Multifocal breast cancers are more prevalent in BRCA2 versus BRCA1 mutation carriers

Current understanding and distinct features of multifocal and multicentric breast cancers

BACKGROUND

Multifocal (MF) and multicentric (MC) breast cancers are referred to as synchronous, multiple ipsilateral breast cancers; however, the definitions vary among the literature, which has made understanding and analyzing these diseases challenging.

RECENT FINDINGS

The incidence ranges from 1% to 60%, with a higher prevalence in pre-menopausal women. MF and MC breast cancers, compared with unifocal breast cancers, tend to be more aggressive and are associated with lower survival rates, higher recurrence, and lymph node metastasis. Typically, patients with MF/MC breast cancers are treated with radical surgery, while breast conservation therapy may also be considered. Investigations have focused on elucidating the distinct biological features of MF/MC breast cancers, including the clonality of the cancers, the genetic alterations, and the impact of these features on disease aggressiveness and patient prognosis.

CONCLUSION

These findings will broaden the understanding of these breast cancer subtypes and aid in the development of more tailored treatment plans for patients.

Synchronous Bilateral Breast Cancer With Discordant Receptor Status: Treating One Patient but Two Diseases

The expression of hormone receptors (estrogen and progesterone) and human epidermal growth factor receptor-2 (HER2) has been used for both therapeutic and prognostic purposes in the management of breast cancer. The presence of a discordant receptor status complicates the approach to treatment in patients with synchronous bilateral breast cancer. We describe the case of a 45-year-old female with synchronous bilateral breast cancer with a triple-negative tumor and a contralateral HER2-positive tumor and discussed the impact of this on the approach to therapeutic management.

Impact of multifocal or multicentric disease on local recurrence and survival in breast cancer patients with or without BRCA1/2 variants

PURPOSE

Multifocal or multicentric (MFMC) breast cancer is mainly focused on breast cancer patients with unknown BRCA status, the incidence and clinical relevance of MFMC disease in BRCA1/2 carriers is less explored to date. Our study was to investigate the incidence of MFMC disease in BRCA1/2 carriers and whether MFMC disease influences local recurrence and clinical outcomes.

METHODS

In this retrospective study, 479 breast cancer patients with BRCA1/2 variants and 1437 age-matched noncarriers were enrolled and patients received either breast-conserving therapy (BCT) or mastectomy with or without radiotherapy.

RESULTS

The rates of MFMC disease in BRCA1 and BRCA2 carriers, and noncarriers were 33.0% (61 of 185), 37.4% (110 of 294), and 31.2% (449 of 1437), respectively. MFMC disease in BRCA2 carriers was significantly higher than that in noncarriers (P = 0.039). After a median follow-up of 8.1 years, among patients treated with BCT, BRCA2 carriers with MFMC disease experienced a significantly higher rate of ipsilateral breast tumor recurrence (IBTR) than those with unifocal disease (16.7% vs 4.1%, P = 0.044). Moreover, BRCA2 carriers with MFMC disease had a significantly worse RFS (unadjusted hazard ratio [HR], 3.65 [95% CI 1.40-9.52]; P = 0.008), DRFS (unadjusted HR, 3.07 [95% CI 1.07-8.80]; P = 0.037), and OS (unadjusted HR, 4.96 [95% CI 1.18-20.02]; P = 0.029) than those with unifocal disease when treated with BCT.

CONCLUSION

MFMC breast cancer is more common in BRCA2 carriers, and BRCA2 carriers with MFMC disease treated with BCT exhibit a higher rate of IBTR and may have a poor survival.

Multifocal/multicentric breast cancer: Does each focus matter?

BACKGROUND

Multifocal (MF) and multicentric (MC) breast cancer cases have been increasingly diagnosed owing to the extensive use of improved preoperative breast imaging. The current tumor-node-metastasis staging system uses the dimension of the largest tumor and recommends reporting the pathological features of the largest tumor in MF/MC breast cancers.

AIM

This study aimed to explore whether the largest or aggregate dimensions of MF and MC breast cancers can better predict tumor behavior. We also attempted to study the histological and biological heterogeneities of separate foci in MF and MC breast cancers to determine whether it was necessary to examine each lesion.

