table 1.
New R2 regimen combined with rhGM-CSF increased the number of NK cells
Peripheral blood mononuclear cells (PBMCs) and immune cells were analyzed by flow cytometry in patients before maintenance therapy and after each cycle of maintenance therapy. We found rhGM-CSF plus R2 regimen may upregulate NK cell numbers about for 3 months, that’s why we determine new R2 regimen administration for three months each cycle, but detailed data was not shown in this paper. Table 2 only shows the data before and after the first cycle of maintenance therapy. We observed a statistically significant increase in leukocytes (6.46×109/L vs 4.85×109/L, P = 0.0048), hemoglobin (126.36 g/L vs. 119.08 g/L, P < 0.001), and erythrocytes (4.18 × 1012/L vs. 3.96 × 1012/L, P = 0.0002). Additionally, Table 2 and Figure 2 show that after R2+GM-CSF treatment, the number of lymphocytes (1.19 × 109/L vs. 1.03 × 109/L, P = 0.0062) and NK cells (0.131 × 109/L vs. 0.061 × 109/L, P = 0.0244) increased significantly. Thus, R2+GM-CSF affected the levels of certain immune cells, and in particular, the number of NK cells increased. We found the number of immune cells was increased after R2+GM-CSF (Figure 2), but not significantly. All the details are presented in Table 2 and Figure 2.
The new R2 regimen combined with rhGM-CSF maintained long-term remission of patients with high-risk B cell lymphoma
After receiving different maintenance treatments, the remission status of patients were statistically different. The median duration of remission (DOR) of the 83 patients was 15.0 ± 10.67 months. The DOR in the R2+GM-CSF maintenance group was longer than that in the observation group (18.8 ± 9.32 months vs. 11.3 ± 10.72 months, P = 0.001). Although the recurrence rate of patients in observation group was 1.6-fold higher than that of patients in the R2+GM-CSF group (20.5% vs. 12.8%), the difference was not statistically significant (P = 0.242).
The new R2 regimen combined with rhGM-CSF prolonged PFS and OS of patients with high-risk B cell lymphoma
The median PFS of the 83 patients was 48.9 ± 11.38 (95% confidence interval (CI): 26.55–71.18) months. The R2 regimen combined with rhGM-CSF maintenance treatment enabled patients to achieve longer-term PFS (P = 0.037, Figure 3B). The 1-year PFS rates and 5-year PFS rates of the R2+GM-CSF group and observation group were 100% and 84.1%, 76.9% and 72.7%, respectively, and the differences were statistically significant (P = 0.003, P = 0.037).
However, the difference in OS between two groups was statistically significant (P = 0.015, Figure 3A). The 1-year OS rate of R2+GM-CSF group and observation group were 100% and 95.5%, and there was no significant difference (P = 0.165). However, the 5-year OS rates were 97.4% and 86.4%, respectively, and the difference was statistically significant (P = 0.015).
For elderly patients (> 60 years old), the R2 regimen combined with rhGM-CSF as a maintenance regimen was very helpful to prolong the long-term PFS. If the elderly patients did not continue to be given the corresponding treatment after induction of remission, the disease was progressed easily, which was manifested in a shorter PFS time, although there was no significant difference [P = 0.060, hazard ratio (HR) 0.368 (95% CI 0.129–1.044), Figure 4].
Additionally, a single-factor stratification study found that compared with the observation group, the R2 regimen combined with rhGM-CSF as a maintenance regimen was helpful to prolong the long-term PFS rate, especially for patients who stage III or IV disease [P = 0.005, HR 0.221 (95% CI: 0.078–0.628)], patients with an IPI score ≥ 3 [P =0.012, HR 0.275 (95% CI: 0.101–0.752)], and patients with bone marrow involvement [P = 0.023, HR 0.077 (95% CI: 0.009–0.698)]. All the details are presented in Figure 4 and the Supplementary Table 1.
Safety during maintenance therapy was assessed for 39 patients who undertook at least one new R2 regimen combined with rhGM-CSF. We collected all immediate responses during analyzing side effects. All adverse events and serious adverse events were collected and graded according to the Common Terminology Criteria for Adverse Events (CTCAE-Version 4.0). All adverse events are shown in Table 3. Hematological toxicities that occurred more frequently in the R2+GM-CSF group included anemia (13/39), lymphocytopenia (9/39), and leukopenia (9/39). Of note, all the hematological adverse events were graded 1–2 (16/39), and none were graded 3 or 4. Besides, common treatment-related non-hematological adverse events were of grade 1–2 (16/20), with most frequent ones being nausea or vomiting (6/39). Only one patient had fever because of rhGM-CSF. Notably, only one patient died (1/39) during the study. In short, the side effects so mild that none of them were managed through dose interruptions and/or reductions and other support, and no serious or fatal adverse events (graded above 3) occurred.