Standard Irradiation Technique Research Articles

Preventing Cardiotoxicity in Personalized Breast Irradiation.

This study aims to assess the benefit of a deep inspiration breath hold (DIBH) over the standard irradiation technique, and eventually to identify anatomical and/or treatment preplanning characteristics correlated with the LAD dose. Patients with left-sided breast cancer undergoing whole breast radiotherapy with DIBH were analyzed. All patients included in the analysis had plans in DIBH and free-breathing (FB). Receiving operating characteristics (ROC analysis) were used to identify the cut-off point of parameters to predict the LAD maximum dose > 10 Gy and LAD mean dose > 4 Gy, and the areas under the curve (AUCs) were computed. Post-test probability has been performed to evaluate the effect of parameters' combination. One hundred ninety-seven patients were analyzed. The LAD dose was significantly reduced in DIBH plans with the maximum and mean dose reduced by 31.7% (mean value 3.5 Gy vs. 4.8 Gy, p ≤ 0.001) and 28.1% (mean value 8.2 Gy vs. 12.8 Gy, p ≤ 0.001) in DIBH plans compared to FB plans. The strongest predictor of the LAD dose (maximum > 10 Gy and mean > 4 Gy) was the minimum distance of LAD from tangent open fields. Other parameters were lung volume and heart volume (LAD Dmax > 10 Gy) and lung volume, heart volume, and breast separation (LAD Dmean > 4 Gy). The dosimetric advantage of DIBH is clear in all patients and DIBH should always be preferred.

Radiothérapie adaptative des cancers de la vessie : état de l’art et perspectives pratiques

PurposeRadiation therapy (RT) for muscle invasive bladder cancer (MIBC) is challenging, with observed variations in bladder shape and size resulting in inappropriate coverage of the target volumes (CTV). Large margins were historically applied around the CTV, increasing the dose delivered to organs at risk (OAR). With repositioning imaging and visualization of soft tissues during image guided RT, an opportunity to consider these movements and deformations appeared possible with an adaptive RT approach (ART). Materials and methodsA bibliographic search on the PubMed database has been done in January 2019. Studies focusing on patients with MIBC, treating on ART, with the objectives of feasibility, clinical and/or dosimetric evaluation and comparison with a standard irradiation technique were eligible. The purpose of this review was to define the different ART techniques used in clinical practice, to discuss their advantages compared to conventional RT in terms of target volume's coverage and OAR dose and to describe their feasibility in clinical practice. ResultsA total of 30 studies were selected. The strategies known as “composite offline”, “plan of the day” not individualized or individualized, and “re-optimization” have been identified. All the studies have shown a significant benefit of ART in target coverage and dose of OAR, especially the rectum and small bowel. All ART plans produced are not used during RT sessions. Inter-observer variability for the selection of these plans can be observed. The practical implementation within a department required staff education and training, and increases the duration of treatment preparation. The “A-POLO” approach seems to be the most suitable for practice. ConclusionART is the technique of choice for bladder cancer RT. The “plan of the day” approach, individualized according to the A-POLO methodology, seems to be the most effective. The emergence of daily re-optimization, especially using MRI-Linac, is promising. The correlation between dosimetric benefits and clinical efficacy and safety results should be demonstrated into future trials.

Gestion des doses liées à l’imagerie de positionnement en radiothérapie

Image-guided radiotherapy (IGRT) has become a standard irradiation technique to improve the clinical outcome of patients in terms of toxicity and local control due to better targeting of radiation during the irradiation fraction. Positioning imaging systems, whether embedded or not, such as kV for 2×2D acquisitions and especially kVCBCT for 3D acquisitions are however irradiating in a large volume including the target volume but also healthy tissue, with a theoretical risk of increased toxicity and second cancer. It therefore appears very important both to optimize the absorbed dose due to IGRT practice but also to report it, especially in case of kVCBCT. The AAPM report published in 2018 (« Image guidance doses delivered during radiotherapy: Quantification, management, and reduction ») proposes a management of image guidance doses delivered during radiotherapy. This report is the basis of this focus article that aims at giving orders of magnitude and proposing a management of image guidance doses delivered during radiotherapy in clinical practice. The dose delivered per kVCBCT is about 0.5 to 2 cGy at isocenter according to treatment site. As long as the calculation algorithms are not available in the treatment planning systems, it seems appropriate to use at least the published dose orders of magnitude. This estimate should ultimately allow the clinician to decide on the therapeutic strategy in the event of accumulation of positioning imaging sessions.

