Risk of Contralateral Breast Cancer in Women with and without Pathogenic Variants in BRCA1, BRCA2, and TP53 Genes in Women with Very Early-Onset (<36 Years) Breast Cancer

Clinical Impact of Constitutional Genomic Testing on Current Breast Cancer Care

The most commonly diagnosed cancer in women worldwide is cancer of the breast. Up to 20% of familial cases are attributable to pathogenic mutations in high-penetrance (BReast CAncer gene 1 [BRCA1], BRCA2, tumor protein p53 [TP53], partner and localizer of breast cancer 2 [PALB2]) or moderate-penetrance (checkpoint kinase 2 [CHEK2], Ataxia-telangiectasia mutated [ATM], RAD51C, RAD51D) breast-cancer-predisposing genes. Most of the breast-cancer-predisposing genes are involved in DNA damage repair via homologous recombination pathways. Understanding these pathways can facilitate the development of risk-reducing and therapeutic strategies. The number of breast cancer patients undergoing testing for pathogenic mutations in these genes is rapidly increasing due to various factors. Advances in multigene panel testing have led to increased detection of pathogenic mutation carriers at high risk for developing breast cancer and contralateral breast cancer. However, the lack of long-term clinical outcome data and incomplete understanding of variants, particularly for moderate-risk genes limits clinical application. In this review, we have summarized the key functions, risks, and prognosis of breast-cancer-predisposing genes listed in the National Health Service (NHS) England National Genomic Test Directory for inherited breast cancer and provide an update on current management implications including surgery, radiotherapy, systemic treatments, and post-treatment surveillance.

TP53-associated early breast cancer: new observations from a large cohort

BACKGROUND

A recent large, well-annotated international cohort of patients with Li-Fraumeni syndrome and early-stage breast cancer was examined for shared features.

METHODS

This multicenter cohort study included women with a germline TP53 pathogenic or likely pathogenic variant and nonmetastatic breast cancer diagnosed between 2002 and 2022. Clinical and genetic data were obtained from institutional registries and clinical charts. Descriptive statistics were used to summarize proportions, and differences were assessed using χ2 or Wilcoxon rank sum tests. Metachronous contralateral breast cancer risk, radiation-induced sarcoma risk, and recurrence-free survival were analyzed using the Kaplan-Meier methodology.

RESULTS

Among 227 women who met study criteria, the median age of first breast cancer diagnosis was 37 years (range = 21-71), 11.9% presented with bilateral synchronous breast cancer, and 18.1% had ductal carcinoma in situ only. In total, 166 (73.1%) patients underwent mastectomies, including 67 bilateral mastectomies as first breast cancer surgery. Among those patients with retained breast tissue, the contralateral breast cancer rate was 25.3% at 5 years. Among 186 invasive tumors, 72.1% were stages I to II, 48.9% were node negative, and the most common subtypes were hormone receptor-positive/HER2-negative (40.9%) and hormone receptor positive/HER2 positive (34.4%). At a median follow-up of 69.9 months (interquartile range = 32.6-125.9), invasive hormone receptor-positive/HER2-negative disease had the highest recurrence risk among the subtypes (5-year recurrence-free survival = 61.1%, P = .001). Among those who received radiation therapy (n = 79), the 5-year radiation-induced sarcoma rate was 4.8%.

CONCLUSION

We observed high rates of ductal carcinoma in situ, hormone receptor-positive, and HER2-positive breast cancers, with a worse outcome in the hormone receptor-positive/HER2-negative luminal tumors, despite appropriate treatment. Confirmation of these findings in further studies could have implications for breast cancer care in those with Li-Fraumeni syndrome.

