PARP Inhibitors for Breast Cancer Patients with BRCA Gene Mutations: What Italian Experts Recommend

Table of Contents

• Key Points
• Background: Why BRCA Genes Matter in Breast Cancer
• How PARP Inhibitors Work: The Idea of "Synthetic Lethality"
• How This Consensus Was Built
• Who Should Be Offered Genetic Testing
• Single-Gene Testing vs. Multigene Panels
• Using Olaparib in Early Breast Cancer
• Using PARP Inhibitors in Advanced (Metastatic) Breast Cancer
• Follow-Up and Monitoring on PARP Inhibitors
• Imaging After Bilateral Mastectomy
• Hormone Replacement Therapy After Surgery
• Where the Experts Disagreed
• What This Means for Patients
• Limitations of This Consensus
• Practical Recommendations
• Frequently Asked Questions
• Source Information

Key Points

• For triple-negative breast cancer, or hormone receptor-positive breast cancer diagnosed at age 40 or younger, genetic testing should be suggested before treatment starts, regardless of family history, age, or gender.
• At first testing, a multigene panel covering high- and moderate-penetrance genes is preferred over testing BRCA1/2 alone; targeted testing suits families with a known variant.
• In early triple-negative breast cancer with residual disease after neoadjuvant therapy, adjuvant PARP inhibitor is preferred over standard adjuvant treatment, the panel agreed.
• In advanced triple-negative breast cancer, PDL-1 status decides whether chemotherapy plus immunotherapy or a PARP inhibitor comes first, according to the panel.
• Two questions reached no consensus: extra armpit lymph node surgery to qualify for olaparib, and hormone replacement therapy after ovary removal in young BRCA carriers.

Background: Why BRCA Genes Matter in Breast Cancer

About 10% of all people diagnosed with breast cancer carry a pathogenic germline variant (PGV) — an inherited gene change present from birth — in a critical gene such as BRCA1 or BRCA2. These two genes normally act as tumour suppressors, meaning their job is to protect cells from becoming cancerous.

Specifically, BRCA1 and BRCA2 help repair DNA double-strand breaks through a precise process called homologous recombination. BRCA1 sits on chromosome 17 and BRCA2 on chromosome 13. When either gene is faulty, DNA damage accumulates. Telomeres, the protective caps at the ends of chromosomes, shorten. The risk of tumour development rises, especially for breast cancer and ovarian cancer (OC).

The likelihood of finding a BRCA1 or BRCA2 variant depends on the type of breast cancer a patient has:

• Hormone receptor (HR)-positive breast cancer: 3–5% carry a BRCA1/2 variant, most often in BRCA2.
• Triple-negative breast cancer (TNBC) — cancer that lacks oestrogen receptors, progesterone receptors, and HER2 protein: about 12–15% carry a variant, most often in BRCA1.

Finding a BRCA1/2 variant early matters twice over. First, it can change how an already-diagnosed breast cancer is treated — influencing whether surgery is radical or breast-conserving, whether radiotherapy is added, and which systemic (whole-body) drugs are chosen. Second, it allows family members to be tested and to enter special surveillance or risk-reduction programmes.

Italian eligibility criteria for BRCA1/2 testing, adapted from the Italian Association of Medical Oncology (AIOM) guidelines for early breast cancer (published 8 January 2024), cover genetic, personal, and therapeutic reasons. They include:

• A known pathogenic variant in a predisposing gene in a family member.
• No family history but: male breast cancer or ovarian cancer at any age; female breast cancer diagnosed under age 40; TNBC; or bilateral breast cancer diagnosed before age 50.
• Breast cancer at ages 41–50 with a first-degree relative (parent, sibling, child) who had breast cancer under 50. Non-mucinous or borderline ovarian cancer at any age. Bilateral breast cancer, male breast cancer, pancreatic cancer, or prostate cancer.
• Breast cancer over age 50 with a family history of breast, ovarian, and pancreatic cancer in two or more first-degree relatives. Those relatives must be related to each other, and one of them is a first-degree relative of the patient.

