A New Era in Triple-Negative Breast Cancer: ADCs Outperformed Chemotherapy in the First Line
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Chemotherapy Is Giving Way to Antibody–Drug Conjugates
Triple-negative breast cancer (TNBC)is perhaps one of the most challenging subtypes in cancer biology. These tumors lack the three key molecules underpinning many modern targeted treatments— estrogen receptor (ER), progesterone receptor (PR) and HER2 —making it a cancer with “all three doors closed.” For many years, treatment therefore relied solely on conventional chemotherapy.
The rise of immunotherapy in the 2010s brought hope. However, it worked only in some patients whose tumors expressed a certain level of PD-L1 . A large PD-L1-negative group still lacked effective, durable options. For many patients with TNBC, this meant short survival, rapid recurrence after treatment, and frequent hospitalization.
This is why two major trials announced at ESMO 2025generated considerable excitement among scientists and patients. These trials— ASCENT-03 and TROPION-Breast02 — for the first time in the first line showed a significant survival advantage over chemotherapy using TROP2 cell-surface antigen-targeting antibody–drug conjugates (ADCs) .
ADC technology can be described as “smart chemotherapy.” These drugs attach a potent chemotherapy molecule to an antibody specific to cancer cells. The antibody recognizes the cancer cell and releases its payload directly into it upon finding the target. Thus, healthy cells are largely sparedwhile tumor cells are selectively destroyed.
The first breast cancer approvals for this approach in the early 2020s largely concerned metastatic, resistant disease. With ESMO 2025, data now show that ADCs can compete with chemotherapy even in the first line—the earliest stage of treatment—and in some subgroups are superior .
This is more than a new drug success; it is a paradigm shift . Patients with TNBC are no longer a “group without options.” These findings herald a new era in which first-line chemotherapy-free combinationsmay become possible.
📊 ASCENT-03 (Sacituzumab Govitecan)
Compared with chemotherapy, Sacituzumab delayed cancer progression by approximately 3 months (9.7 versus 6.9 months). Among responders, response duration reached 12 months.
🏁 TROPION-Breast02 (Datopotamab Deruxtecan)
Datopotamab both slowed disease progression (10.8 versus 5.6 months) and extended survival (23.7 versus 18.7 months). This was the first first-line survival advantage seen in triple-negative breast cancer.
🧑⚕️ Quality of Life (ASCENT-04 / KEYNOTE-D19)
Sacituzumab + immunotherapy generally preserved quality of life. Patients felt more energetic and emotionally better, while nausea and diarrhea were slightly less frequent with chemotherapy.
🧪 Trial 1 — ASCENT-03: Sacituzumab Govitecan vs Chemotherapy
- 558 patients participated, all PD-L1-negative and previously untreated.
- The new drug sacituzumab govitecan, compared with chemotherapy, delayed cancer progression by approximately 3 months (9.7 vs 6.9 months).
- Response rates were similar (48% vs 46%), but response duration was significantly longer (12.2 vs 7.2 months).
- High-grade side effects were similar to chemotherapy (66% vs 62%), but the treatment discontinuation rate was lower in the sacituzumab arm (4% vs 12%).
- Overall survival (OS) data are not yet mature, because many patients continued receiving the drug after the trial.
Clinical meaning: For the first time, Sacituzumab provided first-line treatment with this degree of progression control over chemotherapy. The results show that, particularly when hematologic (blood-related) and intestinal side effects are carefully managed, the drug can be used safely for a long time.
🧪 Trial 2 — TROPION-Breast02: Datopotamab Deruxtecan vs Chemotherapy
- 644 patients were enrolled; some had relapsed early, and brain metastases were common.
- Compared with chemotherapy, Datopotamab nearly halved disease progression (10.8 vs 5.6 months).
- Survival also increased significantly: 23.7 vs 18.7 months.
- The response rate was more than double that with chemotherapy (62.5% vs 29.3%).
- High-grade side effects were similar (33% vs 29%). However, stomatitis (mouth sores) and dry eyes require attention.
