Partial breast irradiation: targeting volume or breast molecular subtypes?

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.

Results of accelerated partial breast irradiation in patients not suitable for external beam irradiation stratified by GEC-ESTRO, ASTRO, and ABS guidelines

PURPOSE

This study aims to review the outcome of an institution in multicatheter/interstitial accelerated partial breast irradiation (MC-APBI) for treatment of patients with breast cancer, either with strong criteria for APBI or unable to be treated with whole-breast irradiation. The outcomes were also stratified by the American Society for Radiation Oncology, American Brachytherapy Society, and Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology patient selection criteria.

METHODS

The study includes 118 patients and 120 MC-APBI treatments, treated in a single tertiary center, between November 2003 and August 2016. The analysis is focused on the clinical baseline characteristics, local control, relapse-free survival, disease-specific survival (DSS), and overall survival.

RESULTS

In accordance to the American Society for Radiation Oncology, American Brachytherapy Society, and Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology, 17.1% were "unsuitable," 19.2% were "unacceptable," and 19.5% were "high risk," respectively. The main reasons why high-risk patients were submitted to MC-APBI were as follows: cardiopathy (n = 7), social difficulties (n = 4), and mobility limitations (n = 4). At the median followup period of 86.5 months, ipsilateral breast tumor recurrence was observed in one (0.8%) patient. The 3-year and 5-year relapse-free survival were 100% and 99.1%, respectively. DSS was 100%.

CONCLUSIONS

This study demonstrated excellent control rates, DFS, and DSS of MC-APBI, rendering APBI as an excellent treatment for patients with breast cancer, even those who are not necessarily eligible for this treatment approach. The selection criteria for ABPI diverge according to different guidelines and are based on studies with discrepancies, making extremely possible that these recommendations could be changed.

Should molecular subtype be recommended as one of the selection criteria for accelerated partial breast irradiation? Preliminary results from an Asian cohort

Purpose

The purpose of this study was to report clinical outcomes in patients treated with accelerated partial breast irradiation (APBI), stratified as per molecular subtype and American Society for Therapeutic Radiology and Oncology/Groupe Européen de Curiethérapie and European Society for Radiotherapy & Oncology (ASTRO/GEC-ESTRO) patient selection criteria in order to determine whether molecular subtype should be recommended as one of the selection criteria for APBI.

Material and methods

157 early-stage breast cancers patients, treated with APBI using multi-catheter interstitial brachytherapy with ≥ 6 months follow-up were included. Molecular subtype was assigned based on estrogen/progesterone receptor (ER/PR), Her2neu and tumor grade. Patients were stratified into ASTRO and GEC-ESTRO risk groups, as per updated ASTRO consensus statement (CS) and GEC-ESTRO recommendation, respectively. The Kaplan-Meier method was used to calculate the time to event data of clinical outcomes.

Results

With a median follow-up of 35 months, local control (LC) and locoregional control (LRC) were not significantly different among the different molecular subtypes (p = 0.19, p = 0.41, respectively). None of the APBI guidelines predicted risk of local or locoregional recurrence. Re-analyzing the data by replacing ER status with molecular subtype in the ASTRO-CS did not show any significant difference in LC/LRC across the various categories. Her2neu subtype was associated with significantly lower disease-free survival, cause specific survival, and overall survival than the luminal subtypes.

Conclusions

None of the mentioned APBI guidelines predicted local or locoregional recurrence risk in our study population. Additional follow-up will be needed to recommend inclusion of molecular subtype (or at least HER2 receptor status) in the patient selection criteria for APBI.

Tailoring radiotherapy according to cancer subtypes

Radiotherapy is able to improve locoregional control in breast cancer patients both after breast conserving surgery or mastectomy, with positive impact in high-risk patients for long-term survival. Recent advances in the precision of radiotherapy were based on the choice of the appropriate fractionation and technique. But the concept of adaptive radiotherapy is not only technical, and includes the biologic characterisation of the breast tumor. The knowledge that different subtypes of breast cancer can have distinct locoregional patterns of recurrence is consisted in the literature data. Luminal A tumor are at the lower risk of locoregional failure, and HER2 positive and triple negative at the higher risk. More evidence in the use of molecular markers for adjuvant radiotherapy can held in choosing the best treatment on individual. The combination of radiotherapy with molecular targeted therapies may enhance radiosensitivity, thus increasing the cytotoxic effects and improving treatment response. The appropriateness of an alternative fractionation, partial breast irradiation, intensification or de-intensification approaches, could be assessed better according the stratification of the risk categories.

Personalizing the treatment of women with early breast cancer: highlights of the St Gallen International Expert Consensus on the Primary Therapy of Early Breast Cancer 2013

The 13th St Gallen International Breast Cancer Conference (2013) Expert Panel reviewed and endorsed substantial new evidence on aspects of the local and regional therapies for early breast cancer, supporting less extensive surgery to the axilla and shorter durations of radiation therapy. It refined its earlier approach to the classification and management of luminal disease in the absence of amplification or overexpression of the Human Epidermal growth factor Receptor 2 (HER2) oncogene, while retaining essentially unchanged recommendations for the systemic adjuvant therapy of HER2-positive and 'triple-negative' disease. The Panel again accepted that conventional clinico-pathological factors provided a surrogate subtype classification, while noting that in those areas of the world where multi-gene molecular assays are readily available many clinicians prefer to base chemotherapy decisions for patients with luminal disease on these genomic results rather than the surrogate subtype definitions. Several multi-gene molecular assays were recognized as providing accurate and reproducible prognostic information, and in some cases prediction of response to chemotherapy. Cost and availability preclude their application in many environments at the present time. Broad treatment recommendations are presented. Such recommendations do not imply that each Panel member agrees: indeed, among more than 100 questions, only one (trastuzumab duration) commanded 100% agreement. The various recommendations in fact carried differing degrees of support, as reflected in the nuanced wording of the text below and in the votes recorded in supplementary Appendix S1, available at Annals of Oncology online. Detailed decisions on treatment will as always involve clinical consideration of disease extent, host factors, patient preferences and social and economic constraints.