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How densely a radiation track dumps energy along its path. Sparse tracks (X-rays, most of a proton beam) are easier to repair; dense tracks (the proton's stop-point, carbon ions, alpha particles) punch clustered holes in DNA.
Linear energy transfer is the energy a charged particle deposits per unit length of track, usually in keV per micrometre. Photons and electrons are low-LET. Protons are mostly low-LET along the entrance plateau and rise at the Bragg peak and just beyond it, which is why a constant relative biological effectiveness of 1.1 is only a reporting convention. Carbon ions and alpha particles (around 100 keV per micrometre) are high-LET: they cause clustered double-strand breaks, work in hypoxia, and are less sensitive to fraction size. LET is the physical input to relative biological effectiveness; the two are not the same number.
Showing the technology this term belongs to: Proton therapy.
For men with low- or intermediate-risk prostate cancer, protons and modern IMRT give the same excellent quality of life and cancer control, so the choice can rest on access, cost and convenience rather than on an expected sparing of bowel or bladder. The result removes prostate cancer from the list of adult indications where a proton advantage was assumed but untested.
A proton plan that looks safe on a 1.1 RBE map can still over-dose a late-responding organ sitting on the distal edge. Comparing protons with IMRT without an LET-weighted view asks the wrong physical question.
Two term pages on OnCo cite this paper by its DOI; this record gives the citation a page of its own so a reader can follow it without leaving OnCo. Read the abstract above alongside the citing pages listed under Related; the record was created automatically from the Europe PMC entry and its figures have not been checked by hand.
Shares Bragg peak, Pencil-beam scanning and intensity-modulated proton therapy, Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH, Proton therapy.
Shares The linear-quadratic model and fractionation, Relative biological effectiveness (RBE), Use LET, RBE and alpha/beta to decide when protons beat IMRT, Proton therapy.
Shares Carbon-ion therapy, Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH, Proton therapy, IMRT / IGRT (modern external beam).
Shares Pooled coverage-with-evidence for proton therapy across all centres, Carbon-ion therapy, Proton therapy.
Shares Boron neutron capture therapy, Pencil-beam scanning and intensity-modulated proton therapy, Carbon-ion therapy, Proton therapy.
Shares PARTIQoL: phase 3 randomised trial of proton therapy versus IMRT for localised prostate cancer (ASTRO 2024 late-breaking abstract), Proton therapy, IMRT / IGRT (modern external beam).
Shares Alpha vs beta emitters, Carbon-ion therapy, Targeted alpha therapy.
Shares Pooled coverage-with-evidence for proton therapy across all centres, Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH, Proton therapy.