Primary breast diffuse large B‐cell lymphoma in the rituximab era: Therapeutic strategies and patterns of failure

Primary breast diffuse large B‐cell lymphoma (PB‐DLBCL) is a rare subtype of DLBCL with limited data on patterns of failure. This multicenter study aimed to define the optimum treatment strategy and patterns of failure for PB‐DLBCL patients. We retrospectively reviewed data on 108 PB‐DLBCL patients from 21 Chinese medical centers. Only patients with localized disease (involvement of breast and localized lymph nodes) were included. After a median follow‐up of 3.2 years, 32% of patients developed progression or relapse. A continuous pattern of relapse was observed, characterized by frequent late relapses in the contralateral breast and central nervous system (CNS). Although rituximab significantly reduced the overall cumulative risk of progression or relapse (5‐year cumulative risk 57% vs 24%, P = .029), it had limited effect on the reduction of breast relapse (P = .46). Consolidative radiotherapy significantly decreased the risk of breast relapse, even in the subgroup of patients treated with rituximab (5‐year cumulative risk 21.2% vs 0%, P = .012). A continuous risk of CNS progression or relapse up to 8.2 years from diagnosis was observed (10‐year cumulative risk 28.3%), with a median time to CNS relapse of 3.1 years. Neither rituximab nor prophylactic intrathecal chemotherapy significantly decreased the risk of CNS relapse. In summary, our study indicates that PB‐DLBCL has a continuous pattern of relapse, especially with frequent late relapses in the CNS and contralateral breast. Rituximab and RT confer complementary benefit in the reduction of relapse. However, neither the addition of rituximab nor prophylactic intrathecal chemotherapy could effectively prevent CNS relapse for PB‐DLBCL patients.