Hypofractionated stereotactic body radiotherapy for localized prostate cancer - first Nordic clinical experience.

BACKGROUND: The use of hypofractionated stereotactic body radiotherapy (SBRT) as primary treatment modality in clinically localized prostate cancer (PCa) is emerging, because the low α/ß-ratio favors the use of high dose per fraction in PCa. There is a need for more data about SBRT, especially in high-risk PCa patients. The purpose of this retrospective study was to evaluate the safety and the short-term efficacy of robotic SBRT in a clinical patient cohort with localized PCa including also high-risk patients (D'Amico risk stratification). MATERIALS AND METHODS: A total of 240 consecutive patients with clinically localized PCa were treated primarily with SBRT to total doses of 35 Gy or 36.25 Gy in 5 fractions using a robotic SBRT device (CyberKnife®). All risk groups (D'Amico risk stratification) were represented as follows: 48 (22%), 59 (27%) and 111 (51%) of the patients representing low-, intermediate- and high-risk group, respectively. Data on acute and intermediate-term toxicities and early PSA responses were analyzed. RESULTS: Neither acute grade 3 or higher GU nor rectal toxicity was observed. Regardless of the fact that 29 (13.3%) patients experienced intermediate-term toxicity requiring diagnostic interventions, the rates of intermediate-term grade 3 GU, rectal and infectious toxicity were low, 1.8%, 0.9% and 1.4%, respectively. A biochemical relapse was observed in ten (4.6%) patients. With the median follow-up time of 23 months the biochemical relapse-free survival (bRFS) rate was 100%, 96.6% and 92.8% in low-, intermediate- and high-risk group, respectively. CONCLUSIONS: The toxicity of robotic SBRT in a large clinical cohort of PCa patients was tolerable and the early PSA response was good in all risk groups. The hypofractionated SBRT offers a possibility to high dose per fraction and to provide the whole radiotherapy treatment within two to three weeks.

Volumetric modulated arc therapy for synchronous bilateral whole breast irradiation - A case study.

PURPOSE: The treatment planning of bilateral breast irradiation (BBI) is a challenging task. The overlapping of tangential fields is usually unavoidable without compromising the target coverage. The purpose of this study was to investigate the technical feasibility and benefits of a single isocentre volumetric modulated arc therapy (VMAT) in BBI. METHODS AND MATERIALS: Two women with bilateral breast cancer were included in this case study. The first patient (Pat#1) underwent a bilateral breast-conserving surgery and sentinel lymph node biopsy. The second patient (Pat#2) underwent a bilateral ablation and axillary lymph node dissection. Planning target volumes (PTV) and organs at risk were delineated on CT images. VMAT plans were created with four (two for both sides, Pat#1) or two (one for each breast, Pat#2) separate VMAT fields. Subsequently, traditional tangential field plans were generated for each patient and the dosimetric parameters were compared. RESULTS: The treatment times of the patients with VMAT were less than 15 min with daily CBCT imaging. When compared to the standard tangential field technique, the VMAT plans improved the PTV dose coverage and dose homogeneity with improved sparing of lungs and heart. With traditional field arrangement, the overlapping of the tangential fields was inevitable without significantly compromising the target coverage, whereas with VMAT the hotspots were avoided. The patients were treated with the VMAT technique and no acute skin toxicity was observed with either of the patients. CONCLUSIONS: A single isocentre VMAT technique has been implemented clinically for BBI. With the VMAT techniques, the dose delivery was quick and the hotspots in the field overlapping areas were avoided. The PTV dose coverage was superior in VMAT plans when compared with conventional tangential technique plans.

Flattening filter free technique in breath-hold treatments of left-sided breast cancer: The effect on beam-on time and dose distributions.

BACKGROUND AND PURPOSE: The use of flattening filter free (FFF) beams has potential to speed up deep-inspiration breath-hold treatments. In this study, the beam-on time and dose characteristics of left-sided breast treatment plans with FFF and flattened beams were evaluated. MATERIAL AND METHODS: Twelve plans were generated for 20 patients. The techniques utilized were volumetric modulated arc therapy with two limited tangential arcs (tVMAT) and tangential intensity modulated radiotherapy with dynamic (dIMRT) as well as step-and-shoot (FinF) dose delivery. Each technique was planned with FFF and flattened beams with 6 and 10MV photons. All plans were irradiated and the beam-on times were measured. Dose characteristics of planning target volume (PTV) and organs at risk (OAR) were evaluated. RESULTS: The mean beam-on times were reduced by 18-39% using FFF. Mean PTV dose coverage was least reduced with tVMAT (0.6-0.8%) compared to dIMRT (4%) and FinF (5.6-9.1%), when FFF beams were used instead of flattened beams. Only small differences were observed in OAR doses between equivalent plans (FFF vs. flattened). CONCLUSIONS: A significant reduction was observed in beam-on time when utilizing FFF beams with tVMAT, dIMRT and FinF. tVMAT was the only technique for which the use of FFF did not degrade the treatment plan dose distributions.

Tangential volumetric modulated arc therapy technique for left-sided breast cancer radiotherapy.

BACKGROUND: The aim of the present study was to introduce a new restricted tangential volumetric modulated arc therapy (tVMAT) technique for whole breast irradiation and compare its dosimetric properties to other currently used breast cancer radiotherapy techniques. METHOD: Ten consecutive women with left-sided breast cancer were enrolled in this retrospective study. Four treatment plans were generated for each patient: 1) standard tangential field-in-field (FinF), 2) tangential intensity modulated radiotherapy (tIMRT), 3) tangential VMAT (tVMAT) with two dual arcs of 50-60° and 4) continuous VMAT (cVMAT) with a dual arc of 240°. The plans were created with Monaco® (tIMRT, tVMAT and cVMAT) and Oncentra® (FinF) treatment planning systems. RESULTS: With both VMAT techniques significantly higher cardiac avoidance, dose coverage and dose homogenity were achieved when compared with FinF or tIMRT techniques (p < 0.01). VMAT techniques also decreased the high dose areas (above 20 Gy) of ipsilateral lung. There were no significant differences in the mean dose of contralateral breast between the tVMAT, tIMRT and FinF techniques. The dose coverage (V47.5 Gy) was greatest with cVMAT. However, with cVMAT the increase of contralateral breast dose was significant. CONCLUSIONS: The present results support the hypothesis that the introduced tVMAT technique is feasible for treatment of left-sided breast cancer. With tVMAT dose to heart and ipsilateral lung can be reduced and the dose homogeneity can be improved without increasing the dose to contralateral breast or lung.