METHODS

We retrospectively analyzed 121 patients with MF/MC (103 with MF and 18 with MC) breast cancers and 484 patients with unifocal breast cancer who were treated at the First Affiliated Hospital of Nanjing Medical University. Two methods were used to record the T stage (using the dimensions of the largest lesion and aggregate dimensions of all lesions). The histological grade, immunohistochemical parameters, and molecular subtypes of the largest lesion and other lesions in MF/MC breast cancers were studied to assess intertumoral heterogeneity.

RESULTS

The use of aggregate dimensions upstaged 63 patients with MF/MC breast cancers to a more advanced stage and removed the independent effect of cancer multiplicity on lymph node positivity compared with the use of the largest dimension. Mismatches were found in the pathological type (9.9%), histological grade (4.1%), and molecular subtype (8.3%) among different foci.

CONCLUSION

The tendency of MF/MC breast tumors to metastasize may be related to tumor load, which can be better predicted by the aggregate dimensions of all foci. The use of the current staging systems may require further evaluation and modification. Intertumoral heterogeneity indicates the necessity for pathological and immunohistochemical assessments of each lesion in patients with MF/MC breast cancers.

Learning to distinguish progressive and non-progressive ductal carcinoma in situ

Ductal carcinoma in situ (DCIS) is a non-invasive breast neoplasia that accounts for 25% of all screen-detected breast cancers diagnosed annually. Neoplastic cells in DCIS are confined to the ductal system of the breast, although they can escape and progress to invasive breast cancer in a subset of patients. A key concern of DCIS is overtreatment, as most patients screened for DCIS and in whom DCIS is diagnosed will not go on to exhibit symptoms or die of breast cancer, even if left untreated. However, differentiating low-risk, indolent DCIS from potentially progressive DCIS remains challenging. In this Review, we summarize our current knowledge of DCIS and explore open questions about the basic biology of DCIS, including those regarding how genomic events in neoplastic cells and the surrounding microenvironment contribute to the progression of DCIS to invasive breast cancer. Further, we discuss what information will be needed to prevent overtreatment of indolent DCIS lesions without compromising adequate treatment for high-risk patients.

Characterization of the HER2 status in BRCA-mutated breast cancer: a single institutional series and systematic review with pooled analysis

BACKGROUND

Pathogenic variants (PVs) in BRCA1/2 genes account for ∼6% of breast and 20% of ovarian cancers. Most breast tumors developed by BRCA1 carriers are triple negative. BRCA2 tumors have similar rates of estrogen receptor positivity as sporadic controls but are less likely to be human epidermal growth factor receptor 2 (HER2)-positive. Prevalence of HER2 positivity among breast cancers (BCs) in BRCA1/2 mutation carriers is poorly and variably described, ranging from 0% to 10% and 0% to 13% in BRCA1 and BRCA2 carriers, respectively.

PATIENTS AND METHODS

We assessed the prevalence of HER2 positivity among a single institutional cohort of 398 BCs developed in carriers of BRCA1/2 PVs (240 BRCA1, 158 BRCA2). Subsequently, a systematic review of the literature and pooled analysis was carried out.

RESULTS

In our series we found a 7% HER2 positivity rate among all first BRCA1/2 BCs overall. In BRCA1 carriers, 5.4% of BCs were HER2-positive compared with 9.5% in BRCA2-mutated patients. Among bilateral BCs, HER2-positive cases were 15.2% in the BRCA1 group and 23.1% in the BRCA2 group. Notably, six BRCA1 and eight BRCA2 carriers showed discordant HER2 status between BC and bilateral BC (23.7%, 14/59). The systematic review included 21 083 BRCA1/2 patients from 73 eligible studies. The pooled rate of BRCAmut/HER2-positive BCs is 9.1% (95% confidence interval 7.3% to 11.2%). BRCA1 and BRCA2 when reported as separate data ranged from 0% to 33.3% (mean 8.3%) and from 0% to 86% (mean 10.3%), respectively.