Clinical meaning: Datopotamab deruxtecan became the first targeted drug to extend survival in PD-L1-negative triple-negative breast cancer . Side effects were generally mild and manageable. These findings may begin the transition from an era with chemotherapy as the only option to an era of targeted drugs .
🧩 Quality of Life (PRO) — ASCENT-04 / KEYNOTE-D19
- PD-L1-positive patients received sacituzumab + immunotherapy in comparison with chemotherapy.
- Patients generally reported similar quality of life , but those taking sacituzumab had less pain and better emotional balance .
- Nausea and diarrhea were less frequent with chemotherapy, indicating different side-effect profiles.
Comment: These findings show that new drugs can not only extend survival but also preserve quality of life . Understanding effects on daily life has become as important as clinical data.
📚 Key Results Side by Side
| Parameter | Sacituzumab Govitecan | Datopotamab Deruxtecan |
|---|---|---|
| Participants | 558 | 644 |
| Disease progression (mPFS) | 9.7 months vs 6.9 | 10.8 months vs 5.6 |
| Survival (mOS) | Not yet mature | 23.7 months vs 18.7 |
| Treatment response rate | %48 | %62.5 |
| Response duration | 12.2 months | 12.3 months |
| Serious side effects | %66 | %33 |
| Treatment discontinuation | %4 | %4 |
| Prominent side effects | Low blood counts, gastrointestinal problems | Mouth sores, dry eyes |
DROZDOGAN Academy Commentary
- On the threshold of a paradigm shift: A nonchemotherapy first-line backbone in PD-L1-negative advanced TNBC could fundamentally change practice. Dato-DXd's OS advantage (HR 0.79) is the strongest evidence for this shift; SG's substantial PFS benefit and long response duration (mDOR ≈ 12 months) support its clinical value.
- The trap of direct cross-trial comparisons: In TROPION-Breast02, relapse <6 months and brain metastases were more common, making the cohort relatively higher-risk. In ASCENT-03, possible chemotherapy→SG crossover may complicate OS interpretation. Cross-trial comparisons must therefore consider differences in population and context .
- Manage toxicity in advance: For SG, hematologic/GI toxicities require preventive support planning (G-CSF needs, antiemetic strategies, diarrhea protocols). With Dato-DXd, stomatitis (oral hygiene, prophylactic care) and ocular side effects (artificial tears, early referral) require proactive monitoring .
- The PRO message: With SG+pembro, emotional function and pain showed signals of improvement, while nausea and diarrhea favored chemotherapy. Quality-of-life differences are small but may influence clinical decisions; patient preferences matter.
- Sequencing and combinations: After first-line ADC use, rethink 2L/3L options (platinum, taxanes, and PARP inhibitors in appropriate subgroups). ADC + IO combinations may, as results mature, particularly in the PD-L1-negative group, enable chemotherapy-free approaches .
- The biomarker reality: TROP2 staining is not a routine selection determinant; tumor burden, spread patterns, comorbidities and patient preference are practical markers. The clinical goal: early control + tolerability.
- Access and implementation: Differences in ADC dose and timing (e.g., SG: days 1-8, q3w; Dato-DXd: q3w) should be discussed in relation to work–life balance and center capacity. Cost-effectiveness and reimbursement should enter the multidisciplinary board discussion early.
Our Practical Recommendation
- High-risk biology / Need for rapid control: Dato-DXd should be considered (OS advantage + strong PFS).
- Hematologic vulnerability / Significant GI comorbidity: Dato-DXd may offer a favorable toxicity profile.
- Ocular or oral mucositis history / Risk: SG may be an option because of its different profile.
- For both agents, early side-effect education, intensive monitoring during the first 2 cycles and supportive measures increase the chance of continuing treatment.
📎 References
- ASCENT-03 (LBA20) — Sacituzumab govitecan vs chemotherapy; superior PFS; OS not yet mature.
- TROPION-Breast02 (LBA21) — Datopotamab deruxtecan vs chemotherapy; superior PFS and OS .
- ASCENT-04/KEYNOTE-D19 (LBA22) — SG + pembrolizumab vs chemotherapy + pembrolizumab; PRO analyses.
- Background: Oncologist. 2025;30:oyaf034 — 1L approach to PD-L1-negative mTNBC.
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