Table 1.
Characteristics of studies included in the analysis
| Characteristics of selected studies | % of selected studies |
|---|---|
| Year of publication | |
| 1990–1994 | 16.0 |
| 1995–1999 | 25.0 |
| 2000–2004 | 28.5 |
| 2005–2010 | 30.6 |
| Definition of surrogate endpoint | |
| PFS | 49.3 |
| TTP | 49.3 |
| Inconsistent definition | 1.4 |
| Possibility for crossover after progression | |
| Yes | 37.5 |
| No | 19.4 |
| Subsequent therapy after progression given at physician’s discretion | 6.9 |
| Not reported | 36.1 |
| Type of therapy under investigation | |
| Chemotherapy (monotherapy) | 20.1 |
| Hormone therapy (monotherapy) | 15.3 |
| Biological therapy (monotherapy)* | 2.1 |
| Anti-HER2 therapy | 2.1 |
| Anti-VEGF therapy | 0 |
| Combination with chemotherapy | 43.1 |
| Combination including hormone therapy | 11.1 |
| Combination including biological therapy* | 8.3 |
| Anti-HER2 combination | 0.7 |
| Anti-HER2 plus chemotherapy | 4.9 |
| Anti-HER2 plus hormone therapy | 1.4 |
| Anti-VEGF plus chemotherapy | 1.4 |
| Prior chemotherapy for metastatic disease allowed | |
| Yes | 29.9 |
| No | 61.8 |
| Not reported | 8.3 |
| Prior hormone therapy for metastatic disease allowed | |
| Yes | 52.8 |
| No | 11.1 |
| Not reported | 36.1 |
| Mean patient age (years) | |
| 40–49 | 5.6 |
| 50–59 | 64.6 |
| 60–69 | 23.6 |
| Mean age not reported | 6.3 |
| mBC phenotypes based on ER/PR receptor status | |
| Studies with a predominance of patients with ER/PR+** | 38.9 |
| Studies with a predominance of patients with ER−/PR− | 1.4 |
| Studies with a predominance of patients with ER/PR unknown | 9.7 |
| ER/PR status not reported | 50.0 |
| mBC phenotypes based on HER2, ER and PR receptor status | |
| Studies with HER2+, ER/PR any*** as a selection criteria | 6.9 |
| Studies with a predominance of patients with HER2+, ER/PR+** | 3.5 |
| Studies with a predominance of patients with HER2+, ER−/PR− | 1.4 |
| Studies with a predominance of patients with HER2−, ER/PR any*** | 5.6 |
| Studies with a predominance of patients with HER2−, ER/PR+** | 4.9 |
| Studies with a predominance of patients with HER2−, ER−/PR− | 0.0 |
| HER2, ER/PR status not reported | 86.1 |
| Menopausal status | |
| Studies with a predominance of patients with premenopausal status | 2.8 |
| Studies with a predominance of patients with peri or postmenopausal status | 57.6 |
| Menopausal status not reported | 39.6 |
| ECOG performance score | |
| Studies with a predominance of patients with ECOG score 0 | 37.5 |
| Studies with a predominance of patients with ECOG score 1 | 27.1 |
| Studies with a predominance of patients with ECOG score 0–1; as reported | 6.9 |
| ECOG performance score not reported | 28.5 |
| Dominant metastatic site | |
| Studies with a predominance of patients with bone metastases as a dominant site | 13.2 |
| Studies with a predominance of patients with soft tissue metastases as a dominant site | 9.0 |
| Studies with a predominance of patients with visceral metastases as a dominant site | 69.4 |
| Studies with a predominance of patients with another dominant site | 0.7 |
| Dominant metastatic site not reported | 7.6 |
| Number of metastatic sites | |
| Studies with a predominance of patients with one metastatic site | 12.5 |
| Studies with a predominance of patients with two metastatic sites | 22.9 |
| Studies with a predominance of patients with three or more metastatic sites | 16.0 |
| Number of metastatic sites not reported | 48.6 |
| Jadad score | |
| Jadad score 1 | 0.7 |
| Jadad score 2 | 28.5 |
| Jadad score ≥3 | 70.8 |
Notes:
*
Biological therapy includes anti-HER2 therapy (trastuzumab, lapatinib or canertinib) and anti-VEGF therapy (bevacizumab)
**
ER/PR+ is defined as ER+/PR+, ER+/PR−, and ER−/PR+
***
ER/PR any includes ER+/PR+, ER+/PR− and ER−/PR+, ER−/PR− and ER/PR unknown.
Abbreviations: ECOG, Eastern Cooperative Oncology Group; ER, estrogen receptor; HER2, human epidermal growth factor receptor 2; mBC, metastatic breast cancer; PFS, progression-free survival; PR, progesterone receptor; TTP, time to progression; VEGF, vascular endothelial growth factor.