CyberKnife versus multicatheter interstitial brachytherapy for accelerated partial breast irradiation: a dosimetrical assessment with focus on organs at risk.

Background: The purpose of the study was to dosimetrically compare multicatheter interstitial brachytherapy (MIBT) and stereotactic radiotherapy with CyberKnife (CK) for accelerated partial breast irradiation with special focus on dose to organs at risk (OARs). Materials and methods: Treatment plans of thirty-one patients treated with MIBT were selected and additional CK plans were created on the same CT images. The OARs included ipsilateral non-target and contralateral breast, ipsilateral and contralateral lung, skin, ribs, and heart for left sided cases. The fractionation was identical (4 × 6.25 Gy). Dose-volume parameters were calculated for both techniques and compared. Results: The D90 of the PTV for MIBT and CK were similar (102.4% vs. 103.6%, p = 0.0654), but in COIN the MIBT achieved lower value (0.75 vs. 0.91, p < 0.001). Regarding the V100 parameter of non-target breast CK performed slightly better than MIBT (V100: 1.1% vs. 1.6%), but for V90, V50 and V25 MIBT resulted in less dose. Every examined parameter of ipsilateral lung, skin, ribs and contralateral lung was significantly smaller for MIBT than for CK. Protection of the heart was slightly better with MIBT, but only the difference of D2cm3 was statistically significant (17.3% vs. 20.4%, p = 0.0311). There were no significant differences among the dose-volume parameters of the contralateral breast. Conclusion: The target volume can be properly irradiated by both techniques with high conformity and similar dose to the OARs. MIBT provides more advantageous plans than CK, except for dose conformity and the dosimetry of the heart and contralateral breast. More studies are needed to analyze whether these dosimetrical findings have clinical significance.

External beam accelerated partial breast irradiation: dosimetric assessment of conformal and three different intensity modulated techniques.

Background The aim of the study was to evaluate and compare four different external beam radiotherapy techniques of accelerated partial breast irradiation (APBI) considering target coverage, dose to organs at risk and overall plan quality. The investigated techniques were three dimensional conformal radiotherapy (3D-CRT), "step and shoot" (SS) and "sliding window" (SW) intensity-modulated radiotherapy (IMRT), intensity-modulated arc therapy (RA). Patients and methods CT scans of 40 APBI patients were selected for the study. The planning objectives were set up according to the international recommendations. Homogeneity, conformity and plan quality indices were calculated from volumetric and dosimetric parameters of target volumes and organs at risk. The total monitor units and feasibility were also investigated. Results There were no significant differences in the coverage of the target volume between the techniques. The homogeneity indices of 3D-CRT, SS, SW and RA plans were 0.068, 0.074, 0.058 and 0.081, respectively. The conformation numbers were 0.60, 0.80, 0.82 and 0.89, respectively. The V50% values of the ipsilateral breast for 3D-CRT, SS, SW and RA were 47.5%, 40.2%, 39.9% and 31.6%, respectively. The average V10% and V40% values of ipsilateral lung were 13.1%, 28.1%, 28%, 36% and 2.6%, 1.9%, 1.9%, 3%, respectively. The 3D-CRT technique provided the best heart protection, especially in the low dose region. All contralateral organs received low doses. The SW technique achieved the best plan quality index (PQI). Conclusions Good target volume coverage and tolerable dose to the organs at risk are achievable with all four techniques. Taking into account all aspects, we recommend the SW IMRT technique for APBI.

On the impact of improved dosimetric accuracy on head and neck high dose rate brachytherapy.

PURPOSE: To study the effect of finite patient dimensions and tissue heterogeneities in head and neck high dose rate brachytherapy. METHODS AND MATERIALS: The current practice of TG-43 dosimetry was compared to patient specific dosimetry obtained using Monte Carlo simulation for a sample of 22 patient plans. The dose distributions were compared in terms of percentage dose differences as well as differences in dose volume histogram and radiobiological indices for the target and organs at risk (mandible, parotids, skin, and spinal cord). RESULTS: Noticeable percentage differences exist between TG-43 and patient specific dosimetry, mainly at low dose points. Expressed as fractions of the planning aim dose, percentage differences are within 2% with a general TG-43 overestimation except for the spine. These differences are consistent resulting in statistically significant differences of dose volume histogram and radiobiology indices. Absolute differences of these indices are however small to warrant clinical importance in terms of tumor control or complication probabilities. CONCLUSIONS: The introduction of dosimetry methods characterized by improved accuracy is a valuable advancement. It does not appear however to influence dose prescription or call for amendment of clinical recommendations for the mobile tongue, base of tongue, and floor of mouth patient cohort of this study.

[Status report of Hungarian radiotherapy based on treatment data, available infrastucture, and human resources]. / A magyar sugárterápia helyzete a betegellátási adatok, a rendelkezésre álló infrastruktúra és emberi eroforrás tükrében.

