RESUMO
Background: In patients with expander-based reconstruction a few dosimetric analyses detected radiation therapy dose perturbation due to the internal port of an expander, potentially leading to toxicity or loss of local control. This study aimed at adding data on this field. Materials and methods: A dosimetric analysis was conducted in 30 chest wall treatment planning without and with correction for port artifact. In plans with artifact correction density was overwritten as 1 g/cm3. Medium, minimum and maximum chest wall doses were compared in the two plans. Both plans, with and without correction, were compared on an anthropomorphic phantom with a tissue expander on the chest covered by a bolus simulating the skin. Ex vivo dosimetry was carried out on the phantom and in vivo dosimetry in three patients by using film strips during one treatment fraction. Estimated doses and measured film doses were compared. Results: No significant differences emerged in the minimum, medium and maximum doses in the two plans, without and with correction for port artifacts. Ex vivo and in vivo analyses showed a good correspondence between detected and calculated doses without and with correction. Conclusions: The port did not significantly affect dose distribution in patients who will receive post-mastectomy radiation therapy.
RESUMO
BACKGROUND Synchronous bilateral breast cancer is rare. A case is presented where whole breast irradiation (WBI) was planned after breast conserving surgery in a patient with synchronous bilateral breast cancer. A comparison was made between the feasibility of helical tomotherapy and direct tomotherapy. CASE REPORT A 60-year-old woman was found to have bilateral breast nodules on routine mammographic screening, resulting in bilateral lumpectomy and sentinel lymph node biopsy. Histopathology showed a 6 mm diameter invasive ductal carcinoma in the right breast (Grade 1, hormone receptor positive, HER2 negative) and an 8mm diameter tubular carcinoma in the left breast (Grade 1, hormone receptor positive, HER2 negative). Lymph node biopsy and histology, chest X-ray, abdominal ultrasound scan, and bone scintigraphy were negative for metastases (both tumors were Stage 1). Adjuvant therapy with commenced with anastrozole, but no chemotherapy was given. Clinical target volumes (CTVs) were contoured on computed tomography (CT) images. For planning target volumes (PTVs), CTVs were expanded by 1 cm in all directions, except for the medial 5 mm. Since dose constraints to organs at risk (OARs) were beyond established limits, CTVs were expanded by 5 mm. For PTVs, OAR doses and homogeneity indices for helical tomotherapy and direct tomotherapy were compared. Helical tomotherapy provided better target volume coverage and OAR sparing than direct tomotherapy. CONCLUSIONS In a case of bilateral synchronous Stage 1 and Grade 1 breast cancer, helical tomotherapy appeared more suitable than direct tomotherapy.
