In this study we analyzed prostate intrafraction motion during the course of stereotactic radiotherapy (STRT). STRT (5 fraction of 7.25Gy) was performed in 31 primary patients with prostate cancer. At least 3 gold fiducial markers were implanted in prostate of every patient 3-5 days before simulation. Prostate position on treatment table was verified with cone beam CT just before and immediately after the end of each radiotherapy session. This data help to determine prostate displacement in cranio-caudal, anterior-posterior and lateral axes. Average values of intra-fractional prostate displacement were as follows: 0,8+/-1,2mm - in cranio-caudal, 0.9+/-1,0mm - in lateral and 1.3+/-1,3mm - in anterior-posterior directions. In 5%-8,3% cases prostate displacement in cranio-caudal and lateral directions exceeded 2mm with maximal value of 5mm. In accordance with obtained average shifts we recommend following PTV margins: 1mm - in anterior-posterior and 3mm - in all other directions. In this case average intrafractional prostate shifts would not compromise dose delivery to prostate (V100 - 98%, D90 - 101%) and in comparison with standard (3mm, 5mm, 5mm, 5mm) margins would permit 16% reduction of rectum volume incorporated in 80% isodose. We propose that small average intrafractional displacement of prostate permits the use of narrower PTV margins without compromising coverage of the target and significant reduction of rectum volume covered by 80% isodose.

Purpose: the aim of the study is to assess the effectiveness and safety of prostate cancer treatment (PCa) with high dose rate brachytherapy (BT-HDR) in monotherapy on 5 years of follow-up. Materials and methods: BT-HDR is performed in 198 patients of PCa. The fractionation schedule was presented by two options: two fractionations of 13 Gy in the first group (67 people) and three fractionations of 11.5 Gy in the second (131 patients). The treatment was carried out with 192Ir (Microselectron). Results: the median for patient care was: I group - 59.2 (41.4-90.3), II - 56.1 (39.4-86.4) months. During the follow-up, no patients died from the progression of the PCa. The three-year survival rate without biochemical progression was 98.5%, while the second group had 92.8%; 88.8% and 88.1%, respectively. There were no significant differences in survival rates between the BT-HDR fractionation regimes compared. In most cases, late genito-urinary radiation toxicity was represented by changes that could be characterized as 1st degree. A total of 161 patients with a three-year follow-up period had three cases (1.8%) radiation-induced stenosis urethra (complications of 3 degrees): two of them in the first group, one in the second group. Only one patient (I group) (1.5%) recorded late recto-intestinal toxicity of the 2nd degree. There were no third or higher violations in the observed groups. Conclusions: the studied mono-modes of fractionation of BT- HDR PCa (two factions of 13 Gy and three factions of 11.5 Gy) demonstrated quite acceptable indicators of effectiveness and safety with a five-year period of observation. It has been established that there are no significant differences in the frequency of biochemical relapses, as well as the severity of early and late radiation toxicity in the groups compared.

Purpose: dosimetric comparison of high dose rate interstitial brachytherapy (HDR) and irradiation with electrons for radiation boost after whole-breast irradiation. Material and methods: in 62 patients with рТ1N0М0-рТ2№М0 breast cancer we used HDR brachytherapy for delivering boost to tumor bed. In all cases insertion of plastic needles was performed under CT control with subsequent 3D planning. Pre-insertion CT were used for 3D planning of boost delivery with electrons. Results: Boost delivery with HDR brachytherapy had several important advantages when compared with boost with electrons. HDR brachytherapy demonstrated more accurate irradiation of tumor bed: D90 HDR - 93,1 % (69,1 % - 118 %), D90 electrons - 86,2 % (47,6 % - 104,1 %). Boost delivery with HDR brachytherapy help to minimize radiation burden to left main coronary artery - Dmax electrons - 14.8 % (0.2 %-71.8%), Dmax HDR - 5.2 % (0.7 %-14.2 %). Radiation burden to left anterior descending artery is also decreasing: Dmax electrons - 21.9 % (0.8 %-94.1 %), Dmax HDR - 10.5 % (1.9 %-31.5 %). Radiation dose absorbed in ip-silateral lung also significantly lower with HDR brachytherapy: Dmed electrons - 6,5 % (0,5 % - 19,3 %), Dmed HDR - 2,3 % (0,8 % - 10,8 %). Conclusions: the present dosimetric analysis indicated that boost delivery with HDR brachytherapy is more accurate than irradiation with electrons.

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