Purpose: High amounts of intratumoral macrophages have been shown to correlate with poor prognosis in patients with follicular lymphoma (FL) treated with chemotherapy without rituximab. We tried to establish whether intratumoral macrophage count (MC) definitely is able to predict the outcome of FL patients in the rituximab era.
Patients and methods: We analyzed immunohistochemical CD68 expression in 194 FL patients from the FL-2000 trial, randomly assigned to receive cyclophosphamide, doxorubicin, etoposide, prednisolone, and interferon (CHVP-I) or rituximab plus CHVP-I. Immunohistochemistry was performed on paraffin sections using anti-CD68 KP1 antibody, and stained macrophages were scored on high-power field (hpf) in either intrafollicular (IF) or extrafollicular (EF) areas.
Results: For IF MC, the best cutoff point was estimated at 10 macrophages/hpf. Low IF MC was significantly associated with a better event-free survival (EFS; P = .011). However, this effect was observed only in the CHVP-I arm (P = .012) and not in the rituximab plus CHVP-I arm. Using a cutoff of 15 IF MC, we found no significant association with EFS. For EF MC, fewer than 22 macrophages/hpf were associated with better EFS in the CHVP-I arm (P = .02) but not in the rituximab plus CHVP-I arm.
Conclusion: These results show that MC can predict outcome of FL patients and that rituximab is able to circumvent the unfavorable outcome associated with high MC.