Validation of the analytical irradiator model and Monte Carlo dose engine in the small animal irradiation treatment planning system µ-RayStation 8B.

Dose calculation in preclinical context with a clinical level of accuracy is a challenge due to the small animal scale and the medium photon energy range. In this work, we evaluate the effectiveness and accuracy of an analytical irradiator model combined with Monte Carlo (MC) calculations in the irradiated volume to calculate the dose delivered by a modern small animal irradiator. A model of the XRAD225Cx was created in µ-RayStation 8B, a preclinical treatment planning system, allowing arc and static beams for seven cylindrical collimators. Calculations with the µ-RayStation MC dose engine were compared with EBT3 measurements in water for all static beams and with a validated GATE model in water, heterogeneous media and a mouse CT. The GATE model is a complete MC representation of the XRAD225Cx. In water, µ-RayStation calculations, compared to GATE calculations and EBT3 measurements, agreed within a maximal error of 3.2% (mean absolute error of 0.6% and 0.8% respectively) and maximal distance-to-agreement (DTA) was 0.2 mm at 50% of the central dose. For a 5 mm static beam in heterogeneous media, the maximal absolute error between µ-RayStation and GATE calculations was below 1.3% in each medium and DTA was 0.1 mm at interfaces. For calculations on a mouse CT, µ-RayStation and GATE calculations agreed well for both static and arc beams. The 2D local gamma passing rate was >98.9% for 1%/0.3 mm criteria and >92.9% for 1%/0.2 mm criteria. Moreover, µ-RayStation reduces calculation time significantly comparing with GATE (speed-up factor between 120 and 680). These findings show that the analytical irradiator model presented in this work combined with the µ-RayStation MC dose engine accurately computes dose for the XRAD225Cx irradiator. The improvements in calculation time and availability of functionality and tools for managing, planning and evaluating the irradiation makes this platform very useful for pre-clinical irradiation research.

[Chemoradiation for oesophageal cancer: A critical review of the literature]. / Chimioradiothérapie des cancers de l'œsophage : revue critique de la littérature.

Locally advanced oesophageal cancer treatment requires a multidisciplinary approach with the combination of chemotherapy and radiotherapy for preoperative and definitive strategy. Preoperative chemoradiation improves the locoregional control and overall survival after surgery for locally advanced oesophageal cancer. Definitive chemoradiation can also be proposed for non-resectable tumours or medically inoperable patients. Besides, definitive chemoradiation is considered as an alternative option to surgery for locally advanced squamous cell carcinomas. Chemotherapy regimen associated to radiotherapy consists of a combination of platinum derived drugs (cisplatinum or oxaliplatin) and 5-fluorouracil or a weekly scheme combination of carboplatin and paclitaxel according to CROSS protocol in a neoadjuvant strategy. Radiation doses vary from 41.4Gy to 45Gy for a preoperative strategy or 50 to 50.4Gy for a definitive treatment. The high risk of lymphatic spread due to anatomical features could justify the use of an elective nodal irradiation when the estimated risk of microscopic involvement is higher than 15% to 20%. An appropriate delineation of the gross tumour volume requires an exhaustive and up-to-date evaluation of the disease. Intensity-modulated radiation therapy represents a promising approach to spare organs-at-risk. This critical review of the literature underlines the roles of radiotherapy for locally advanced oesophageal cancers and describes doses, volumes of treatment, technical aspects and dose constraints to organs-at-risk.

[Which rules apply to hypofractionated radiotherapy?]. / Radiothérapie hypofractionnée : quelles sont les règles à suivre ?

Hypofractionated radiotherapy is now more widely prescribed due to improved targeting techniques (intensity modulated radiotherapy, image-guided radiotherapy and stereotactic radiotherapy). Low dose hypofractionated radiotherapy is routinely administered mostly for palliative purposes. High or very high dose hypofractionated irradiation must be delivered according to very strict procedures since every minor deviation can lead to major changes in dose delivery to the tumor volume and organs at risk. Thus, each stage of the processing must be carefully monitored starting from the limitations and the choice of the hypofractionation technique, tumour contouring and dose constraints prescription, planning and finally dose calculation and patient positioning verification.

[Clinical and paraclinical follow-up after radiotherapy for head and neck cancer]. / Suivi clinique et paraclinique après radiothérapie pour un cancer des voies aérodigestives supérieures.