A glance on quality assurance in EORTC study 22922 evaluating techniques for internal mammary and medial supraclavicular lymph node chain irradiation in breast cancer

Purpose: To evaluate the irradiation techniques used for the irradiation of the internal mammary and medial supraclavicular lymph node chain (IM-MS) in the EORTC 22922 study, which evaluates its impact on survival in stage I–III breast cancer patients with axillary node invasion and/or central or medial location of the primary tumour. Materials and methods: The analysis was performed based on the dummy run data of the Quality Assurance Programme of the study. A standard irradiation technique was proposed within the study protocol, and the use of other treatment set-up techniques was allowed. Results: By March 2000, 39 centres from 12 different countries had participated in the study; 32 of these had already fulfilled the dummy run procedure. No centres had to be excluded from the study. Seventy-eight percent of the centres are using the standard irradiation technique, 64% of these with minor variations. Twenty-two percent of the centres developed an alternative irradiation technique. The remarks to the centres using the standard set-up were most often related to the junction problem and the possible under- or overdosage in the target volumes. The remarks to the centres with alternative techniques most often concerned the possible enhanced dose to the lungs and the heart. Conclusion: In a multi-centre trial an easy irradiation technique applicable in a large number of centres should be provided. A quality assurance programme allows early detection of possible problems with treatment planning and delivery. The analysis of the dummy run data showed that if the recommendations of the Quality Assurance Committee are applied, both standard and alternative IM-MS irradiation techniques produce acceptable dose distributions.

Intensity modulation with electrons: calculations, measurements and clinical applications

Intensity modulation of electron beams is one step towards truly conformal therapy. This can be realized with the MM50 racetrack microtron that utilizes a scanning beam technique. By adjusting the scan pattern it is possible to obtain arbitrary fluence distributions. Since the monitor chambers in the treatment head are segmented in both x- and y-directions it is possible to verify the fluence distribution to the patient at any time during the treatment. Intensity modulated electron beams have been measured with film and a plane parallel chamber and compared with calculations. The calculations were based on a pencil beam method. An intensity distribution at the multileaf collimator (MLC) level was calculated by superposition of measured pencil beams over scan patterns. By convolving this distribution with a Gaussian pencil beam, which has propagated from the MLC to the isocentre, a fluence distribution at isocentre level was obtained. The agreement between calculations and measurements was within 2% in dose or 1 mm in distance in the penumbra zones. A standard set of intensity modulated electron beams has been developed. These beams have been implemented in a treatment planning system and are used for manual optimization. A clinical example (prostate) of such an application is presented and compared with a standard irradiation technique.

“Nidoxital”: A clinical trial

Summary 1.A clinical trial of a new anti-emetic drug, “Nidoxital,” is reported. 2.Fifty-one cases of carcinoma of the breast treated by simple mastectomy and a standard irradiation technique are surveyed as a randomised series using “Nidoxital,” Pyridoxine and a Placebo. 3.“Nidoxital” therapy ensures that two-thirds of the cases remain asymptomatic throughout treatment as compared with one-third of the controls. This result is statistically significant at the 10 per cent level. 4.Survey of the symptoms in detail shows that without treatment, anorexia and nausea are the two commonest and loss of taste and vomiting the least common to arise. 5.With “Nidoxital” anorexia is apparently the easiest symptom to control and nausea, headache and malaise the most difficult. Summary 1.A clinical trial of a new anti-emetic drug, “Nidoxital,” is reported. 2.Fifty-one cases of carcinoma of the breast treated by simple mastectomy and a standard irradiation technique are surveyed as a randomised series using “Nidoxital,” Pyridoxine and a Placebo. 3.“Nidoxital” therapy ensures that two-thirds of the cases remain asymptomatic throughout treatment as compared with one-third of the controls. This result is statistically significant at the 10 per cent level. 4.Survey of the symptoms in detail shows that without treatment, anorexia and nausea are the two commonest and loss of taste and vomiting the least common to arise. 5.With “Nidoxital” anorexia is apparently the easiest symptom to control and nausea, headache and malaise the most difficult.