Mathematical evaluation of post-radiotherapy salivary gland function using salivary gland scintigraphy

Objective: Xerostomia is the most common treatment-related toxicity after radiotherapy (RT) for head and neck carcinoma, reducing the quality of life of patients due to a decrease in salivary gland function. Methods: Salivary gland scintigraphy was performed to quantitatively evaluate the salivary gland functions in patients undergoing RT. It was done chronologically for 62 salivary glands of 31 patients before RT and retested 12 months later. Results: The salivary gland functions of most patients deteriorated post-RT and recovered when the radiation dose to the salivary gland was not high. The mean dose to the salivary gland was found to be the most reliable factor in deteriorating salivary gland function, and the tolerance dose was determined to be 46 Gy. The recovery rate of salivary gland function after 1 year of RT was 72% in the RT alone group (n = 10), 56% in the conformal radiotherapy group (n = 15), and 44% in the bioradiotherapy group (n = 6). Conclusion: Scintigraphy revealed that the salivary glands recovered from post-RT hypofunction when decreased doses were administered. The determined tolerance dose of 46 Gy may guide the approach to minimizing associated xerostomia in RT. Advances in knowledge: In this study, the average tolerated dose to the salivary glands was 46 Gy.

Rectal dose-sparing effect with bioabsorbable spacer placement in carbon ion radiotherapy for sacral chordoma: dosimetric comparison of a simulation study

It is difficult to treat patients with an inoperable sarcoma adjacent to the gastrointestinal (GI) tract using carbon ion radiotherapy (C-ion RT), owing to the possible development of serious GI toxicities. In such cases, spacer placement may be useful in physically separating the tumor and the GI tract. We aimed to evaluate the usefulness of spacer placement by conducting a simulation study of dosimetric comparison in a patient with sacral chordoma adjacent to the rectum treated with C-ion RT. The sacral chordoma was located in the third to fourth sacral spinal segments, in extensive contact with and compressing the rectum. Conventional C-ion RT was not indicated because the rectal dose would exceed the tolerance dose. Because we chose spacer placement surgery to physically separate the tumor and the rectum before C-ion RT, bioabsorbable spacer sheets were inserted by open surgery. After spacer placement, 67.2 Gy [relative biological effectiveness (RBE)] of C-ion RT was administered. The thickness of the spacer was stable at 13–14 mm during C-ion RT. Comparing the dose–volume histogram (DVH) parameters, Dmax for the rectum was reduced from 67 Gy (RBE) in the no spacer plan (simulation plan) to 45 Gy (RBE) in the spacer placement plan (actual plan) when a prescribed dose was administered to the tumor. Spacer placement was advantageous for irradiating the tumor and the rectum, demonstrated using the DVH parameter analysis.

Phase I dose-escalation trial of S-1 combined with carbon-ion radiotherapy for sinonasal squamous cell carcinoma

This study aimed to determine the maximum tolerance dose (MTD) and to estimate the recommended dose (RD) of concomitant S-1 with carbon-ion radiotherapy (RT) for sinonasal squamous cell carcinoma (SCC). Nine patients with sinonasal SCC received carbon-ion RT with escalating doses of S-1 according to phase I methods. Doses of 40, 60 and 80 mg/m2/day were administered twice daily in dose levels 1, 2 and 3, respectively, from days 1 to 14 and 22 to 35. Carbon-ion RT was administered at a dose of 70.4 Gy (relative biological effectiveness) in 32 fractions, 5 days a week. Two patients developed grade 3 acute dermatitis. However, none developed dose-limiting toxicities. Therefore, the MTD of S-1 could not be determined; the RD was estimated to be 80 mg/m2/day with concurrent carbon-ion RT. Partial response and stable disease were noted in 5 and 4 patients, respectively. The 2-year overall survival and local control rates were 56 and 74%, respectively. Overall, 2 patients developed ≥grade 3 late toxicities; among them, 1 patient developed grade 3 cataract and the other developed grade 4 cataract, optic nerve disorder and hearing impairment. To the best of our knowledge, this phase I study is the first clinical trial to evaluate concomitant S-1 with carbon-ion RT for sinonasal SCC. The MTD of S-1 could not be determined, and the RD was estimated to be 80 mg/m2/day. This study demonstrated a manageable safety profile for this combination. The observed outcomes may facilitate further evaluation of this novel therapy.