Therapeutic indications are reasons based on treatment decisions rather than family history. These include HR-positive early breast cancer with 4 or more positive lymph nodes. They also include residual disease after neoadjuvant therapy (NAT, treatment given before surgery) with a CPS/EG score of 3 or higher. For TNBC, the thresholds are a node-positive tumour (N≥1) or tumour size 2 cm or larger (T≥2 cm). Another threshold is no pathological complete response (pCR, meaning no cancer cells found in removed tissue) after NAT.

How PARP Inhibitors Work: The Idea of "Synthetic Lethality"

PARP inhibitors target poly (ADP-ribose) polymerase, an enzyme (PARP) that helps cells repair single-strand DNA breaks. The first therapeutic "synthetic lethal" interaction identified for BRCA1/2 deficiency was PARP inhibition.

Synthetic lethality is a simple but powerful concept: cells that already have faulty BRCA1/2 cannot repair DNA reliably. If you also block PARP, those cells accumulate so much DNA damage that they die. Normal cells, with working BRCA genes, survive the same drug exposure largely unharmed. This gives a treatment that preferentially kills cancer cells.

Several experimental models have been proposed to explain these effects, including action on single-strand DNA breaks, trapping of PARP-1 at DNA damage sites, and interference with homologous recombination. Whatever the precise mechanism, the clinical result is that patients with breast cancer and BRCA1/2 variants can benefit meaningfully from PARP inhibitors in both the early and advanced settings.

How This Consensus Was Built

A scientific board of 27 internationally recognised Italian breast cancer experts wrote a series of statements on BRCA genetic testing and PARP inhibitor use between March and August 2023. Then, from 30 August to 30 September 2023, a group of 60 Italian local oncologists working in breast units was surveyed using a modified Delphi method.

The Delphi method is a structured survey approach designed to measure how much experts agree or disagree, in order to build a consensus. For each statement, voters chose one of five options:

1. Completely disagree
2. Partially disagree
3. Partially agree
4. Agree
5. Completely agree

Consensus was considered reached only when more than 66.6% of responses fell in one direction (agreement or disagreement). Anything less counted as no consensus. Results were then discussed at a meeting of both the scientific board and the local oncologists using the Nominal Group Technique (NGT) in December 2023.

Of the 60 breast unit specialists surveyed, roughly two-thirds (44 of 60) worked at central hub centres, while 27.1% worked at peripheral spoke centres. About 30% held the position of breast unit coordinator. Participants were spread across Italy, with the north contributing the largest share — Lombardy alone accounted for 30%, and Emilia Romagna, Lazio, and Veneto each contributed 10.2% of the sample.

The survey covered three broad areas: genetic testing of critical genes in breast cancer, patterns of care for patients with BRCA1/2 variants, and management of PARP inhibitors plus follow-up.

Who Should Be Offered Genetic Testing

Consensus was reached on every statement about access to genetic testing. The agreements, with their measured agreement levels, were:

• Triple-negative breast cancer: genetic testing should be suggested before starting cancer treatment, regardless of family history, age, or gender. Agreement level: 98.3%
• HR-positive breast cancer diagnosed at age 40 or younger: testing should be suggested before starting cancer treatment, regardless of family history, age, or gender. Agreement level: 100%
• Patients already eligible because of family history: testing should be proposed for prognostic (outcome-predicting) or therapeutic reasons. Agreement level: 100%
• HR-positive breast cancer with more than 4 lymph nodes involved at surgery: testing should be proposed for therapeutic purposes. Agreement level: 94.9%
• HR-positive breast cancer treated with neoadjuvant therapy, with residual disease and high relapse risk (CPS/EG score of 3 or higher): testing should be proposed for therapeutic purposes. Agreement level: 96.6%

Notice the pattern: for TNBC and very young patients, testing is recommended regardless of family history. The panel treats these cancers as strong enough signals on their own.

Single-Gene Testing vs. Multigene Panels

Consensus was also reached on how to do the testing itself.

• Use a multigene panel covering genes of high and moderate penetrance (for example, fewer than 50 genes) rather than looking only for BRCA1/2 variants. Agreement level: 91.3%
• Targeted testing (looking only at specific genes) is appropriate only when a pathogenic variant has already been identified in the family. Agreement level: 89.7%

In plain terms: when a patient is being tested for the first time, a broad panel gives more useful information. When a relative already knows exactly which variant runs in the family, testing can be narrowed to that single change.

