• Asian Pacific Journal of Cancer Prevention
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• v.14 no.10
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• pp.5631-5635
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• 2013

Cochlea hair cell death is regarded to be responsible for the radiation-induced sensorineural hearing loss (SNHL), which is one of the principal complications of radiotherapy (RT) for head and neck cancers. In this mini-review, we focus on the current progresses trying to unravel mechanisms of radiation-induced hair cell death and find out possible protection. P53, reactive oxygen species (ROS) and c-Jun N-terminal kinase (JNK) pathways have been proposed as pivotal in the processes leading to radiation hair cell death. Potential protectants, such as amifostine, N-acetylcysteine (NAC) and epicatechin (EC), are claimed to be effective at reducing radiation-inducedhair cell death. The RT dosage, selection and application of concurrent chemotherapy should be pre-examined in order to minimize the damage to cochlea hair cells.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.4
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• pp.1685-1689
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• 2016

Physical wedges still can be used as missing tissue compensators or filters to alter the shape of isodose curves in a target volume to reach an optimal radiotherapy plan without creating a hotspot. The aim of this study was to investigate the dosimetric properties of physical wedges filters such as off-axis photon fluence, photon spectrum, output factor and half value layer. The photon beam quality of a 6 MV Primus Siemens modified by 150 and 450 physical wedges was studied with BEAMnrc Monte Carlo (MC) code. The calculated present depth dose and dose profile curves for open and wedged photon beam were in good agreement with the measurements. Increase of wedge angle increased the beam hardening and this effect was more pronounced at the heal region. Using such an accurate MC model to determine of wedge factors and implementation of it as a calculation algorithm in the future treatment planning systems is recommended.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.164-167
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• 1997

The treatment setup of patients during irradiation is an important aspect in relation to the success of radiotherapy. Imaging with the treatment beam is a widely used method or verification of the radiation field position relative to the target area, prior to or during irradiation. In this paper, Real time digital radiography system was implemented or verification of local error between simulation plan and radiation therapy machine. Portal image can be acquired by CCD camera, image board and pentium PC after therapy Radiation was converted into light by a metal/fluorescent Screen. The resulting image quality is comparable to film, so the imaging system represents a promising alternative to film as a method of verifying patient positioning in radiotherapy. Edge detection and field size measurement were also implemented and detected automatically for verification of treatment position. Field edge was added to the original image or checking the anatomical treatment verification by therapy technicians. By means of therapy efficiency improvement and decrease of Radiation side effects with these techniques, Exact Radiation treatments are expected.

• Radiation Oncology Journal
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• v.35 no.1
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• pp.1-15
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• 2017

Locoregional failure is the most frequent pattern of failure in locally advanced head and neck cancer patients and it leads to death in most of the patients. Second primary tumors occurring in the other head and neck region reach up to almost 40% of long-term survivors. Recommended and preferred retreatment option in operable patients is salvage surgical resection, reporting a 5-year overall survival of up to 40%. However, because of tumor location, extent, and underlying comorbidities, salvage surgery is often limited and compromised by incomplete resection. Reirradiation with or without combined chemotherapy is an appropriate option for unresectable recurrence. Reirradiation is carefully considered with a case-by-case basis. Reirradiation protocol enrollment is highly encouraged prior to committing patient to an aggressive therapy. Radiation doses greater than 60 Gy are usually recommended for successful salvage. Despite recent technical improvement in intensity-modulated radiotherapy (IMRT), the use of concurrent chemotherapy, and the emergence of molecularly targeted agents, careful patient selection remain as the most paramount factor in reirradiation. Tumors that recur or persist despite aggressive prior chemoradiation therapy imply the presence of chemoradio-resistant clonogens. Treatment protocols that combine novel targeted radiosensitizing agents with conformal high precision radiation are required to overcome the resistance while minimizing toxicity. Recent large number of data showed that IMRT may provide better locoregional control with acceptable acute or chronic morbidities. However, additional prospective studies are required before a definitive conclusion can be drawn on safety and effectiveness of IMRT.