CONCLUSIONS

As compared with sporadic cases, BCs occurring in BRCA1 and/or BRCA2 PVs carriers are less frequently HER2-positive. Prevalence of HER2 positivity in our series was consistent with pooled analysis and did not exceed 10%. Although not common, co-existence of BRCA mutations and HER2 overexpression and/or gene amplification should be acknowledged. More research is needed to better characterize this subgroup of patients who should not be excluded a priori from clinical trials of targeted therapy for BRCA1/2-driven cancers.

The Critical Role of Breast Specimen Gross Evaluation for Optimal Personalized Cancer Care

Gross examination is the foundation for the pathologic evaluation of all surgical specimens. The rapid identification of cancers is essential for intraoperative assessment and preservation of biomolecules for molecular assays. Key components of the gross examination include the accurate identification of the lesions of interest, correlation with clinical and radiologic findings, assessment of lesion number and size, relationship to surgical margins, documenting the extent of disease spread to the skin and chest wall, and the identification of axillary lymph nodes. Although the importance of gross evaluation is undeniable, current challenges include the difficulty of teaching grossing well and its possible perceived undervaluation compared with microscopic and molecular studies. In the future, new rapid imaging techniques without the need for tissue processing may provide an ideal melding of gross and microscopic pathologic evaluation.

The cell of cancer origin provides the most reliable roadmap to its diagnosis, prognosis (biology) and therapy

Cancers arise from single transformed cells from virtually every organ of the body, divide in a relatively uncontrolled manner, and metastasize widely. A search for a "magic bullet" to precisely diagnose, characterize, and ultimately treat cancer has largely failed because cancer cells do not differ significantly from their organ-specific cells of origin. Instead of searching for genomic, epigenetic, transcriptional, and translational differences between cancers and their cells of origin, we should paradoxically focus on what cancer cells have in common with their untransformed cells of origin. This redirected search will lead to improved diagnostic and therapeutic strategies where therapeutic index considerations and drug-limiting toxicities can largely be circumvented. We cite three cancer examples that illustrate this paradigm-shifting strategy: pseudomyxoma peritonei (PP), metastasis of unknown origin (cancers of unknown primary) (MUO), and cancers that arise from potentially dispensable organs (CAD). In each of these examples, the cell of cancer origin still provides the most reliable road map to its diagnosis, prognosis (biology), and therapy.

Use of constitutive and inducible oncogene-containing iPSCs as surrogates for transgenic mice to study breast oncogenesis

BACKGROUND

Powerful constitutive and inducible transgenic / bitransgenic / tritransgenic murine models of breast cancer have been used over the past two decades to shed light on the molecular mechanisms by which the given transgenic oncogenes have interacted with other cellular genes and set in motion breast cancer initiation and progression. However, these transgenic models, as in vivo models only, are expensive and restrictive in the opportunities they provide to manipulate the experimental variables that would enable a better understanding of the molecular events related to initial transformation and the target cell being transformed.

METHODS

To overcome some of these limitations, we derived oncogene-containing induced pluripotent stem cell (iPSC) clones from tail vein fibroblasts of these transgenic mice and manipulated them both in vitro and in vivo in non-transgenic background mice. We created the iPSC clones with a relatively low M.O.I, producing retroviral integrations which averaged only 1 to 2 sites per retroviral plasmid construct used.

RESULTS

Most iPSC clones derived from each group displayed an essentially normal murine karyotype, strong expression of the exogenous reprogrammable genes and significant expression of characteristic endogenous murine surface stem cell markers including SSEA-1 (CD15), PECAM-1 (CD31), Ep-Cam (CD326), and Nectin (CD112), but no expression of their transgene. A majority (75%) of iPSC clones displayed a normal murine karyotype but 25% exhibited a genomically unstable karyotype. However, even these later clones exhibited stable and characteristic iPSC properties. When injected orthotopically, select iPSC clones, either constitutive or inducible, no longer expressed their exogenous pluripotency reprogramming factors but expressed their oncogenic transgene (PyVT or ErbB2) and participated in both breast ontogenesis and subsequent oncogenesis. When injected non-orthotopically or when differentiated in vitro along several different non-mammary lineages of differentiation, the iPSC clones failed to do so. Although many clones developed anticipated teratomas, select iPSC clones under the appropriate constitutive or inducible conditions exhibited both breast ontogenesis and oncogenesis through the same stages as exhibited by their transgenic murine parents and, as such, represent transgenic surrogates.

