Comparison of Virtual Wedge versus Physical Wedge Affecting on Dose Distribution of Treated Breast and Adjacent Normal Tissue for Tangential Breast Irradiation / 대한방사선종양학회지

PURPOSE: The ideal breast irradiation method should provide an optimal dose distribution in the treated breast volume and a minimum scatter dose to the nearby normal tissue. Physical wedges have been used to improve the dose distribution in the treated breast, but unfortunately introduce an increased scatter dose outside the treatment field, particularly to the contralateral breast. The typical physical wedge (PW) was compared with the virtual wedge (VW) to determine the difference in the dose distribution affecting on the treated breast and the contralateral breast, lung, heart and surrounding peripheral soft tissue. METHODS AND MATERIALS: The data collected consisted of a measurement taken with solid water, a Humanoid Alderson Rando phantom and patients. The radiation doses at the ipsilateral breast and skin, contralateral breast and skin, surrounding peripheral soft tissue, and ipsilateral lung and heart were compared using the physical wedge and virtual wedge and the radiation dose distribution and DVH of the treated breast were compared. The beam-on time of each treatment technique was also compared. Furthermore, the doses at treated breast skin, contralateral breast skin and skin 1.5 cm away from the field margin were also measured using TLD in 7 patients of tangential breast irradiation and compared the results with phantom measurements. RESULTS: The virtual wedge showed a decreased peripheral dose than those of a typical physical wedge at 15degrees, 30degrees, 45degrees, and 60degrees. According to the TLD measurements with 15degrees and 30degrees virtual wedge, the irradiation dose decreased by 1.35% and 2.55% in the contralateral breast and by 0.87% and 1.9% in the skin of the contralateral breast respectively. Furthermore, the irradiation dose decreased by 2.7% and 6.0% in the ipsilateral lung and by 0.96% and 2.5% in the heart. The VW fields had lower peripheral doses than those of the PW fields by 1.8% and 2.33%. However the skin dose increased by 2.4% and 4.58% in the ipsilateral breast. VW fields, in general, use less monitor units than PW fields and shortened beam-on time about half of PW. The DVH analysis showed that each delivery technique results in comparable dose distribution in treated breast. CONCLUSIONS: A modest dose reduction to the surrounding normal tissue and uniform target homogeneity were observed using the VW technique compare to the PW beam in tangential breast irradiation The VW field is dosimetrically superior to the PW beam and can be an efficient method for minimizing acute, late radiation morbidity and reduce the linear accelerator loading by decreasing the radiation delivery time.

The Effects of Preoperative Radiation Therapy in Resectable Rectal Cancer: in view of pathologic aspects / 대한치료방사선과학회지

PURPOSE: To evaluate the pathologic effects of preoperative radiotherapy on the resectable distal rectal cancer, we analyzed the results of postoperative pathologic findings for the patients with preoperative radiotherapy and surgery. MATERIALS AND METHODS: From July 1995 to April 1996, we treated sixteen patients of resectable rectal cancer with preoperative radiation therapy and curative surgery. At diagnosis, Thomas Jefferson (TJ) system was used for the clinical stage of the patients. We treated the patients with conventional radiation therapy of 4500-5000cGy before surgery. The surgery was carried out 4 weeks after completion of radiation therapy. Modified Astler Coller (MAC) system was used for the postoperative pathologic stage. We analyzed the pathologic stages and findings according to preoperative clinical stage and compared with those of the control group in similar clinical stages. RESULTS: All patients were treated with sphincter preservation surgery after preoperative radiation therapy. Pathologic complete response (CR) was shown in 1 case (6.3%). We compared the results between preoperative radiation therapy group (Preop.RT group) and surgery only group (control group). In TJ stage II, among nine patients of Preop.RT group, 8 patients (88.9%) were in MAC stage B except 1 CR patient, but among 17 patients of control group, 11 patients (64.7%) were in MAC stage B and 6 patients (35.3%) in MAC stage C. In TJ stage III, among 7 patients of Preop.RT group, 4 patients (57.1%) were in MAC stage B and 3 patients (42.9%) in MAC stage C. Among 14 patients of control group, 4 patients (28.6%) were in MAC stage B and 10 patients (71.4%) in MAC stage C. Above results showed that postoperative pathologic stage was decreased in Preop.RT group with statistical significance (p=0.049). The postoperative pathologic findings (blood vessel invasion, lymphatic vessel invasion, perineural invasion) were decreased in the Preop.RT group compared with those of control group. But statistical significance was found only in lymphatic vessel invasion (p=0.019). CONCLUSION: The postoperative pathologic stages and adverse prognostic pathologic findings were decreased in preoperative radiation therapy group. The lymphatic vessel invasion and MAC stage C findings were abruptly decreased in preoperative radiation therapy group. The preoperative radiation therapy was found to be effective in resectable rectal cancer. The patients group in our study was very small and long term follow up was not done. Therefore, further study about this issues is needed .

Radiation Treatment of Postmastectomy Lymphangiosarcoma / 대한치료방사선과학회지

Since the entity of postmastectomy lymphangiosarcoma was first reported by Stewart and Traves in 1948, postmastectomy lymphangiosarcoma has become a well recognized, uncommon malignant tumor which occurs in the upper extremity following mastectomy for mammary carcinoma. The postmastectomy lymphangiosarcoma occurred at an average age of 63.9 years and at an average of 10 years and 3 months following mastectomy. The lymphangiosarcoma raised from blood and lymphatic vessel. The histologic appearance has been observed edematous dermis and dilated lymphatics lining with malignant cells. Most authors recommend radical amputation for treatment, either shoulder disarticulation or forequarter amputation. Other modalities of treatment including radiotherapy were considered as ineffective. The present report provides a case of the regression of postmastectomy lymphangiosarcoma with chronic lymphedima by external irradiation. Radiation therapy was used as primary therapy. Total tumor dose of 6500 cgy in 9 weeks was delivered using 6 MV x-ray and 8 MeV electron.