Three hundred fifty-nine pretreatment @-hydroxyvitamin D@ ( @ -LSB- OH -RSB- D@ ) serum levels from the RICOVER-@ study ( Six Versus Eight Cycles of Biweekly CHOP-@ With or Without Rituximab in Elderly Patients With Aggressive CD@ + B-Cell Lymphomas ) and @ from the RICOVER-noRTh study ( an amendment to the RICOVER-@ study in which patients received six cycles of cyclophosphamide , doxorubicin , vincristine , and prednisone administered at an interval of @ weeks plus two cycles of rituximab -LSB- R-CHOP-@ -RSB- , but without radiotherapy ) were determined by chemoluminescent immunoassay .