Using Olaparib in Early Breast Cancer

Olaparib was approved for early breast cancer based on the phase 3 OlympiA trial. In that trial, patients were randomly assigned to receive olaparib or a placebo for one year after completing (neo)adjuvant chemotherapy (CT, chemotherapy given before or after surgery).

The trial's eligibility rules were specific. Patients with TNBC needed a pathologically confirmed tumour larger than 2 cm, or a positive lymph node (LN), or failure to achieve pathological complete response after neoadjuvant therapy. Patients with HR-positive disease needed at least 4 confirmed positive axillary (armpit) lymph nodes, or failure to achieve pCR after NAT with a CPS/EG score of 3 or higher.

The panel voted on six statements about where olaparib fits. Five reached consensus:

• TNBC, stage II–III, with BRCA1/2 variants who had NAT with anthracycline/taxane chemotherapy plus platinum salts and still had residual disease afterwards: adjuvant (post-surgery) PARP inhibitor treatment is preferable to standard adjuvant treatment (capecitabine, or continuing pembrolizumab if the KEYNOTE-522 regimen was used). Agreement level: 94.8%
• TNBC, stage II–III, with BRCA1/2 variants who had NAT following the KEYNOTE-522 schedule and had residual disease: combining pembrolizumab with a PARP inhibitor after surgery would be desirable. Agreement level: 87.9%
• HR-positive breast cancer, stage II–III, with BRCA1/2 variants who had NAT and are eligible for olaparib: adjuvant endocrine therapy (ET) plus a PARP inhibitor is preferable to standard adjuvant treatment (ET plus abemaciclib). Agreement level: 96.6%
• HR-positive breast cancer with BRCA1/2 variants and 4 or more positive lymph nodes after surgery who completed adjuvant chemotherapy: ET plus a PARP inhibitor is preferable to standard adjuvant treatment (ET plus abemaciclib). Agreement level: 94.8%
• HR-positive breast cancer with BRCA1/2 variants having limited breast and axillary surgery: proceeding with further axillary surgery (dissection or sampling) to look for 4 or more positive lymph nodes, purely to open access to olaparib, is preferable only in selected cases. Agreement level: 74.2%

One early-setting statement did not reach consensus: whether to always perform further axillary surgery to look for 4 or more positive lymph nodes specifically to qualify a patient for olaparib. Support was 62.1% and disagreement 37.9% — close, but below the required threshold.

For patients with metastatic (spread beyond the breast) HR-positive disease, testing is also relevant. These patients received anthracyclines or taxanes, unless unfit for them. Their disease progressed on endocrine treatment followed by a CDK4/6 inhibitor (cyclin-dependent kinase 4/6 inhibitor) for advanced disease. These patients are covered by the therapeutic indication.

Using PARP Inhibitors in Advanced (Metastatic) Breast Cancer

Two phase 3 randomised clinical trials, OlympiAD (olaparib) and EMBRACA (talazoparib), showed a significant benefit in progression-free survival (PFS — the time before the cancer worsens) for patients with previously treated metastatic HER2-negative breast cancer carrying BRCA1/2 variants. Neither trial showed a statistically significant improvement in overall survival (OS — living longer), and that distinction matters when weighing benefits.

For this indication, TNBC patients should have already received an anthracycline and/or a taxane in the neoadjuvant, adjuvant, or metastatic setting. TNBC patients should also have received platinum-based drugs, unless they were ineligible for those treatments. Patients whose metastatic HR-positive cancer has had no more than three prior lines of treatment can be prescribed talazoparib. Notably, 7.80% of patients in the EMBRACA study had been pretreated with CDK4/6 inhibitors.

All statements about olaparib in the advanced setting reached consensus.

