Does hormone therapy modify the position of the gold markers in the prostate during irradiation? A daily evaluation with kV-images

AbstractPurpose arkers are frequently used for a better daily repositioning of the prostate before irradiation. The purpose of this work was to analyze if the combination of an androgen deprivation with the external irradiation could modify the position of the gold markers in the prostate. ts and methods tients have been treated for a prostate cancer, using three implanted gold markers. The variations of the intermarker distances in the prostate were measured and collected on daily OBI® kilovoltage images acquired at 0° and 90°. Five patients had a 6-month androgen deprivation started before the external irradiation (H group) and five did not (NH group). s l number of 1062 distances were calculated. No distance variation greater than 3.7 mm was seen between two markers, in any of the two groups. The median standard deviations of the daily intermarker distance differences were 0.7 mm (range 0.3–1.2 mm) for the H group and 0.6 mm (range 0.2–1.2 mm) for the NH group. The intermarker distances variations were noted as greater than –2 mm, between –2 mm and 2 mm and greater than 2 mm in 16.4, 83.4 and 0.2% for the H group and 1.3, 98.5 and 0.2% for the NH group, respectively. sion stance variations remained less than 4 mm in both groups and for all the measurements. In the NH group, the variation of the distance between two markers remained below 2 mm in 98.5%. In the H group, the presence of a reduction of distance above 2 mm in 16.4% of measurements could indicate the shrinkage of the prostate volume.