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Secondary tumors after irradiation for carcinoma of the breast
SUKOVÁ, Denisa
One of the most common cancers in women is breast cancer. The incidence of breast cancer is great and its incidence increases after 50 years of age. In 2009, 5,975 women were newly diagnosed. Despite the fact that the treatment of breast cancer, especially in its early stages, is very successful, breast cancer still remains the leading cause of cancer death in women. In 2009, 1,607 women succumbed to this pestilential disease. The main treatment modality is surgical treatment. Breast cancer is moderately chemosensitive and radiosensitive, which suggests a potential treatment using chemotherapy and radiotherapy. Other treatment modalities include hormonal and biological therapies. Radiotherapy is a medical discipline that uses ionizing radiation to treat malignant as well as benign diseases. When applying ionizing radiation, tolerance doses of organs and tissues must be observed. As a result of exceeding the tolerance doses, significant changes and complications reducing the quality of life arise. Because the survival rate of cancer patients is increasing, the study of late effects of cancer treatment is becoming more important. One of the serious late side effects is the formation of secondary tumour. The practical part of the thesis focuses on the issues of radiation-induced tumours in women who have been treated with radiotherapy for breast cancer. The research group consists of patients who were exposed to radiation at a hospital in České Budějovice between 2000 and 2004. The entire group included 516 patients who were exposed to radiation aimed to the breast or chest wall. I monitored in these patients the eventual formation of a duplicate tumour, its location, type, and latency time. I also focused on the calculation of relative risk. After the completion of radiation therapy, a secondary tumour formed in 32 patients, i.e. 6.2 %. Two new tumours were found in one of the patients, the total of 33 secondary tumours was diagnosed. The most frequent types of newly formed tumours were cancers of contralateral breast and non-melanoma skin cancers (basal cell epithelioma). Both tumour types were represented in the number of seven. Furthermore, six lung tumours, three rectal tumours, and two cases of cervical, kidney and bladder tumours were found. In addition, a duplicate tumour of the brain and the meninx, a myeloma, a thyroid tumour, and an endometrial tumour were found. 58 % cases of duplicate tumours were located outside the irradiated areas. Four of the six newly formed lung tumours, three of the seven newly formed skin tumours, and seven tumours in the contralateral breast were identified in the irradiated areas. Latency time till the formation of duplicate tumours ranged from two to twelve years. The median of the latency time was seven years. Within five years after irradiation a total of 14 secondary tumours formed, i.e. 42 % of the total. Within ten years after irradiation most of the duplicate tumours formed. 17 duplicates were diagnosed in this category, i.e. 52 %. 52 %. In one type of cancer (3 %), brain tumour, and meninges, the latency time was 12 years. Furthermore, I calculated relative risk. The values of relative risk determined were greater than 1 for all types of tumours. The lowest value relative risk was observed in skin cancer, which was 1,939. On the other hand, the highest value of the relative risk was observed in endometrial neoplasm. The value of relative risk reached 48.78. Through this calculation of relative risks I confirmed the hypothesis that after irradiation of breast cancer there is an increasing number of duplicate tumours in comparison with the occurrence of tumours in the general population. Despite the increased values of relative risk, the benefits of radiotherapy in cancer treatment are irreplaceable. When using radio therapy, it is necessary to count with some risk of late complications.
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