Dose de tolérance des tissus sains : le cœur

Dosimetric Comparison of the Heart and Left Anterior Descending Artery in Patients With Left Breast Cancer Treated With Three-Dimensional Conformal and Intensity-Modulated Radiotherapy

Background Adjuvant radiotherapy plays an important role in the management of breast cancer, along with surgery and chemotherapy. However, postoperative radiotherapy poses an increased risk of radiation-induced heart diseases in patients with left-sided breast cancer due to damage of the coronary arteries, which can cause myocardial fibrosis and coronary artery disease; however, there is a lack of sufficient evidence for it. Hence, the present study aimed to assess the dosimetric parameters of the heart and left anterior descending (LAD) coronary artery in patients with left breast cancer treated with three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT). Methodology This study included 20 patients with left-sided breast cancer treated between January and July 2019. Patients were equally divided into two groups as follows: group I included those treated with 3DCRT and group II included those treated with IMRT. Radiotherapy was administered to the chest wall and regional lymph nodes. The dose administered for the planning target volume was 50 Gy in 25 daily fractions over five weeks with 6 MV photons. Dosimetric parameters of planning tumor volume (PTV; V95%, V90%, Dmax, Dmin, Dmean, V53.5 Gy, conformity index, and homogeneity index) along with the heart (V5%, V30%, and Dmean) and LAD artery (mean and V25%) were evaluated. Dose-volume histograms were generated and compared. The LAD artery was contoured virtually retrospectively during the study to determine the dosimetric parameters; the dose to the LAD artery was not considered during planning. Results Dosimetric parameters of the PTV were similar for 3DCRT and IMRT; D95 (38.53 vs. 41.61 Gy), D90 (43.67 vs. 44.77 Gy), Dmean (48.3 vs. 48.72 Gy), conformity index (1.10 vs. 1.06), and homogeneity index (0.50 and 0.28) did not show a significant difference. The Dmean for the LAD artery was significantly higher than that for the heart on 3DCRT (23.66 Gy vs. 8.46 Gy; p < 0.0000) and IMRT (31.53 vs. 17.7 Gy; p < 0.0000). The V25 for the LAD artery was significantly higher than that for the heart on 3DCRT (40.27 vs. 14.13 Gy; p < 0.0024) and IMRT (66.21 vs. 27.74 Gy; p < 0.0002). Conclusions Radiation doses to the LAD artery and heart must be evaluated prior to radiotherapy in patients with left breast cancer. Long-term follow-up is needed to evaluate cardiac complications and their association with dosimetric parameters.

MEDiastinal Irradiation and CArdio-Toxic Effects (MEDICATE): Exploring the Relationship between Cardiac Irradiation and High Sensitivity Troponins

AIMS

Radiation-induced heart disease is a late effect of cardiac irradiation and has been shown in patients with lymphoma and thoracic cancers. There is no established measurement tool to detect acute cardiac damage. However, high sensitivity troponin I and T (HsTnI and HsTnT) and echocardiograms have shown promise in some studies. A pilot trial was conducted to characterise whether these instruments may detect subclinical radiotherapy-induced cardiac damage.

MATERIALS AND METHODS

Eligible patients received high cardiac doses defined by either at least 30 Gy to 5% of cardiac volume or a mean dose of 4 Gy. HsTnI and HsTnT were measured before radiotherapy and after 2 and 4 weeks of radiotherapy; three-dimensional echocardiograms were completed before and 1 year after radiotherapy.

RESULTS

Of 19 patients, the median 'mean left ventricular dose' was 3.1 Gy and the 'mean cardiac dose' was 8.6 Gy. Significant positive associations between HsTnI and HsTnT were observed at all time points, but there was no significant association with cardiac dose. The mean left ventricular dose and the maximum left ventricular dose were, however, associated with a decrease in ejection fraction (P = 0.054, 0.043) as well as an increase in left ventricular strain (P = 0.058).

CONCLUSION

This study suggests that HsTnI and HsTnT are intimately related, but detection of acute cardiac damage was not shown, potentially due to limitations of these markers or low radiotherapy doses using conformal techniques. Our results also suggest subacute damage at 1 year may depend on the dose to the left ventricle. Further studies are needed, as identification of early damage could facilitate the ability to closely monitor and intervene in patients at risk for radiation-induced heart disease.

