M. Aznar

Estimated risk of cardiovascular disease and secondary cancers with modern highly conformal radiotherapy for early-stage mediastinal Hodgkin lymphoma

BACKGROUNDnHodgkin lymphoma (HL) survivors have an increased morbidity and mortality from secondary cancers and cardiovascular disease (CD). We evaluate doses with involved node radiotherapy (INRT) delivered as 3D conformal radiotherapy (3D CRT), volumetric modulated arc therapy (VMAT), or proton therapy (PT), compared with the extensive Mantle Field (MF).nnnPATIENTS AND METHODSnFor 27 patients with early-stage, mediastinal HL, treated with chemotherapy and INRT delivered as 3D CRT (30 Gy), we simulated an MF (36 Gy), INRT-VMAT and INRT-PT (30 Gy). Dose to the heart, lungs, and breasts, estimated risks of CD, lung (LC) and breast cancer (BC), and corresponding life years lost (LYL) were compared.nnnRESULTSn3D CRT, VMAT or PT significantly lower the dose to the heart, lungs and breasts and provide lower risk estimates compared with MF, but with substantial patient variability. The risk of CD is not significantly different for 3D CRT versus VMAT. The risk of LC and BC is highest with VMAT. For LYL, PT is the superior modern technique.nnnCONCLUSIONSnIn early-stage, mediastinal HL modern radiotherapy provides superior results compared with MF. However, there is no single best radiotherapy technique for HL-the decision should be made at the individual patient level.

OC-0162: Liquid fiducial markers' performance in non small cell lung cancer during radiotherapy

Conclusion: Within the limitations of a retrospective study, our results show that the growth and shift of brain metastasis over time can be significant and may vary over patient groups. Given the typical steep dose gradient in SRS treatments (>10%/mm), tumour growths and shifts may have a significant impact on the tumour dose. Therefore, this phenomenon must be considered if the workup and treatment of SRS for brain metastasis is encompassing multiple days.

Residual Setup Errors Towards the Heart After Image Guidance Linked With Poorer Survival in Lung Cancer Patients: Do We Need Stricter IGRT Protocols?

PURPOSEnImage guided radiation therapy (IGRT) is widely used, but data directly relating set-up errors to patient outcome are scarce. This study investigates the relationship between residual IGRT shifts and overall patient survival and uses the observed relations to identify structures sensitive to radiation dose.nnnMETHODS AND MATERIALSnResidual shift data for 780 patients with non-small cell lung cancer were summarized for each patient over the course of treatment by determining the mean shifts, standard deviations, and the vector shift in the direction of the heart. These variables were related to overall survival, and significant variables were used to produce Kaplan-Meier plots of survival. The effect of shift directionality was studied by splitting the cohort into left, right, anterior, posterior, superior, and inferior groups and by analyzing the vector shift in the direction of the heart. The observed relationship was independently validated in an esophageal cancer cohort (n = 177).nnnRESULTSnThe shift data showed strong associations with survival. Left and right cohorts showed opposite directional shift effects, suggesting shifts toward the mediastinum have a negative effect on survival. Projection of the vector shift in the direction of the heart showed that patients with a residual shift toward the heart have significantly worse overall survival (P = .007, hazard ratio 1.091). The same effect was observed in the esophageal cancer cohort (P = .041, hazard ratio 1.164).nnnCONCLUSIONSnResidual shift metrics derived from IGRT data can categorize patients with non-small cell lung cancer and those with esophageal cancer into populations with significantly different survival times on the basis of the size of the residual shift in the direction of the heart, thus providing evidence of the importance of using strict IGRT protocols to spare organs at risk and highlighting the heart as a dose-sensitive organ.

Retrospective estimation of heart and lung doses in pediatric patients treated with spinal irradiation

BACKGROUND AND PURPOSEnThe purpose of this study was to investigate whether treatment information from medical records can be used to estimate radiation doses to heart and lungs retrospectively in pediatric patients receiving spinal irradiation with conventional posterior fields.nnnMATERIAL AND METHODSnAn algorithm for retrospective dosimetry in children treated with spinal irradiation was developed in a cohort of 21 pediatric patients with available CT-scans and treatment plans. We developed a multivariable linear regression model with explanatory variables identifiable in case note review for retrospective estimation of minimum, maximum, mean and V10%-V80% doses to the heart and lungs. Doses were estimated for both linear accelerator (Linac) and 60Co radiation therapy modalities.nnnRESULTSnAge and spinal field width were identified as statistically significant predictors of heart and lung doses in multivariable analyses (pu202f<u202f0.01 in all models). Models showed excellent predictive performance with R2u202f=u202f0.70 for mean heart dose and 0.79 for mean lung dose, for Linac plans. In leave-one-out cross-validation analysis the average difference between predicted and actual mean heart dose was 6.7% and 7.6% of the prescription dose for Linac and 60Co plans, respectively, and 5.2% and 4.9% for mean lung dose. Due to the small sample size and large inter-patient variation in heart and lung dose, prospective studies validating these findings are highly warranted.nnnCONCLUSIONSnThe models presented here provide retrospective estimates of heart and lung doses for historical cohorts of pediatric patients, thus facilitating studies of long-term adverse effects of radiation.