Genetic Testing of Breast Cancer Patients with Very Early-Onset Breast Cancer (≤30 Years) Yields a High Rate of Germline Pathogenic Variants, Mainly in the BRCA1, TP53, and BRCA2 Genes

Early-onset breast cancer constitutes a major criterion for genetic testing referral. Nevertheless, studies focusing on breast cancer patients (≤30 years) are limited. We investigated the contribution and spectrum of known breast-cancer-associated genes in 267 Greek women with breast cancer ≤30 years while monitoring their clinicopathological characteristics and outcomes. In this cohort, a significant proportion (39.7%) carried germline pathogenic variants (PVs) distributed in 8 genes. The majority, namely 36.7%, involved BRCA1, TP53, and BRCA2. PVs in BRCA1 were the most prevalent (28.1%), followed by TP53 (4.5%) and BRCA2 (4.1%) PVs. The contribution of PVs in CHEK2, ATM, PALB2, PTEN, and RAD51C was limited to 3%. In the patient group ≤26 years, TP53 PVs were significantly higher compared to the group 26-30 years (p = 0.0023). A total of 74.8% of TP53 carriers did not report a family history of cancer. Carriers of PVs receiving neoadjuvant chemotherapy showed an improved event-free survival (p < 0.0001) compared to non-carriers. Overall, many women with early-onset breast cancer carry clinically actionable variants, mainly in the BRCA1/2 and TP53 genes. The inclusion of timely testing of TP53 in these patients provides essential information for appropriate clinical management. This is important for countries where reimbursement involves the cost of genetic analysis of BRCA1/2 only.

Cancer genetic counselling for hereditary breast cancer in the era of precision oncology

A relevant percentage of breast cancers (BCs) are tied to pathogenetic (P)/likely pathogenetic (LP) variants in predisposing genes. The knowledge of P/LP variants is an essential element in the management of BC patients since the first diagnosis because it influences surgery and subsequent oncological treatments and follow-up. Moreover, patients with metastatic BCs can benefit from personalized treatment if carriers of P/LP in BRCA1/2 genes. Multigene panels allow the identification of other predisposing genes with an impact on management. Cascade genetic testing for healthy family members allows personalized preventive strategies. Here, we review the advances and the challenges of Cancer Genetic Counseling (CGC). We focus on the area of oncology directed to hereditary BC management describing the peculiar way to lead CGC and how CGC changes over time. The authors describe the impact of genetic testing by targeted approach or universal approach on the management of BC according to the stage at diagnosis. Moreover, they describe the burden of CGC and testing and future perspectives to widely offer testing. A new perspective is needed for models of service delivery of CGC and testing, beyond formal genetic counselling. A broader genetic test can be quickly usable in clinical practice for comprehensive BC management and personalized prevention in the era of precision oncology.

The Role of the Surgeon in the Germline Testing of the Newly Diagnosed Breast Cancer Patient

For patients with newly diagnosed breast cancer, information regarding hereditary predisposition can influence treatment decisions. From a surgical standpoint, patients with known germline mutations may alter decisions of local therapy to reduce the risk of second breast primaries. This information may also be considered in the choice of adjuvant therapies or eligibility for clinical trials. In recent years, the criteria for the consideration of germline testing in patients with breast cancer has expanded. Additionally, studies have shown a similar prevalence of pathogenic mutations in those patients outside of these traditional criteria, prompting calls for genetic testing for all patients with a history of breast cancer. While data confirms the benefit of counseling by certified genetics professionals, the capacity of genetic counselors may no longer meet the needs of these growing numbers of patients. National societies assert that counseling and testing can be performed by providers with training and experience in genetics. Breast surgeons are well positioned to offer this service, as they receive formal genetics training during their fellowship, manage these patients daily in their practices, and are often the first providers to see patients after their cancer diagnosis.

The impact of coding germline variants on contralateral breast cancer risk and survival

