Hiroshi Seto

Comparison of radiation dose to the left anterior descending artery by whole and partial breast irradiation in breast cancer patients

Purpose Breast conserving surgery (BCS) followed by whole breast irradiation (WBI) is the standard of care for breast cancer patients. However, there is a risk of coronary events with WBI therapy. In this study, we compared the radiation dose in the left anterior descending artery (LAD) in patients receiving partial breast irradiation (PBI) with WBI. Material and methods We evaluated consecutive patients who underwent adjuvant radiotherapy after BCS between October 2008 and July 2014. Whole breast irradiation patients received 50 Gy in fractions of 2 Gy to the entire breast. Partial breast irradiation was performed using multicatheter brachytherapy at a dose of 32 Gy in eight fractions. The mean and maximal cumulative doses to LAD were calculated. The radiotherapeutic biologically effective dose of PBI was adjusted to WBI, and radiation techniques were compared. Results Of 379 consecutive patients with 383 lesions receiving radiotherapy (151 WBI and 232 PBI lesions), 82 WBI and 100 PBI patients were analyzed. In WBI patients, the mean and maximal cumulative doses for left-sided breast cancer (2.13 ± 0.11 and 8.19 ± 1.21 Gy, respectively) were significantly higher than those for right-sided (0.37 ± 0.02 and 0.56 ± 0.03 Gy, respectively; p < 0.0001). In PBI patients with left-sided breast cancer, the doses for tumors in inner quadrants or central location (2.54 ± 0.21 and 4.43 ± 0.38 Gy, respectively) were significantly elevated compared to outer quadrants (1.02 ± 0.17 and 2.10 ± 0.29 Gy, respectively; p < 0.0001). After the adjustment, the doses in PBI patients were significantly reduced in patients with tumors only in outer quadrants (1.12 ± 0.20 and 2.43 ± 0.37 Gy, respectively; p = 0.0001). Conclusions Tumor control and dose to LAD should be considered during treatment since PBI may reduce the risk of coronary artery disease especially in patients with lateral tumors in the left breast.

Efficacy of single-stage breast-conserving treatment using multicatheter partial breast brachytherapy evaluated by GEC-ESTRO phase 3 trial

Purpose The GEC-ESTRO has reported the equivalent outcomes of partial breast irradiation (PBI) using multicatheter interstitial brachytherapy (MCB) to whole breast irradiation (WBI) in breast-conserving therapy (BCT). We performed single-stage BCT with partial breast brachytherapy by intraoperative catheter placement. After the categorization of patients into inclusion and exclusion criteria on this trial, our databases were evaluated in order to translate it to Japanese patients. Material and methods Patients undergoing BCT were retrospectively examined between November 2007 and December 2015. The technique is an open-cavity implant with a dose of 32 Gy in 8 fractions. The 4-year clinical outcomes of MCB-PBI were evaluated in the 2 distinct categories, and the comparison of the outcomes of MCB-PBI with WBI was performed in patients with unfavorable features. Results Of a total of 501 lesions undergoing BCT, 301 lesions were treated with MCB-PBI and 200 lesions with WBI. At the median follow-up time of 52 months, the 4-year rate of ipsilateral breast tumor recurrence (IBTR)-free, disease-free (DFS), and overall survival (OS) in patients with MCB-PBI and WBI were 98.9% vs. 98.0% (p = 0.56), 97.0% vs. 95.3% (p = 0.78), and 99.6% vs. 98.2% (p = 0.38), respectively. Although in exclusion cohort treated with MCB-PBI, IBTR-free, and disease-free survival were significantly worse than in inclusion cohort, non-significantly worse outcomes was demonstrated than in exclusion cohort with WBI; IBTR-free survival (95.0% vs. 97.2%, p = 0.24), and disease-free survival (95.0% vs. 95.8%, p = 0.31). Conclusions Single-stage BCT using MCB-PBI offered similar tumor control rates compering to WBI. However, further research is needed to define the benefit for patients with an exclusion criteria.

Abstract P1-15-22: Comparison of cardiac dose between accelerated partial-breast irradiation and whole-breast irradiation in breast cancer patients

[Background] Breast-conserving surgery (BCS) followed by whole-breast irradiation (WBI) has now become the standard treatment for early-stage breast cancer. However, WBI is associated with an increased risk of coronary events, especially in patients with preexisting cardiac risk factors. In radiotherapy (RT), the highest dose is likely delivered to the left anterior descending artery (LAD), which is the typical site for ischemic heart disease. We initiated a prospective, observational study on accelerated partial-breast irradiation (APBI) using multicatheter brachytherapy after BCS. In this study, we compared the radiation dose to LAD between patients receiving APBI and those receiving WBI. [Methods] The study participants included a cohort selected from consecutive patients who underwent BCS followed by RT since November 2007. In the WBI group, patients received 50 Gy in fractions of 2 Gy to the entire breast. APBI was initiated on the day of primary surgery in the form of multicatheter brachytherapy, at a dose of 32 Gy in 8 fractions. The planned target volume was defined as the estimated tumor volume plus a 20-mm margin. Dose distribution analysis was performed on the basis of postoperative CT using dose–volume histograms. LAD was outlined from its origin to each visible end using the planning CT images. First, the mean and maximal total doses to LAD were calculated. Second, the radiotherapeutic biologically effective dose of APBI was adjusted to that of WBI for comparisons between the two different RT schedules. [Results] Of the 359 consecutive patients who underwent BCS followed by RT, we retrospectively reviewed 182 patients for radiation dose to LAD. The 82 patients receiving WBI were randomly selected; 42 patients had right breast cancer and 40 had left breast cancer. We selected 100 consecutive APBI patients with left breast cancer treated between September 2009 and December 2013 because the LAD dose is considered to be virtually zero in right breast cancer patients. In the WBI patients, the mean and maximal total LAD dose were significantly higher in left breast cancer patients (2.1 ± and 8.2 ± 1.2 Gy, respectively) than in right breast cancer patients (0.4 ± 0.02 and 0.6 ± 0.03 Gy, respectively; p [Conclusions] Our results show that APBI may decrease the risk of coronary artery disease, especially in patients with outer quadrant tumors in the left breast. Although APBI should be carefully interpreted until mature phase-III data are available, the risk of ipsilateral breast tumor recurrences and LAD dose must be considered together while administering RT after BCS. Citation Format: Kazuhiko Sato, Yoshio Mizuno, Hiromi Fuchikami, Naoko Takeda, Takahiro Shimo, Jun Kubota, Yuko Inoue, Hiroshi Seto, Masahiro Kato. Comparison of cardiac dose between accelerated partial-breast irradiation and whole-breast irradiation in breast cancer patients [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-22.