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Title: A dosimetric skin study on postmastectomy breast cancer patients undergoing radiation therapy
Keywords: Breast, postmastectomy, radiation therapy, treatment planning system, skin, ultrasound,
Issue Date: 21-Jul-2011
Citation: WONG MEI MEI, SHARON (2011-07-21). A dosimetric skin study on postmastectomy breast cancer patients undergoing radiation therapy. ScholarBank@NUS Repository.
Abstract: Postmastectomy radiation therapy (PMRT) has been proven to decrease locoregional recurrence and increase survival for women with large tumors and/or node-positive disease. However, the clinical benefit of radiotherapy in the treatment of breast cancer must be balanced against the documented risk for early and late toxicity. Adverse effects after breast irradiation have been reported in a range of organs with the skin being the most commonly affected during breast cancer radiation. The focus of this thesis is to evaluate the skin reactions of postmastectomy breast cancer patients undergoing radiation therapy treatments and its dosimetric effects. The proteomic response of human skin cells after exposure to PMRT regimens and the expression of apoptotic biomarkers that reflect cell death or biology using multiplexed immunoassays have also been studied in depth. Accurate assessments of skin doses in PMRT are important to ensure sufficient dose to the surface target volume without excessive skin reaction. In our first study, we assessed the accuracy of surface dose calculation by a clinically used 3D treatment planning system (TPS) and those measured by Thermoluminescence dosimeters (TLDs) in a customized chest wall phantom. Dose accuracy of up to 2.21% was found. The deviations from the calculated absorbed doses were overall larger when wedges and bolus were used. These findings suggest that 3D TPS is a useful and accurate tool to assess the accuracy of surface dose and that radiation treatment accuracy can be accurately predicted for tangential treatment of the chest wall after mastectomy. Skin reaction is the most common side effects during breast cancer irradiation. Unfortunately, current clinical assessment of radiation induced skin changes is generally limited to clinician-based rating scales, which are usually not sufficient for quantitative and objective evaluations. In our study, we determined the usefulness of ultrasonography in the assessment of post radiotherapy skin changes in PMRT breast cancer patients. Our results demonstrated statistical significant difference between the skin thickness of irradiated chestwall and the contral lateral non-irradiated breast and a predisposition to severe chronic reactions was found in patients with RTOG scoring of grade 1 and grade 2. Knowledge of the pathophysiology of the irradiated skin is important to understand the tolerance and cosmetic response of the human skin to radiation. Unfortunately the cellular radiation response of the skin to different radiation therapy treatment regimen has never been studied. The practice of radiotherapy would also greatly benefit from the discovery of biomarkers that correlate with symptoms and side effects pertaining to tissues within the irradiated volume. We investigated the radiation induced apoptotic cell death and apoptotic proteins expression in human skin after exposure to PMRT regimens. There is strong evidence of cellular damaged and accumulation of apoptotic proteins caused by ionizing radiation and these are radiation dosage and fraction size dependent. In summary, results derived from this thesis have demonstrated that radiation induced skin reaction in PMRT breast cancer patients can be accurately predicted using image-based technology and multiplexed immunoassays. Taken together, it is conceivable that in the near future these measures will be used to monitor therapeutic response and predict local control and toxicity to Radiation Therapy.
Appears in Collections:Ph.D Theses (Open)

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