In MCF-7 cells, increasing DPP under matched ADR conditions consistently reduced clonogenic survival, with the strongest effect at 10 Gy, where survival decreased from 0.0880 to 0.0325 ( p = 0.082, near-significant), while differences at 5 and 20 Gy were non-significant ( p = 0.197 and 0.136, respectively).
When the SSD was shortened to 75 cm to elevate both DPP and IDR, clonogenic survival decreased consistently in FFF (E) compared with FF (D), although these differences did not reach statistical significance ( p = 0.097, 0.193, and 0.112 at 5, 10, and 20 Gy, respectively).
In MCF-7 cells, higher DPP at the same ADR yielded a consistent reduction in the survival fraction, with the 10 Gy comparison approaching significance, an effect that aligned with the expectation that a lower α/β phenotype is more sensitive to large single fractions.