Impact of Increasing Margin Around the Lumpectomy Cavity to Define the Planning Target Volume for 3D Conformal External Beam Accelerated Partial Breast Irradiation

The purpose of this study was to evaluate the dose to normal tissues as a function of increasing margins around the lumpectomy cavity in accelerated partial breast irradiation (APBI) using 3D-conformal radiotherapy (3DCRT). Eight patients with Stage 0-I breast cancer underwent treatment planning for 3DCRT APBI. The clinical target volume (CTV) was defined as a 15-mm expansion around the cavity limited by the chest wall and skin. Three planning target volumes (PTV1, PTV2, PTV3) were generated for each patient using a 0, 5-, and 10-mm expansion around the CTV, for a total margin of 15, 20, and 25 mm. Three treatment plans were generated for every patient using the 3 PTVs, and dose-volume analysis was performed for each plan. For each 5-mm increase in margin, the mean PTV:total breast volume ratio increased 10% and the relative increase in the mean ipsilateral breast dose was 15%. The mean volume of ipsilateral breast tissue receiving 75%, 50%, and 25% of the prescribed dose increased 6% to 7% for every 5 mm increase in PTV margin. Compared to lesions located in the upper outer quadrant, plans for medially located tumors revealed higher mean ipsilateral breast doses and 20% to 22% more ipsilateral breast tissue encompassed by the 25% IDL. The use of 3DCRT for APBI delivers higher doses to normal breast tissue as the PTV increases around the lumpectomy cavity. Efforts should be made to minimize the overall PTV when this technique is used. Ongoing studies will be necessary to determine the clinical relevance of these findings.     

Accelerated partial breast irradiation for suitable elderly women using a single fraction of multicatheter interstitial high-dose-rate brachytherapy: Early results of the Single-Fraction Elderly Breast Irradiation (SiFEBI) Phase I/II trial

Purpose/ObjectiveTo evaluate feasibility and early clinical outcomes of a single fraction of multi-catheter interstitial high-dose rate brachytherapy for accelerated partial breast irradiation (APBI) in the elderly.Material/MethodsFrom November 2012 to September 2014, 26 patients (≥70) with early breast cancer were enrolled in a prospective phase II trial (NCT01727011). After lumpectomy, intra-operative catheter implant was performed for post-operative APBI (single fraction 16 Gy). Surveillance was achieved at 1, 3 and 6 months after APBI, then twice a year. Acute toxicity was investigated. Early cosmetic outcome was analyzed (patient, radiation oncologist, 2 observers). Local and regional relapse-free survival, cancer specific survival and overall survival were analyzed.ResultsMedian age was 77 years [69–89]. Median CTV was 41 cc [22-95]. Acute toxicity was observed in 18 pts (70%) with a total of 44 events: G1: 75.7%; G2: 22.8%; G3: 4.5%. Breast fibrosis (31.8%), puncture site inflammation (13.6%) and skin hyperpigmentation (11.4%) were the most frequent side effects. Cosmetic evaluation at 6 months was excellent/good in 88%, 92%, 85% and 88% for patient, radiation oncologist, observer #1 and #2 respectively. With a median follow-up of 37.2 months [35.6-42.3], side effects were G1: 4 pts (15%) and G2: 1 pt (4%). Three-year Local and regional relapse-free survival, cancer specific survival and overall survival rates were 100%, 100%, 100% and 95.2% respectively.ConclusionsFor elderly early breast cancer, a post-operative multi-catheter interstitial high-dose rate brachytherapy single dose (16 Gy) appears feasible. Acute toxicity is acceptable as well as early cosmetic outcome. Oncologic outcome seems encouraging and allows going forward with new clinical trials focusing on single fraction APBI.     

乳腺癌保乳术后部分乳腺三种放疗计划的剂量学比较

目的 比较容积弧形调强（VMAT）、固定野动态调强（IMRT）及三维适形放疗（3D-CRT）技术对乳腺癌保乳术后采用部分乳腺放疗的剂量学差异。方法 选取20例临床分期为T_1-2N₀M₀的早期乳腺癌保乳术后患者进行VMAT,并同时设计IMRT及3D-CRT,比较3种计划的剂量学参数,包括剂量-体积直方图（DVH）、靶区剂量适形度、靶区及危及器官的剂量、机器跳数及治疗时间。结果 IMRT及VMAT计划靶区剂量分布优于3D-CRT计划,其中最大剂量,平均剂量及适形指数（CI）组间比较差异具有统计学意义（F=14.86、8.57、18.23,P<0.05）。正常组织受量：VMAT计划在患侧乳腺V₅上优于IMRT及3D-CRT计划（F=5.83,P<0.05）;IMRT在患侧肺V₂₀、V₅及D₅上有优势（F=16.39、3.62、4.81,P<0.05）;在对侧肺的统计中,IMRT计划在最大剂量及D₅上可以得到比VMAT和3D-CRT更低的剂量（F=3.99、3.43,P<0.05）;VMAT、3D-CRT和IMRT计划所需机器跳数值分别为621.0±111.9、707.3±130.9、1161.4±315.6,计划间的差异有统计学意义（F=31.30,P<0.05）。VMAT、3D-CRT和IMRT计划所需治疗时间分别为（1.5±0.2）、（7.0±1.6）、（11.5±1.9）min。结论 IMRT和VMAT计划靶区剂量分布优于3D-CRT计划,而不提高患侧肺剂量。对于部分乳腺癌的放疗,容积弧形调强放疗在降低机器跳数和减少治疗时间方面具有明显优势。