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<\/p>\nAs Breast Cancer Awareness Month approaches in October, advances in antibody\u2013drug conjugates, endocrine therapy and molecular profiling are changing the management of metastatic breast cancer.<\/p>\n
Breast Cancer Awareness Month in October traditionally concentrates attention on screening and early diagnosis. For patients with metastatic breast cancer (MBC), however, the clinical picture is changing in another important way. Although metastatic disease remains generally incurable, an expanding range of systemic treatments is producing increasingly prolonged disease control, and in some patient groups, survival is now measured in years.<\/p>\n
The recently updated ESMO guideline for MBC illustrates how rapidly the field has evolved.1 The familiar classification into hormone receptor (HR)-positive\/HER2-negative, HER2-positive and triple-negative breast cancer remains useful, but it is no longer sufficient to guide treatment throughout the course of disease.<\/p>\n
Repeated assessment of tumour biology is becoming increasingly important. Where clinically appropriate, metastatic tissue should be reassessed for ER, PR and HER2, while molecular testing may identify ESR1, PIK3CA, AKT1, PTEN and germline BRCA1\/2 alterations with therapeutic implications.<\/p>\n
HER2 itself has ceased to be a simple positive-or-negative marker. The emergence of HER2-low and, more recently, HER2-ultralow disease as therapeutically meaningful categories is one of the most important developments of recent years.<\/p>\n
HR-positive disease: beyond CDK4\/6 inhibition
Endocrine treatment combined with a CDK4\/6 inhibitor remains the standard first-line approach for most patients with HR-positive\/HER2-negative metastatic disease in the absence of a visceral crisis. The more complicated question arises at endocrine resistance.<\/p>\n
Here, treatment is increasingly dictated by tumour genomics.<\/p>\n
Patients with PIK3CA-mutated disease have several possible targeted approaches. In the phase III INAVO120 trial, the combination of inavolisib, palbociclib and fulvestrant produced an overall-survival benefit in patients with PIK3CA-mutated, HR-positive\/HER2-negative advanced breast cancer that had relapsed during, or shortly after, adjuvant endocrine therapy. Median overall survival was 34.0 months compared with 27.0 months with palbociclib and fulvestrant alone.2<\/p>\n
Targeting the oestrogen receptor itself is also becoming more sophisticated. Oral selective oestrogen-receptor degraders (SERDs) offer an important option in ESR1-mutated disease, particularly after previous aromatase inhibitor and CDK4\/6 inhibitor treatment.<\/p>\n
Perhaps more significant than the arrival of another drug is the possibility of acting on molecular resistance before radiological progression occurs.<\/p>\n
In SERENA-6, patients receiving first-line aromatase inhibition plus a CDK4\/6 inhibitor underwent serial circulating tumour DNA testing. When an ESR1 mutation emerged without radiological progression, patients either switched endocrine therapy to camizestrant while continuing their CDK4\/6 inhibitor or remained on the existing regimen. Median progression-free survival was 16.0 months following the switch compared with 9.2 months with continued aromatase inhibition.3<\/p>\n
This is potentially a significant change in the philosophy of metastatic treatment: rather than waiting for resistant disease to become radiologically visible, therapy may increasingly be altered according to molecular evidence that resistance is emerging.<\/p>\n
The EMBER-3 study adds to this changing endocrine landscape. Among patients with ESR1-mutated ER-positive\/HER2-negative advanced breast cancer, the oral SERD imlunestrant improved progression-free survival compared with standard endocrine therapy. Combining imlunestrant with abemaciclib produced a median progression-free survival of 9.4 months compared with 5.5 months with imlunestrant alone in the relevant randomised population.4<\/p>\n
Antibody\u2013drug conjugates redraw the map
The most conspicuous therapeutic development in metastatic breast cancer has arguably been the growth of antibody\u2013drug conjugates (ADCs).<\/p>\n
