A phase I/II study piloting accelerated partial breast irradiation using CT-guided intensity modulated radiation therapy in the prone position

作者：Bergom Carmen; Prior Phillip; Kainz Kristofer; Morrow Natalya V; Ahunbay Ergun E; Walker Alonzo; Li X Allen; White Julia^*

来源：Radiotherapy and Oncology, 2013, 108(2): 215-219.

DOI：10.1016/j.radonc.2013.05.039

• Breast cancer
• Accelerated partial breast irradiation
• Image-guided radiation therapy
• Prone
• Intensity modulated radiation therapy
• CT guidance

Background and purpose: External beam accelerated partial breast irradiation (EB-aPBI) is noninvasive with broader potential applicability than aPBI using brachytherapy. However, it has inherent challenges in daily reproducibility. Image-guide radiotherapy (IGRT) can improve daily reproducibility, allowing smaller treatment margins. Our institution proposed IG-IMRT in the prone position to evaluate dose homogeneity, conformality, normal tissue avoidance, and reliable targeting for EB-aPBI. We report preliminary results and toxicity from a phase I/II study evaluating the feasibility of EB-aPBI in the prone position using IG-IMRT. %26lt;br%26gt;Materials and methods: Twenty post-menopausal women with node-negative breast cancer, excised tumors %26lt;3.0 cm, negative sentinel lymph node biopsy, and surgical clips demarcating the lumpectomy cavity underwent prone EB-aPBI using IG-IMRT on an IRB-approved phase I/II study. All patients underwent CT planning in the prone position. The lumpectomy cavity PTV represented a 2.0 cm expansion. 38.5 Gy was delivered in 10 fractions over 5 days, such that 95% of the prescribed dose covered %26gt;99% of the PTV. Dose constraints for the whole breast, lungs and heart were met. %26lt;br%26gt;Results: The median patient age was 61.5. Mean tumor size was 1.0 cm. 35% of patients had DCIS. Median Ply was 243 cc (108-530) and median breast reference volume was 1698 cc (647-3627). Average daily shifts for IGRT were (0.6, -4.6, 1.7 mm) with standard deviations of (6.3, 6.5, 6.4 mm). Acute toxicity was Cl erythema in 80%, and G2 erythema, G2 fatigue, and G2 breast pain each occurred in 1 patient. With a median follow-up of 18.9 months (12-35), 40% of patients have G1 fibrosis and 30% have G1 hyperpigmentation. 95% of patients have good to excellent cosmesis. There have been no recurrences. %26lt;br%26gt;Conclusions: These data demonstrate that EB-aPBI in the prone position using IG-IMRT is well tolerated, yields good dosimetric conformality, and results in promising early toxicity profiles.

• 出版日期2013-8