Selection of Germline Genetic Testing Panels in Patients with Cancer Guideline
Ms. Charité Ricker, MS, CGC and Dr. Nadine Tung, MD, FASCO share updates from the new ASCO guideline on selection of germline genetic testing panels in patients with cancer. They discuss highlights on family history collection, when and how multigene panel germline genetic testing should be used, which genes are generally recommended for testing, and how germline genetic testing interfaces with somatic genetic testing. Ms. Ricker and Dr. Tung also note the importance of the guideline and the impact of these new recommendations on clinicians and patients with cancer.
Read the full guideline, “Selection of Germline Genetic Testing Panels in Patients with Cancer: ASCO Guideline” at www.asco.org/molecular-testing-and-biomarkers-guidelines.
TRANSCRIPT
GDL 24E13
This guideline, clinical tools, and resources are available at www.asco.org/molecular-testing-and-biomarkers-guidelines. Read the full text of the guideline and review authors’ disclosures of potential conflicts of interest in the Journal of Clinical Oncology, https://ascopubs.org/doi/10.1200/JCO.24.00662
Brittany Harvey: Hello and welcome to the ASCO Guidelines Podcast, one of ASCO’s podcasts delivering timely information to keep you up to date on the latest changes, challenges and advances in oncology. You can find all the shows, including this one at asco.org/podcasts
My name is Brittany Harvey, and today I'm interviewing Dr. Nadine Tung, a medical oncologist from Beth Israel Deaconess Medical Center in Boston, and Ms. Charité Ricker, a cancer genetic counselor with the Norris Comprehensive Cancer Center at the University of Southern California and Los Angeles General Medical Center, co-chairs on, “Selection of Germline Genetic Testing Panels in Patients with Cancer: ASCO Guideline.”
Thank you for being here, Ms. Ricker and Dr. Tung.
Dr. Nadine Tung: Pleasure.
Ms. Charité Ricker: Thank you.
Brittany Harvey: Then, before we discuss this guideline, I'd like to note that ASCO takes great care in the development of its guidelines and ensuring that the ASCO conflict of interest policy is followed for each guideline. The disclosures of potential conflicts of interest for the guideline panel, including Dr. Tung and Ms. Ricker, who have joined us here today, are available online with the publication of the guideline in the Journal of Clinical Oncology, which is linked in the show notes.
So then, to start us off first, Dr. Tung, could you provide us a broad overview of both the purpose and scope of this guideline?
Dr. Nadine Tung: Sure. A main impetus for creating the guideline is that oncologists are increasingly being tasked with ordering genetic testing for hereditary cancer risk for their cancer patients. More and more now, they may find themselves sending the test and then seeking guidance from genetic experts to interpret the result. And these panels range from focused tests with just a few genes to comprehensive ones that include over 100 genes. So it can be very overwhelming for an oncologist to be able to understand ordering these tests and explaining them to their patients. So, we believe that it was important to offer some guidance and direction on the use of these multigene panels.
Brittany Harvey: Thank you for setting the stage for this guideline and the recommendations that come from it.
So then, Ms. Ricker, this guideline addresses four overarching clinical questions. I'd like to review the recommendations based on each of those questions for our listeners. So starting with that first question, what is the importance of family history collection in the setting of germline multigene panel testing and which elements of family history are the most important?
Ms. Charité Ricker: Thanks. As a genetic counselor, this is probably one of my favorite questions. I love the opportunity we have to sit with families and really dig into family history. But family history collection can be overwhelming and a big lift sometimes in busy clinics where genetics is not the focus. So, what we tried to do was to break down the key elements of what components of family history are most relevant to informing which test to do, and also the interpretation of those test results. And I like to think about the key pieces of family history as being the who, what, and when of somebody's family cancer history. Who was diagnosed with cancer within their close relatives? And usually we're most focused on first and second degree relatives. So parents, siblings, grandparents, aunts, and uncles. But sometimes relevant history might go into third degree relatives like cousins or more distant. So the who being who has cancer on both sides of the family? And then the what: what kind of cancer was it? Or where did that cancer begin? And the when: how old was that individual at the time they were diagnosed? Often we ask patients maybe not to fixate on the exact age, but to give us a sense. So was this somebody who was diagnosed young, in their 20s or 30s or older, in their 60s or 70s? Because that at least gives us a ballpark around what might be relevant for understanding the genes that should be included on somebody's test.