For TNBC with BRCA1/2 variants previously treated with anthracyclines or taxanes:

• If the tumour is PDL-1 negative, first-line treatment with a PARP inhibitor is preferable to standard chemotherapy. Agreement level: 96.6%
• If the tumour is PDL-1 positive, first-line chemotherapy plus immunotherapy (IO) is preferable to a PARP inhibitor. Agreement level: 88%
• If the patient already received chemotherapy plus immunotherapy under the KEYNOTE-522 schedule and the PDL-1-positive disease relapsed, first-line PARP inhibitor is preferable to chemotherapy plus immunotherapy for advanced disease. Agreement level: 91.4%

For TNBC with BRCA1/2 variants previously treated with a platinum-containing regimen in the neoadjuvant or adjuvant phase and relapse after 6 months:

• If PDL-1 negative, first-line PARP inhibitor is preferable to standard chemotherapy. Agreement level: 98.3%
• If PDL-1 positive, first-line chemotherapy plus immunotherapy is preferable to a PARP inhibitor. Agreement level: 86.2%
• After first-line therapy (chemotherapy or chemotherapy plus immunotherapy), a PARP inhibitor is preferable to sacituzumab govitecan or another antibody-drug conjugate (ADC), if accessible, to prevent progression. Agreement level: 91.4%

For HR-positive breast cancer with BRCA1/2 variants:

• This applies after failure of chemotherapy, endocrine therapy, and a CDK4/6 inhibitor in the neoadjuvant or adjuvant setting. A PARP inhibitor is preferable to a CDK4/6 inhibitor as first-line treatment if relapse occurred within 12 months. Agreement level: 96.6%
• The same approach is preferable if relapse occurred after 12 months, though with weaker support. Agreement level: 70.7%
• In the case of early progression on a CDK4/6 inhibitor plus endocrine therapy: a PARP inhibitor is preferable to chemotherapy. Agreement level: 98.3%
• In the case of late progression on a CDK4/6 inhibitor plus endocrine therapy: a PARP inhibitor is preferable to chemotherapy. Agreement level: 94.8%

Follow-Up and Monitoring on PARP Inhibitors

Consensus was reached on how closely patients should be monitored during treatment.

• Before starting: after an initial period of 4–6 months of PARP inhibitor therapy, if the drug is well tolerated, patients should undergo clinical evaluation every three months. Agreement level: 88%

The panel also agreed on a general monitoring statement with 98.3% agreement, covering the structure of routine follow-up for patients on these drugs.

Imaging After Bilateral Mastectomy

For patients with BRCA variants who have had breast cancer and undergone bilateral (both-sided) mastectomy, the panel recommends a specific imaging sequence. It is preferable to perform breast MRI (magnetic resonance imaging) as the first check-up after surgery, to define whether any glandular breast tissue remains. If no residual tissue is found, follow-up can continue with physical examination and breast ultrasound every 6 to 12 months. Agreement level: 84.5%

This recommendation matters because removing both breasts does not guarantee that all breast tissue is gone. Confirming this with MRI prevents unnecessary ongoing scans — or, conversely, catches the small amount of tissue that remains.

Hormone Replacement Therapy After Surgery

This is one of the two questions the panel could not resolve. In young patients with BRCA variants who had surgery for TNBC, bilateral mastectomy plus risk-reducing salpingo-oophorectomy (RRSO) may follow. In these patients, it might be appropriate to consider hormone replacement therapy (HRT) until the age of natural menopause. RRSO is removal of the fallopian tubes and ovaries to lower cancer risk.

The vote was 62.1% in favour and 37.9% against. This fell below the 66.6% threshold, so no consensus was declared. The tension is understandable. Removing the ovaries abruptly drops hormone levels and can cause symptoms and long-term health effects in young women. But HRT after a hormone-sensitive cancer raises safety questions. In TNBC specifically, the cancer is not driven by hormones, which is one argument in favour — but the evidence is not yet settled.

Where the Experts Disagreed

Two areas of divergence became clear, and both deserve attention:

1. Axillary (armpit) surgery for therapeutic purposes. The panel split on whether to always remove or sample more lymph nodes in patients with HR-positive, BRCA-mutated breast cancer who had limited axillary surgery. The purpose would be purely to find 4 or more positive nodes and thereby open access to olaparib. Support reached 62.1%, short of the required threshold.
2. Hormone replacement therapy after bilateral mastectomy and risk-reducing salpingo-oophorectomy in young patients treated for triple-negative breast cancer. Again 62.1% support versus 37.9% disagreement — no consensus.

The authors are explicit that additional research is needed in these specific domains to improve care for breast cancer patients with increased genetic risk.

What This Means for Patients

The unified message from this expert group is that genetic testing and PARP inhibitor therapy are now standard parts of breast cancer care for people with BRCA1/2 variants. But the details matter enormously.