Contouring workload in adjuvant breast cancer radiotherapy

PURPOSE

To measure the impact of contouring on worktime in the adjuvant radiation treatment of breast cancer, and to identify factors that might affect the measurements.

MATERIAL AND METHODS

The dates and times of contouring clinical target volumes and organs at risk were recorded by a senior and by two junior radiation oncologists. Outcome measurements were contour times and the time from start to approval. The factors evaluated were patient age, type of surgery, radiation targets and setup, operator, planning station, part of the day and day of the week on which the contouring started. The Welch test was used to comparatively assess the measurements.

RESULTS

Two hundred and three cases were included in the analysis. The mean contour time per patient was 34minutes for a mean of 4.72 structures, with a mean of 7.1minutes per structure. The clinical target volume and organs at risk times did not differ significantly. The mean time from start to approval per patient was 29.4hours. Factors significantly associated with longer contour times were breast-conserving surgery (P=0.026), prone setup (P=0.002), junior operator (P<0.0001), Pinnacle planning station (P=0.026), contouring start in the morning (P=0.001), and contouring start by the end of the week (P<0.0001). Factors significantly associated with time from start to approval were age (P=0.038), junior operator (P<0.0001), planning station (P=0.016), and contouring start by the end of the week (P=0.004).

CONCLUSION

Contouring is a time-consuming process. Each delineated structure influences worktime, and many factors may be targeted for optimization of the workflow. These preliminary data will serve as basis for future prospective studies to determine how to establish a cost-effective solution.

The INTER-ROMA Project - a Survey among Italian Radiation Oncologists on Their Approach to the Treatment of Bone Metastases

Aims and background

Radiotherapy has an established palliative role for bone metastases but despite the large number of patients treated there is still controversy surrounding the optimal radiotherapy schedule to prescribe. The aim of this survey was to determine the decision patterns of Italian radiation oncologists in four different clinical cases of patients with bone metastases.

Methods and study design

During the latest national meeting of the Italian Association of Radiation Oncology (AIRO), four clinical cases were presented to attending radiation oncologists. The cases were different with respect to the histology of the primary tumor, performance status, pain before and after analgesics, tumor site, and radiological characteristics of the metastatic lesions. For each clinical case the respondents were asked to give an indication for treatment; prescribe doses, volumes and treatment field arrangements; decide whether to prescribe prophylactic supportive therapy or not; and provide information about factors that particularly influenced prescription. Finally, a descriptive statistical analysis was performed.

Results

Three hundred questionnaires were distributed to radiation oncologists attending the congress. One hundred twenty-five questionnaires were returned but only 122 (40.6%) were adequately completed and considered for the analysis. Considerable differences were observed among radiation oncologists in prescribing and delivering radiotherapy for bone metastases. There was also a notable divergence from international guidelines, which will be discussed in this report.

Conclusions

Despite the results of clinical trials, Italian radiation oncologists differ considerably in their decisions on treatment doses and volumes. National guidelines are needed in order that patients can be treated uniformly and better data will become available for evidence-based palliative radiotherapy.

Superior sulcus non-small cell lung carcinoma: A comparison of IMRT and 3D-RT dosimetry

AIM

A dosimetric study comparing intensity modulated radiotherapy (IMRT) by TomoTherapy to conformational 3D radiotherapy (3D-RT) in patients with superior sulcus non-small cell lung cancer (NSCLC).

BACKGROUND

IMRT became the main technique in modern radiotherapy. However it was not currently used for lung cancers. Because of the need to increase the dose to control lung cancers but because of the critical organs surrounding the tumors, the gains obtainable with IMRT is not still demonstrated.

MATERIAL AND METHODS

A dosimetric comparison of the planned target and organs at risk parameters between IMRT and 3D-RT in eight patients who received preoperative or curative intent irradiation.

RESULTS

In the patients who received at least 66 Gy, the mean V95% was significantly better with IMRT than 3D-RT (p = 0.043). IMRT delivered a lower D2% compared to 3D-RT (p = 0.043). The IH was significantly better with IMRT (p = 0.043). The lung V 5 Gy and V 13 Gy were significantly higher in IMRT than 3D-RT (p = 0.043), while the maximal dose (D max) to the spinal cord was significantly lower in IMRT (p = 0.043). The brachial plexus D max was significantly lower in IMRT than 3D-RT (p = 0.048). For patients treated with 46 Gy, no significant differences were found.

