How low is the α/β ratio for prostate cancer?

• Published in: International journal of radiation oncology, biology, physics Vol. 57; no. 4; pp. 1116 - 1121
• Main Authors: Kal, Henk B, Van Gellekom, Marion P.R
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 15.11.2003; Elsevier
• Subjects: Alpha/beta; Biological and medical sciences; Brachytherapy; DNA Repair; Edema; Edema - complications; Humans; Iodine Radioisotopes - therapeutic use; Linear Models; Male; Medical sciences; Palladium - therapeutic use; Prostate cancer; Prostatic Diseases - complications; Prostatic Neoplasms - radiotherapy; Radioisotopes - therapeutic use; Radiotherapy Dosage; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Reference Values; Relative Biological Effectiveness; Repopulation; Technology. Biomaterials. Equipments. Material. Instrumentation; Edema; Brachytherapy; Alpha/beta; Repopulation; Prostate cancer; Biomedical engineering
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/S0360-3016(03)01455-X

Recently, low α/β values of 1.2 and 1.5 Gy for prostate tumors have been derived from clinical results of external beam radiotherapy and of permanent implants of 125I and 103Pd. In the analyses the contributions of tumor repopulation, and edema as a result of inserting radioactive seeds in the prostate, have been ignored. In this paper we reanalyzed the clinical data and introduced the contribution of repopulation and edema. The linear quadratic–biologically effective dose model was used for reanalysis. In this model, the influence of repopulation and edema has been taken into account. The biologically effective dose was calculated as a function of α/β for 2 brachytherapy regimens with 125I and 103Pd and 2 fractionated treatments, and for different half-times for repair of sublethal damage for the brachytherapy regimens. We have found a plausible α/β value of 3.1 to 3.9 Gy, an α value of 0.1 to 0.15 Gy −1, and a half-time of repair of about 0.5 h. It seems now that the α/β value is low, 3.1–3.9 Gy, but not as low as the 1.2 and 1.5 Gy reported earlier.