A Single-Institution Retrospective Study of Three-Fraction HDR Accelerated Partial Breast Irradiation

PURPOSEAccelerated partial breast irradiation (APBI) delivered with high-dose-rate brachytherapy is a standard of care treatment typically delivered over 10 fractions. The TRIUMPH-T multi-institutional study recently demonstrated promising results using a shorter three fraction regimen, however there are limited additional published series using this regimen. Here, we report our experience and outcomes for patients treated as per the TRIUMPH-T regimen.METHODS AND MATERIALSThis study was a retrospective single-institution analysis of patients who underwent lumpectomy followed by APBI (22.5 Gy in 3 fractions delivered over 2–3 days) using a Strut Adjusted Volume Implant (SAVI) applicator between November 2016 and January 2021. Dose-volume metrics were obtained from the clinically treated plan. Chart review was performed to determine locoregional recurrence and toxicities according to CTCAE v5.0.RESULTSBetween 2016 and 2021, 31 patients were treated per the TRIUMPH-T protocol. Median followup was 31 months from completion of brachytherapy. There were no acute/late Grade 3 or higher toxicities. Cumulative late Grade 1 and 2 toxicities were seen in 58.1% and 9.7% of patients, respectively. Of note, four patients experienced locoregional recurrence: three ipsilateral breast tumor recurrences and one nodal recurrence. All three ipsilateral breast tumor recurrences occurred in patients who would be classified as “cautionary” based on ASTRO consensus guidelines due to age ≤50, lobular histology, or high grade.CONCLUSIONSThree-fraction HDR brachytherapy APBI was well-tolerated with no grade 3 or higher toxicities and an acceptably small percentage of grade 2 toxicities. Given the small sample size, the number of recurrences suggests that attention to appropriate patient selection is necessary until more long-term followup data is available.     

瘤段切除结合内照射治疗恶性骨肿瘤临床分析

目的观察高剂量率骨内插植内照射治疗骨肿瘤的保肢效果。方法8例恶性骨肿瘤均在术中置管进行内照射,每次治疗10 Gy,2次/周,共6次,总剂量60 Gy。治疗后2周有5例行瘤段切除术。结果所有病人都能耐受治疗,瘤段切除标本见瘤段区均有广泛坏死、出血、死骨残存及组织退变,肿瘤的边缘3~6 Gy照射区发现有少量退变不明显的瘤细胞存在,生存1年和3年分别有7例和5例。结论高剂量率骨内插植内照射结合瘤段切除治疗骨肿瘤是可行的。     

Dosimetric Parameters in Partial Breast Irradiation Through Brachytherapy

The objective of this work is to evaluate biological models and dose homogeneity in a new partial breast irradiation method, the MammoSite RTS. The study is based on 11 patients who received the therapy. For each patient, we determined the dose volume distribution delivered to the breast. Based on these data, we estimate some important biological parameters. Eleven patients with early-stage, invasive, ductal breast cancer were treated using MammoSite RTS brachytherapy, which delivers radiation through a balloon placed in the lumpectomy bed. The radiation was provided by an Iridium-192 source, and 340 cGy were delivered per fraction twice daily. We calculated some commonly used dosimetric parameters, and evaluated the biological parameters tumor control probability (TCP) and normal tissue complication probability (NTCP). We also looked for correlations among these parameters. The average equivalent uniform dose (EUD), NTCP, and TCP were 43.66 Gy, 47.95%, and 91.78%, respectively. The coefficient of variation (CV) among the patients was very low for all 3 parameters. Two dose homogeneity indices (DHI and the S-index) are strongly correlated (r = −0.815). The area under the dose-volume histogram (DVH) and the treatment volume (TXV) also showed a strong correlation (r = 0.995, p < 0.0001). A simplified logit Poisson–EUD model is suitable for determining NTCP and TCP. Other factors such as the area under the DVH and dose homogeneity indices are also useful in planning radiotherapy treatments for early breast cancer.