• Korean Journal of Head & Neck Oncology
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• v.27 no.1
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• pp.66-69
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• 2011

Skull base osteoradionecrosis(ORN)is a rare complication of radiotherapy for nasopharyngeal carcinoma, but is one of the most severe and possibly fatal condition followed by radiotherapy. However, the treatment of skull base ORN has seldom been thoroughly described yet. Here we report a case of skull base ORN that was successfully treated with hyperbaric oxygen therapy(HBO). A 52-year-old man visited our department complaining of trismus and foul odor. He was diagnosed with nasopharyngeal cancer with multiple lymph node metastasis one year ago and underwent concurrent chemoradiotherapy. On the physical examination, mucopus and crusts with exposed necrotic bone was seen in the right nasopharynx. On the paranasal sinus magnetic resonance imaging, osteoradionecrosis which was extending from the right nasopharynx to the clivus, petrous apex, and cavernous sinus was noted. Nasopharynx biopsy resulted of ulcer with no malignant cells. HBO therapy was performed with debridement of nasopharynx for 3 months. There was no sign of recurrence or residual ORN 18 months after HBO therapy.

• Progress in Medical Physics
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• v.33 no.4
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• pp.37-52
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• 2022

Over the past decades, radiation therapy combined with imaging modalities that ensure optimal image guidance has revolutionized cancer treatment. The two major purposes of using imaging modalities in radiotherapy are to clearly delineate the target prior to treatment and set up the patient during radiation delivery. Image guidance secures target position prior to and during the treatment. High quality images provide an accurate definition of the treatment target and the possibility to reduce the treatment margin of the target volume, further lowering radiation toxicity and improving the quality of life of cancer patients. In this review, the various types of image guidance modalities used in radiation therapy are distinguished into ionized (kilovoltage and megavoltage image) and nonionized imaging (magnetic resonance image, ultrasound, surface imaging, and radiofrequency). The functional aspects, advantages, and limitation of imaging using these modalities are described as a subsection of each category. This review only focuses on the technological viewpoint of these modalities and any clinical aspects are omitted. Image guidance is essential, and its importance is rapidly increasing in modern radiotherapy. The most important aspect of using image guidance in clinical settings is to monitor the performance of image quality, which must be checked during the periodic quality assurance process.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.3
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• pp.1089-1092
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• 2016

Breast cancer is the most commonly occurring and leading cause of cancer deaths among women globally. Hereditary cases account 5-10% of all the cases and CHEK2 is considered as a moderate penetrance breast cancer risk gene. CHEK2 plays a crucial role in response to DNA damage to promote cell cycle arrest and repair DNA damage or induce apoptosis. Our objective in the current study was to analyze mutations in the CHEK2 gene related to breast cancer in Balochistan. A total of 271 individuals including breast cancer patients and normal subjects were enrolled. All 14 exons of CHEK2 were amplified and sequenced. The majority of the patients (>95%) had invasive ductal carcinomas (IDCs), 52.1% were diagnosed with tumor grade III and 56.1% and 27.5% were diagnosed with advance stages III and IV. Two novel nonsense variants i.e. c.58C>T (P.Q20X) and c.256G>T (p.E85X) at exon 1 and 2 in two breast cancer patients were identified in the current study. Both the variants identified were novel and have not been reported elsewhere.

