Customizing local and systemic therapies for women with early breast cancer: the St. Gallen International Consensus Guidelines for treatment of early breast cancer 2021

Abstract

The 17th St Gallen International Breast Cancer Consensus Conference in 2021 was held virtually, owing to the global COVID-19 pandemic. More than 3300 participants took part in this important bi-annual critical review of the 'state of the art' in the multidisciplinary care of early-stage breast cancer. Seventy-four expert panelists (see Appendix 1) from all continents discussed and commented on the previously elaborated consensus questions, as well as many key questions on early breast cancer diagnosis and treatment asked by the audience. The theme of this year's conference was 'Customizing local and systemic therapies.' A well-organized program of pre-recorded symposia, live panel discussions and real-time panel voting results drew a worldwide audience of thousands, reflecting the far-reaching impact of breast cancer on every continent. The interactive technology platform allowed, for the first time, audience members to ask direct questions to panelists, and to weigh in with their own vote on several key panel questions. A hallmark of this meeting was to focus on customized recommendations for treatment of early-stage breast cancer. There is increasing recognition that the care of a breast cancer patient depends on highly individualized clinical features, including the stage at presentation, the biological subset of breast cancer, the genetic factors that may underlie breast cancer risk, the genomic signatures that inform treatment recommendations, the extent of response before surgery in patients who receive neoadjuvant therapy, and patient preferences. This customized approach to treatment requires integration of clinical care between patients and radiology, pathology, genetics, and surgical, medical and radiation oncology providers. It also requires a dynamic response from clinicians as they encounter accumulating clinical information at the time of diagnosis and then serially with each step in the treatment plan and follow-up, reflecting patient experiences and treatment response.

Keywords: adjuvant; genetic testing; neoadjuvant; radiation therapy; surgery; survivorship.

Figure 1

Defining threshold for Ki67 to recommend adjuvant chemotherapy in ER-positive, HER2-negative, node-negative breast cancer. Numbers are percentage of panelists endorsing a Ki67 level. HER2, human epidermal growth factor receptor 2.

Figure 2

Panel recommendations for genomic signature testing in ER positive, HER2 negative early stage breast cancer. Numbers denote percentage of panelists favoring routine testing, testing in select cases or no testing zones.

Figure 3

Moderately hypofractionated radiation therapy. Percentage of panelists endorsing moderately hypofractionated schedules of radiation therapy. After immed recon, after immediate reconstruction; PMRT, postmastectomy radiation therapy; RNI, regional nodal irradiation.

Figure 4

Is axillary dissection required for residual cancer in lymph nodes after standard neoadjuvant chemotherapy?^a Percentage of panelists favoring axillary dissection. ITC, isolated tumor cells; SLN, sentinel lymph nodes. ^a It was assumed that post-surgical radiation therapy would be given regardless.

Figure 5

Size threshold for initiating systemic therapy by tumor type and treatment. Percentage of panelists recommending therapy by tumor size. CT, computed tomography; ER, estrogen receptor; ET, endocrine therapy; HER2, human epidermal growth factor receptor 2; TNBC, triple-negative breast cancer.

Figure 6

Estimated percentage of chemotherapy benefit due to ovarian suppression in premenopausal women with lower risk genomic signatures (recurrence score ≤25).

Figure 7

Panelist recommendations for optimal therapy for premenopausal, ER-positive cancers by stage and recurrence score (RS). (A) Node-negative, RS 16-25. (B) Node-positive (one to three positive nodes), RS ≤25. Chemo, chemotherapy; ET, endocrine therapy; OFS, ovarian function suppression.

Figure 8

Panelists advice on alcohol consumption: how many drinks can a breast cancer survivor consume without increasing the risk of cancer recurrence? Percentage of panelists voting in favor. Avg, average.