TEDDI: Radiotherapy delivery in deep inspiration for pediatric patients - A NOPHO feasibility study

BackgroundRadiotherapy (RT) delivered in deep inspiration breath-hold (DIBH) is a simple technique, in which changes in patient anatomy can significantly reduce the irradiation of the organs at risk (OARs) surrounding the treatment target. DIBH is routinely used in the treatment of some adult patients to diminish the risk of late effects; however, no formalized studies have addressed the potential benefit of DIBH in children.Methods/DesignTEDDI is a multicenter, non-randomized, feasibility study. The study investigates the dosimetric benefit of RT delivered in DIBH compared to free breathing (FB) in pediatric patients. Also, the study aims to establish the compliance to DIBH and to determine the accuracy and reproducibility in a pediatric setting. Pediatric patients (aged 5–17xa0years) with a tumor in the mediastinum or upper abdomen with the possible need of RT will be included in the study. Written informed consent is obligatory. Prior to any treatment, patients will undergo a DIBH training session followed by a diagnostic PET/CT- or CT-staging scan in both DIBH and FB. If the patient proceeds to RT, a RT planning CT scan will be performed in both DIBH and FB and two separate treatment plans will be calculated. The superior treatment plan, i.e. equal target coverage and lowest overall dose to the OARs, will be chosen for treatment. Patient comfort will be assessed daily by questionnaires and by adherence to the respiratory management procedure.DiscussionRT in DIBH is expected to diminish irradiation of the OARs surrounding the treatment target and thereby reduce the risk of late effects in childhood cancer survivors.Trial registrationThe Danish Ethical Committee (H-16035870, approved November 24th 2016, prospectively registered). The Danish Data Protection Agency (2012–58-0004, approved January 1st 2017, prospectively registered). Registered at clinicaltrials.gov (NCT03315546, October 20th xa02017, retrospectively registered).

OC-0151: Radiation induced toxicity and tumour control in pts treated for uveal melanoma with ru-106 plaques

S69 ______________________________________________________________________________________________________ dose rate brachytherapy with Ir192 source used to deliver 10 Gy/1fr at 1 cm radius from the center of source. PTBD tube was replaced by 10 mm, non sheathed self expandable metallic modified Giantruco Z stent. In EBRT group, stenting, followed by EBRT(dose of 45Gy/25fr/ 5 weeks) by conformal technique to primary tumour and stent area. All the patients were given single agent 5-Fluorouracil chemotherapy 370 mg/m2 Day1-5 at 4 weekly for 6 cycles.

PO-0692: A novel endoscopically injected liquid-gel marker for image guided radiotherapy of thoracic tumours

Purpose or Objective: As per published guidelines, SABR is the recommended curative treatment option for those stage I non-small cell lung cancer patients (NSCLC) who either cannot or will not have surgery. This study investigates whether patient reported weight loss at presentation is a prognostic factor in a retrospective cohort of biopsy-proven stage I NSCLC patients who received SABR at one institution.

OC-0153: Dual energy CT and iterative metal artefact reduction for accurate tumour delineation

Material and Methods: A set of teeth containing an amalgamfilled removable tooth and an artificial polycaprolactone tumour was placed in water and CT scanned (Siemens Somatom Definition AS) at 120 kVp, 80 kVp, and 140 kVp. The two latter scans were used to reconstruct virtual monochromatic (VM) images. All image sets were additionally reconstructed with metal artefact reduction (MAR) software (iMAR, Siemens Healthcare). The following 4 MAR reconstructions were studied: 1) 130 keV VM 2) 70 keV VM with MAR, 3) 120 kVp with MAR, 4) 130 keV VM with MAR. A conventional 120 kVp CT was also taken and a 120 kVp image where the metal tooth was removed was used as control. 3 oncologists and 2 radiologists contoured the tumour volume on all 6 image sets while blinded to the image reconstruction type. A 7th high-quality image of only the artificial tumour was contoured to obtain the true shape of the tumour. Maximal Hausdorff distances and DICE coefficients of the 5 delineated contours compared to the true contour was were used to quantify delineation accuracy in all 6 image sets. Statistically, a Friedman-test was used for primary comparisons and a Nemenyi-test is performed for pairwise post hoc analysis.

181 oral ESTIMATED LIFE YEARS LOST DUE TO FATAL LATE COMPLICATIONS AFTER PHOTON OR PROTON RADIOTHERAPY

Conclusions: A mechanistic model of normal-tissue damage is an effective framework for summarising the radiobiological knowledgebase of radiation pneumonitis, and plausible parameter values have been derived. Future predictive mechanistic modelling would require more quantitative histopathological studies on relevant local dose effects, thereby providing stronger evidence for the local dose-response relationship. This would provide a stepping stone from which the mechanisms of organ function loss, as a result of 3D distributions of FSU inactivation, could be studied separately.