BluePrint breast cancer molecular subtyping recognizes single and dual subtype tumors with implications for therapeutic guidance

Purpose

BluePrint (BP) is an 80-gene molecular subtyping test that classifies early-stage breast cancer (EBC) into Basal, Luminal, and HER2 subtypes. In most cases, breast tumors have one dominant subtype, representative of a single activated pathway. However, some tumors show a statistically equal representation of more than one subtype, referred to as dual subtype. This study aims to identify and examine dual subtype tumors by BP to understand their biology and possible implications for treatment guidance.

Methods

The BP scores of over 15,000 tumor samples from EBC patients were analyzed, and the differences between the highest and the lowest scoring subtypes were calculated. Based upon the distribution of the differences between BP scores, a threshold was determined for each subtype to identify dual versus single subtypes.

Results

Approximately 97% of samples had one single activated BluePrint molecular subtype, whereas ~ 3% of samples were classified as BP dual subtype. The most frequently occurring dual subtypes were the Luminal-Basal-type and Luminal-HER2-type. Luminal-Basal-type displays a distinct biology from the Luminal single type and Basal single type. Burstein’s classification of the single and dual Basal samples showed that the Luminal-Basal-type is mostly classified as ‘luminal androgen receptor’ and ‘mesenchymal’ subtypes, supporting molecular evidence of AR activation in the Luminal-Basal-type tumors. Tumors classified as Luminal-HER2-type resemble features of both Luminal-single-type and HER2-single-type. However, patients with dual Luminal-HER2-type have a lower pathological complete response after receiving HER2-targeted therapies in addition to chemotherapy in comparison with patients with a HER2-single-type.

Conclusion

This study demonstrates that BP identifies tumors with two active functional pathways (dual subtype) with specific transcriptional characteristics and highlights the added value of distinguishing BP dual from single subtypes as evidenced by distinct treatment response rates.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10549-022-06698-x.

Distribution of breast cancer molecular subtypes within receptor classifications: Lessons from the I-SPY2 Trial and FLEX Registry

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Background: Expression-based molecular subtypes of breast cancer (BC) predict tumor behavior and therapeutic response. Subtype distributions by age and sociodemographics can inform strategies for BC screening, treatment, and prognosis. The conventional approach, adopted by NCI’s Surveillance, Epidemiology, and End Results (SEER) Program, uses HR and HER2 to label: “triple negative” (HR-HER2-), “HER2-enriched” (HR-HER2+), “luminal A” (HR+HER2-), and “luminal B” (HR+HER2+). However, immunohistochemical (IHC)-based receptor labels may not reflect clinically and epidemiologically relevant molecular subtypes that share the same nomenclature, e.g., luminal B. Methods: We compared IHC labels by HR/HER2 to molecular subtypes by MammaPrint (MP) and BluePrint (BP) for patients in the phase II neoadjuvant I-SPY2 TRIAL for high-risk, stage II-III BC (NCT01042379, n = 981) and in the multicenter, prospective FLEX Registry for stage I-III BC (NCT03053193, n = 5,679). Results: IHC labels were discordant with MP/BP in 52% of I-SPY2 and 43% of FLEX cases (Table 1). HR-HER2- had the highest concordance with basal-type (99% in I-SPY2, 88% in FLEX). HR+ labels had the least agreement with MP/BP: HR+HER2- tumors were molecularly luminal B and basal in 71% and 29% of I-SPY2 and 40% and 4% of FLEX cases, respectively. HR+HER2+ tumors were molecularly luminal A and HER2-type in 10% and 60% of I-SPY2 and 15% and 36% of FLEX cases, respectively. Of molecularly luminal B cases, only 14% in I-SPY2 and 7% in FLEX were HR+HER2+. Conclusions: IHC markers collected by population-based registries (SEER) enable BC surveillance. However, IHC labels cannot be used as surrogates for molecular subtypes by MP/BP, especially for luminal B tumors. Given the unmet need to improve management of luminal B BC, we anticipate the growing importance of molecular subtyping to inform treatment and epidemiological research. We propose that the BC research community work with SEER to update its IHC labels to avoid overlap with molecular subtype nomenclature and incorporate such modern classifications when available. [Table: see text]

MammaPrint and BluePrint comprehensively capture the cancer hallmarks in early-stage breast cancer patients

MammaPrint® (MP) is a 70‐gene signature that stratifies early‐stage breast cancer patients into low‐ and high risk of distant relapse. Further stratification of MP risk results identifies four risk subgroups, ultra‐low (UL), low, high 1, and high 2, with specific prognostic and predictive outcomes. BluePrint® (BP) is an 80‐gene signature that classifies breast tumors as basal, luminal, or HER2 molecular subtype. To gain insight into their biological significance, we annotated the MP 70‐ and BP 80‐genes with respect to the 10 hallmarks of cancer (HoC). Furthermore, we related gene expression profiles of the extreme ends of the MP low‐ and high‐risk patients (here called, ultra‐low (UL) and ultra‐high (UH) or High2, respectively), to the 10 HoC per BP subtype by differential gene expression and pathway analysis. MP and BP gene functions reflected all 10 HoCs. Most MP and BP genes were associated with sustaining proliferative signaling, followed by genome instability and mutation categories. Based on the gene expression profiles, UL and UH subgroup pathways were down ‐or upregulated, respectively, reflecting proliferative and metastatic features, such as G2M checkpoint, DNA repair, oxidative phosphorylation, immune invasion, PI3K/AKT/mTOR signaling, and hypoxia pathways. Notably, the UH HER2‐type was enriched in several immune signaling pathways, such as IL2/STAT5 signaling and TNFα signaling via NFκB. Our results show that MP and BP gene signatures represent and capture all 10 HoCs and highlight underlying biological processes of MP extreme samples, which might guide treatment decisions as the signature captures the full spectrum of early breast cancers.

Delphi-panel analysis of appropriateness of high-dose therapy and bone marrow autotransplants in newly diagnosed multiple myeloma

There is controversy whether high-dose therapy and a bone marrow autotransplant or conventional chemotherapy is a better treatment for newly diagnosed multiple myeloma. Data from 1 comparative study and 1 randomized trial provide insufficient subject-level data to advise specific people whether to have an autotransplant. We analyzed appropriate use of high-dose therapy and bone marrow autotransplants in people with newly diagnosed, multiple myeloma using a modified Delphi-panel group judgment process. The panel consisted of 9 myeloma experts from diverse geographic sites and practice settings who reviewed Boolean MEDLINE searches of multiple myeloma and chemotherapy or autotransplants. The panel rated a metric of 64 clinical setting developed by permuting age, performance score, disease-stage and disease-related prognostic variables and response to initial therapy. Each panelist rated appropriateness of high-dose therapy and an autotransplant versus conventional-dose chemotherapy on a 9-point ordinal scale (1, most inappropriate, 9, most appropriate). An appropriateness index was developed based on median rating and amount of disagreement. Relationship of appropriateness indices to the permuted clinical variables was considered by analysis of variance and recursive partitioning. Autotransplants were rated appropriate in persons <55 years old with stage 3 disease and a complete or partial response or stable disease after initial chemotherapy, inappropriate in persons with stage 1 or 2 disease, a performance score <70% and a complete or partial response or stable disease after initial chemotherapy and uncertain in all other settings.