Radiosurgery and stereotactic irradiation of multiple and contiguous brain metastases: A practical proposal of dose prescription methods and a literature review.

PURPOSE: In literature, there are no guidelines on how to prescribe dose in the case of radiosurgery (SRS) or stereotactic irradiation of multiple and adjacent BM. Aim of this work is to furnish practical proposals of dosimetric methods for multiple neighboring BM, and to make a literature review about the SRS treatment of multiple BM, comparing radiotherapy techniques on the basis of different dosimetric parameters. MATERIALS AND METHODS: A theoretical proposal of dosimetric approaches to prescribe dose in case of multiple contiguous BM is done. A literature review between 2010 and 2020 was performed on MEDLINE and Cochrane databases according to the PRISMA methodology, with the following keywords dose prescription, radiosurgery, multiple BM. Papers not reporting dosimetric solutions to irradiate multiple BM were excluded. RESULTS: Only one article in the literature reports a practical modality of dose prescription for multiple adjacent BM. Thus, we proposed other five practical solutions to prescribe radiation dose in case of two or more neighboring BM, describing advantages and drawbacks of each method in terms of different dosimetric parameters. The literature review about dosimetric solutions to irradiate multiple BM led to 56 titles; 14 articles met the chosen criteria and we reported their results in terms of dosimetric indexes and low doses to the normal brain tissue. CONCLUSIONS: The six dosimetric approaches here described can be used by physicians for multiple contiguous BM, depending on the clinical situation. These methods may be applied in clinical studies to better evaluate their usefulness in practice.

[Construction of radiobiological models as TCP (tumor control probability) and NTCP (normal tissue complication probability): from dose to clinical effects prediction]. / Construction des modèles radiobiologiques de type TCP (tumor control probability) et NTCP (normal tissue complication probability) : de la dose à la prédiction des effets cliniques.

In radiotherapy, the dose prescription is currently based on discretized dose-effects records that do not take into fully account for the complexity of the patient-dose-response relationship. Their predictive performance on both anti-tumour efficacy and toxicity can be optimized by integrating radiobiological models. It is with this in mind that the calculation models TCP (Tumor Control Probability) and NTCP (Normal Tissue Complication Probability) have been developed. Their construction involves several important steps that are necessary and important to understand. The first step is based on radiobiological models allowing to calculate according to more or less complexity the rate of surviving cells after irradiation. Two additional steps are required to convert the physical dose into an equivalent biological dose, in particular a 2Gy equivalent biological dose (EQD2): first to take into account the effect of the fractionation of the dose for both the target volume and the organs at risk; second to convert an heterogeneous dose to an organ into an homogeneous dose having the same effect (Niemierko generalized equivalent uniform dose (gEUD)). Finally, the process of predicting clinical effects based on radiobiological models transform doses into tumour control (TCP) or toxicity (NTCP) probabilities using parameters that reflect the radiobiological characteristics of the tissues in question. The use of these models in current practice is still limited, but since the radiotherapy softwares increasingly integrate them, it is important to know the principle and limits of application of these models.

[Radiation-related heart toxicity: Update in women]. / Lésions cardiaques radio-induites chez la femme : mise au point.

Breast cancer is a common diagnosis in women and thus women are at risk of radiation-induced heart disease, in particular during radiotherapy for left breast cancer and when the internal mammary chain is included. Rates of major cardiac events increase with younger age at the time of irradiation, diagnosis before 1990s, higher radiation doses, coexisting cardiovascular risk factors and adjuvant cardiotoxic chemotherapy. Radiation-induced heart disease comprises a spectrum of cardiac pathologies, including pericardial disease, cardiomyopathy, coronary artery disease and valvular disease. The cardiac injury can appear a long time after radiotherapy and can consist of complex lesions with poor prognosis. The disciplines of cardiology and oncology have increasingly recognized the benefits of collaborating in the care of cancer patients with cardiac disease, developing guidelines for the assessment and management of radiation-related cardiovascular disease. We could consider screening patients with previous chest radiation every 5 years with transthoracic echocardiography and functional imaging. However, prevention remains the primary goal, using cardiac sparing doses and avoidance techniques in radiotherapy to improve patient survival.

