Dosimetric comparison of four high performance techniques for irradiation of breast cancer patients

PURPOSE

The use of IMRT for the treatment of breast cancer has been growing considerably in our institution since 2009. Alternatively, helical tomotherapy (HT) using a field width of 2.5 and 5cm (HT_FW_5), volumetric-modulated arc therapy (VMAT), or proton therapy with pencil-beam scanning (PT-PBS) have also been used to reduce treatment duration or optimize organ-at-risk (OAR) sparing. The purpose of this study was to compare the 4 treatment modalities available at our site.

PATIENTS AND METHODS

We studied 10 patients treated for breast cancer with lymph node involvement. The prescribed dose was 51.8Gy to the breast with a simultaneous integrated boost up to 63Gy, and 50.4Gy to lymph nodes in 28 fractions. The CTV was delineated according to ESTRO Guidelines. Dosimetric planning in routine clinical practice was performed using HT_FW_2.5. The approved clinical plan was compared to the 3 other plans. Dosimetric goals for PTV coverage were D95%≥95% and D2%≤107% of the prescribed dose. Mean and maximum doses to OAR were recorded.

RESULTS

HT_FW_5 and VMAT plans ensure equivalent or even better PTV coverage compared to the initial clinically approved plan but at the cost of poorer OAR sparing. PT_PBS plans showed that an excellent PTV coverage can be maintained with significantly lower doses to OAR.

CONCLUSION

HT_FW_5 and VMAT plans allow a significant reduction of treatment duration and can be a good alternative to HT_FW_2.5 for specific populations. HT_FW_2.5 could be chosen for patients at higher risk of side effects. In addition, PT_PBS should be considered in the near future as it has been shown to have a major potential benefit to lower the risk of side effects with the same level of PTV coverage.

[Hot topics in 2017 in oncology and hematology. A selection by the editorial board of Bulletin du Cancer]

Actuality was dense in 2017 for oncology and hematology. The editorial board of the Bulletin du Cancer proposes a selection of key data distinguishing four trends: precision medicine, immunotherapy, focus on early stages and global management of metastatic disease. A summary of results which have been published or presented in congresses is proposed and the impact on daily practices is discussed.

[Technical aspects of protontherapy: Setup, equipment and radioprotection]

The number of protontherapy facilities is still increasing rapidly with more than 30 ongoing projects and close to 60 currently under operation. Although the technology is now validated and robust, a proton facility cannot be considered as a standard radiation therapy equipment: its constraints in terms of building, services, project management are of paramount impact at the level of the hospital. Therefore, a protontherapy project must be carefully considered and prepared, which is mandatory for further fluid and efficient clinical operation.

[French organization of paediatric radiation treatment: Results of a survey conducted by the radiotherapy Committee of the French Society of Paediatric Cancers (SFCE)]

PURPOSE

Radiotherapy is a rare indication in paediatric oncology, with 800 to 900 children in treatment per year in France. Child cancers represent approximately 1% of cancers in France and half occur before the age of 5 years. Paediatric radiation requires appropriate tools, local, time and specific training. In France, in 2015, 18 centres are accredited by the French National Cancer Institute (INCa) for this activity.

MATERIAL AND METHODS

Survey conducted in February 2015 on the care of children (0 to 18 years) in radiotherapy departments in France. The survey was sent to the radiation oncologists involved in the 18 centres. The questions concerned the qualitative and quantitative aspect, medical and organizational aspects, and the involvement of assistant practitioners in the management of this activity.

RESULTS

Seventeen centres responded. In 2014, 889 children under 18 were treated in radiotherapy departments. These departments are working together with one to four paediatric oncology departments. Regarding access to general anaesthesia: three centres perform one to seven treatment(s) under anaesthesia per year, three centres eight to ten treatments under anaesthesia per year, three centres ten to 24 treatments under anaesthesia per year and nine centres out of 17 use hypnosis techniques. In terms of human resources, in 2015, 29 radiation therapists have a paediatric radiotherapy activity. Involvement of assistant practitioners is growing and specific training are desired. Regarding treatment preparation and delivery, 13 centres have specific paediatric contentions, 14 of 16 centres employ radiation intensity modulated if dosimetry is more satisfying with 11 regularly to the craniospinal irradiation. Radiotherapy on moving areas with respiratory gating or hypofractionation is under developed.

CONCLUSION

Paediatric radiation therapy is a specific activity requiring a dedicated management, both in human, organizational, medical and scientific aspects.

[Ballistic quality assurance]

This review describes the ballistic quality assurance for stereotactic intracranial irradiation treatments delivered with Gamma Knife® either dedicated or adapted medical linear accelerators. Specific and periodic controls should be performed in order to check the mechanical stability for both irradiation and collimation systems. If this step remains under the responsibility of the medical physicist, it should be done in agreement with the manufacturer's technical support. At this time, there are no recent published guidelines. With technological developments, both frequency and accuracy should be assessed in each institution according to the treatment mode: single versus hypofractionnated dose, circular collimator versus micro-multileaf collimators. In addition, "end-to-end" techniques are mandatory to find the origin of potential discrepancies and to estimate the global ballistic accuracy of the delivered treatment. Indeed, they include frames, non-invasive immobilization devices, localizers, multimodal imaging for delineation and in-room positioning imaging systems. The final precision that could be reasonably achieved is more or less 1mm.

Conservation of salivary function and new external head and neck radiation techniques

INTRODUCTION

New radiation therapy techniques seek to adapt dose distribution to three-dimensional tumor geometry, so as to deliver the lowest possible dose to normal tissue and at-risk organs. This is expected to enhance locoregional control and survival and to reduce complications and thereby improve quality of life. Post-radiation xerostomia significantly deteriorates quality of life.

MATERIAL AND METHODS

New external radiation techniques (such as intensity-modulated conformal radiation therapy, RapidArc VMAT arc therapy, tomotherapy, CyberKnife(®), protontherapy, use of carbon ions) applicable in ENT are reviewed.

RESULTS

Preliminary data show interesting results in terms of salivary function with highly conformal techniques.

CONCLUSION

In France, assessment is ongoing, financed under the Health Ministry's "Support for Expensive Innovatory Techniques" scheme (STIC [Soutien aux techniques innovantes coûteuses]), as routine use is growing rapidly.

[Particle therapy: carbon ions]

Carbon ion therapy is an innovative radiation therapy. It has been first proposed in the forties by Robert Wilson, however the first dedicated centres for human care have been build up only recently in Japan and Germany. The interest of carbon ion is twofold: 1) the very sharp targeting of the tumour with the so called spread out Bragg peak that delivers most of the beam energy in the tumour and nothing beyond it, sparing very efficiently the healthy tissues; 2) the higher relative biological efficiency compared to X rays or protons, able to kill radioresistant tumour cells. Both properties make carbon ions the elective therapy for non resectable radioresistant tumours loco-regionally threatening. The technical and clinical experience accumulated during the recent decades is summarized in this paper along with a detailed presentation of the elective indications. A short comparison between conventional radiotherapy and hadrontherapy is proposed for the indications which are considered as priority for carbon ions.