Background-The continual reassessment method (CRM) is an adaptive model-based design used to estimate the maximum tolerated dose in dose finding clinical trials. A way to evaluate the sensitivity of a given CRM model including the functional form of the dose-toxicity curve, the prior distribution on the model parameter, and the initial guesses of toxicity probability at each dose is using indifference intervals. While the indifference interval technique provides a succinct summary of model sensitivity, there are infinitely many possible ways to specify the initial guesses of toxicity probability. In practice, these are generally specified by trial and error through extensive simulations.

PurposeThe proteasome inhibitor bortezomib may enhance activity of chemoimmunotherapy in lymphoma. We evaluated dose-escalated bortezomib plus standard cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) plus rituximab (R) in patients with diffuse large B-cell lymphoma (DLBCL) and mantle cell lymphoma (MCL).Patients and MethodsSeventy-six subjects with untreated DLBCL (n = 40) and MCL (n = 36) received standard CHOP every 21 days (CHOP-21) with R plus bortezomib at 0.7 mg/m2(n = 4), 1.0 mg/m2(n = 9), or 1.3 mg/m2(n = 63) on days 1 and 4 for six cycles.ResultsMedian age was 63 years (range, 20 to 87), and International Prognostic Index (IPI) scores were generally unfavorable (39% with IPI of 2, and 49% with IPI of 3 to 5), as were Mantle Cell Lymphoma International Prognostic Index scores in patients with MCL (28% intermediate risk and 39% high risk). Toxicity was manageable, including neuropathy in 49 subjects (8% grade 2 and 4% grade 3) and grade 3/4 anemia (13%), neutropenia (41%), and thrombocytopenia (25%). For DLBCL, the evaluable overall response rate (ORR) was 100% with 86% complete response (CR)/CR unconfirmed (CRu; n = 35). Intent-to-treat (ITT, n = 40) ORR was 88% with 75% CR/CRu, 2-year progression-free survival (PFS) of 64% (95% CI, 47% to 77%) and 2-year overall survival (OS) of 70% (95% CI, 53% to 82%). For MCL, the evaluable ORR was 91% with 72% CR/CRu (n = 32). The ITT (n = 36) ORR was 81% with 64% CR/CRu, 2-year PFS 44% (95% CI, 27% to 60%) and 2-year OS 86% (95% CI, 70% to 94%). IPI and MIPI correlated with survival in DLBCL and MCL, respectively. Unlike in DLBCL treated with R-CHOP alone, nongerminal center B cell (non-GCB) and GCB subtypes had similar outcomes.ConclusionBortezomib with R-CHOP-21 can be safely administered and may enhance outcomes, particularly in non-GCB DLBCL, justifying randomized studies.