Peer mentoring for radiotherapy planning skills development: A pilot study

Introduction: This study aimed to determine the potential role and guidelines for implementation of skill-based peer mentoring for radiotherapy planning education. Methods: After four weekly mentoring sessions, both Year 3 mentors (n=9) and Year 2 mentees (n=9) were invited to complete a short online questionnaire relating to the impact of the initiative. The tool contained a mixture of Likert-style questions concerning student enjoyment and perceived usefulness of the initiative as well as more qualitative open questions that gathered perceptions of the peer mentoring process, implementation methods and potential future scope. Results: Several key discussion themes related to benefits to each stakeholder group, challenges arising, improvements and potential future directions. There were high levels of enjoyment and perceived value of the mentoring from both sides with 100% of the 18 respondents enjoying the experience. The informal format encouraged further learning, while mentors reported acquisition of valuable skills and gains in knowledge. Conclusions: Peer mentoring has a valuable and enjoyable role to play in radiotherapy planning training and helps consolidate theoretical understanding for experienced students. An informal approach allows for students to adopt the most appropriate mentoring model for their needs while providing them with a free space to engender additional discussion.

CBCT-guided radiotherapy for locally advanced head and cancer: dosimetric impact of weight loss on VMAT and IMRT plans for selected organs at risk structures (OARs)

Purpose: It is common for head and neck patients to be affected by time trend errors as a result of weight loss during a course of radiation treatment. The objective of this planning study was to investigate the impact of weight loss on Volumetric Modulated Arc Therapy (VMAT) as well as Intensity modulated radiation therapy (IMRT) for locally advanced head and neck cancer using automatic co-registration of the CBCT. Methods and Materials: A retrospective analysis of previously treated IMRT plans for 10 patients with locally advanced head and neck cancer patients was done. A VMAT plan was also produced for all patients. We calculated the dose–volume histograms (DVH) indices for spinal cord planning at risk volumes (PRVs), the brainstem PRVs (SC+0.5cm and BS+0.5cm, respectively) as well as mean dose to the parotid glands. Results: The results show that the mean difference in dose to the SC+0.5cm was 1.03% and 1.27% for the IMRT and VMAT plans, respectively. As for dose to the BS+0.5, the percentage difference was 0.63% for the IMRT plans and 0.61% for the VMAT plans. The analysis of the parotid gland doses shows that the percentage change in mean dose to left parotid was -8.0% whereas that of the right parotid was -6.4% for the IMRT treatment plans. In the VMAT plans, the percentages change for the left and the right parotid glands were -6.6% and -6.7% respectively. Conclusions: This study shows a clinically significant impact of weight loss on DVH indices analysed in head and neck organs at risk. It highlights the importance of adaptive radiotherapy in head and neck patients if organ at risk sparing is to be maintained.

Accuracy of absorbed dose in external photon beam radiotherapy : what level is sufficient and how to approach it?

Radiation therapy (RT) plays currently significant role in curative treatments of several cancers. External beam RT is carried out mostly by using megavoltage beams of linear accelerators. Tumor eradication and normal tissue complications correlate to dose absorbed in tissues. Normally this dependence is steep and it is crucial that actual dose within patient accurately correspond to the planned dose. All factors in a RT procedure contain uncertainties requiring strict quality assurance. From hospital physicist´s point of a view, technical quality control (QC), dose calculations and methods for verification of correct treatment location are the most important subjects. Most important factor in technical QC is the verification that radiation production of an accelerator, called output, is within narrow acceptable limits. The output measurements are carried out according to a locally chosen dosimetric QC program defining measurement time interval and action levels. Dose calculation algorithms need to be configured for the accelerators by using measured beam data. The uncertainty of such data sets limits for best achievable calculation accuracy. All these dosimetric measurements require good experience, are workful, take up resources needed for treatments and are prone to several random and systematic sources of errors. Appropriate verification of treatment location is more important in intensity modulated radiation therapy (IMRT) than in conventional RT. This is due to steep dose gradients produced within or close to healthy tissues locating only a few millimetres from the targeted volume. The thesis was concentrated in investigation of the quality of dosimetric measurements, the efficacy of dosimetric QC programs, the verification of measured beam data and the effect of positional errors on the dose received by the major salivary glands in head and neck IMRT. A method was developed for the estimation of the effect of the use of different dosimetric QC programs on the overall uncertainty of dose. Data were provided to facilitate the choice of a sufficient QC program. The method takes into account local output stability and reproducibility of the dosimetric QC measurements. A method based on the model fitting of the results of the QC measurements was proposed for the estimation of both of these factors. The reduction of random measurement errors and optimization of QC procedure were also investigated. A method and suggestions were presented for these purposes. The accuracy of beam data was evaluated in Finnish RT centres. Sufficient accuracy level was estimated for the beam data. A method based on the use of reference beam data was developed for the QC of beam data. Dosimetric and geometric accuracy requirements were evaluated for head and neck IMRT when function of the major salivary glands is intended to be spared. These criteria are based on the dose response obtained for the glands. Random measurement errors could be reduced enabling lowering of action levels and prolongation of measurement time interval from 1 month to even 6 months simultaneously maintaining dose accuracy. The combined effect of the proposed methods, suggestions and criteria was found to facilitate the avoidance of maximal dose errors of up to even about 8 %. In addition, their use may make the strictest recommended overall dose accuracy level of 3 % (1SD) achievable.

