Patients aged <70 years with histologically confirmed DLBCL and no prior history of any anti-cancer treatment, including chemotherapy or radiotherapy, were eligible. All patients had the following characteristics: an Eastern Cooperative Oncology Group (ECOG) performance status of 0-2; at least 1 unidimensionally measurable lesion; and adequate organ functions, defined as absolute neutrophil count (ANC) of ≥1,500/mm³, platelet count of ≥75,000/mm³, serum creatinine level of ≤2.0 mg/dL, estimated creatinine clearance of ≥50 mL/min, bilirubin level of <1.25× the upper limit of normal (ULN), and serum aminotransferase level ≤2.5×ULN. Patients with any of the following characteristics were excluded: grade 2 or higher peripheral neuropathy; a history of hypersensitivity to bortezomib, boron, or mannitol; or a serious medical or psychiatric illness. Women who were pregnant or breast-feeding were also excluded from the study. The study was approved by the ethics committee of each participating institution, and all patients were provided written informed consent. The study was performed in accordance with the Declaration of Helsinki and Good Clinical Practice guidelines.

This study had a non-comparative phase I/II design. In phase I, we identified the MTD of bortezomib when it was combined with the CHOP-14 regimen, which was the recommended dose for phase II. In phase II, we evaluated the efficacy and safety of the bortezomib plus CHOP-14 regimen.

CHOP-14 treatment consisted of cyclophosphamide 750 mg/m² on day 1, doxorubicin 50 mg/m² on day 1, vincristine 1.4 mg/m² (up to 2 mg/m²) on day 1, and prednisolone 100 mg/d on day 1 through 5 every 14 days. The maximum number of cycles was 6, unless patients showed progressive disease or unacceptable toxicity, or withdrew consent. Patients also received 5 µg/kg/d lenograstim (Neutrogin®, JW Pharmaceutical Corp., Seoul, Korea) subcutaneously on day 4-13. Bortezomib was administered on day 1 and 4.

In phase I, bortezomib was administered at doses of 1.0, 1.3, and 1.6 mg/m² to consecutive cohorts with 3 patients each; dose escalation over 1.6 mg/m² was not planned according to a previous phase I study of bortezomib and CHOP-21 [15, 16]. DLTs were defined as grade 4 neutropenia associated with fever for more than 3 days; grade 4 neutropenia lasting for more than 10 days; grade 3-4 thrombocytopenia with grade 2 hemorrhage; or grade 3-4 non-hematologic toxicity during the first treatment cycle.

Three patients were enrolled at each dose level, and dose escalation continued, if no DLT was observed in any of the patients; however, intra-patient dose escalation was not allowed. When DLT was observed in a single patient, 3 additional patients were treated with the same dose. When 2 or more of 6 patients developed DLT, the previous dose level was considered as the MTD. When only 1 of 6 patients developed DLT, dose escalation continued.

Patients with an ANC of ≥1,500/mm³, platelet count of ≥75,000/mm³, and non-hematologic toxicity of ≤grade 1 were administered the same treatment as that in the previous treatment cycle. Doses of cyclophosphamide and doxorubicin were reduced by 25%, if ANC and platelet recovery exceeded 1 week; the doses were reduced by 50%, if the delay was more than 2 weeks. When a 3-week delay was required to recover from bortezomib-related toxicity, bortezomib dose was reduced by 1 dose level (e.g., from 1.6 to 1.3 mg/m²) in the subsequent cycles. If the next cycle was also delayed for more than 3 weeks because of toxicity, the subject was withdrawn from the study.

During phase II, we evaluated the complete response (CR) rate, event-free survival (EFS), overall survival (OS), and safety of the bortezomib plus CHOP-14 regimen.

Toxicity was evaluated every week by history taking, physical examination, complete blood counts, biochemical tests, and other appropriate studies. Toxicities were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) version 3. Treatment response was evaluated after 3 cycles and 6 cycles by using the International Working Group response criteria [17]. After the end-of-study visit, patients were followed every 4-12 weeks for a minimum of 2 years after enrollment and if possible for 5 years.

All time-to-event variables were estimated using the Kaplan-Meier method. EFS was defined as the interval between the date of start of treatment and the date of documented disease progression or death from any cause, whichever happened first. OS was defined as the interval between the date of start of treatment and date of death from any cause.

