Patient characteristics
From April 2021 to July 2023, 48 patients with metastatic cancer were selected for treatment with T-DXd. Among them, 20 patients had BMs, and 15 patients previously received pyrotinib therapy and experienced disease progression (Fig. 1). The median age of the patients was 51 years (32–66), and 5 patients were positive for hormone receptors. A total of 14 patients had extracranial metastases and intracranial metastases. The median number of metastatic sites was 5 (1–6). The median number of therapy lines for T-DXd was 7 (3–12). All patients in the study previously received trastuzumab and pyrotinib, 13 patients (86.7%) previously received pertuzumab therapy, and 9 patients (60%) previously received T-DM1. After being diagnosed with BMs, 13 patients (86.7%) received trastuzumab plus pertuzumab, 8 patients (53.3%) received pyrotinib, and 5 patients (33.3%) received T-DM1. The median number of anti-HER2 therapy lines before T-DXd was 2 (0–5) after the diagnosis of BMs. Seven patients (46.7%) previously received whole-brain radiotherapy ± stereotactic radiotherapy, 6 patients (40.0%) received stereotactic radiotherapy ± surgery, and 2 did not receive local therapy for BMs. The median time between the initiation of T-DXd treatment and the last local therapy for BMs was 8.1 months (1.1–36.8 months). Nine patients (60.0%) had active BMs (new BMs or progressive BMs), 6 patients (40.0%) had stable BMs (received prior local treatment and remained stable), and 10 (66.7%) of the patients had multiple BMs. Six patients (40.0%) experienced symptoms such as dizziness, headache, nausea, or others related to BMs (Table 1).
Table 1
Patient demographics (n = 15)
Characteristic | No. (%) |
Age (years) | |
Median (range) | 51 (32–66) |
ECOG performance status | |
0 | 2 (13.3%) |
1 | 8 (53.3%) |
2 | 3 (20.0%) |
3 | 2 (13.3%) |
Hormone receptor status | |
ER/PR positive | 5 (33.3%) |
ER and PR negative | 10 (66.7%) |
HER2 status | |
IHC 3+ | 14 (93.3%) |
IHC 2+/ISH+ | 1 (6.7%) |
Extracranial metastases | 14 (93.3%) |
Target lesion | |
Intracranial | 9 (60.0%) |
Extracranial | 14 (93.3%) |
Intracranial and extracranial | 15 (100%) |
Number of metastasis sites | |
1 | 1 (6.7%) |
2 | 0 (0.0%) |
≥3 | 14 (93.3%) |
Metastasis sites | |
Bone | 11 (73.3%) |
Visceral | 14 (93.3%) |
Liver | 9 (60.0%) |
Lung | 10 (66.7%) |
Brain | 15 (100%) |
Brain metastases status | |
Active | 9 (60.0%) |
Stable | 6 (40.0%) |
Time from breast cancer diagnosis to brain metastases (months) | |
Median (range) | 41.0 (4.6–88.9) |
Time from metastases breast cancer diagnosis to brain metastases (months) | |
Median (range) | 19.2 (0-69.6) |
Symptoms of brain metastases | |
Yes | 6 (40.0%) |
No | 9 (60.0%) |
Prior local therapy for brain metastases | |
Surgery | 2 (13.3%) |
Whole-brain radiation therapy | 7 (46.7%) |
Stereotactic radiotherapy | 8 (53.3%) |
Time from last local brain treatment to enrollment (months) | |
Median (range) | 8.1 (1.1–36.8) |
Previous anti-HER2 therapy | |
Trastuzumab | 15 (100%) |
Pertuzumab | 13 (86.7%) |
T-DM1 | 9 (60.0%) |
Pyrotinib | 15 (100%) |
Anti-HER2 therapy after brain metastases | |
Trastuzumab | 13 (86.7%) |
Pertuzumab | 11 (73.3%) |
T-DM1 | 5 (33.3%) |
Pyrotinib | 8 (53.3%) |
Number of prior lines of anti-HER2 therapy for MBC | |
Median (range) | 5(2–9) |
2 | 2 (13.3%) |
≥3 | 13 (86.7%) |
Number of prior lines of chemotherapy for MBC | |
Median (range) | 5 (2–11) |
2 | 2 (13.3%) |
≥3 | 13 (86.7%) |
Number of treatment lines from the time of brain metastases diagnosis to enrollment | |
Median (range) | 2 (0–5) |
0 | 1 (6.7%) |
1 | 3 (20.0%) |
≥ 2 | 11 (73.3%) |
Line of T-DXd treatment | |
Median (range) | 7 (3–12) |
3 | 1 (6.7%) |
≥4 | 14 (93.3%) |
ECOG, Eastern Cooperative Oncology Group; ER, estrogen receptor; PR, progesterone receptor; HER2, human epidermal growth factor receptor 2; IHC, immunohistochemistry; ISH, in situ hybridization; T-DXd, trastuzumab deruxtecan; MBC, metastatic breast cancer |
Efficacy
As of September 2023, the median follow-up time was 8.6 months (2.1–23.3 months). Five patients continued T-DXd treatment, 10 patients discontinued treatment due to disease progression, 6 of whom experienced simultaneous intracranial and extracranial progression, and 4 of whom experienced only extracranial progression. Eight patients (57.1%) died due to progression of breast cancer. The median CNS-PFS was 7.4 months [95% confidence interval (CI), 6.1–8.8 months] (Fig. 2A), the median PFS for patients with extracranial/total lesions was 6.4 months (95% CI, 4.4–8.3 months) (Fig. 2B), and the median OS was 9.8 months (95% CI, 5.9–13.8 months) (Fig. 2C).
