Comparing ultrasound with computerized tomography images to choose electron energy for radiotherapy boost field in breast cancer patients with breast conserving surgery.

PURPOSE: To compare ultrasonographic (US) with computerized tomographic (CT) images in order to choose electron energy for radiotherapy (RT) boost field in patients with breast conserving surgery (BCS). METHODS: Thirty-seven consecutive patients with breast cancer treated by BCS and RT in our department were evaluated. Median age was 49 years (range 32-82). According to the Dokuz Eylul Breast Tumor Group Protocol (DEBTG), in patients with BCS, RT (5000 cGy to the whole breast ± lymphatic area) and boost with electron energy to the primary tumor bed (1000 cGy if surgical margin negative, or 1600 cGy if surgical margin positive was delivered. Before January 2003, the distances between skin-the deepest point of tumor bed (STD), skin-clips (SCD), and skin-fascia (SFD) were measured with US to choose electron energy in boost field. Since then, CT simulation images were used to this purpose. These two imaging systems were compared in this study. Electron energy was selected after measurement of the deepest metallic clips in CT simulation images (90%) or measurement of the STD if no clips were present (10%). RESULTS: Median measurements with US and CT were as follows: STD: US 12 mm (range 4-35), CT 28 mm (range 2-54); SFD: US 25 mm (range 6-57), CT 31 mm (range 2-93); SCD: US 14 mm (range 7-26), CT 29 mm (range 2-68). The median electron energy was 9 MeV é (range 6-12) for US and 12 MeV é (range 6-21) for CT. Concordance in US and CT measurements was 27%. CONCLUSION: This preliminary study reveals that CT-based SCD measurements are deeper than US measurements, and selected electron energy with CT is 3 MeV higher than US. These two factors can affect local control and side effects. We noticed only one local recurrence in 37 patients. We did not evaluate side effects in this study. These could be a subject of a future study.

Evaluation of contralateral breast skin doses by thermoluminescent dosimeters of patients receiving adjuvant radiotherapy for breast cancer.

PURPOSE: It is reported that low dose radiation received by the contralateral breast (CLB) during adjuvant radiotherapy (RT) is carcinogenic. This trial was planned to evaluate the CLB skin doses received during adjuvant RT of breast carcinoma. PATIENTS AND METHODS: Twenty-four breast carcinoma patients treated locally or locoregionally with adjuvant RT were included. RT was performed with only tangential fields (TA) in 6 patients whereas 9 patients had an extra internal mammary (IM) field (TAIM). The remaining 9 patients received 5-field locoregional RT (5FLR). All patients were treated with wedge filters except for 3 TA patients. Of 9 5FLR patients IM fields were treated with Co60 in 5 and with electrons in the remaining 4 patients. LiF(2)-based Ribbon type thermoluminescent dosimeters (TLD) were used for dose evaluation. An average of 10 TLD's, placed with 1 cm gaps beginning from the medial border of the treatment field along the central axis were used to obtain dose measurements. Median measure of TLD's between 2-8 cm and maximum dose point (MDP) values in the same range were used to evaluate the CLB dose. RESULTS: In TA patients the CLB skin received 6.3% of the total dose in patients treated with wedge filters and 7.13% with half-beam blocks. For 6 TAIM patients with IM fields treated with Co60, the CLB dose was 7.24%. In 5 of 9 5FLR patients, whose IM fields were treated with Co60 the CLB skin received 8.8% of the total dose, while for electron beam therapy the CLB dose was 5.44%. CLB median MDP values were as follows: 12.76% in TA patients treated with wedge filters and 11.45% with half-beam blocking; 11.89% in TAIM patients with IM fields treated with Co60 and 7.83% with electron beams; 12.29% in 5FLR patients of whose IM fields were treated with Co60 and 8.94% with electron beams. CONCLUSION: When compared to wedge filters, halfbeam blocks caused 13% increase in CLB doses. If IM fields were added, 27.5% and 62% increases at CLB doses were established with Co60 when compared to electron beam RT in 3-field and 5-field treatments, respectively. CLB doses increased by 15-40% with the increased number of treatment fields. MDP values were also found to be higher with IM fields treated with Co60, but the number of treatment fields and accessories used seemed to have no effect on MDP doses. We conclude that by using wedge filters instead of half-beam blocks and by increasing the number of fractions treated with electron energies for IM fields, apparent decreases in CLB doses can be obtained. Large number of cases is needed to statistically establish the significant differences between subgroups.