Prostate Stereotactic Ablative Radiation Therapy Using Volumetric Modulated Arc Therapy to Dominant Intraprostatic Lesions

PurposeTo investigate boosting dominant intraprostatic lesions (DILs) in the context of stereotactic ablative radiation therapy (SABR) and to examine the impact on tumor control probability (TCP) and normal tissue complication probability (NTCP).Methods and MaterialsTen prostate datasets were selected. DILs were defined using T2-weighted, dynamic contrast-enhanced and diffusion-weighted magnetic resonance imaging. Four plans were produced for each dataset: (1) no boost to DILs; (2) boost to DILs, no seminal vesicles in prescription; (3) boost to DILs, proximal seminal vesicles (proxSV) prescribed intermediate dose; and (4) boost to DILs, proxSV prescribed higher dose. The prostate planning target volume (PTV) prescription was 42.7 Gy in 7 fractions. DILs were initially prescribed 115% of the PTVProstate prescription, and PTVDIL prescriptions were increased in 5% increments until organ-at-risk constraints were reached. TCP and NTCP calculations used the LQ-Poisson Marsden, and Lyman-Kutcher-Burman models respectively.ResultsWhen treating the prostate alone, the median PTVDIL prescription was 125% (range: 110%-140%) of the PTVProstate prescription. Median PTVDIL D50% was 55.1 Gy (range: 49.6-62.6 Gy). The same PTVDIL prescriptions and similar PTVDIL median doses were possible when including the proxSV within the prescription. TCP depended on prostate α/β ratio and was highest with an α/β ratio = 1.5 Gy, where the additional TCP benefit of DIL boosting was least. Rectal NTCP increased with DIL boosting and was considered unacceptably high in 5 cases, which, when replanned with an emphasis on reducing maximum dose to 0.5 cm3 of rectum (Dmax0.5cc), as well as meeting existing constraints, resulted in considerable rectal NTCP reductions.ConclusionsBoosting DILs in the context of SABR is technically feasible but should be approached with caution. If this therapy is adopted, strict rectal constraints are required including Dmax0.5cc. If the α/β ratio of prostate cancer is 1.5 Gy or less, then high TCP and low NTCP can be achieved by prescribing SABR to the whole prostate, without the need for DIL boosting

Developing a class solution for Prostate Stereotactic Ablative Body Radiotherapy (SABR) using Volumetric Modulated Arc Therapy (VMAT)

Background and purpose To develop a class solution for prostate Stereotactic Ablative Radiotherapy (SABR) using Volumetric Modulated Arc Therapy (VMAT). Materials and methods Seven datasets were used to compare plans using one 360° arc (1FA), one 210° arc (1PA), two full arcs and two partial arcs. Subsequently using 1PA, fifteen datasets were compared using (i) 6 mm CTV–PTV margins, (ii) 8 mm CTV–PTV margins and (iii) including the proximal SV within the CTV. Monaco™ 3.2 (Elekta™) was used for planning with the Agility™ MLC system (Elekta™). Results Highly conformal plans were produced using all four arc arrangements. Compared to 1FA, 1PA resulted in significantly reduced rectal doses, and monitor units and estimated delivery times were reduced in six of seven cases. Using 6 mm CTV–PTV margins, planning constraints were met for all fifteen datasets. Using 8 mm margins required relaxation of the uppermost bladder constraint in three cases to achieve adequate coverage, and, compared to 6 mm margins, rectal and bladder doses significantly increased. Including the proximal SV required relaxation of the uppermost bladder and rectal constraints in two cases, and rectal and bladder doses significantly increased. Conclusions Prostate SABR VMAT is optimal using 1PA. 6 mm CTV–PTV margins, compatible with daily fiducial-based IGRT, are consistently feasible in terms of target objectives and OAR constraints

Effect of Algorithm-Based Therapy vs Usual Care on Clinical Success and Serious Adverse Events in Patients with Staphylococcal Bacteremia: A Randomized Clinical Trial

