We present central-to-peripheral nuclear modification factors, R _CP, for the p_T distributions of K_S⁰, Λ, Λ, and negatively charged particles, measured at central rapidity in Pb-Pb collisions at top SPS energy. The data cover the 55% most central fraction of the inelastic cross section. The K_S⁰ and Λ R_CP(p_T) are similar in shape to those measured at √s_NN = 200 GeV at RHIC, though they are larger in absolute value. We have compared our K_S⁰ R_CP data to a theoretical calculation. The prediction overestimates the data at p_T ≈ 3-4 GeV/c, unless sizeable parton energy loss is included in the calculation.