If you have triple-negative breast cancer, or HR-positive breast cancer diagnosed at age 40 or younger, genetic testing is recommended before you start cancer treatment, even with no family history. That is a change from older practice, where family history often drove testing decisions.

If you carry a BRCA1/2 variant, the specific placement of a PARP inhibitor depends on several factors. These factors are your cancer subtype, your stage, how many lymph nodes were involved, whether you had neoadjuvant therapy, how much residual disease remained, and your PDL-1 status.

For patients with PDL-1-positive TNBC, the experts favour chemotherapy plus immunotherapy first — with a PARP inhibitor reserved for later. For PDL-1-negative TNBC, a PARP inhibitor moves to the front of the line. This is a nuanced, biomarker-driven decision, not a one-size-fits-all rule.

One practical point stands out. Olaparib in the early setting requires 4 or more positive lymph nodes in HR-positive disease. Because of this, there is genuine debate about whether to perform extra lymph node surgery to meet that threshold. Patients facing this decision should discuss the trade-offs — surgical risks versus access to a targeted drug — with their breast surgeon and oncologist.

Limitations of This Consensus

A few important caveats apply when interpreting this work.

First, this is a consensus document, not a clinical trial. It reflects the collective judgement of Italian breast cancer specialists, weighted by measured agreement levels, rather than head-to-head evidence comparing every treatment choice.

Second, agreement levels alone do not measure certainty. Some statements reached consensus with 100% agreement; one (relapse after 12 months) reached only 70.7%, and others hovered just above the 66.6% threshold. A statement can technically achieve consensus while remaining genuinely contested.

Third, the surveyed group was heavily weighted toward central hub centres (44 of 60 participants), so the views expressed may not perfectly reflect practice in smaller peripheral centres.

Fourth, reimbursement rules in different countries and regions do not always align with clinical evidence. The panel notes that clinical use of PARP inhibitors may compete with alternative treatment options in both early and metastatic settings. The panel also notes that local reimbursement policies can constrain what is actually available to patients.

Finally, the two areas without consensus remain open questions. The panel is candid that further research is needed.

Practical Recommendations

1. Ask about genetic testing early. If you have TNBC, or HR-positive breast cancer diagnosed at 40 or younger, testing should be offered before treatment begins — regardless of family history, age, or gender.
2. Advocate for a multigene panel at first testing rather than BRCA1/2 alone, unless a specific family variant is already known.
3. Understand where a PARP inhibitor fits your situation. In early TNBC with residual disease after neoadjuvant therapy, adjuvant PARP inhibitor is preferred over standard treatment. In early HR-positive disease with 4 or more positive nodes or high-risk residual disease, ET plus a PARP inhibitor is preferred over ET plus abemaciclib.
4. Know your PDL-1 status if you have TNBC. It determines whether immunotherapy or a PARP inhibitor comes first in the advanced setting.
5. Plan monitoring every three months after the first 4–6 months of PARP inhibitor therapy, if the drug is well tolerated.
6. After bilateral mastectomy, a breast MRI is the preferred first post-surgical check. If no glandular tissue remains, physical examination and ultrasound every 6–12 months can follow.
7. Discuss unresolved questions openly. Decisions about extra axillary surgery and hormone replacement therapy after ovary removal are not settled. Ask your team to walk you through the trade-offs.

Frequently Asked Questions

I have triple-negative breast cancer. Should I have genetic testing?

An Italian expert panel agreed that genetic testing should be suggested before starting cancer treatment for anyone with triple-negative breast cancer, regardless of family history, age, or gender. Agreement was 98.3%. This marks a shift from older practice, where family history often drove testing decisions. Testing can change how your cancer is treated and allow relatives to be tested.

I was diagnosed with hormone receptor-positive breast cancer at age 38. Does that change my testing?

Yes. The panel agreed, with 100% agreement, that genetic testing should be suggested before starting cancer treatment for hormone receptor-positive breast cancer diagnosed at age 40 or younger. This applies regardless of family history, age, or gender. Finding an inherited BRCA1 or BRCA2 variant early can influence surgery, radiotherapy, and which systemic drugs are chosen.

What is a PARP inhibitor and how does it work?

