Patients diagnosed with stage III/IV, highly aggressive B-cell lymphoma or T-cell lymphoma between August 2000 and June 2013 were identified from a database of prospective observational research on ASCT in malignant lymphoma. The analysis was approved by the Institutional Review Board of the Cancer Institute/Hospital, Chinese Academy of Medical Science and Peking Union Medical College (CAMS and PUMC). All patient diagnoses were histologically confirmed at the Department of Pathology, Cancer Institute/Hospital, CAMS and PUMC. All patients were required to be younger than 65 years old and to have adequate organ function. Patients were excluded if they had human immunodeficiency virus (HIV) infection, central nervous system (CNS) disease, active hepatitis B or C, or grade ≥2 peripheral neuropathy. Patients were staged according to the Ann Arbor Classification before mobilization. Staging procedures included physical examination, reporting of B symptoms, computer tomography (CT) or positron emission tomography (PET)-CT scans, and bone marrow biopsy. Because this was a retrospective study, the use of PET-CT to aid in the assessment of the response had varied over time. All patients exhibited at least a partial response (PR) at the time of mobilization and were on their first mobilization attempt.
Patients were treated with induction chemotherapy regimens such as CHOP; bleomycin, epirubicin, cyclophosphamide, vincristine, plus prednisone (BACOP); and prednisone, doxorubicin, cyclophosphamide, etoposide, cytarabine, bleomycin, vincristine, plus methotrexate (ProMACE/CytaBOM) before mobilization.
Mobilization chemotherapy included dose-adjusted CHOP or CHOP-like regimens alone (CHOP group) or in combination with rituximab (R-CHOP group) according to CD20 expression and patients’ financial circumstances. The dose-adjusted CHOP regimen consists of cyclophosphamide (1–2 g/m2 per day), vincristine (1.4 mg/m2 per day, maximum 2 mg), and doxorubicin (50 mg/m2 per day) or epirubicin (75 mg/m2 per day) all on day 1 and prednisone (100 mg/day) on days 1–5. The CHOPE regimen consists of CHOP plus etoposide (100–200 mg/m2 per day) on days 1–3. The BACEP regimen consists of bleomycin (15 mg/day) on days 3 and 10, epirubicin (75 mg/m2 per day) on day 1, cyclophosphamide (1 g/m2 per day) on day 1, etoposide (100 mg/m2 per day) on days 1–3, prednisone (100 mg/day) on days 1–5. Rituximab was administered at 375 mg/m2 per day on the day before mobilization, day 7 after mobilization, the day before APBSC infusion, and day 8 after infusion .
The first dose of rhG-CSF was administered subcutaneously at a fixed dose of 300 µg/day (150 µg/day for patients weighing less than 45 kg) beginning on the day when the white blood cell (WBC) count first rose after the nadir following chemotherapy, continuing until the day before the last apheresis. To determine the first day of apheresis, the WBC count and the percentage of CD34+ cells in peripheral blood (defined as the ratio of CD34+ cells to mononuclear cells [MNCs]) were monitored daily after chemotherapy. When the WBC count exceeded 10 × 109/L, the MNC count exceeded 2 × 109/L, and the percentage of CD34+ cells in peripheral blood exceeded 1% , continuous APBSC collection was conducted daily with a CS-3000 Plus blood cell separator (Baxter Healthcare Corp., Deerfield, IL, USA) until a target collection of at least 2 × 106 CD34+ cells/kg body weight or 4 × 108 MNCs/kg body weight was achieved. The blood volume processed by each single apheresis was 110–150 mL/kg body weight at a speed of 40–70 mL/min. Venous access was obtained by a double lumen catheter (Arrow International Inc., Reading, PA, USA) placed in a femoral vein [17, 18]. After mobilization, the amount of CD34+ cells in the apheresis product was measured after each collection by flow cytometry using a class III monoclonal antibody (Becton–Dickinson, Franklin Lakes, NJ, USA) . Dimethylsulfoxide was added to the products at a final concentration of 10% to protect the cells from the stress or death caused by cryopreservation. The products were stored at −80°C with an uncontrolled freezing rate. Twenty-four hours later, the samples were transferred into a liquid nitrogen container (Thermo Scientific, Waltham, MA, USA) and stored at −196°C .
Successful mobilization was defined as the collection of a minimum of 2 × 106 CD34+ cells/kg body weight in a single mobilization. Optimal mobilization was defined as 5 × 106 CD34+ cells/kg body weight collection in a single mobilization . Failed mobilization was defined as the failure to collect at least 2 × 106 CD34+ cells/kg body weight by aphaeresis.
Conditioning regimen and engraftment
The conditioning regimens were BEAC [carmustine (300 mg/m2, day −5), etoposide (800 mg/m2, days −4 to −2), cytarabine (1600 mg/m2, days −4 to −2), cyclophosphamide (1.8 g/m2, days −6 to −5)], BEAM [carmustine (300 mg/m2, day −5), etoposide (800 mg/m2, days −4 to −2), cytarabine (1600 mg/m2, days −4 to −2), melphalan (140–160 mg/m2 for oral administration, day −6)], CBV [cyclophosphamide (1.8 g/m2, days −3 to −2), carmustine (450–600 mg/m2, day −7), etoposide (900–1600 mg/m2, days −6 to −4)], and CE-TBI [cyclophosphamide (1.8 g/m2, days −3 to −2), etoposide (750 mg/m2, days −6 to −4), total body irradiation (800–900 Gy, day −7)]. The day APBSCs were infused was defined as day 0. rhG-CSF (300 µg/day) was administered after APBSC infusion on day 6 and was continued until the neutrophil count recovered to at least 0.5 × 109/L on two consecutive days, defined as neutrophil engraftment. Platelet (PLT) engraftment was taken as the time when the PLT count recovered to more than 50 × 109/L for two consecutive days without transfusion support.
Evaluation of mobilization responses, toxicities, and survival
Response to treatment was evaluated according to the International Workshop Criteria , and all adverse reactions were recorded and graded according to the National Cancer Institute criteria . Overall survival (OS) and progression-free survival (PFS) were measured from the date of mobilization to the end of follow-up. Routine follow-up by imaging analysis was performed every 3 months for the first 2 years, every 6 months for the next 3 years, and then annually or whenever clinically indicated. The last follow-up was on November 30, 2013.
All calculations and statistical analyses were conducted using SPSS software (version 19.0, SPSS Inc., Chicago, IL, USA). For quantitative variables, medians, ranges, and proportions were determined and analyzed by descriptive statistics and frequency analysis. Comparisons of categorical variables between groups were tested by the Chi square test or Fisher’s exact test, and continuous variables were compared between two groups by the Mann–Whitney U test. For univariate analysis, a Spearman correlation analysis was conducted for continuous variables, and a Mann–Whitney U test was conducted for categorical variables to explore the effect of pre-mobilization factors on the yield of CD34+ cells. A linear stepwise regression was used for multivariate analysis. Survival data were analyzed using the Kaplan–Meier method, and survival curves were compared using the log-rank test. A two-tailed P value of <0.05 was considered significant.