When we are thinking about the purpose of this history, as Dr. Tung said, often the range of multigene panels might be from a few very focused genes to a very broad panel. Family history can help us understand if we need to step beyond the very focused genes that might be relevant for the patient's history of cancer and include other genes that might be indicated based on that family history. So I think about the role that family history has at the time of identifying which test to do and then its role when interpreting what those results mean for the patient and their family. Again, Dr. Tung touched on the fact that we are often testing very large panels. However, we still don't know everything. And so a negative genetic test result does not mean that somebody does not have additional cancer risk. And family history becomes our kind of guiding star for understanding if there is still a need to change the cancer screening and prevention management for that individual and their family members.
Brittany Harvey: Absolutely. Those are key points to understanding the important role of family history for each individual patient.
So then moving to the next clinical question, Dr. Tung, what does the panel recommend regarding when and how multigene panel germline testing should be used, when germline genetic testing is indicated?
Dr. Nadine Tung: Well, anytime multiple genes need to be tested, as Ms. Ricker said, because of the patient's own personal cancer history, or their family history of cancer and close relatives, it's appropriate to consider a multi-gene panel. And in truth, we rarely ever just order one gene these days. Perhaps we do if there's a known gene like a BRCA gene in the family, and a relative just wants to know if they have that. But it's not all that common. And to be clear, as Ms. Ricker is going to cover a bit later, we are recommending that the appropriate minimal panel at least include the genes relevant to the patient's own cancer and the cancers in their relatives.
But it's worth thinking about what are some of the pros and cons of ordering genes beyond that, beyond the patient's own cancer or their relatives? Well, for pros, since a patient's awareness of their family history may be incomplete, testing for a larger number of cancer risk genes does ensure that significant pathogenic variants won't be overlooked. And sometimes, even if the family history is well known, pathogenic variants in important cancer risk genes can be found even when the family history would not have prompted testing for them. But it is important for clinicians to appreciate that bigger isn't necessarily better. Some larger panels may include genes for which management of pathogenic variants is not entirely clear and that can create anxiety or unnecessary screening. And if the clinician receiving the information is not well informed about the significance of the finding, that can lead to unnecessary treatment and sometimes even unnecessary surgeries.
And I'd add one final point that clinicians must have a system for communicating reclassification of these variants, the ones with uncertain significance that we call VUS. Because as the number of genes tested increases, so does the likelihood of encountering these VUS. So I would say those are some of the main points about when to use the panel and when to think about larger or smaller panels.
Brittany Harvey: Yes, I appreciate you reviewing both the pros and cons of expanding the genes included in multi-gene panel testing and the importance of variants of uncertain significance.
So then Dr. Tung just touched on this, but speaking of minimal panels and which genes should be included, Ms. Ricker, what are the recommendations on which genes are generally recommended for germline genetic testing?
Ms. Charité Ricker: I think this is one of the harder questions that our group took on as we were working on this guideline. I don't think there is a one size fits all and one easy answer to this question. However, we chose to approach it by selecting the more common solid tumors that oncologists see in their clinics and the ones where the role of genetic testing is most well defined, as well as some very rare tumors where they're kind of easy. So we know that all individuals with certain types of cancers, even though they are rare, should merit genetic testing regardless of age of diagnosis, family history.
And so as we approached it, and I really appreciate ASCO’s support in helping us develop some tools and tables that hopefully will be important aids for clinicians who are trying to make these decisions, we took the approach of, as Dr. Tung mentioned, selecting kind of a minimal set of recommended genes where most individuals who are informed in this area would agree that if nothing else was done, these genes should be done, but then also acknowledged that there is an expanding understanding about the impact of certain genes on cancer risk, and so then also provided a kind of a next level if somebody wanted to be more expansive, what we would recommend less strongly, but would be reasonable to consider. Then I think the other last piece that the committee felt was important to acknowledge is that given how common, in comparison to some of these genetic conditions that we work with, pathogenic variants in BRCA1 and BRCA2 can be, and also the important clinical impact of those genes along with the genes associated with Lynch syndrome, we felt that those were important to think about in the setting of all cancer patients. So if you're approaching a panel and thinking about what genes to include, looking at that kind of minimally recommended based on the patient's personal and family history, maybe the next level, which might include some additional genes that we have included in kind of the less strongly recommended category for those tumor types. And then consideration of the BRCA1 and 2 genes and genes associated with lynch syndrome, if they weren't already encapsulated by your other personal and family history considerations.