Evidence linking coding germline variants in breast cancer (BC)-susceptibility genes other than BRCA1, BRCA2, and CHEK2 with contralateral breast cancer (CBC) risk and breast cancer-specific survival (BCSS) is scarce. The aim of this study was to assess the association of protein-truncating variants (PTVs) and rare missense variants (MSVs) in nine known (ATM, BARD1, BRCA1, BRCA2, CHEK2, PALB2, RAD51C, RAD51D, and TP53) and 25 suspected BC-susceptibility genes with CBC risk and BCSS. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated with Cox regression models. Analyses included 34,401 women of European ancestry diagnosed with BC, including 676 CBCs and 3,449 BC deaths; the median follow-up was 10.9 years. Subtype analyses were based on estrogen receptor (ER) status of the first BC. Combined PTVs and pathogenic/likely pathogenic MSVs in BRCA1, BRCA2, and TP53 and PTVs in CHEK2 and PALB2 were associated with increased CBC risk [HRs (95% CIs): 2.88 (1.70-4.87), 2.31 (1.39-3.85), 8.29 (2.53-27.21), 2.25 (1.55-3.27), and 2.67 (1.33-5.35), respectively]. The strongest evidence of association with BCSS was for PTVs and pathogenic/likely pathogenic MSVs in BRCA2 (ER-positive BC) and TP53 and PTVs in CHEK2 [HRs (95% CIs): 1.53 (1.13-2.07), 2.08 (0.95-4.57), and 1.39 (1.13-1.72), respectively, after adjusting for tumor characteristics and treatment]. HRs were essentially unchanged when censoring for CBC, suggesting that these associations are not completely explained by increased CBC risk, tumor characteristics, or treatment. There was limited evidence of associations of PTVs and/or rare MSVs with CBC risk or BCSS for the 25 suspected BC genes. The CBC findings are relevant to treatment decisions, follow-up, and screening after BC diagnosis.

Germline TP53 pathogenic variants and breast cancer: A narrative review

Approximately 10% of breast cancers are associated with the inheritance of a pathogenic variant (PV) in one of the breast cancer susceptibility genes. Multiple breast cancer predisposing genes, including TP53, are responsible for the increased breast cancer risk. Tumor protein-53 (TP53) germline PVs are associated with Li-Fraumeni syndrome, a rare autosomal dominant inherited cancer predisposition syndrome associated with early-onset pediatric and multiple primary cancers such as soft tissue and bone sarcomas, breast cancer, brain tumors, adrenocortical carcinomas and leukemias. Women harboring a TP53 PV carry a lifetime risk of developing breast cancer of 80-90%. The aim of the present narrative review is to provide a comprehensive overview of the criteria for offering TP53 testing, prevalence of TP53 carriers among patients with breast cancer, and what is known about its prognostic and therapeutic implications. A summary of the current indications of secondary cancer surveillance and survivorship issues are also provided. Finally, the spectrum of TP53 alteration and testing is discussed. The optimal strategies for the treatment of breast cancer in patients harboring TP53 PVs poses certain challenges. Current guidelines favor the option of performing mastectomy rather than lumpectomy to avoid adjuvant radiotherapy and subsequent risk of radiation-induced second primary malignancies, with careful consideration of radiation when indicated post-mastectomy. Some studies suggest that patients with breast cancer and germline TP53 PV might have worse survival outcomes compared to patients with breast cancer and wild type germline TP53 status. Annual breast magnetic resonance imaging (MRI) and whole-body MRI are recommended as secondary prevention.

Local treatment in patients with hereditary breast cancer: decision-making process in low-, moderate-, high-penetrance pathogenic germline mutation carriers

PURPOSE OF REVIEW

We summarize recent evidence regarding commonly tested breast cancer susceptibility genes and review indications derived from recently published guidelines regarding management of carriers affected by early breast cancer (BC).

RECENT FINDINGS

Management of affected women with a known genetic predisposition to BC was matter of debate at the most relevant international conferences, such as St. Gallen International Consensus Conference and San Antonio Breast Cancer Symposium held both in 2021. At the same time, a joint Experts Panel from American Society of Clinical Oncology/American Society for Radiation Oncology/Society of Surgical Oncology (ASCO/ASTRO/SSO) convened to develop recommendations to support clinical decision-making in this specific setting and results about administration of new systemic therapies such as poly adenosine diphosphate-ribose polymerase (PARP) inhibitors became available.

SUMMARY

Population of patients affected by BC and carriers of mutations in susceptibility genes is progressively increasing, but new mutations identified do not always have a clear clinical impact.To date, we have data to support consideration of different local management choices for affected patients carrying specific mutations, but some issues especially relating to breast-conserving surgery or administration of radiotherapy in these patients, still need to be better addressed. Opinions about the best way to treat these patients are still heterogeneous and information deriving from different sources seems to be conflicting at times. Our purpose is to offer a synopsis of the different evidence available that may be helpful in clinical decision making.