CONCLUSION

Our study showed that IMRT is relevant for SS-NSCLC. In patients treated with a curative dose, it led to a reduction of the exposure of critical organs, allowing a better dose distribution in the tumor. For the patients treated with a preoperative schedule, our results provide a basis for future controlled trials to improve the histological complete response by increasing the radiation dose.

Comparison of organs' shapes with geometric and Zernike 3D moments

The morphological similarity of organs is studied with feature vectors based on geometric and Zernike 3D moments. It is particularly investigated if outliers and average models can be identified. For this purpose, the relative proximity to the mean feature vector is defined, principal coordinate and clustering analyses are also performed. To study the consistency and usefulness of this approach, 17 livers and 76 hearts voxel models from several sources are considered. In the liver case, models with similar morphological feature are identified. For the limited amount of studied cases, the liver of the ICRP male voxel model is identified as a better surrogate than the female one. For hearts, the clustering analysis shows that three heart shapes represent about 80% of the morphological variations. The relative proximity and clustering analysis rather consistently identify outliers and average models. For the two cases, identification of outliers and surrogate of average models is rather robust. However, deeper classification of morphological feature is subject to caution and can only be performed after cross analysis of at least two kinds of feature vectors. Finally, the Zernike moments contain all the information needed to re-construct the studied objects and thus appear as a promising tool to derive statistical organ shapes.

Whole breast and excision cavity radiotherapy plan comparison: Conformal radiotherapy with sequential boost versus intensity-modulated radiation therapy with a simultaneously integrated boost

Introduction

A comparative study was conducted comparing the difference between (1) conformal radiotherapy (CRT) to the whole breast with sequential boost excision cavity plans and (2) intensity-modulated radiation therapy (IMRT) to the whole breast with simultaneously integrated boost to the excision cavity. The computed tomography (CT) data sets of 25 breast cancer patients were used and the results analysed to determine if either planning method produced superior plans.

Methods

CT data sets from 25 past breast cancer patients were planned using (1) CRT prescribed to 50 Gy in 25 fractions (Fx) to the whole-breast planning target volume (PTV) and 10 Gy in 5Fx to the excision cavity and (2) IMRT prescribed to 60 Gy in 25Fx, with 60 Gy delivered to the excision cavity PTV and 50 Gy delivered to the whole-breast PTV, treated simultaneously. In total, 50 plans were created, with each plan evaluated by PTV coverage using conformity indices, plan maximum dose, lung dose, and heart maximum dose for patients with left-side lesions.

Results

CRT plans delivered the lowest plan maximum doses in 56% of cases (average CRT = 6314.34 cGy, IMRT = 6371.52 cGy). They also delivered the lowest mean lung dose in 68% of cases (average CRT = 1206.64 cGy, IMRT = 1288.37 cGy) and V20 in 88% of cases (average CRT = 20.03%, IMRT = 21.73%) and V30 doses in 92% of cases (average CRT = 16.82%, IMRT = 17.97%). IMRT created more conformal plans, using both conformity index and conformation number, in every instance, and lower heart maximum doses in 78.6% of cases (average CRT = 5295.26 cGy, IMRT = 5209.87 cGy).

Conclusion

IMRT plans produced superior dose conformity and shorter treatment duration, but a slightly higher planning maximum and increased lung doses. IMRT plans are also faster to treat on a daily basis, with shorter fractionation.

[Gated radiotherapy in breast cancer]

Postoperative radiotherapy is a cornerstone of the local treatment in breast cancer. It has been proved with high level of evidence that it decreases local relapse and improves survival of patients. However, radiotherapy comes with healthy tissue toxicity, heart and lung in particular. With constant improvement of radiation techniques, several methods have been developed to decrease the dose to the heart and the lungs. Sometimes, respiratory maneuvers can help, due to patient's anatomy: the radiotherapy is gated with patient's breath. The Deep Inspiration Breath Hold technique is the most popular and there are several ways to perform it. This note will describe the different systems with published data in order to help the radiation oncologist in the daily practice.