Preliminary testing of GaN-based dosimeters for electron beam radiotherapy.

The response of an implantable in vivo dosimetric system based on gallium nitride radioluminescence was investigated for electron beam radiotherapy using ELEKTA SLi and VARIAN Clinac 2100 CD Linear Accelerators. A bi-channel method has been implemented for fibre background rejection. The percentage depth dose (PDD) profiles were measured in polymethyl methacrylate for 6, 12 and 18 MeV electron beams. The PDD results were in excellent agreement with those measured with reference to ionisation chambers.

Fiber background rejection and crystal over-response compensation for GaN based in vivo dosimetry.

For dosimetric measurements using an implantable optical fiber probe with GaN (Gallium Nitride) scintillator as radioluminescence (RL) transducer, a bi-channel method is proposed to reject the background contribution of the irradiated fiber segment. It is based on spectral differences between the narrow-band light emission from GaN and the large-band background from the irradiated optical fiber. Experimental validation of this method using 6 MV photon beam has shown that the remaining background contribution after subtraction is below 1.2% for square field sizes ranging from 3 cm to 20 cm. Furthermore, a compensation method for the over-response of GaN is also proposed, since GaN is not tissue equivalent. The over-response factor of GaN exhibits a linear increase with square field aperture and depends on depth from phantom surface. This behaviour is modelled to allow compensation in specific conditions. The proposed method has been evaluated and has shown a maximum deviation of 3% for a 6 MV photon beam and 1% for an 18 MV photon beam at a depth beyond the build-up region.

Leiomyosarcoma of the inferior nasal concha: a case report and literature review.

Leiomyosarcomas (LMSs) of the sinonasal tracts are rarely reported. We present a case of an LMS of the left inferior nasal concha, and discuss the management options with review of the literature. A 72-year-old female patient presented with epistaxis. Clinical examination and medical imaging showed a tumour arising from the left inferior nasal concha. An endoscopic resection was performed. Anatomopathological and immunohistochemical analyses revealed the tumour to be a grade 3 LMS with uncertain posterior margins. The patient was a Jehovah's Witness and refused more radical surgical resection due to religious beliefs; therefore, adjuvant conformal radiotherapy (60 Gy) was performed. LMS of the nasal cavity is a rare and locally aggressive tumour with a high tendency of recurrence, requiring radical surgical resection and long-term follow-up. The prognosis of a nasal cavity LMS is better than that of an LMS located in the paranasal sinuses.

[Meckel's diverticulum and obstruction of the small intestine in adult patients: report of two cases]. / Diverticule de Meckel et occlusion de l'intestin grêle chez l'adulte: propos de deux cas.

Meckel's Diverticulum (MD) is the most frequent congenital anomaly of the ileum. However, its clinical manifestations in adult patients are rare. In this paper, we report cases with two different mechanisms of small intestine obstruction due to MD and we discuss diagnosis and management of these symptomatic lesions in adult patients.

Stromal tumour of the rectum: laparoscopic approach of a rare localization of GIST.

The authors present the case of a 60 year-old man known for a rectal polyp which was diagnosed in 1994 and since then followed-up by means of a colonoscopy associated with periodic biopsies. Recently, the results of a biopsy revealed positive markers for the diagnosis of Gastro-Intestinal Stromal Tumor (GIST). Despite the absence of malignant criteria, an anterior resection of the rectum was performed by laparoscopy and the patient rapidly recovered. Epidemiology, diagnosis and management of this rare location of GIST's are discussed.

[Infection with lymphadenopathy associated virus. Clinical case report in a child]. / Infection à "lymphadenopathy associated virus". Observation clinique chez l'enfant.

The authors describe the case of a little girl from Zaïre presenting a proven HTLVIII infection. The interest of this observation lies in the fact that the clinical symptoms, leading to this diagnosis, fall within the competence of stomatology.