Trastuzumab deruxtecan has already challenged the traditional definition of HER2-negative breast cancer. DESTINY-Breast06 studied patients with HR-positive metastatic disease classified as HER2-low or HER2-ultralow who had received endocrine treatment but no previous chemotherapy for metastatic disease.<\/p>\n
Among patients with HER2-low tumours, median progression-free survival was 13.2 months with trastuzumab deruxtecan compared with 8.1 months with chemotherapy.5<\/p>\n
For the clinician, an immediate consequence is the need for careful HER2 pathological assessment. A tumour historically described simply as HER2-negative may contain information that now directly determines systemic treatment.<\/p>\n
ADCs are also moving earlier in unequivocally HER2-positive disease. In the phase III DESTINY-Breast09 trial, first-line trastuzumab deruxtecan plus pertuzumab produced median progression-free survival of 40.7 months compared with 26.9 months with the established taxane, trastuzumab and pertuzumab regimen. The risk of progression or death was reduced by 44 per cent.6<\/p>\n
These efficacy gains require appropriate vigilance. Interstitial lung disease\/pneumonitis remains an important toxicity associated with trastuzumab deruxtecan, and early recognition, treatment interruption and appropriate corticosteroid management are critical.<\/p>\n
Management of CNS metastases has also improved. Several HER2-directed regimens now demonstrate meaningful intracranial activity, making systemic treatment an increasingly important component of management alongside stereotactic radiotherapy, surgery and other local approaches.<\/p>\n
Triple-negative disease
The therapeutic range is widening in metastatic triple-negative breast cancer (TNBC) as well.<\/p>\n
Checkpoint inhibition combined with chemotherapy remains important in appropriately selected PD-L1-positive disease, but ADCs are moving progressively earlier.<\/p>\n
In ASCENT-04\/KEYNOTE-D19, first-line sacituzumab govitecan plus pembrolizumab was compared with chemotherapy plus pembrolizumab in previously untreated PD-L1-positive advanced TNBC. Median progression-free survival was 11.2 months compared with 7.8 months in the chemotherapy group.7<\/p>\n
Datopotamab deruxtecan has meanwhile produced encouraging phase III results among patients with previously untreated advanced TNBC for whom immunotherapy was not an option. In TROPION-Breast02, median progression-free survival was 10.8 months versus 5.6 months with chemotherapy, while median overall survival was 23.7 months compared with 18.7 months.8<\/p>\n
The emerging problem may therefore be sequencing rather than scarcity: which ADC should be given first, whether activity can be retained when moving from one ADC to another, and how target expression, payload, previous therapy, CNS disease and toxicity should influence the decision.<\/p>\n
Irish patients and clinical trials
Irish patients also have opportunities to participate in research in this rapidly developing field. Current Cancer Trials Ireland studies include the PRISM precision-oncology programme in metastatic breast cancer, DESTINY-Breast15 in HER2-low and HER2-IHC 0 metastatic disease, and trials investigating newer TROP2-directed ADCs.<\/p>\n
Clinical-trial referral should consequently be considered throughout the treatment pathway rather than being regarded solely as an option after established therapies have been exhausted.<\/p>\n
None of these developments removes the importance of supportive and multidisciplinary care. Bone-modifying agents, radiotherapy, analgesia, rehabilitation, psychological support and specialist palliative care remain integral to management and should accompany active anticancer treatment according to need.<\/p>\n
As Breast Cancer Awareness Month approaches, early detection will rightly dominate the public conversation. There is, however, another important message for patients and clinicians. Metastatic breast cancer is becoming a collection of increasingly precisely defined biological diseases, with treatment changing accordingly.<\/p>\n
The disease remains life-limiting, but the therapeutic trajectory is moving decisively towards more individualised treatment, longer disease control and, for a growing proportion of patients, longer survival. <\/p>\n
Key Points for Clinicians<\/p>\n
Reassess biology: ER, PR and HER2 status may change, while molecular testing for ESR1, PIK3CA, AKT1, PTEN and BRCA1\/2 can directly affect treatment selection.