Risk of ipsilateral breast tumor recurrence and contralateral breast cancer in patients with and without TP53 variant in a large series of breast cancer patients

Background

The association between breast cancer patients with a TP53 pathogenic variant and risk of local recurrence and contralateral breast cancer remains largely unknown.

Methods

The study population of 11093 patients was derived from two cohorts at the Breast Center of Peking University Cancer Hospital in China from November 2003, to March 2018. TP53 germline variants were determined for all patients.

Results

In the study, forty-one (0.37%) carried a TP53 germline pathogenic variant, and 11052 were non-carriers (99.63%). Nineteen TP53 carriers (46.3%) and 4173 non-carriers (37.8%) were treated with breast-conserving therapy (BCT), while the remaining were treated with mastectomy. After a median follow-up of 6.7 years, the rate of ipsilateral breast tumor recurrence (IBTR) in TP53 carriers was significantly higher than that in non-carriers when treated with BCT (21.1% vs 3.8%, P = 0.006). No difference in the rate of IBTR was found between TP53 carriers and non-carriers when treated with mastectomy (0.0% vs 2.6%, P = 1.0). Furthermore, the rate of IBTR in TP53 carriers treated with BCT was significantly higher than that in those treated with mastectomy (21.1% vs 0.0%, P = 0.038). The 10-year cumulative risk of contralateral breast cancer in TP53 carriers was significantly higher than that in non-carriers (17.9% vs 3.6%, hazard ratio (HR) = 7.0, 95% CI: 3.3–14.9, P < 0.001).

Conclusions

Patients with TP53 variants have a high risk of IBTR when treated with BCT, and exhibit a very high risk of contralateral breast cancer. TP53 carriers may not be suitable for BCT and prophylactic contralateral mastectomy might be considered.

•

Patients with a TP53 variant have a high risk of IBTR when treated with BCT.

•

TP53 carriers exhibit a very high risk of contralateral breast cancer.

•

TP53 carriers may not be suitable for BCT.

•

Prophylactic contralateral mastectomy may be considered for TP53 carriers.

Breast Cancer Phenotype Associated With Li-Fraumeni Syndrome: A Brazilian Cohort Enriched by TP53 p.R337H Carriers

Breast cancer (BC) is the most prevalent malignancy in women with Li-Fraumeni syndrome (LFS). The literature on BC in LFS is limited due to its rarity worldwide. A TP53 founder pathogenic variant (c.1010G>A; p.R337H) is responsible for the higher prevalence of this syndrome among women of Brazilian ancestry.

Breast cancer in young and very young women; Is age related to outcome?

Background

Breast cancer in young women is associated with aggressive biology. We analyzed histopathological and clinical properties of breast cancer patients diagnosed at ≤40 years of age.

Methods

Breast cancer patients who were admitted between 2015 and 2019 were included. Baseline characteristics of the patients with treatment-related outcomes were assessed. The study group was divided into two subgroups; <35 years old as "very young" and ≥35 years old as "young."

Results

The data of 137 patients (60 patients <35 years) were reviewed. The mean age was 34.7 years. The mean follow-up duration was 44.45 ± 26.39 months, and the mean disease-free survival was 36.17 ± 21.97 months. 11.4% of the patients were diagnosed with Stage 4 disease. Pathologic subtype was invasive ductal carcinoma in 86% of patients. 16.8% of the patients were luminal A, 38.7% luminal B, 30.5% were human epidermal growth factor receptor-2-positive type, and 15.3% were triple-negative. Only 5 (3.3%) patients had given birth after chemotherapy. During the follow-up period of early-staged diagnosed patients, metastatic disease occurred in 24.6%. The rate of distant metastasis development was statistically higher in the very young group (31% vs. 11%; P = 0.004). Thirteen patients (10.7%) died due to disease progression. Thirty-seven percent of the patients had a positive family history for either breast or ovarian cancer.

Conclusions

Very young breast cancer patients seem to have a more aggressive disease course. The low rate of childbearing in this young patient population is conspicuous. An interdisciplinary approach for the management of this special patient population should be taken into consideration.

