Efficacy of Single-Plane Implant Technique in Partial Breast Brachytherapy in Small-Breasted Patients

Retrospective Analysis of the Clinical Usefulness of a Strut-Adjusted Volume Implant in a Single Center

OBJECTIVE

Reports demonstrating the effectiveness and safety of strut-adjusted volume implants (SAVI) in Japan are limited. Therefore, this study aimed to compare the treatment outcomes of SAVI and whole-breast irradiation (WBI) at a single facility.

MATERIALS AND METHODS

Data were retrospectively extracted from the medical records of patients treated with SAVI or WBI following partial mastectomy (Bp). Patients undergoing Bp, sentinel lymph node biopsy, and SAVI spacer insertion followed by brachytherapy with the SAVI device were compared to those followed with WBI. Local recurrence was assessed annually by physical examination, bilateral mammography, and breast ultrasonography.

RESULTS

The SAVI and WBI groups comprised 53 and 113 patients, with a median age of 55 and 52 years, respectively; among them, 47 and 91 patients had a pathological tumor diameter ≤2 cm and six and 22 had a pathological tumor diameter >2 cm, respectively. Recurrence events, acute adverse events, and late adverse events were observed in the SAVI and WBI groups in 1 and 3 (p = 0.726), 24 and 79 (p = 0.01), and 24 and 18 patients (p = 0.00002), respectively, with median observation periods of 60.0 and 47.8 months, respectively. All adverse events were grades 1-2, with dermatitis being the most common in the acute phase. In the late phase, pigmentation was common in both groups.

CONCLUSION

The local recurrence rate does not differ between SAVI and WBI within the relatively short-term follow-up period. Longer follow-up is required to confirm our results in the Japanese population.

Preliminary report on ultrashort perioperative partial-breast irradiation with multicatheter interstitial brachytherapy for early-stage breast cancer

PURPOSE

Perioperative partial-breast irradiation (PBI) with multicatheter interstitial brachytherapy (MIB) is less invasive and more convenient than postoperative one. This study aimed to compare ultrashort perioperative MIB-PBI (uPBI) and conventional perioperative MIB-PBI (cPBI) performed during the same period of time.

METHODS

Inclusion criteria of the study were patients aged ≥ 40 years and those with T0-2 (≤ 3 cm), N0-mi, and negative margins on mammography. The locoregional recurrence (LRR) and toxicity rates were compared between uPBI at a dose of 25.2 Gy in four fractions and cPBI at a dose of 32 Gy in eight fractions.

RESULTS

In total, 198 patients (151 with uPBI and 47 with cPBI) were evaluated. At a median follow-up of 20.1 months, one (0.66%) patient in the uPBI group had LRR. The 2-year ipsilateral breast tumor recurrence-free survival rates of the uPBI and cPBI groups were 98.7% and 100%, respectively. The highest toxicity grades were grade 1 in 23 (15.2%) and grade 2 in 2 (1.3%) patients in the uPBI group, and grade 1 in 8 (17.0%) and grade 2 in 1 (2.1%) patient in the cPBI group. None of the patients in the two groups presented with grade 3 and higher toxicities. The toxicity rates between the two groups did not significantly differ. Further, 22 (14.6%) patients in the uPBI group and 8 (17.0%) in the cPBI group, and 3 (2.0%) patients in the uPBI group and 1 (2.1%) in the cPBI had acute and late toxicities, respectively. The timing of toxicity development between the two groups did not significantly differ.

CONCLUSIONS

Although this preliminary report included a small sample size and had a short follow-up period, the local control and toxicity rates were similar between the uPBI and cPBI groups. Further research is warranted to investigate the ideal dose schedule of MIB-PBI.

Impact of de-escalating systemic therapy guided by 21-gene assay on locoregional recurrence after partial-breast irradiation

PURPOSE

Partial-breast irradiation (PBI) has been performed as alternative to whole-breast irradiation (WBI) in breast-conserving therapy (BCT). Recently, the 21-gene recurrence score (RS) was introduced to determine the adjuvant therapy for estrogen receptor (ER)-positive, and human epidermal growth factor receptor 2 (HER2)-negative diseases. However, the impact of RS-based systemic therapy on locoregional recurrence (LRR) following BCT with PBI remains uninvestigated.

METHODS AND MATERIALS

Patients with ER-positive, HER2-negative, and node-negative breast cancer who underwent BCT with PBI were examined during May 2012-March 2022. In addition to immunohistochemistry (IHC), RS was available to decide on adjuvant therapy.

RESULTS

In total, 431 patients were evaluated with a median followup of 48.6 months. The 4-year LRR-free survival rates were 97.3% and 96.4% in the IHC and RS cohorts, respectively (p = 0.50). Ki67 of >20% was significantly associated with LRR in the multivariate analysis (HR 4.39, p < 0.05). For patients with Ki67 > 20%, 29 of 71 (40.8%) and 46 of 59 (78.0%) patients received only endocrine therapy in the IHC and RS cohorts, respectively (p < 0.0001). For patients with Ki67 >20% who received only endocrine therapy, the 4-year LRR-free survival rates were 91.8% in the IHC cohort and 94.6% in the RS cohort (p = 0.29) CONCLUSIONS: Although the introduction of RS increased the number of patients receiving endocrine therapy alone for Ki67 >20% of disease by two times, the LRR-free survival after BCT with PBI could be maintained. However, further studies from multiple institutions with longer followup data are required.