[Organs at risk and target volumes: definition for conformal radiation therapy in breast cancer]

Adjuvant radiotherapy is a standard component of breast cancer treatment. The addition of radiotherapy after breast conserving surgery has been shown to reduce local recurrence rate and improve long-term survival. Accurate delineation of target volumes and organs at risk is crucial to the quality of treatment planning and delivered accomplished with innovate technologies in radiation therapy. This allows the radiation beam to be shaped specifically to each individual patient's anatomy. Target volumes include the mammary gland and surgical bed in case of breast conserving surgery, the chest wall in case of mastectomy, and if indicated, regional lymph nodes (axillary, supra- and infraclavicular and internal mammary). Organs at risk include lungs, thyroid, brachial plexus, heart, spinal cord and oesophagus. The aim of this article is to encourage the use of conformal treatment and delineation of target volumes and organs at risk and to describe specifically the definition of these volumes.

[Single French centre retrospective analysis of local control after high dose radiotherapy with or without chemotherapy and local control for Pancoast tumours]

PURPOSE

Superior sulcus non-small cell lung cancer represents less than 5% of all lung cancers and is a challenge for the physicians because of clinical presentation, treatments related toxicities and poor prognosis. The aim of this preliminary retrospective report is to present outcomes of patients affected by a superior sulcus non-small cell lung cancer, treated by high dose radiotherapy (>60 Gy) with or with our chemotherapy.

PATIENTS AND METHODS

All adult inoperable or unresectable patients (≥18 years) with a clinical and radiological diagnosis of superior sulcus non-small cell lung cancer treated in our department by radiotherapy with or without chemotherapy were retrospectively analysed. Primary endpoint was the local control. Overall survival, metastasis free survival and toxicity rates were also analysed and reported.

RESULTS

From January 1999 to June 2009, 12 patients were treated by exclusive high-dose radiochemotherapy. Median age was 53 years (range: 33-64 years); mean follow-up time was 20 months (range: 2-75 months). Mean local control, overall survival and metastasis free survival were 20.2, 22 and 20 months, respectively. At the time of this analysis, seven patients died of cancer and three of them presented only a metastatic disease progression. One patient died of acute cardiac failure 36 months after the end of radiochemotherapy and was disease free. Treatment was well tolerated and any acute and/or late G3-4 toxicity was recorded (NCI-CTC v 3.0 score).

CONCLUSION

This analysis confirms the interest of exclusive high-dose radiochemotherapy in treating inoperable superior sulcus non-small cell lung cancer patients, in achieving good local control and overall survival rates.

[Pacemaker, implanted cardiac defibrillator and irradiation: Management proposal in 2010 depending on the type of cardiac stimulator and prognosis and location of cancer]

Ionizing radiation may interfere with electric components of pacemakers or implantable cardioverter-defibrillators. The type, severity and extent of radiation damage to pacemakers, have previously been shown to depend on the total dose and dose rate. Over 300,000 new cancer cases are treated yearly in France, among which 60% are irradiated in the course of their disease. One among 400 of these patients has an implanted pacemaker or defibrillator. The incidence of pacemaker and implanted cardioverter defribillator increases in an ageing population. The oncologic prognosis must be weighted against the cardiologic prognosis in a multidisciplinary and transversal setting. Innovative irradiation techniques and technological sophistications of pacemakers and implantable cardioverter-defibrillators (with the introduction of more radiosensitive complementary metal-oxide-semiconductors since 1970) have potentially changed the tolerance profiles. This review of the literature studied the geometric, dosimetric and radiobiological characteristics of the radiation beams for high energy photons, stereotactic irradiation, protontherapy. Standardized protocols and radiotherapy optimization (particle, treatment fields, energy) are advisable in order to improve patient management during radiotherapy and prolonged monitoring is necessary following radiation therapy. The dose received at the pacemaker/heart should be calculated. The threshold for the cumulated dose to the pacemaker/implantable cardioverter-defibrillator (2 to 5 Gy depending on the brand), the necessity to remove/displace the device based on the dose-volume histogram on dosimetry, as well as the use of lead shielding and magnet are discussed.