Of the 15 patients included in the study, 9 had evaluable intracranial lesions, and 14 had evaluable extracranial lesions. The ORR rates for intracranial, extracranial, and overall lesions were 33.3%, 71.4%, and 73.3%, respectively, while the CBR rates for intracranial, extracranial, and overall lesions were 53.3%, 66.7%, and 73.3%, respectively. The median time to response was 1.5 months for intracranial lesions, 1.4 months for extracranial lesions, and 1.6 months for overall lesions, while the median duration of response was 4.9 months for intracranial lesions, 5.7 months for extracranial lesions, and 6.0 months for overall lesions (Fig. 3).
Nine patients had active BMs, of whom 8 had target lesions in the brain, and 7 progressed after previous local treatment. Three patients achieved PR in their intracranial lesions, all of whom had progressed after previous local BM treatment (Fig. 4). Six patients presented with symptoms related to BMs, such as dizziness and nausea, 4 of whom experienced symptom alleviation after T-DXd treatment. Six patients had stable BMs, of whom 1 had a target lesion in the brain and none presented with symptoms related to BMs. The intracranial ORR, CBR, CNS-PFS, and OS in patients with active BMs were 33.3%, 44.4%, 7.4 months, and 8.3 months, respectively, while those in patients with stable BMs were 0%, 71.4%, 7.0 months, and 20.3 months, respectively (Fig. 5).
Safety
Treatment-emergent adverse events in 5% or more of the patients are shown in Table 2, most of which were grade 1/2 and thus controllable. Adverse events of grade 3 or higher with an incidence rate ≥ 5% included leukopenia (20.0%), neutropenia (13.3%), thrombocytopenia (6.7%), and nausea (6.7%). Adverse events of specific interest, interstitial lung disease or pneumonitis, occurred in 2 patents (13.3%), and both were grade 1. Two patients had a dose reduction of T-DXd due to nausea and vomiting of Grade 2.
Table 2
Treatment-emergent adverse events in 5% or more of the patients (n = 15)
Event, No. (%) | Any grade | Grade ≥ 3 |
Anemia | 10 (66.7%) | 0 (0.0%) |
Leukocytopenia | 6 (40.0%) | 3 (20.0%) |
Neutropenia | 6 (40.0%) | 2 (13.3%) |
Thrombocytopenia | 3 (20.0%) | 1 (6.7%) |
Lymphocyte count decreased | 9 (60.0%) | 1 (6.7%) |
Hypokalemia | 4 (26.7%) | 0 (0.0%) |
Elevated AST | 7 (46.7%) | 0 (0.0%) |
Elevated ALT | 3 (20.0%) | 0 (0.0%) |
Elevated bilirubin | 3 (20.0%) | 0 (0.0%) |
Nausea | 14 (93.3%) | 1 (6.7%) |
Vomiting | 7 (46.7%) | 0 (0.0%) |
Diarrhea | 1 (6.7%) | 0 (0.0%) |
Constipation | 3 (20.0%) | 0 (0.0%) |
Stomatitis | 2 (13.3%) | 0 (0.0%) |
Fatigue | 13 (86.7%) | 0 (0.0%) |
Palpitation | 1 (6.7%) | 0 (0.0%) |
Headache | 2 (13.3%) | 0 (0.0%) |
Xerophthalmia | 2 (13.3%) | 0 (0.0%) |
Rash | 1 (6.7%) | 0 (0.0%) |
ILD/pneumonitis | 2 (13.3%) | 0 (0.0%) |
Decreased ejection fraction | 0 (0.0%) | 0 (0.0%) |
Prolonged QT interval | 0 (0.0%) | 0 (0.0%) |
AST, aspartate transaminase; ALT, alanine aminotransferase; ILD, interstitial lung disease |