A Japanese prospective multi-institutional feasibility study on accelerated partial breast irradiation using multicatheter interstitial brachytherapy: clinical results with a median follow-up of 60 months

BACKGROUND

We carried out the first multi-institutional prospective study on accelerated partial breast irradiation (APBI) via multicatheter interstitial brachytherapy in a shorter period for early breast cancer in Japan.

METHODS

Patient eligibility criteria included positive hormone receptors, tumors ≤ 3 cm and TNM stage pN0M0. After breast-conserving surgery (Japanese cylindrical resection) and histological confirmation of negative surgical margins and the absence of lymph node metastasis, applicator implantation was performed either postoperatively or intraoperatively. High-dose-rate brachytherapy of 36 Gy in 6 fractions was delivered.

RESULTS

Forty-six patients from six institutions received this treatment regimen, and the median follow-up time was 60 months (range 57-67 months). The median resected breast tissue volume was 81 cm³ (range 28-260 cm³). No Grade 4 late sequela, local recurrence nor death due to breast cancer were observed. Grade 2-3 sequelae such as rib fracture (2%), soft tissue necrosis (9%), fibrosis (20%), and breast pain (9%) were observed. The resected breast tissue volumes of the patients who had Grade ≥ 2 fibrosis and Grade < 2 fibrosis were 105.9 ± 32.3 cm³ and 76.3 ± 45.6 cm³, respectively, p = 0.02. The overall cosmetic outcome score of Excellent/Good was 74% at 60 months after APBI. Grade ≥ 1 fibrosis was observed in 44% and 92% of patients who scored Excellent/Good and Fair/Poor, respectively, p = 0.004.

CONCLUSIONS

This study showed excellent local control and survival results with minimal late sequelae.

Computed tomography-guided partial-breast brachytherapy using implanted catheters as fiducial markers versus co-registered magnetic resonance imaging

PURPOSE

Partial-breast irradiation (PBI) needs accurate cavity delineation with computed tomography (CT). In perioperative PBI using multicatheter-interstitial brachytherapy (MIB), catheters implanted during surgery were enabled as fiducial markers. Magnetic resonance imaging (MRI) can also assist delineation with CT.

METHODS

Patients receiving MIB-PBI were analyzed. Cavity visualization scores (CVSs) were categorized with CT. With catheter-based delineation (CBD), the relationship between cavity boundaries and catheters were used to contour the tumor bed. Co-registered MRI delineation (CMD) was also performed. The correlation between cavity volume and the excised tissue weight was compared for the two techniques.

RESULTS

The association between CVS and preoperative characteristics in 159 patients showed mammographic breast density (MBD) remained correlated to CVS on multiple regression analyses; CVS = 5.2-0.61 x MBD (p < 0.0001). In 43 patients, the cavity volumes determined with CBD vs CMD were 12.8 ± 6.4 cm³ vs 16.1 ± 12.4 cm³ (p < 0.0001), and their plots with excised weights showed the best fitting lines were 0.29 vs 0.48 (p < 0.0001), respectively. The correlation coefficients for CBD vs CMD were 0.65 vs 0.55 (p = 0.20) in low (CVS 1-3, n = 27) and 0.72 vs 0.58 (p = 0.36) in high visualized cavities (CVS 4-5, n = 16), respectively.

CONCLUSIONS

The use of implanted catheters as fiducial markers was associated with smaller cavities and greater correlations with the excised tissue weights than co-registration with MRI. This might be a useful technique, especially for patients with dense breasts on mammography.

Predicting adherence of dose-volume constraints for personalized partial-breast irradiation technique

PURPOSE

Multicatheter interstitial brachytherapy (MIB) and external-beam (EB) radiotherapy are established partial-breast irradiation (PBI) techniques. Although EB-PBI is widely available, it requires extra irradiated margins for target uncertainties. We examined the impact of EB-PBI on dose-volume constraints as compared to MIB-PBI.

METHODS AND MATERIALS

Among 653 patients receiving MIB-PBI between October 2008 and April 2020, consequent 159 patients after September 2018 were examined. Clinical target volume (CTV) included the lumpectomy cavity plus 1.0 cm. Planning target volume (PTV) for EB-PBI was defined as CTV with 1.0-cm expansion. Because the ratio of PTV to breast volume (RPB) was related to cosmesis, <25% of RPB was defined as suitable for the ipsilateral breast constraints. Preoperative breast size was classified as very small (<350 cm³), small (350-699 cm³), and medium or large (≥700 cm³). According to each category, the dose-volume constraints of the organs at risk were compared between the two PBI techniques.

RESULTS

Patients including 84 very small, 59 small, and 16 moderate to large breasts were examined. Although RPB was suitable in all patients receiving MIB-PBI, it was achieved in 74 patients (46.5%) receiving EB-PBI (p < 0.0001). The suitable RPB in patients with very small, small, and moderate to large breast was 32.1%, 55.9%, and 100%, respectively (p < 0.0001). Normal-tissue constraints for the other organs could be satisfied in patients with moderate to large breasts.

CONCLUSION

Although EB-PBI may be an appropriate option for patients with moderate to large breasts, MIB-PBI could still be a crucial technique, especially for patients with small breasts.