\nHER2-negative is no longer enough: HER2-low and HER2-ultralow status can identify patients likely to benefit from an ADC.
\nctDNA is becoming clinically relevant: SERENA-6 provides proof of principle that treatment can potentially be changed on detection of molecular resistance before radiological progression.
\nADCs are moving earlier: Their role now extends across HER2-positive, HER2-low\/ultralow and triple-negative disease.
\nWatch for ADC-specific toxicity: In particular, interstitial lung disease\/pneumonitis requires prompt recognition with trastuzumab deruxtecan.
\nSequencing is the next challenge: With multiple endocrine, targeted and ADC options, treatment choice increasingly depends on previous exposure, tumour genomics, toxicity and CNS involvement.
\nConsider trials early: The expanding Irish metastatic breast cancer research portfolio provides opportunities for molecular profiling and access to emerging therapies.<\/p>\n
References:<\/p>\n
de Azambuja E, Barrios CH, Bartsch R, et al. Metastatic breast cancer: ESMO Clinical Practice Guideline for diagnosis, treatment and follow-up. Ann Oncol. 2026;37(9):1203-1219. doi:10.1016\/j.annonc.2026.05.707<\/a>.
\nJhaveri KL, Im SA, Saura C, et al. Overall Survival with Inavolisib in PIK3CA-Mutated Advanced Breast Cancer. N Engl J Med. 2025;393:151-161. doi:10.1056\/NEJMoa2501796<\/a>.
\nBidard FC, Mayer EL, Park YH, et al. First-Line Camizestrant for Emerging ESR1-Mutated Advanced Breast Cancer. N Engl J Med. 2025;393:569-580. doi:10.1056\/NEJMoa2502929<\/a>.
\nJhaveri KL, et al. Imlunestrant with or without Abemaciclib in Advanced Breast Cancer. N Engl J Med. 2025;392:1189-1202. doi:10.1056\/NEJMoa2410858<\/a>.
\nBardia A, Hu X, Dent R, et al. Trastuzumab Deruxtecan after Endocrine Therapy in Metastatic Breast Cancer. N Engl J Med. 2024;391:2110-2122. doi:10.1056\/NEJMoa2407086<\/a>.
\nTolaney SM, Jiang Z, Zhang Q, et al. Trastuzumab Deruxtecan plus Pertuzumab for HER2-Positive Metastatic Breast Cancer. N Engl J Med. 2026;394:551-562. doi:10.1056\/NEJMoa2508668<\/a>.
\nTolaney SM, de Azambuja E, Kalinsky K, et al. Sacituzumab Govitecan plus Pembrolizumab for Advanced Triple-Negative Breast Cancer. N Engl J Med. 2026;394:354-366. doi:10.1056\/NEJMoa2508959<\/a>.
\nDent R, Shao Z, Schmid P, et al. Datopotamab deruxtecan in patients with untreated, advanced triple-negative breast cancer (TROPION-Breast02): a randomised, open-label, international, phase III trial. Ann Oncol. 2026;37(8):1066-1080. doi:10.1016\/j.annonc.2026.03.008<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"As Breast Cancer Awareness Month approaches in October, advances in antibody\u2013drug conjugates, endocrine therapy and molecular profiling are…\n","protected":false},"author":2,"featured_media":648613,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[2121,1239,40966,258,275193,103,61,60,219556,10223],"class_list":["post-648612","post","type-post","status-publish","format-standard","has-post-thumbnail","category-health","tag-womens-health","tag-breast-cancer","tag-breast-cancer-awareness-month","tag-cancer","tag-esmo","tag-health","tag-ie","tag-ireland","tag-metastatic-breast-cancer","tag-radiology"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/648612","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/comments?post=648612"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/posts\/648612\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media\/648613"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/media?parent=648612"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/categories?post=648612"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/ie\/wp-json\/wp\/v2\/tags?post=648612"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}