Breast Cancer — Precision Subtype Treatment & Global Specialist Access

Breast cancer is not one disease — it is a collection of molecularly distinct subtypes that respond to completely different treatments. The main subtypes are: ER-positive/HER2-negative (most common, ~60–70% of cases; treated primarily with endocrine therapy ± CDK4/6 inhibitors); HER2-positive (~15–20%; treated with anti-HER2 targeted therapy + chemotherapy); and Triple-Negative Breast Cancer (TNBC, ~15%; ER, PR, and HER2 all negative; treated with chemotherapy, pembrolizumab, and sacituzumab). Additionally, HER2-low (IHC 1+ or 2+/FISH−) is a newly recognized category eligible for trastuzumab deruxtecan (T-DXd). Knowing your subtype determines which treatment is most effective for your specific cancer.

HER2-positive breast cancer is defined by amplification or overexpression of the HER2 (Human Epidermal Growth Factor Receptor 2) protein, which drives aggressive tumor growth. It accounts for approximately 15–20% of breast cancers. The development of targeted anti-HER2 therapies has transformed this subtype from one of the worst-prognosis subtypes to one with excellent outcomes. Standard treatment for early HER2+ disease includes trastuzumab and pertuzumab (dual HER2 blockade) combined with chemotherapy, given before or after surgery. For metastatic HER2+ disease, trastuzumab deruxtecan (T-DXd) is the preferred second-line standard. Tucatinib-based combinations specifically address brain metastases in HER2+ disease.

Triple-Negative Breast Cancer (TNBC) is defined by the absence of estrogen receptor (ER), progesterone receptor (PR), and HER2 expression. It accounts for approximately 15% of breast cancers and is more common in younger women and those with BRCA1 mutations. Unlike ER+ or HER2+ breast cancer, TNBC cannot be treated with endocrine therapy or anti-HER2 agents. Treatment relies on chemotherapy (anthracycline-taxane-based regimens), now combined with pembrolizumab (anti-PD-1 immunotherapy) in early high-risk TNBC (KEYNOTE-522) and metastatic TNBC with PD-L1 CPS ≥10. Sacituzumab govitecan (anti-Trop-2 ADC) is approved for metastatic TNBC. For BRCA1/2-mutant TNBC, olaparib or talazoparib are effective PARP inhibitor options.

Current guidelines recommend germline BRCA1/2 testing for all patients with invasive breast cancer — not just those with a strong family history. Results have important treatment implications: BRCA1/2-positive patients with HER2-negative metastatic breast cancer are eligible for PARP inhibitors (olaparib or talazoparib), which are more effective than chemotherapy in this setting. A positive result also enables discussion about risk-reducing surgery (contralateral mastectomy and salpingo-oophorectomy) and cascade testing for family members. In most countries, a blood sample for germline BRCA testing is arranged through your oncologist or a genetic counselor.

CDK4/6 inhibitors — palbociclib, ribociclib, and abemaciclib — block proteins (CDK4 and CDK6) that drive cell cycle entry and proliferation in ER+ breast cancer cells. They are used in combination with endocrine therapy (aromatase inhibitors or fulvestrant) for hormone receptor-positive, HER2-negative advanced or metastatic breast cancer. Adding a CDK4/6 inhibitor to endocrine therapy has approximately doubled progression-free survival compared to endocrine therapy alone in this setting and is now the global standard of care for metastatic ER+/HER2− disease. Abemaciclib is also approved in the adjuvant (post-surgery) setting for high-risk early ER+ breast cancer (monarchE trial).

Trastuzumab deruxtecan (brand name Enhertu; T-DXd) is a next-generation antibody-drug conjugate that combines a HER2-targeting antibody with a highly potent topoisomerase I inhibitor payload. It is important for two reasons: first, it is approved for HER2-positive metastatic breast cancer as second-line therapy and has demonstrated superior efficacy over the previous standard (T-DM1) in the DESTINY-Breast03 trial. Second — and very significantly — it is also approved for HER2-low metastatic breast cancer (IHC 1+ or 2+/FISH−), a newly recognized category encompassing approximately 50–60% of all metastatic breast cancer patients who previously had no HER2-directed treatment option. T-DXd has transformed the treatment landscape for metastatic breast cancer.

Yes — for most early breast cancers, breast-conserving surgery (lumpectomy or wide local excision) followed by radiotherapy is the standard of care and has equivalent long-term survival to mastectomy while preserving the breast. The suitability for breast conservation depends on tumor size relative to breast size, number of tumor sites (multifocal tumors may require mastectomy), and patient preference. Neoadjuvant chemotherapy can shrink large tumors before surgery, often converting a mastectomy candidate to a lumpectomy candidate. Some patients choose mastectomy for personal reasons (fear of recurrence, avoiding radiotherapy) or because of BRCA1/2 mutation status. For those requiring mastectomy, immediate or delayed breast reconstruction is routinely offered.

Oncotype DX is a 21-gene expression assay performed on tumor tissue from patients with early-stage ER+/HER2−/node-negative breast cancer. It generates a Recurrence Score (0–100) that estimates the 10-year risk of distant recurrence and — critically — predicts whether the individual patient will benefit from chemotherapy in addition to endocrine therapy. For postmenopausal women with a score of 0–25 (approximately 70% of those tested), chemotherapy can be safely omitted without compromising outcomes — this finding from the TAILORx trial has spared thousands of women unnecessary chemotherapy. For scores 26–100, adding chemotherapy to endocrine therapy is beneficial. The test significantly reduces overtreatment in early ER+ breast cancer.

Yes. CancerFax provides comprehensive specialist support for breast cancer patients at every stage of their treatment journey. We review ER/PR/HER2 receptor reports, Ki-67 and grade assessments, Oncotype DX and other genomic profiling results, BRCA1/2 germline test results, imaging and staging reports, and treatment history — then connect patients with leading breast oncologists and specialist breast cancer programs in India, South Korea, Germany, Japan, the UAE, and other countries. We assist with second opinions on subtype characterization and treatment plans, guidance on CDK4/6 inhibitors, T-DXd, sacituzumab govitecan, olaparib, and pembrolizumab access, clinical trial identification, and end-to-end coordination for international treatment including surgery, medical oncology, and advanced systemic therapy.