The American College of Medical Genetics and Genomics (ACMG) has released a clinical practice resource from a global team of specialists in cancer genetics that will help inform the clinical management of patients who harbor a PALB2 variant and may be at increased risk of developing breast, pancreatic, and ovarian cancers. The resource was published by Tischkowitz et al in Genetics in Medicine.
PALB2 Variants
PALB2 germline pathogenic variants are associated with substantially increased breast cancer risk and a smaller increased risk for pancreatic and ovarian cancers. Germline pathogenic/likely pathogenic (P/LP) variants in PALB2 were first associated with increased cancer risk in 2007, and clinical testing has been available since then. It has come to be considered as the third most important breast cancer–related gene after BRCA1 and BRCA2. Despite the emerging importance of this gene, there has been a dearth of resources to guide clinical management of women and men with PALB2 germline P/LP variants.
“PALB2 is sometimes referred to as ‘BRCA3,’ given its importance in risk of breast cancer. People who harbor a germline pathogenic or likely pathogenic variant in PALB2 face challenging questions, especially about their personal risk to develop cancers of the breast, ovaries, and pancreas, and how to manage that risk. In developing this clinical practice resource, we sought to help guide patients and their treating providers to make the best possible decisions based on current high-quality peer-reviewed evidence and a worldwide network of practicing physicians with expertise in cancer genetics,” said Douglas R. Stewart, MD, FACMG, author and past Chair of the ACMG Professional Practice and Guidelines Committee.
Key Guideline Recommendations
Key recommendations include the following:
- Personalized risk estimates (eg, CanRisk) should be used in guiding clinical management
- PALB2 VUS (variants of uncertain significance) should not be used to guide clinical management
- Prospective collection of clinical data from PALB2 patients should be used to establish clear metrics on treatment outcome and survival
- PALB2 patients should be offered similar surveillance to BRCA1/2, modified according to individual risk
- Risk-reducing mastectomy can be considered as an option, guided by personalized risk assessments
- Pancreatic cancer surveillance may be considered in the context of family history, ideally as part of a clinical trial
- Ovarian cancer surveillance should not be offered; risk-reducing salpingo-oophorectomy should include shared decision-making and should rarely be considered before age 50
- Given the mechanistic similarities, PALB2 patients may be considered for therapeutic regimens and trials as those for BRCA1/2.
- ACMG does not recommend testing partners of PALB2 patients in the reproductive setting unless it can be justified by the partner’s family history of cancer.
The clinical practice resource concludes that this guidance is similar to those for patients with BRCA1/2. While the range of the cancer risk estimates overlap with BRCA1/2, it is lower in patients with PALB2 variants, so individualized estimates are important for management decisions. Systematic prospective data collection is needed to determine as-yet unanswered questions, such as the risk of contralateral breast cancer and survival after cancer diagnosis.
“This new document is landmark for the ACMG in a couple of ways,” said Marc S. Williams, MD, FAAP, FACMG, FACMI, President of the American College of Medical Genetics and Genomics. “First, it reflects a commitment of the ACMG to develop guidance for use of germline genetic information for the treatment of patients with cancer. Second, this represents the first of what we hope will be many guidance documents that reflect a diverse, global perspective. The working group included experts on PALB2 from around the world, so that the guidance will have relevance for patients from diverse backgrounds receiving care in a variety of settings.”
Disclosure: For full disclosures of the study authors, visit acmg.net.
