A method for treating cancer comprising applying peripheral blood from a patient or subject to an apheresis column loaded with a solid support comprising one or more binding reagents capable of specifically binding to a chemokine receptor, optionally the chemokine receptor CCR7, CCR5, CCR6, CCR8, CXCR4, CXCR7, CCR4, CCR9, CCR10, CXCR3 or CXCR5 or to a Treg receptor immobilized directly or indirectly on the support thus removing one or more chemokine receptor, optionally CCR7, CCR5, CCR6, CCR8, CXCR4, CXCR7, CCR4, CCR9, CCR10, CXCR3 or CXCR5 or Treg receptor expressing cells from the peripheral blood of the patient or subject. Various companion diagnostic methods and useful binding reagents are also described.