Radiation-Associated Sarcoma of the Breast in a Patient With a Germline Tumor Protein p53 Mutation

Radiation-induced sarcoma of the breast is a rare complication that is primarily treated with surgical resection but in patients with advanced disease, a multimodality treatment approach is often required. This case report discusses a 37-year-old female with a history of a pT3N3M0, estrogen receptor (ER)+, progesterone receptor (PR)+, human epidermal growth factor receptor 2 (HER2)+, right breast cancer, and a germline tumor protein (TP) p53 mutation who underwent right modified radical mastectomy, adjuvant systemic therapy, and radiation therapy, and subsequently developed a radiation-induced sarcoma.

The patient is a 37-year-old female who has a history of pT3N3M0, ER/PR+, HER2+, and right breast cancer diagnosed in 2014. At the time of diagnosis, she had locally advanced disease and underwent right modified radical mastectomy followed by adjuvant chemotherapy, radiation, delayed right breast implant-based reconstruction, and left breast augmentation with mastopexy. Upon completion of adjuvant chemotherapy, she was started on hormonal therapy. In February 2020, she underwent genetic testing given her early onset of breast cancer and was found to have a germline TP53 mutation. Routine MRI for breast implant evaluation showed two irregular enhancing masses with an additional satellite lesion in the right breast. Right breast ultrasound (US)-guided biopsy revealed two separate foci of high-grade pleomorphic fibroblastic/myofibroblastic sarcoma. Further staging workup with a whole-body MRI was negative for evidence of metastatic disease. Her case was discussed in multidisciplinary sarcoma tumor board and consensus was for surgical resection. She underwent radical resection of the right chest wall masses and subcutaneous tissue, removal of right breast implant and capsulectomy, and left breast mastectomy with left breast implant removal and capsulectomy. The final pathology revealed two separate foci of high-grade pleomorphic fibroblastic/myofibroblastic sarcoma, 1.2 cm and 1.1 cm in their greatest dimensions with negative margins. Her case was re-discussed in multidisciplinary sarcoma tumor board and due to T1 size of the tumors and the negative resection margins, close surveillance with annual whole-body MRI and quarterly chest MRI imaging was recommended.

In patients with a germline TP53 mutation and breast cancer, the utilization of adjuvant radiotherapy should be considered cautiously given the increased risk of radiation-associated sarcoma.

Uptake and timing of bilateral and contralateral risk-reducing mastectomy in women with Li-Fraumeni syndrome

PURPOSE

Women with Li-Fraumeni Syndrome (LFS) often consider risk-reducing mastectomy (RRM) due to extremely high risk of breast cancer at early ages. Data on uptake of RRM in LFS are scarce, and are inferred from experience in women with pathogenic variants (PVs) in BRCA1/2, despite differences in cancer risks. This study evaluated RRM uptake in a cohort of women with LFS.

METHODS

Women (n = 205) with LFS enrolled in NCI's LFS study reported lifetime cancer diagnoses and mastectomies and completed questionnaires regarding reproductive history, cancer worry and risk perceptions. A subset of women participating in an annual cancer screening study received counseling regarding RRM.

RESULTS

65% (n = 71) of women diagnosed with presumed unilateral breast cancer (n = 109) underwent contralateral RRM over their lifetime. Nearly half (49%, n = 25) of the women who did not complete contralateral RRM within one year of their breast cancer diagnosis (n = 51) developed contralateral breast cancer (median interval = 6 years). Only 18.5% (n = 15) of women without breast cancer history (n = 81) underwent bilateral RRM. Median age at bilateral RRM of 39 years was sub-optimal for breast cancer risk reduction. Contralateral RRM was associated with early genetic diagnosis, participation in the screening study, and fewer prior cancers. Bilateral RRM uptake was associated with having had children, having breastfed, and high cancer worry.

CONCLUSION

Uptake of contralateral RRM is high in women with LFS. The frequency of contralateral breast cancer necessitates active discussion of benefits of contralateral RRM and counseling regarding bilateral RRM should be tailored to the early age at risk of breast cancer onset in LFS. There is a need for research into the survival and long-term benefits of RRM in LFS.

Breast cancer characteristics and surgery among women with Li-Fraumeni syndrome in Germany-A retrospective cohort study

Background

Women with Li‐Fraumeni syndrome (LFS) have elevated breast cancer (BC) risk. Optimal BC treatment strategies in this population are yet unknown.