Estramustine and its Derivatives in Potentiating Radiotherapy of Prostate Cancer

The purpose of this study was to deepen our knowledge of the combined use of estramustine and radiotherapy in the treatment of prostate cancer. Prostate cancer is a common disease, with a high variability between subjects in its malignant potential. In many cases, the disease is an incidental finding with little or no clinical significance. In other cases, however, prostate cancer may be an aggressive malignant disease, which, if the initial treatment fails, lacks an effective cure and may lead to severe symptoms, metastasis, and death despite all treatment. In many cases, the methods of treatment available at the moment provide cure or significant regression of symptoms, but often at the cost of considerable side effects. Estramustine, a cytostatic drug used for treating advanced cancer of the prostate, has been shown to inhibit prostate cancer progression and also to increase the sensitivity of cancer cells to radiotherapy. The goals of this study were, first, to find out whether it is possible to use either estramustine or an antibody against estramustine binding protein as carrier molecules for bringing therapeutic radioisotopes into prostate cancer cells, and, secondly, to gain more understanding of the mechanisms behind the known radiosensitising effect of estramustine. Estramustine and estramustine binding protein antibody were labelled with iodine-125 to study the biodistribution of these substances in mice. In the first experiment, both of the substances accumulated in the prostate, but radioiodinated estramustine also showed affinity to the liver and the lungs. Since the radiolabelled antibody was found out to accumulate more selectively to the prostate, we studied its biodistribution in nude mice with DU-145 human prostate cancer implants. In this experiment, the prostate and the tumour accumulated more radioactivity than other organs, but we concluded that the difference in the dose of radiation compared to other organs was not sufficient for the radioiodinated antibody to be advocated as a carrier molecule for treating prostate cancer. Mice with similar DU-145 prostate cancer implants were then treated with estramustine and external beam irradiation, with and without neoadjuvant estramustine treatment. The tumours responded to the treatment as expected, showing the radiation potentiating effect of estramustine. In the third experiment, this effect was found without an increase in the amount of apoptosis in the tumour cells, despite previous suggestions to the contrary. In the fourth experiment, we gave a similar treatment to the mice with DU-145 tumours. A reduction in proliferation was found in the groups treated with radiotherapy, and an increased amount of tumour hypoxia and tumour necrosis in the group treated with both neoadjuvant estramustine and radiation. This finding is contradictory to the suggestion that the radiation sensitising effect of estramustine could be attributed to its angiogenic activity.

Toward More Precise Radiotherapy Treatment of Lung Tumors

A computational framework for modeling the respiratory motion of lung tumors provides a 4D parametric representation that tracks, analyzes, and models movement to provide more accurate guidance in the planning and delivery of lung tumor radiotherapy.

Radiotherapy plus nimotuzumab or placebo in the treatment of high grade glioma patients: results from a randomized, double blind trial