Nine patients were enrolled between December 2006 and April 2007 for the phase I study, and 37 patients were subsequently enrolled until November 2009 for the phase II study. The phase II study included 40 patients, including 3 patients from cohort 3 of the phase I study (Fig. 1). Patient characteristics are summarized in Table 1. The median patient age was 54 years (range, 27-70 years), and most patients (71.4%) had stage IV disease.

No DLT was seen at the 3 dose levels of bortezomib (1.0, 1.3, and 1.6 mg/m²) during the first cycle. Therefore, the recommended dose of bortezomib for phase II was determined to be 1.6 mg/m² when combined with CHOP-14. A patient in cohort 1 (dose, 1.0 mg/m² bortezomib) refused to receive bortezomib on d 4 of cycle 6 because of grade 2 neuropathic pain; this patient was not replaced. In cohort 2 (dose, 1.3 mg/m²), a patient showed disease progression after 5 cycles and received salvage chemotherapy. In cohort 3 (dose, 1.6 mg/m²), 1 patient experienced grade 3 abdominal pain with nausea and vomiting, followed by paralytic ileus after the second cycle. Because these symptoms were determined to be associated with treatment-related neuropathy, which did not resolve to grade 1 within 3 weeks, the patient was dropped from the study. This patient, however, was treated with CHOP-14, without bortezomib, during cycles 3-6. There were no other dose reductions or delays.

The most common reason for withdrawal from either phase was adverse events. In the phase I study, 1 of the 3 patients in cohort 1 failed to complete the 6 cycles of treatment because of neuropathic pain, and 1 patient of 3 in cohort 3 failed to complete treatment because of paralytic ileus accompanied by neuropathy (Fig. 1). One patient in cohort 2 showed progressive disease before completion of the 6 cycles of therapy and stopped treatment.

In phase II, 30 patients (75.0%) completed 6 cycles of bortezomib plus CHOP-14; 10 patients did not complete treatment. Five patients discontinued treatment because of severe adverse events, including severe sensory neuropathy, severe infection, small bowel perforation, pneumonitis with bilateral pulmonary infiltration, and uncontrolled delirium; each of these events was observed in 1 patient. Two patients refused to continue treatment; 2 died of severe pneumonia with septic shock during treatment; and 1 showed poor tolerance to treatment followed by rapid disease progression. Overall, 40 patients received 214 cycles of bortezomib plus CHOP-14. The median number of cycles administered per patient was 6. The mean percentages of the planned doses (i.e., the actual dose divided by the planned full dose) of bortezomib, cyclophosphamide, vincristine, and doxorubicin were 90.6%, 99.2%, 98.6%, and 99.2%, respectively.

Grade 3 or 4 adverse events during phases I and II are summarized in Table 2. During both phases, myelosuppression was rare. Among non-hematologic toxicities, sensory neuropathy was the most common adverse event, occurring in 22.2% of patients in both phases I and II; 9 patients showed grade 3 sensory neuropathy (3 patients after 3 cycles of treatment and 6 patients after 4 cycles of treatment). Three patients showed grade 3 motor neuropathy. Grade 1 and 2 neuropathy was also common, occurring in 17.5% (grade 1) and 30.0% (grade 2) of patients, respectively.

Of the 40 patients in the phase II trial, 22 (55.0%) required bortezomib dose reduction from 1.6 mg/m² to 1.3 mg/m² because of toxicities. The most common toxicity was grade ≥3 neuropathy, which occurred after median 4 cycles of treatment. Three patients required 2 dose reductions of bortezomib from 1.6 mg/m² to 1.0 mg/m² because of neuropathy.

Two patients in cohort 1 of phase I achieved CR, 1 patient achieved PR after 3 cycles of treatment. In cohort 2 of phase I, all 3 achieved CR after completion of treatment and 2 patients achieved CR and 1 achieved PR after 3 cycles of treatment; however, 1 patient showed tumor progression after completion of treatment (Table 3).

In phase II, 25 patients achieved CR and 13 patients achieved PR after 3 cycles of treatment. After completion of treatment, 32 patients achieved CR and 6 patients achieved PR, with an overall response rate (ORR) of 95%. At median follow-up of 16.1 months, 10 patients showed disease progression or relapse and 8 died. The overall 2-year EFS rate was 60.6% and the 2-year OS rate was 75.1% (Fig. 2).