Marked Activity of Bortezomib, Rituximab, and Dexamethason in Relapsed and Refractory Mantle Cell Lymphoma.

Bortezomib (B) belongs to a new class of anti-cancer agents, the proteasome inhibitors, and has documented activity in multiple myeloma and mantle cell lymphoma (MCL). Preclinical studies suggest that B has synergistic activity with rituximab (R), which provides a rationale for the exploration of treatment combinations. We have initiated a phase II study in relapsed/chemotherapy refractory MCL to evaluate the activity and safety of B in combination with R and dexamethasone (BORID). A treatment cycle consists of B at 1.3 mg/m² administered on days 1, 4, 8, and 11, R at 375 mg/m² administered on day 1, and dexamethasone 40 mg orally on days 1 to 4. Cycles are repeated every 3 weeks for a total of 6 treatment cycles. Patients (pts) with progressive MCL after at least one prior line of therapy (including CHOP or a CHOP-like regimen) are eligible. We have now enrolled 14 pts at a median age of 69 years (range, 48 to 75 years) after a median of 3 lines of prior therapies (range, 1 to 6) including R in 12 pts, high-dose therapy in 4 pts, and thalidomide in 7 pts. Median time between start of frontline therapy and study inclusion was 43 months (range, 11 to 98 months). Severe adverse events (> grade II) included infections (herpes zoster in 2 pts, bacterial pneumonia, mucosal candidiasis), peripheral neuropathy (3 pts), fatigue (2 pts), vasculitic skin infiltrates in 3 pts, and hyponatremia in 1 pt. Thrombopenia (< 50 G/L) occured in 2 pts. All adverse events were managable by standard means of supportive care and prolongation of the treatment interval between cycles. Of 12 pts evaluable for efficacy, 9 have achieved a response (3 CR, 6 PR), and 2 pts experienced stable disease. Pts in CR were also negative for disease activity by PET scanning. Skin infiltrates (histologically proven T-cell infiltrates) preceded achievement of CR in 2 pts. All 3 pts who achieved a CR are still progression-free at 12 months after treatment initiation. Among pts in PR, 3 pts have relapsed (progression-free survival 14, 11, and 6 months, respectively), and 3 pts are still progression-free beyond 6 months from initiation of treatment. In summary, the BORID treatment regimen has promising activitiy and managable toxicity in patients with heavily pretreated MCL, and development of a vasculitic rash may be an early indicator of a favorable and durable response.