- Prediction of late distant recurrence in patients with oestrogen-receptor-positive breast cancer: a prospective comparison of the breast-cancer index (BCI) assay, 21-gene recurrence score, and IHC4 in the TransATAC study population.
Prediction of late distant recurrence in patients with oestrogen-receptor-positive breast cancer: a prospective comparison of the breast-cancer index (BCI) assay, 21-gene recurrence score, and IHC4 in the TransATAC study population.
Biomarkers to improve the risk-benefit of extended adjuvant endocrine therapy for late recurrence in patients with oestrogen-receptor-positive breast cancer would be clinically valuable. We compared the prognostic ability of the breast-cancer index (BCI) assay, 21-gene recurrence score (Oncotype DX), and an immunohistochemical prognostic model (IHC4) for both early and late recurrence in patients with oestrogen-receptor-positive, node-negative (N0) disease who took part in the Arimidex, Tamoxifen, Alone or in Combination (ATAC) clinical trial. In this prospective comparison study, we obtained archival tumour blocks from the TransATAC tissue bank from all postmenopausal patients with oestrogen-receptor-positive breast cancer from whom the 21-gene recurrence score and IHC4 values had already been derived. We did BCI analysis in matched samples with sufficient residual RNA using two BCI models-cubic (BCI-C) and linear (BCI-L)-using previously validated cutoffs. We assessed prognostic ability of BCI for distant recurrence over 10 years (the primary endpoint) and compared it with that of the 21-gene recurrence score and IHC4. We also tested the ability of the assays to predict early (0-5 years) and late (5-10 years) distant recurrence. To assess the ability of the biomarkers to predict recurrence beyond standard clinicopathological variables, we calculated the change in the likelihood-ratio ฯ(2) (LR-ฮฯ(2)) from Cox proportional hazards models. Suitable tissue was available from 665 patients with oestrogen-receptor-positive, N0 breast cancer for BCI analysis. The primary analysis showed significant differences in risk of distant recurrence over 10 years in the categorical BCI-C risk groups (p<0ยท0001) with 6ยท8% (95% CI 4ยท4-10ยท0) of patients in the low-risk group, 17ยท3% (12ยท0-24ยท7) in the intermediate group, and 22ยท2% (15ยท3-31ยท5) in the high-risk group having distant recurrence. The secondary analysis showed that BCI-L was a much stronger predictor for overall (0-10 year) distant recurrence compared with BCI-C (interquartile HR 2ยท30 [95% CI 1ยท62-3ยท27]; LR-ฮฯ(2)=22ยท69; p<0ยท0001). When compared with BCI-L, the 21-gene recurrence score was less predictive (HR 1ยท48 [95% CI 1ยท22-1ยท78]; LR-ฮฯ(2)=13ยท68; p=0ยท0002) and IHC4 was similar (HR 1ยท69 [95% CI 1ยท51-2ยท56]; LR-ฮฯ(2)=22ยท83; p<0ยท0001). All further analyses were done with the BCI-L model. In a multivariable analysis, all assays had significant prognostic ability for early distant recurrence (BCI-L HR 2ยท77 [95% CI 1ยท63-4ยท70], LR-ฮฯ(2)=15ยท42, p<0ยท0001; 21-gene recurrence score HR 1ยท80 [1ยท42-2ยท29], LR-ฮฯ(2)=18ยท48, p<0ยท0001; IHC4 HR 2ยท90 [2ยท01-4ยท18], LR-ฮฯ(2)=29ยท14, p<0ยท0001); however, only BCI-L was significant for late distant recurrence (BCI-L HR 1ยท95 [95% CI 1ยท22-3ยท14], LR-ฮฯ(2)=7ยท97, p=0ยท0048; 21-gene recurrence score HR 1ยท13 [0ยท82-1ยท56], LR-ฮฯ(2)=0ยท48, p=0ยท47; IHC4 HR 1ยท30 [0ยท88-1ยท94], LR-ฮฯ(2)=1ยท59, p=0ยท20). BCI-L was the only significant prognostic test for risk of both early and late distant recurrence and identified two risk populations for each timeframe. It could help to identify patients at high risk for late distant recurrence who might benefit from extended endocrine or other therapy. Avon Foundation, National Institutes of Health, Breast Cancer Foundation, US Department of Defense Breast Cancer Research Program, Susan G Komen for the Cure, Breakthrough Breast Cancer through the Mary-Jean Mitchell Green Foundation, AstraZeneca, Cancer Research UK, and the National Institute for Health Research Biomedical Research Centre at the Royal Marsden (London, UK).