CONCLUSIONS

The iPSC clones offer a number of advantages over transgenic mice including cost, the ability to manipulate and tag in vitro, and create an in vitro model of breast ontogeny and oncogenesis that can be used to gain additional insights into the differentiated status of the target cell which is susceptible to transformation. In addition, the use of these oncogene-containing iPSC clones can be used in chemopreventive studies of breast cancer.

Regulation of breast cancer oncogenesis by the cell of origin's differentiation state

Human breast cancer which affects 1/8 women is rare at a cellular level. Even in the setting of germline BRCA1/BRCA2, which is present in all breast cells, solitary cancers or cancers arising at only several foci occur. The overwhelming majority of breast cells (10⁹-10¹² cells) resist transformation. Our hypothesis to explain this rareness of transformation is that mammary oncogenesis is regulated by the cell of origin's critical window of differentiation so that target cells outside of this window cannot transform. Our novel hypothesis differs from both the multi-hit theory of carcinogenesis and the stem/progenitor cell compartmental theory of tumorigenesis and utilizes two well established murine transgenic models of breast oncogenesis, the FVB/N-Tg (MMTV-PyVT)634Mul/J and the FVB-Tg (MMTV-ErbB2) NK1Mul/J. Tail vein fibroblasts from each of these transgenics were used to generate iPSCs. When select clones were injected into cleared mammary fat pads, but not into non-orthotopic sites of background mice, they exhibited mammary ontogenesis and oncogenesis with the expression of their respective transgenes. iPSC clones, when differentiated along different non-mammary lineages in vitro, were also not able to exhibit either mammary ontogenesis or oncogenesis in vivo. Therefore, in vitro and in vivo regulation of differentiation is an important determinant of breast cancer oncogenesis.

Why is cancer so common a disease in people yet so rare at a cellular level?

Cancers are common diseases in people and yet, on a cellular level, are quite rare. The vast majority of both sporadic, spontaneous cancers and inherited germline cancers arise in single foci from singly transformed cells despite the fact that, in the former, carcinogenic factors bathe fields of millions of potential target cells and, in the latter, the predisposing germline mutations are present in every cell of a given organ and, in fact, every cell of the body. Although the multi-hit theory of carcinogenesis has been invoked to explain such things as cancer latency, which is the period between cancer initiation and emergence and the cancer-aging relationship where an accumulation of "hits" over a period of time are necessary for cancer emergence, the multi-hit theory falls short in explaining the rareness of transformation at a cellular level. This is so because many cancers are not due to multiple hits, and even for those that are, it would be expected that many cells would be exposed to those factors inducing the hits. Although the tumor stem/progenitor cell compartmental theory of tumorigenesis characterizes a tumor compartment that is capable of self-renewal and multipotency, accounting for cancer relapses and recurrences, this compartmental theory alone cannot account for the rareness of initial transformation at a cellular level as the cancer stem/progenitor cell compartment is already transformed and considerable in size. This study advances a different and novel hypothesis that oncogenesis is regulated and ultimately determined by a cell of origin's critical state of differentiation. Before and after this critical state of differentiation has been reached, target cells cannot transform and give rise to cancer even when they receive the necessary carcinogenic insults or have the requisite transforming tumor suppressor genes or oncogenes. As support for this hypothesis, the study cites preliminary evidence using oncogene-containing transgenic mice that develop mammary carcinomas, to derive tail vein fibroblasts converted to iPSCs which, when left undifferentiated, and injected into the cleared fat pads of non-transgenic background mice give rise to mammary gland ontogeny and mammary gland carcinogenesis. However, when first differentiated in vitro into multiply different non-mammary lineages prior to injection, they fail to do so. The hypothesis has widespread implications for chemopreventive strategies.