Importance: The appropriate duration of antibiotics for staphylococcal bacteremia is unknown. Objective: To test whether an algorithm that defines treatment duration for staphylococcal bacteremia vs standard of care provides noninferior efficacy without increasing severe adverse events. Design, Setting, and Participants: A randomized trial involving adults with staphylococcal bacteremia was conducted at 16 academic medical centers in the United States (n = 15) and Spain (n = 1) from April 2011 to March 2017. Patients were followed up for 42 days beyond end of therapy for those with Staphylococcus aureus and 28 days for those with coagulase-negative staphylococcal bacteremia. Eligible patients were 18 years or older and had 1 or more blood cultures positive for S aureus or coagulase-negative staphylococci. Patients were excluded if they had known or suspected complicated infection at the time of randomization. Interventions: Patients were randomized to algorithm-based therapy (n = 255) or usual practice (n = 254). Diagnostic evaluation, antibiotic selection, and duration of therapy were predefined for the algorithm group, whereas clinicians caring for patients in the usual practice group had unrestricted choice of antibiotics, duration, and other aspects of clinical care. Main Outcomes and Measures: Coprimary outcomes were (1) clinical success, as determined by a blinded adjudication committee and tested for noninferiority within a 15% margin; and (2) serious adverse event rates in the intention-to-treat population, tested for superiority. The prespecified secondary outcome measure, tested for superiority, was antibiotic days among per-protocol patients with simple or uncomplicated bacteremia. Results: Among the 509 patients randomized (mean age, 56.6 [SD, 16.8] years; 226 [44.4%] women), 480 (94.3%) completed the trial. Clinical success was documented in 209 of 255 patients assigned to algorithm-based therapy and 207 of 254 randomized to usual practice (82.0% vs 81.5%; difference, 0.5% [1-sided 97.5% CI, -6.2% to ∞]). Serious adverse events were reported in 32.5% of algorithm-based therapy patients and 28.3% of usual practice patients (difference, 4.2% [95% CI, -3.8% to 12.2%]). Among per-protocol patients with simple or uncomplicated bacteremia, mean duration of therapy was 4.4 days for algorithm-based therapy vs 6.2 days for usual practice (difference, -1.8 days [95% CI, -3.1 to -0.6]). Conclusions and Relevance: Among patients with staphylococcal bacteremia, the use of an algorithm to guide testing and treatment compared with usual care resulted in a noninferior rate of clinical success. Rates of serious adverse events were not significantly different, but interpretation is limited by wide confidence intervals. Further research is needed to assess the utility of the algorithm. Trial Registration: ClinicalTrials.gov Identifier: NCT01191840

Use of natural oral contrast agents in upper-abdominal magnetic resonance imaging: a systematic scoping review protocol.

Systematic scoping review protoco

Improvements in target coverage and reduced spinal cord irradiation using intensity-modulated radiotherapy (IMRT) in patients with carcinoma of the thyroid gland

Improvements in target coverage and reduced spinal cord irradiation using intensity-modulated radiotherapy (IMRT) in patients with carcinoma of the thyroid gland. Background and purpose: External beam radiotherapy for thyroid carcinoma poses a significant technical challenge as the target volume lies close to or surrounds the spinal cord. The potential of intensity-modulated radiotherapy (IMRT) to improve the dose distributions was investigated. Materials and methods: A planning study was performed on patients with thyroid carcinoma. Plans were generated to irradiate the thyroid bed alone or to treat the thyroid bed and the loco-regional lymph nodes in two phases. Conventional plans with minimal beam shaping were compared to three-dimensional conformal radiotherapy (3DCRT) and inverse-planned IMRT plans to assess target coverage and normal tissue sparing. IMRT techniques were optimized to find the minimum number of equispaced beams required to achieve the clinical benefit and a concomitant boost technique was explored. Results: For the thyroid bed alone and the thyroid bed plus loco-regional lymph nodes, conventional and conformal techniques produced low minimum doses to the planning target volume (PTV) if spinal cord tolerance was respected. 3DCRT reduced the irradiated volume of normal tissue (P=0.01). IMRT plans achieved the goal dose to the PTV (P<0.01) and also reduced the spinal cord maximum dose (P<0.01). IMRT, using a concomitant boost technique, produced better target coverage than a two-phase technique. For both the two-phase and concomitant boost techniques, IMRT plans with seven and five equispaced fields produced similar dose distributions to nine fields, but three fields were significantly worse. Conclusions: 3DCRT reduced normal tissue irradiation compared to conventional techniques, but did not improve PTV or spinal cord doses. IMRT improved the PTV coverage and reduced the spinal cord dose. A simultaneous integrated boost technique with five equispaced fields produced the best dose distribution. IMRT should reduce the risk of myelopathy or may allow dose escalation in patients with thyroid cancer