Background The prognosis of patients bearing high grade glioma remains dismal. Epidermal Growth Factor Receptor (EGFR) is well validated as a primary contributor of glioma initiation and progression. Nimotuzumab is a humanized monoclonal antibody that recognizes the EGFR extracellular domain and reaches Central Nervous System tumors, in nonclinical and clinical setting. While it has similar activity when compared to other anti-EGFR antibodies, it does not induce skin toxicity or hypomagnesemia. Methods A randomized, double blind, multicentric clinical trial was conducted in high grade glioma patients (41 anaplastic astrocytoma and 29 glioblastoma multiforme) that received radiotherapy plus nimotuzumab or placebo. Treatment and placebo groups were well-balanced for the most important prognostic variables. Patients received 6 weekly doses of 200 mg nimotuzumab or placebo together with irradiation as induction therapy. Maintenance treatment was given for 1 year with subsequent doses administered every 3 weeks. The objectives of this study were to assess the comparative overall survival, progression free survival, response rate, immunogenicity and safety. Results The median cumulative dose was 3200 mg of nimotuzumab given over a median number of 16 doses. The combination of nimotuzumab and RT was well-tolerated. The most prevalent related adverse reactions included nausea, fever, tremors, anorexia and hepatic test alteration. No anti-idiotypic response was detected, confirming the antibody low immunogenicity. The mean and median survival time for subjects treated with nimotuzumab was 31.06 and 17.76 vs. 21.07 and 12.63 months for the control group. Conclusions In this randomized trial, nimotuzumab showed an excellent safety profile and significant survival benefit in combination with irradiation.

Experimental verification of therapeutic doses for the superficially-placed tumor radiotherapy with heavy ions at HIRFL

Up to now, clinical trials of heavy-ion radiotherapy for superficially placed tumors have been carried out for six times and over 60 selected patients have been treated with 80—100 MeV/u carbon ions supplied by the Heavy Ion Research Facility in Lanzhou (HIRFL) at the Institute of Modern Physics, Chinese Academy of Sciences since November, 2006. A passive irradiation system and a dose optimization method for radiotherapy with carbon-ion beams have been developed. Experimental verification of longitudinally ...

Studies on advantages of heavy ions in radiotherapy compared with gamma-rays

Hepatoma and melanoma cells were exposed to C-12(6+) beams generated by HIRFL facility and gamma-rays and the cell response was studied by colony assays as well as the analysis of RBE of carbon ions was evolved. The survival curves of cells irradiated by heavy ions were different from those of cells irradiated by gamma-rays. And two kinds of cell showed the obvious discrepancy in response to the photon and ion irradiation. The results showed that heavy ions have special physical properties and mighty potency to kill cell in both single and fractional irradiation meanwhile it can kill tumor cells with high radioresistance more efficiently. When involved in clinical therapy, heavy ions will enhance the therapy efficiency and decrease the suffering of patients because it can impair the repair for sublethal damage of cells which can lead to fewer irradiation fractions.

Conformal irradiation to moving targets in heavy ion radiotherapy with raster-scanning beam delivery system: (II) feasibility experiments

Within the framework of the pilot heavy-ion therapy facility at GSI equipped with an active beam delivery system of advanced raster scanning technique, a feasibility study on actively conformal heavy-ion irradiation to moving tumors has been experimentally conducted. Laterally, real-time corrections to the beam scanning parameters by the raster scanner, leading to an active beam tracing, compensate for the lateral motion of a target volume. Longitudinally, a mechanically driven wedge energy degrader (called depth scanner) is applied to adjust the beam energy so as to locate the high-dose Bragg peak of heavy ion beam to the slice under treatment for the moving target volume. It has been experimentally shown that compensations for lateral target motion by the raster scanner and longitudinal target shift by the depth scanner are feasible.

重离子束治疗皮肤恶性肿瘤的初步临床结果；Clinical trial of carbon ion radiotherapy for malignant neoplasm of skin

目的:评价重离子束对皮肤恶性肿瘤放射治疗的近期疗效和毒副反应。方法:29例皮肤恶性肿瘤患者分6批接受重离子束放射治疗,其中恶性黑色素瘤13例,皮肤鳞癌及Bowen’s病各6例,基底细胞癌2例,其他皮肤恶性肿瘤2例。照射总剂量(50～70)GyE/(6～12)d,单次剂量5.5～11.67GyE,1f/d,连续治疗。采用RTOG标准和WHO近期疗效标准分别评价毒副反应和近期疗效。结果:截止2009-05,中位随访时间为13.5个月(1～25个月),随访率为100%。29例患者中完全缓解(CR)24例(82.8%),部分缓解(PR)5例(17.2%),有效率(RR)为100%,中位生存时间为22.8个月(95%CI:20.6～24.9)。皮肤反应0度11例(37.9%),Ⅰ度9例(31.0%),Ⅱ度6例(20.7%),Ⅲ度2例(6.9%),Ⅳ度1例(3.4%);血液毒副反应治疗前后无明显改变。结论:重离子束(12C6+)放射治疗皮肤恶性肿瘤近期疗效好,并发症轻,远期疗效、晚期副反应等尚需进一步长期全面的观察和更多的研究提供依据。