Effects of trastuzumab on locoregional recurrence in human epidermal growth factor receptor 2-overexpressing breast cancer patients treated with chemotherapy and radiotherapy

Omission of radiation therapy post breast conserving surgery

Radiation therapy (RT) after breast conserving surgery decreases the risks of local recurrence and breast cancer mortality in the multidisciplinary management of patients with breast cancer. However, breast cancer is a heterogeneous disease, and the absolute benefit of post-operative RT in individual patients varies substantially. Clinical trials aiming to identify patients with low-risk early breast cancer in whom post-operative RT may be safely omitted, based on conventional clinical-pathologic variables alone, have not provided sufficiently tailored information on local recurrence risk assessment to guide treatment decisions. The majority of patients with early breast cancer continue to be routinely treated with RT after breast conserving surgery. This approach may represent over-treatment for a substantial proportion of the patients. The clinical impact of genomic signatures on local therapy decisions for early breast cancer has been remarkably modest due to the lack of high-level evidence supporting their clinical validity for assessment of the risk of local recurrence. Efforts to personalise breast cancer care must be supported by high level evidence to enable balanced, informed treatment decisions. These considerations underpin the importance of ongoing biomarker-directed clinical trials to generate the high-level evidence necessary for setting the future standard of care in personalised local therapy for patients with early breast cancer.

Radiotherapy as a tool to elicit clinically actionable signalling pathways in cancer

A variety of targeted anticancer agents have been successfully introduced into clinical practice, largely reflecting their ability to inhibit specific molecular alterations that are required for disease progression. However, not all malignant cells rely on such alterations to survive, proliferate, disseminate and/or evade anticancer immunity, implying that many tumours are intrinsically resistant to targeted therapies. Radiotherapy is well known for its ability to activate cytotoxic signalling pathways that ultimately promote the death of cancer cells, as well as numerous cytoprotective mechanisms that are elicited by cellular damage. Importantly, many cytoprotective mechanisms elicited by radiotherapy can be abrogated by targeted anticancer agents, suggesting that radiotherapy could be harnessed to enhance the clinical efficacy of these drugs. In this Review, we discuss preclinical and clinical data that introduce radiotherapy as a tool to elicit or amplify clinically actionable signalling pathways in patients with cancer.

Personalization in Modern Radiation Oncology: Methods, Results and Pitfalls. Personalized Interventions and Breast Cancer

Breast cancer, the most frequent malignancy in women worldwide, is a heterogeneous group of diseases, characterized by distinct molecular aberrations. In precision medicine, radiation oncology for breast cancer aims at tailoring treatment according to tumor biology and each patient’s clinical features and genetics. Although systemic therapies are personalized according to molecular sub-type [i.e. endocrine therapy for receptor-positive disease and anti-human epidermal growth factor receptor 2 (HER2) therapy for HER2-positive disease] and multi-gene assays, personalized radiation therapy has yet to be adopted in the clinical setting. Currently, attempts are being made to identify prognostic and/or predictive factors, biomarkers, signatures that could lead to personalized treatment in order to select appropriate patients who might, or might not, benefit from radiation therapy or whose radiation therapy might be escalated or de-escalated in dosages and volumes. This overview focuses on what has been achieved to date in personalized post-operative radiation therapy and individual patient radiosensitivity assessments by means of tumor sub-types and genetics.

Breast-conserving Surgery Without Radiation Therapy for Invasive Cancer

Radiotherapy (RT) after breast-conserving surgery (BCS) halves the risk of local recurrence, and it is considered the standard of care for the vast majority of patients with early invasive breast cancer. However, the majority of patients treated with BCS will not recur locally, even in the absence of RT. Over the past several decades, the improved and widespread use of systemic therapy has significantly decreased the rate of local recurrence. This has stimulated interest in identifying favorable patient subsets not requiring RT. Randomized controlled trials have shown in women aged ≥ 70 years with stage I estrogen receptor-positive (ER⁺) tumors, RT can be safely omitted. To better identify patients with favorable prognosis, ongoing trials have incorporated biological markers and genomic assays. Despite great research efforts to de-escalate locoregional treatment, real-world data indicate that omission of RT in low-risk patients is inconsistent. Better decision-making is warranted to reduce overtreatment and financial toxicity.

Impact of Trastuzumab on Ipsilateral Breast Tumor Recurrence for Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer after Breast-Conserving Surgery

Purpose

Trastuzumab is effective in early and advanced human epidermal growth factor receptor 2 (HER2)-positive breast cancer. However, few studies have reported the effect of trastuzumab on ipsilateral breast tumor recurrence (IBTR), whose incidence is higher in the HER2-positive subtype than in other subtypes.

Methods

We retrospectively investigated 959 patients who underwent breast-conserving surgery (BCS), chemotherapy, and radiotherapy for HER2-positive breast cancer between 2000 and 2017. IBTR was compared between the patients who received neoadjuvant or adjuvant trastuzumab (Tmab group) for a total duration of 1 year and those who received no trastuzumab (N-Tmab group).

Results

Propensity score matching designated 426 and 142 patients in the Tmab and N-Tmab groups, respectively. The median follow-up period for all patients after matching was 73.79 months. The IBTR-free survival rate was significantly higher in the Tmab group than in the N-Tmab group (10-year IBTR-free survival rate, 92.9% vs. 87.3%; p = 0.002). The multivariate analysis showed a significant association between the N-Tmab and Tmab group (hazard ratio, 3.03; 95% confidence interval, 1.07–8.59) and IBTR in addition to close or positive resection margin and hormone receptor (HR) positivity. The subgroup analysis showed that adjuvant treatment with trastuzumab significantly reduced IBTR among the patients with HR-negative or lymph node-negative breast cancer.

Conclusion

Significantly reduced IBTR after BCS was observed in the patients who received 1 year of adjuvant/neoadjuvant trastuzumab treatment for HER2-positive breast cancer.