Brittany Harvey: Definitely. This was a big lift for the panel to tackle, and the tools and tables that you mentioned are all available online with the publication in the Journal of Clinical Oncology. So listeners who are looking for more specifics on that can definitely refer to those tools and tables there.
Dr. Tung, the last clinical question: which patient should be offered germline genetic testing, who will have or who have previously had somatic genetic testing?
Dr. Nadine Tung: Identifying which genes identified through the tumor testing should trigger germline testing is really important for assessing our patients’ future risk of cancer and their relatives. So during the development of our guidelines, the ASCO expert panel became aware that the ESMO Precision Medicine Working group had updated their recommendations for this topic, namely germline testing in response to tumor test findings. And these recommendations were based on the Memorial Sloan Kettering IMPACT registry, which consists of nearly 50,000 tumors and paired germline testing. Given the sheer volume of that data and the methods that ESMO used, our group decided to use that as a framework to develop our recommendations. The ASCO guideline provides a list of genes that, if found in the tumor, a pathogenic variant in those genes may prompt germline testing.
And we offered or proposed two different approaches. The first approach, which is broad and perhaps simplest, involves doing germline testing if a pathogenic variant is found in any of the genes listed. But then we offer a conservative approach to test the germline for all highly actionable genes, like BRCA1 and 2, or lynch genes that are found in a tumor, but for less actionable genes, testing the germline only if the pathogenic variant is found in a tumor relevant to that gene. So, for example, ATM, if found in breast cancer or pancreatic cancer, would trigger germline testing with this approach, but not if found in lung cancer, whereas with the permissive first approach, you would simply test the germline if any pathogenic variant is found in any of the genes on the list. This latter, more conservative approach, while less sensitive for identifying every germline pathogenic variant, increases the likelihood that a pathogenic variant found in the tumor will actually be germline. That approach considers the limited resources available, such as genetic counselors, and respects trying not to overwhelm a system already stressed.
Brittany Harvey: Thank you for reviewing both of those approaches and to you both for discussing all of the recommendations included in this guideline.
Finally, to wrap us up, in your view, Ms. Ricker, what is the importance of this guideline and how will it impact both clinicians and patients with cancer?
Ms. Charité Ricker: I hope that this guideline can open the door for more expansive and appropriate utilization of germline genetic testing. For me, I think about, from both the clinical and patient side, for example, all ovarian cancer patients have had a recommendation for germline genetic testing for many years. Nonetheless, data from multiple research studies has shown us that ovarian cancer patients still are not being tested universally, and this has important implications for their treatment plans and for their family members. And so even in the setting where genetic testing, if I can use the phrase, has been simple in that it didn't require family history, it didn't require even a specific age criteria, it was just broad, testing is not utilized as much as it should be, and then you step into the world of more complex decision making around genetic testing for other tumor types. And so we hope that this provides a framework to simplify that decision making process for providers to increase appropriate utilization.
And then from the patient perspective, I also think about the lack of access of genetic testing in underrepresented communities and minoritized patient populations where there's many barriers that patients face in accessing genetic services. And so if we can help reduce the barriers for this piece of the genetic testing process, my hope is that that opens up better avenues for access to testing, not just for patients with certain tumor types, but for all patients from all communities and backgrounds.
Brittany Harvey: Yes, those are key points. We hope that this guideline helps all patients access the appropriate testing to better inform their cancer prevention and treatment.
So I want to thank you both so much for your work on this comprehensive guideline on germline genetic testing and all of the work that you put into it. And thank you for your time today. Ms. Ricker and Dr. Tung,
Dr. Nadine Tung: Thank you.
Ms. Charité Ricker: It was a pleasure to be here. Thank you.
Brittany Harvey: And thank you to all of our listeners for tuning in to the ASCO Guidelines Podcast. To read the full guideline, go to www.asco.org/molecular-testing-and-biomarkers-guidelines. You can also find many of our guidelines and interactive resources in the free ASCO Guidelines app, available in the Apple App Store or the Google Play Store. If you have enjoyed what you've heard today, please rate and review the podcast and be sure to subscribe so you never miss an episode.
The purpose of this podcast is to educate and to inform. This is not a substitute for professional medical care and is not intended for use in the diagnosis or treatment of individual conditions.
Guests on this podcast express their own opinions, experience, and conclusions. Guest statements on the podcast do not express the opinions of ASCO. The mention of any product, service, organization, activity, or therapy should not be construed as an ASCO endorsement.
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