Methods

BC subtypes and treatment were retrospectively investigated between December 2016 and January 2019 in a multicentre study. BC risks were evaluated according to the type of surgery.

Results

Thirty‐five women of our study population (35/44; 79.5%) had developed 36 breast lesions at first diagnosis at a mean age of 34 years. Those breast lesions comprised 32 invasive BCs (89%), three ductal carcinoma in situ alone (8%) and one malignant phyllodes tumour (3%). BCs were mainly high‐grade (18/32), of no special type (NST; 31/32), HER2‐enriched (11/32) or luminal‐B‐(like)‐type (10/32). Affected women (n = 35) received breast‐conserving surgery (BCS, n = 17) or a mastectomy (ME, n = 18) including seven women with simultaneous contralateral prophylactic mastectomy (CPM) at first diagnosis. Nineteen women suffered 20 breast or locoregional axillary lesions at second diagnosis with mean age of 36. Median time between first and second diagnosis was 57 months; median time to contra‐ and ipsilateral recurrence depended on surgical strategies (BCS: 46 vs. unilateral ME: 93 vs. bilateral ME > 140 months). Women with a primary treatment of solitaire therapeutic ME suffered from contralateral BC earlier compared to those with therapeutic ME and CPM (median: 93 vs. >140 months).

Conclusion

Aggressive BC subtypes occur among women with LFS. Surgical treatment, i.e. ME and CPM, may prolong time to a second BC diagnosis. Conclusion on long‐term survival benefit is pending. Individual competing tumour risks and long‐term outcomes need to be taken into consideration.

Multigene assessment of genetic risk for women for two or more breast cancers

PURPOSE

The prevalence, penetrance, and spectrum of pathogenic variants that predispose women to two or more breast cancers is largely unknown.

METHODS

We queried clinical and genetic data from women with one or more breast cancer diagnosis who received multigene panel testing between 2013 and 2018. Clinical data were obtained from provider-completed test request forms. For each gene on the panel, a multivariable logistic regression model was constructed to test for association with risk of multiple breast cancer diagnoses. Models accounted for age of diagnosis, personal and family cancer history, and ancestry. Results are reported as odds ratios (ORs) with 95% confidence intervals (CIs).

RESULTS

This study included 98,979 patients: 88,759 (89.7%) with a single breast cancer and 10,220 (10.3%) with ≥ 2 breast cancers. Of women with two or more breast cancers, 13.2% had a pathogenic variant in a cancer predisposition gene compared to 9.4% with a single breast cancer. BRCA1, BRCA2, CDH1, CHEK2, MSH6, PALB2, PTEN, and TP53 were significantly associated with two or more breast cancers, with ORs ranging from 1.35 for CHEK2 to 3.80 for PTEN. Overall, pathogenic variants in all breast cancer risk genes combined were associated with both metachronous (OR 1.65, 95% CI 1.53-1.79, p = 7.2 × 10-33) and synchronous (OR 1.33, 95% CI 1.19-1.50, p = 2.4 × 10-6) breast cancers.

CONCLUSIONS

This study demonstrated that several high and moderate penetrance breast cancer susceptibility genes are associated with ≥ 2 breast cancers, affirming the association of two or more breast cancers with diverse genetic etiologies.

From BRCA1 to Polygenic Risk Scores: Mutation-Associated Risks in Breast Cancer-Related Genes

Background

There has been huge progress over the last 30 years in identifying the familial component of breast cancer.

Summary

Currently around 20% is explained by the high-risk genes BRCA1 and BRCA2, a further 2% by other high-penetrance genes, and around 5% by the moderate risk genes ATM and CHEK2. In contrast, the more than 300 low-penetrance single-nucleotide polymorphisms (SNP) now account for around 28% and they are predicted to account for most of the remaining 45% yet to be found. Even for high-risk genes which confer a 40-90% risk of breast cancer, these SNP can substantially affect the level of breast cancer risk. Indeed, the strength of family history and hormonal and reproductive factors is very important in assessing risk even for a BRCA carrier. The risks of contralateral breast cancer are also affected by SNP as well as by the presence of high or moderate risk genes. Genetic testing using gene panels is now commonplace.