The purpose of the study is to report the status of Hungarian radiotherapy (RT) based on the assessment of treatment data in years 2012 to 2014, available infrastructure, and RT staffing. Between December 2014 and January 2015, a RT questionnaire including 3 parts (1. treatment data; 2. infrastructure; 3. staffing) was sent out to all Hungarian RT centers (n=12). All RT centers responded to all questions of the survey. 1. Treatment data: In 2014, 33,162 patients were treated with RT: 31,678 (95.5%) with teletherapy, and 1484 (4.5%) with brachytherapy (BT). Between 2012 and 2014, the number of patients treated with radiotherapy increased with 6.6%, but the number of BT patients decreased by 11%. Forty-two percent of all patients were treated in the two centers of the capital: 9235 patients (28%) at the National Institute of Oncology (NIO), and 4812 (14%) at the Municipial Oncoradiology Center (MOC). Out of the patients treated on megavoltage RT units (n=22,239), only 901 (4%) were treated with intensity-modulated RT (IMRT), and 2018 (9%) with image-guided RT (IGRT). In 2014, 52% of all BT treatments were performed in Budapest: NIO - 539 patients (36%); MOC - 239 patients (16%); and BT was not available in 3 RT centers. Prostate I-125 seed implants and interstitial breast BT was utilized in one, prostate HDR BT in two, and head&neck implants in three centers. 2. Infrastructure: Including ongoing development projects funded by the European Union, by the end of year 2015, 39 megavoltage teletherapy units, and 12 HDR BT units will be in use in 13 available Hungarian RT centers. 3. Staffing: Actually, 92 radiation oncologists (RO), 29 RT residents, 61 medical physicists, and 229 radiation therapy technologists are working in 12 RT centers. There are 23 vacant positions (including 11 RO positions) available at the Hungarian RT centers. According to the professional minimal requirements and WHO guidelines, the implementation of 11 new linear accelerators, and 1 BT units are needed in Hungary. Further resources for the development and upgrade of RT infrastructure and capacity should be allocated to RT centers in Budapest. Brachytherapy and modern teletherapy (e.g. IMRT and IGRT) are underutilized in Hungary compared to other European countries. Implementation of continuous education and practical training programs in leading Hungarian and international RT centers are suggested in an effort to a wider implementation of modern RT techniques in Hungarian RT centers.

Assessment of dose homogeneity in conformal interstitial breast brachytherapy with special respect to ICRU recommendations.

PURPOSE: To present the results of dose homogeneity analysis for breast cancer patients treated with image-based conformal interstitial brachytherapy, and to investigate the usefulness of the ICRU recommendations. MATERIAL AND METHODS: Treatment plans of forty-nine patients who underwent partial breast irradiation with interstitial brachytherapy were analyzed. Quantitative parameters were used to characterize dose homogeneity. Dose non-uniformity ratio (DNR), dose homogeneity index (DHI), uniformity index (UI) and quality index (QI) were calculated. Furthermore, parameters recommended by the ICRU 58 such as minimum target dose (MTD), mean central dose (MCD), high dose volume, low dose volume and the spread between local minimum doses were determined. Correlations between the calculated homogeneity parameters and usefulness of the ICRU parameters in image-based brachytherapy were investigated. RESULTS: Catheters with mean number of 15 (range: 6-25) were implanted in median 4 (range: 3-6) planes. The volume of the PTV ranged from 15.5 cm(3) to 176 cm(3). The mean DNR was 0.32, the DHI 0.66, the UI 1.49 and the QI 1.94. Related to the prescribed dose, the MTD was 69% and the MCD 135%. The mean high dose volume was 8.1 cm(3) (10%), while the low dose volume was 63.8 cm(3) (96%). The spread between minimum doses in central plane ranged from -14% to +20%. Good correlation was found between the DNR and the DHI (R(2)=0.7874), and the DNR correlated well with the UI (R(2)=0.7615) also. No correlation was found between the ICRU parameters and any other volumetric parameters. CONCLUSIONS: To characterize the dose uniformity in high-dose rate breast implants, DVH-related homogeneity parameters representing the full 3D dose distributions are mandatory to be used. In many respects the current recommendations of the ICRU Report 58 are already outdated, and it is well-timed to set up new recommendations, which are more feasible for image-guided conformal interstitial brachytherapy.

[Dosimetric assessment of external treatment plans for breast cancer: the significance of dose prescription selection]. / Emlodaganatos betegek külso besugárzási terveinek dozimetriai vizsgálata: a dóziseloírás megválasztásának jelentosége.

PURPOSE: To analyze the treatment plans of breast irradiation performed with two tangential beams, to discuss the importance of dose prescription, and to estimate the differences in delivered dose due to various dose prescription methods. MATERIAL AND METHODS: A survey was performed between the Hungarian radiotherapy centers in order to compare the dose prescription methods. Then, treatment plans of 125 breast cancer patients treated in our department were evaluated. The irradiations were performed with cobalt unit, and with 6 and 9 MV photon beams of linear accelerators. The dose distributions were normalized to izocenter, then dose values in five points in central plane; local medial, lateral and central maximums (D(med), D(lat) and D(cent)); volumetric maximum and its location were determined. To characterize the dose to lung and to heart at left-sided tumors the central lung distance (CLD) and maximum heart distance (MHD) were used. Based on the results, estimation was made to assess the differences between delivered dose due to various dose prescriptions applied at the institutions. RESULTS: Four types of dose prescription are currently used in our country, and most frequently the isocenter is selected as a reference point. In the central plane the calculated dose in all but one points differed only a little from the dose to isocenter. The mean D(med), D(lat) and D(cent) were 107%, 107% and 101%, respectively. The volumetric maximum was on average 13% higher than the dose to isocenter. Regarding the beam qualities, this value was 16%, 13% and 11% for cobalt unit, 6 MV and 9 MV photon beams, respectively. The mean CLD and MHD were 1.9 and 0.8 cm, respectively. The difference between delivered doses at the institutions was 6% on average, but in extreme cases it can be as high as 20%. CONCLUSIONS: Three-dimensional treatment planning and plan evaluation are recommended at breast irradiation, especially for large breasts. Since the various dose prescriptions may result in significant differences in the delivered doses, use of a standard dose prescription protocol is recommended.