Head and neck cancer management often involves heavy multimodal treatments including radiotherapy. Despite the improvement of intensity-modulated radiation therapy, acute and late toxicities remain important. After such treatment, patients have to face different potential problems, depending on the post-therapeutic delay. In this way, short-term follow-up permits to appreciate the healing of acute toxicities and response to treatment. Long-term follow-up aims to recognize second primitive tumours and distant failure, and to detect and manage late toxicities. Medical and psychosocial supportive cares are essential, even after several years of complete remission. The objective of this article is to review the modalities of short-term and long-term follow-up of patients who receive a radiotherapy for head and neck cancer.

[Radiation therapy of cardiac sarcomas]. / Irradiation des sarcomes cardiaques de l'adulte.

PURPOSE: Primary cardiac sarcomas represent less than 10 yearly cases in France. Their median survival is approximately 18 months. The treatment consists of surgery when possible. The role of chemotherapy and radiation therapy is controversial, especially with respect to limiting cardiac radiation dose that is theoretically incompatible with the requirement of a tumoricidal dose for sarcoma. A recent series of 124 cases of the French Sarcoma Group suggested a benefit of radiation therapy on progression-free survival. PATIENTS AND METHODS: The dosimetric data of 12 patients were analyzed. RESULTS: There was variety in radiotherapy modalities and definition of target volumes, doses and techniques are evolving more conformal plans. Irradiation appeared feasible with conventional fractionation with respect to toxicities (although probably underestimated due to short follow-up and dismal prognosis) and previously demonstrated benefit of radiotherapy for primitive cardiac sarcomas. CONCLUSION: A scheme of 45Gy in 1.8Gy per fraction to a preoperative volume with an additional dose of 14Gy in 7 fractions on areas at risk or residual disease and margins 1cm, may be proposed based on the preliminary data of this study. Intensity modulated radiotherapy with daily cone-beam CT-scanner should be evaluated.

[Helical tomotherapy in the treatment of malignant pleural mesothelioma: The impact of low doses on pulmonary and oesophageal toxicity]. / Tomothérapie hélicoïdale dans le traitement du mésothéliome pleural malin : impact des faibles doses sur la toxicité pulmonaire et œsophagienne.

PURPOSE: To evaluate the adjuvant treatment of malignant pleural mesothelioma by helical tomotherapy and the impact of low doses on esophageal and pulmonary toxicity. PATIENTS AND METHODS: Between June 2007 and May 2011, 29 patients diagnosed with malignant pleural mesothelioma received adjuvant radiotherapy by helical tomotherapy. The median age was 63 years (34-72). Histologically, 83 % of patients had epithelioid malignant pleural mesothelioma. Clinically, 45 % of patients were T3 and 55 % N0. Eighty six percent of the patients were treated by extrapleural pneumonectomy and 35 % received neoadjuvant chemotherapy with platinum and pemetrexed. The median dose in the pneumonectomy cavity was 50Gy at 2Gy/fraction. RESULTS: The mean follow-up was 2.3 years after diagnosis. Overall survival at 1 and 2 years was 65 and 36 % respectively. The median survival from diagnosis was 18 months. Median lung volumes receiving 2, 5, 10, 13, 15 and 20Gy (V2, V5, V10, V13, V15 and V20) were 100, 98, 52, 36, 19 and 5 %. The median of the mean remaining lung dose was 11Gy. Two patients died of pulmonary complications, three patients had grade 3 lung toxicity, while esophageal grade 3-4 toxicity was observed in three other patients. No significant impact of clinical characteristics and dosimetric parameters were found on pulmonary toxicity, however a V10≥50 %, a V15≥15 % and mean lung dose of 10Gy or more had a tendency to be predictive of pulmonary toxicity (P<0.1). Moreover, in our analysis, the mean lung dose seems to have a significant impact on esophageal toxicity (P=0.03) as well as low doses to the controlateral lung: V5, V10 and V13 (P<0.05). CONCLUSION: Helical tomotherapy is a promising technique in the multimodality treatment of malignant pleural mesothelioma. Low doses received by the contralateral lung appear to be the limiting factor. A dosimetric comparison with volumetric modulated arctherapy techniques would be interesting in this setting.

[Surveillance after prostate cancer radiotherapy]. / Suivi après la radiothérapie des cancers de la prostate : bases scientifiques, rapport coût-bénéfice.

Follow-up after prostate cancer radiotherapy aims at detecting local or metastatic relapse, as well as long-term toxicity, requiring adapted treatments. Several scientific societies have published guidelines including clinical, biological and imaging recommendations. More data suggest a role for aggressive salvage therapy in case of local failure following radiotherapy. An adequate follow-up is required for the sake of patients' safety, i.e. to a posteriori validate dose constraints and radiation technique in each radiotherapy department.