A new method for risk factor assessment of organs at risk including conformity index in radiotherapy treatment plan

Introduction: A comprehensive analysing method has been required since long in the field of radiotherapy. The basic purpose of all techniques has been to deliver the prescribed dose safely to the target volume containing tumour and as well as to reduce dose to organs at risk (OARs). The detailed comparison between different treatment techniques is very difficult and inexplicit as well. The gradual improvement in imaging software has made easy to users to assess spatial arrangement of tumour, critical organs and isodose lines in the form of a single 3D representation that can be observed from all angles. The conformity index (CI) alone cannot provide practical information about treatment plans as it is a single isodose line quantity. Aim: The aim of this study was to develop a new method to assess the degree of damage numerically for OARs along with CI assessment for the target. Materials and Methods: The radiotherapy plans of 30 patients of different sites, diagnosed as cancer, were selected for this study irrespective of gender. Out of 30 cases, 8 plans were of head and neck, 2 were of glyoblastoma (GBM), 10 were of pelvis, 5 were of left breast and other 5 were of oesophagus cancer. The mean age was 42 years ranging from 31 to 72 years. Patient’s consents were taken before starting the treatment and carried out this research. Risk factor (RF) for OARs depends on volume of irradiation (VVOI), total volume of the organ (VTVO) and tolerance dose (DTDO). All radiotherapy plans (Intensity Modulated Radiotherapy (IMRT) and Volumetric Modulated Arc Therapy (VMAT)) were generated using eclipse planning system, version 11.0 (Varian Medical System, Palo Alto, California, USA). Result: The formula developed to assess degree of damage of OARs including CI of the target is risk factor conformity index (RFC) = CI + RF. In head and neck cases, for right parotid, the maximum value of RF is 1·50 and minimum value is observed as 0·97. Optic nerve, brainstem and spinal cord are completely safe as their RF values are found to be 0 on RF scale. Conclusion: RFC is a comprehensive evaluation tool encompassing a wider range of clinically relevant parameters, isodose volumes and tolerance dose of OARs. It is an advance analysing method to check both the qualitative and quantitative nature of a conformal plan, and at the same time, it assesses the degree of damage of OARs. If RF ≥ 1, then OAR will be completely damaged as a result of irradiation. If RF = 0, then OAR will remain safe totally during the course of irradiation.

Normal tissue tolerance dose for cervical radiotherapy to the NTCP model using a method of least square fit

The purpose of this study is to evaluate the impact of Normal Tissue Complication Probability (NTCP) models on radiation treatment plans. We estimated NTCP parameters for the organs at risk (OARs) for cervical cancer radiotherapy. We pooled individual patient data from fifty patients who were treated with External Beam Radiotherapy technique between March 2012 and November 2013 in a part of Northern Nigeria with the exclusion of patients who had other gynaecological malignancies. Three basic methods were followed during the radiotherapy planning of these patients which included the pre-planning stage, planning radiotherapy treatment stage and treatment delivery. Various tests were carried out on these patients which helped to confirm the diagnosis after which they were treated using the linear accelerator, computed tomography simulator and the treatment planning system. We calculated the normal tissue tolerance doses for partial volumes of the organs using the values of the above –said parameters for published data on normal tissue tolerance doses. This article shows a graphical representation of the computed NTCP for left femur, right femur and skin presented and a fairly good correspondence is found between the curves for head of femurs and skin. Keywords: Normal Tissue Tolerance Dose, Normal Tissue Complication Probability, Method of Least Square Fit, Cervical Radiotherapy

Medical Applications of the ALPIDE Detector

The CERN Large Hadron Collider (LHC) ALICE detector is undergoing a major upgrade in the Second Long Shutdown of the LHC in 2019–2020. During this upgrade, the innermost detector, the Inner Tracking System, will be completely replaced by a new detector which is built from the ALPIDE sensor. In the Bergen proton computer tomography (pCT) collaboration, we decided to apply these sensors for medical applications. They can be used for positioning in hadron therapies due to their good position resolution and radiation tolerance. Dose planning of hadron therapy is calculated currently from photon CT measurements, which results in large uncertainties in the planning and therefore in a necessary enlargement of the treatment area. This uncertainty can be reduced by performing the CT scan using protons. The current contribution shows the development of a sampling calorimeter built from the ALPIDE detector for proton CT measurements and describes the state of the project.

Radiation Induced Demyelination in Cervical Spinal Cord of the Head and Neck Cancer Patients after Receiving Radiotherapy

Introduction: Cervical spinal cord is important and radiosensitive. It is the most critical organ for the head and neck (H&N) cancer patients during radiotherapy. If dos delivered to the cord is more than tolerance dose, demyelination may occur. Current study aims to analyze the post radiotherapy status of cord in the H&N cancer patients.Materials and Methods: Sixty patients who received more than 50 Gray (Gy) dose for more than 10 cm length of spinal cord participated in the study. All the patients were clinically examined and magnetic resonance imaging (MRI) was performed for patients who had demyelination symptoms. Adequate medical management was provided for all the patients having demyelination.Results: Out of sixty patients, ten cases were reported with demyelination symptoms, and only six cases gave consent for this study. One patient was found to have irreversible demyelination while five patients have reversible demyelination.Conclusions: Demyelination may occur if long segment spinal cord receives dose more than tolerance limit. However target dose should not be compromised up to 54 Gy to spinal cord.