Key-Messages

There is a need for a more parsimonious approach to panels only testing those genes with a definite 2-fold increased risk and only testing those genes with challenging management implications, such as CDH1 and TP53, when there is strong clinical indication to do so. Testing of SNP alongside genes is likely to provide a more accurate risk assessment.

High likelihood of actionable pathogenic variant detection in breast cancer genes in women with very early onset breast cancer

Background

While the likelihood of identifying constitutional breast cancer-associated BRCA1, BRCA2 and TP53 pathogenic variants (PVs) increases with earlier diagnosis age, little is known about the correlation with age at diagnosis in other predisposition genes. Here, we assessed the contribution of known breast cancer-associated genes to very early onset disease.

Methods

Sequencing of BRCA1, BRCA2, TP53 and CHEK2 c.1100delC was undertaken in women with breast cancer diagnosed ≤30 years. Those testing negative were screened for PVs in a minimum of eight additional breast cancer-associated genes. Rates of PVs were compared with cases ≤30 years from the Prospective study of Outcomes in Sporadic vs Hereditary breast cancer (POSH) study.

Results

Testing 379 women with breast cancer aged ≤30 years identified 75 PVs (19.7%) in BRCA1, 35 (9.2%) in BRCA2, 22 (5.8%) in TP53 and 2 (0.5%) CHEK2 c.1100delC. Extended screening of 184 PV negative women only identified eight additional actionable PVs. BRCA1/2 PVs were more common in women aged 26–30 years than in younger women (p=0.0083) although the younger age group had rates more similar to those in the POSH cohort. Out of 26 women with ductal carcinoma in situ (DCIS) alone, most were high-grade and 11/26 (42.3%) had a PV (TP53=6, BRCA2=2, BRCA1=2, PALB2=1). This PV yield is similar to the 61 (48.8%) BRCA1/2 PVs identified in 125 women with triple-negative breast cancer. The POSH cohort specifically excluded pure DCIS which may explain lower TP53 PV rates in this group (1.7%).

Conclusion

The rates of BRCA1, BRCA2 and TP53 PVs are high in very early onset breast cancer, with limited benefit from testing of additional breast cancer-associated genes.

Germline TP53 Testing in Breast Cancers: Why, When and How?

Simple Summary

TP53 variants detected in blood represent a main genetic cause of breast cancers occurring before 31 years of age. TP53 being included in most of the cancer gene panels, patients with breast cancer are offered germline TP53 testing, independently of the age of tumour onset and familial history. Interpretation of TP53 variants is remarkably complex, and detection of a germline disease-causing TP53 variant in a breast cancer patient has drastic medical consequences: radiotherapy contributing to the development of subsequent tumours should be, if possible, avoided. In her family, variant carriers should be offered annual follow-up, including whole-body MRI. Therefore, we consider that, in breast cancer patients, germline TP53 testing should be performed before treatment and that the decision of TP53 testing should not be systematic but based on the age of tumour onset, type of breast cancer, personal and familial history of cancer.

Abstract

Germline TP53 variants represent a main genetic cause of breast cancers before 31 years of age. Development of cancer multi-gene panels has resulted in an exponential increase of germline TP53 testing in breast cancer patients. Interpretation of TP53 variants, which are mostly missense, is complex and requires excluding clonal haematopoiesis and circulating tumour DNA. In breast cancer patients harbouring germline disease-causing TP53 variants, radiotherapy contributing to the development of subsequent tumours should be, if possible, avoided and, within families, annual follow-up including whole-body MRI should be offered to carriers. We consider that, in breast cancer patients, germline TP53 testing should be performed before treatment and offered systematically only to patients with: (i) invasive breast carcinoma or ductal carcinoma in situ (DCIS) before 31; or (ii) bilateral or multifocal or HER2+ invasive breast carcinoma/DCIS or phyllode tumour before 36; or (iii) invasive breast carcinoma before 46 and another TP53 core tumour (breast cancer, soft-tissue sarcoma, osteosarcoma, central nervous system tumour, adrenocortical carcinoma); or (iv) invasive breast carcinoma before 46 and one first- or second-degree relative with a TP53 core tumour before 56. In contrast, women presenting with breast cancer after 46, without suggestive personal or familial history, should not be tested for TP53.