• The Journal of Korean Society for Radiation Therapy
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• v.25 no.2
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• pp.159-165
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• 2013

Purpose: Abdominal compressor is used to control breathing in stereotactic body radiotherapy for lung tumors frequently. We evaluated the dynamic variation aspect of internal tumor volume by breathing. Materials and Methods: We reviewed 20 lung cancer patients (7 upper lung patients, 4 middle lung patients, 9 lower lung patients) who received stereotactic body radiotherapy using abdominal compressor between April 2012 to April 2013. Coordinate shift values were obtained by using four-dimensional cone-beam CT (4D-CBCT) to investigate treatment set-up error and moving tumor position error. To investigate how much difference of each part, we compared 95% confidence interval, maximum values and minimum values of three-dimensional vector value and analyzed conformity degree through the Pearson square correlation coefficient. Results: 95% confidence interval of three-dimensional vector value of each part is 1.8~2.9 mm in upper lobe, 2.3~5.4 mm in middle lobe and 2.2~4.0 mm in lower lobe. Conformity degree was the result that respectively is LR direction 0.75, SI direction 0.68 and AP direction 0.63 in upper lobe, LR direction 0.82, SI direction 0.51 and AP direction 0.92 in middle lobe and LR direction 0.63, SI direction 0.50 and AP direction 0.34 in lower lobe. Conclusion: We showed difference by each site in lung tumor due to respiration by using abdominal compressor. Therefore, we must correct treatment set-up error as well as moving tumor position error by breathing. It is also considered to be useful that it is the use of 4D-CBCT when correcting the error due to various dynamic variation.

• Progress in Medical Physics
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• v.24 no.4
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• pp.295-302
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• 2013

We estimated secondary scattered and leakage doses for intensity-modulated radiotherapy (IMRT), volumetric arc therapy (VMAT) and tomotherapy (TOMO) in patients with liver cancer. Five liver patients were planned by IMRT, VMAT and TOMO. Secondary scatter (and leakage) dose and organ equivalent doses (OEDs) are measured and estimated at various points 20 to 80 cm from the iso-center by using radiophotoluminescence glass dosimeter (RPLGD). The secondary dose per Gy from IMRT, VMAT and TOMO for liver cancer, measured 20 to 80 cm from the iso-center, are 0.01~3.13, 0.03~2.34 and 0.04~1.29 cGy, respectively. The mean values of relative OED of secondary dose of VMAT and TOMO for five patients, which is normalized by IMRT, measured as 75.24% and 50.92% for thyroid, 75.14% and 40.61% for bowel, 72.30% and 47.77% for rectum, 76.21% and 49.93% for prostate. The secondary dose and OED from TOMO is relatively low to those from IMRT and VMAT. OED based estimation suggests that the secondary cancer risk from TOMO is less than or comparable to the risks from conventional IMRT and VMAT.

• Radiation Oncology Journal
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• v.24 no.1
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• pp.21-29
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• 2006

Purpose: This study explored the anal sphincter-saving rate and down-staging rate after preoperative chemoradiotherapy for treating lower rectal cancer. We also explored the prognosis of the patients who refused surgery after preoperative chemoradiotherapy. Materials and Methods: Thirty seven patients with histologically proven lower rectal cancer who underwent preoperative chemoradiotherapy were retrospectively analyzed. In each case, the tumor location was 0 to 5 em from the anal verge, and curative resection of the cancer with performing a sphincter-saving procedure was not feasible before chemoradiotherapy. In each case, the staging examinations, including biopsy, were done before starting radiotherapy and this was repeated at 1 month after radiation therapy. Results: After chemoradiotherapy, among the 37 included patients, 56.8% and 32.4% were downstaged to the T stage and N stage, respectively, when comparing the postradiotherapy stage with pre-radiotherapy stage. Twenty five patients underwent complete resection of cancer at 6 weeks after radiotherapy: eleven, eight and six patients underwent abdominoperineal resection, low anterior resection and local excision, respectively. The sphincter-saving rate among the 24 completely resected cases was 54.2%. Twelve patients refused surgery after radiotherapy. Among 6 patients who refused surgery with biopsy-proven complete remission after chemoradiotherapy, 5 patients were alive without disease at a median follow up period of 31 months, and only 1 patient had local failure. Conclusion: For lower rectal cancer, a high sphincter-saving rate was accomplished with preoperative chemoradiotherapy. The prognosis of the patients who refused surgery with biopsy proven complete remission after chemoradiotherapy was good and these patients need to be kept under close surveillance.