EQD2

Review by the originator of the term biologically effective dose (BED, introduced in Br J Radiol in 1989). Gives the BED formula — nd[1 + d/(α/β)], with an optional overall-time term — and the conversion to the equivalent dose in 2 Gy fractions by dividing BED by 1 + 2/(α/β) (1.2 for α/β = 10 Gy, 1.67 for 3 Gy, 2.0 for 2 Gy). Its worked example: 30 × 2 Gy = 60 Gy is 72 Gy10 to early-responding tissue and 100 Gy3 to late-responding tissue, but 60 Gy EQD2 to both. Full text read in Europe PMC (PMC3473681).

The overview of the EMBRACE II study of image-guided IMRT with chemotherapy followed by MRI-based adaptive brachytherapy for locally advanced cervical cancer. It sets out the study's external beam dose constraints (hard and soft, with separate bowel limits when the para-aortic nodes are treated), the brachytherapy planning aims and limits for the high-risk CTV, GTV, point A, bladder, rectum, sigmoid and bowel in total EQD2, and the vaginal dose points. Open access.

The template NRG Oncology gives investigators for writing the radiation therapy section of a cervical cancer trial, covering external beam (photon, MR-linac and proton) and brachytherapy. It describes supine or prone setup, full- and empty-bladder simulation scans fused to build an internal target volume, diagnostic MRI and PET/CT fusion, standard structure names (including Spc_Bowel and BoneMarrow), example prescriptions, HDR point A and volume-directed (CTV_HR) brachytherapy, and per-protocol and variation-acceptable compliance criteria for both the external beam plan and the combined EBRT + brachytherapy dose. Its values are examples meant to be edited for each trial. DoseLab's cervix tables quote its per-protocol levels.

Recommendations for standardized naming of targets, organs at risk and dose-volume metrics. Section 9 sets out the DVH-metric nomenclature DoseLab follows: Vx (volume receiving at least dose x), Dx (minimum dose to the hottest sub-volume x), CVx and DCx (the "cold" complements), output units in square brackets (Gy or % of prescription; cc or % of the structure), and an EQD2Gy unit with the α/β written in parentheses — for example D90%(10)[EQD2Gy]. Section 10 asks that DVH metrics say whether a lower-dose PTV is segmented (excludes the higher-dose PTV) or not. Read in the AAPM report PDF.

Systematic review of 64 clinical studies reporting α, β and α/β for human tumors. It found large heterogeneity within and between studies; estimates for prostate and breast tumors generally indicated high fractionation sensitivity, those for head & neck, cervix, bladder and liver tumors low sensitivity, and others were mixed. It notes that whether the LQ model holds at large fraction sizes is debated, and recommends choosing parameters by site, histology and model and exploring a range of values. Full text read in Europe PMC (PMC5956964).