PARP inhibitors block an enzyme that helps cells repair single-strand DNA breaks. Cells with faulty BRCA1 or BRCA2 already cannot repair DNA reliably. Blocking PARP as well causes so much DNA damage that those cells die, while normal cells with working BRCA genes largely survive. This is called synthetic lethality, and it preferentially kills cancer cells.

I have early triple-negative breast cancer with residual disease after neoadjuvant therapy. What is preferred?

This applies to stage II–III triple-negative breast cancer with BRCA1/2 variants who had neoadjuvant anthracycline/taxane chemotherapy plus platinum salts and still had residual disease. The panel agreed (94.8%) that adjuvant PARP inhibitor treatment is preferable to standard adjuvant treatment such as capecitabine. It is also preferable to continuing pembrolizumab if the KEYNOTE-522 regimen was used.

Does PDL-1 status affect which treatment I get first for advanced triple-negative breast cancer?

Yes. This applies to advanced triple-negative breast cancer with BRCA1/2 variants previously treated with anthracyclines or taxanes. The panel agreed that if the tumour is PDL-1 negative, first-line PARP inhibitor is preferable to standard chemotherapy (96.6% agreement). If PDL-1 positive, first-line chemotherapy plus immunotherapy is preferable to a PARP inhibitor (88% agreement).

How often will I be monitored while taking a PARP inhibitor?

The panel agreed (88%) that after an initial 4–6 months of PARP inhibitor therapy, if the drug is well tolerated, patients should undergo clinical evaluation every three months. A separate general monitoring statement reached 98.3% agreement, covering the structure of routine follow-up for patients on these drugs. Your own team will set your exact schedule.

I had both breasts removed. What imaging follow-up is recommended?

For BRCA variant carriers who had breast cancer and bilateral mastectomy, the panel recommends breast MRI as the first check-up after surgery, to see whether any glandular breast tissue remains. If none is found, follow-up can continue with physical examination and breast ultrasound every 6 to 12 months. Agreement was 84.5%. Removing both breasts does not guarantee all breast tissue is gone.

When should a patient with BRCA1 or BRCA2 breast cancer seek a second opinion about PARP inhibitor treatment or extra lymph node surgery?

A second opinion is worth considering when the plan hinges on a contested decision. The expert panel could not agree on whether to remove or sample more armpit lymph nodes. The aim would be purely to find 4 or more positive nodes and open access to olaparib in HR-positive disease. The panel also left hormone replacement therapy after ovary removal unresolved. Because PARP inhibitor placement depends on subtype, stage, node count, residual disease and PDL-1 status, an independent review can clarify whether the recommendation fits your situation. Diagnostic Detectives Network provides independent expert second opinions.

Source Information

Original article title: Parp-inhibitors in the therapeutic landscape of breast cancer patients with BRCA1 and BRCA2

Authors: Alberto Zambelli, Laura Cortesi, Mariangela Gaudio, Grazia Arpino, Giampaolo Bianchini, Francesco Caruso, Saverio Cinieri, Giuseppe Curigliano, Lucia Del Mastro, Sabino De Placido, Alessandra Fabi, Lucio Fortunato, Daniele Generali, Alessandra Gennari, Stefania Gori, Giovanni Grandi, Valentina Guarneri, Marco Klinger, Lorenzo Livi, Caterina Marchiò, Isabella Palumbo, Pietro Panizza, Gabriella Pravettoni, Giancarlo Pruneri, Fabio Puglisi, Anna Sapino, Corrado Tinterri, Daniela Turchetti, and Michelino De Laurentiis.

Publication: Cancer Treatment Reviews, volume 130 (2024), article 102815. Published by Elsevier. Received 5 April 2024; revised 26 July 2024; accepted 15 August 2024; available online 21 August 2024. Open access under a CC BY-NC-ND license. DOI: https://doi.org/10.1016/j.ctrv.2024.102815

Corresponding author: Mariangela Gaudio, Humanitas University and Humanitas Clinical and Research Center-IRCCS, Humanitas Cancer Center, Rozzano, Milan, Italy.

This patient-friendly article is based on peer-reviewed research. It is intended for educational purposes and does not replace personalised medical advice. Treatment decisions should always be made with your own oncology team.