Genetic and Genomic Tests: What’s the Difference?

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Welcome to the Breastcancer.org Podcast, the podcast that brings you the latest information on breast cancer research, treatments, side effects, and survivorship issues through expert interviews, as well as personal stories from people affected by breast cancer. Here's your host, Breastcancer.org Senior Editor Jamie DePolo.

Jamie DePolo: Hello, thanks for listening. Our guest is Brian Wojciechowski, MD, who practices medical oncology in Delaware County, Pennsylvania, at Riddle, Taylor, and Crozer hospitals and also serves as Breastcancer.org medical adviser. A native of South Philadelphia, he trained at Temple University School of Medicine and Lankenau Medical Center. Dr. Wojciechowski is a sought-after speaker on the topics of medical ethics and the biology of cancer.

If you've been diagnosed with early-stage breast cancer, your doctor may have talked to you about genomic testing. You also may have heard about genetic testing. The names sound familiar, but the tests are very different. And Dr. Wojciechowski is going to help us understand how the tests are used and what the differences are. Dr. Wojciechowski, welcome to the podcast.

Dr. Brian Wojciechowski: Thanks for having me back, Jamie.

Jamie DePolo: So, let's start with genetic testing. What is genetic testing used for, and how is it done?

Dr. Brian Wojciechowski: All right. So genetic testing refers to when we are testing the patient's own inborn genes, their DNA. It's also called germline testing. And the most common reason we would use it in breast cancer patients is to identify mutations that patients are born with, like BRCA1 and BRCA2, in order to help us make decisions about treatment. So, for example, if someone's positive for BRCA1, we would be much more likely to recommend mastectomy, and you know, also being positive for BRCA1 or 2 can sometimes, in some cases, determine which treatments the patients will get in terms of chemotherapy.

Jamie DePolo: Okay, right. And there are specific treatments, I believe — maybe this is for metastatic disease — if you do have a BRCA1 or 2 mutation, PARP inhibitors are likely to be recommended. Is that right?

Dr. Brian Wojciechowski: Yeah, and PARP inhibitors are also now being used, in some cases, in the adjuvant setting when patients are not metastatic. And the genetic testing can impact that decision.

Jamie DePolo: Okay. Yeah. So, you need to know that before you can make those decisions about those treatments.

Dr. Brian Wojciechowski: That's right. Yeah.

Jamie DePolo: Okay. So, how common is genetic testing? I know there's some controversy about it, because some groups believe that anyone diagnosed with breast cancer should have genetic testing, but I believe that is not the current recommendation.

Dr. Brian Wojciechowski: Yeah. And that's a moving target, Jamie, that seems to be changing, month to month sometimes. I would say in terms of how common is it? I think we're testing more than 50%, now, of our breast cancer patients. So, the incidence is going higher and higher.

Jamie DePolo: Okay. And before we move on to genomic testing, I do also want to ask about somebody who has a strong family history but hasn't been diagnosed, also might be a candidate for genetic testing, correct?

Dr. Brian Wojciechowski: That's right, especially if someone in their family has been diagnosed with a genetic cancer susceptibility syndrome.

Jamie DePolo: Okay. And in that case, then you would use the information to potentially make sort of proactive decisions. So, if you knew you had a mutation that gave you a higher risk of breast cancer, you could potentially have preventive mastectomy or start taking some medicine preventively to lower that risk.

Dr. Brian Wojciechowski: Yeah. Yeah, and that's done quite often. I think, isn't that what happened with Angelina Jolie?

Jamie DePolo: I believe that is correct, because her mother had breast cancer. I don't think she's ever been diagnosed, but she tested positive for — I don't remember if it was BRCA1 or 2, but she had a mutation. So, she decided to have a preventive mastectomy, double mastectomy, I should say.

Dr. Brian Wojciechowski: Yeah, and that's exactly what happened. I think you're right. I don't remember that she was diagnosed with cancer.

Jamie DePolo: Okay. So, let's move on to genomic testing. So, what is genomic testing used for, and how is it done?

Dr. Brian Wojciechowski: So, when someone has cancer, the tumor itself also has genes and DNA. And those genes are all messed up because they're cancer cells, and that's one of the definitions of a cancer cell is a cell that's been genetically altered to reproduce uncontrollably. So, the DNA is different than the DNA that the patient was born with, the normal DNA. So, when we test the genes of the cancer itself, of the tumor, we call that genomic testing. And the most common reason we do that is to determine if and what types of chemotherapy and targeted therapy treatments that patient would be eligible for.

How it’s done? Well, it's usually done on the tumor that has already been removed from the body. It can be done on the actual tumor. In some cases, that can be done in the blood just from a blood draw.

Jamie DePolo: Okay. And say somebody had the cancer removed, you know, six months ago. Can the genomic tests be done on preserved tissue, like on preserved cancer tissue?

Dr. Brian Wojciechowski: Yes. It can be.

Jamie DePolo: Okay. And also, you mentioned specific chemotherapies, but I think, in some cases — like I'm thinking of for Oncotype, some of the ones that are very specific to breast cancer — they're looking at the suite of genes that kind of decide, like, okay, can you benefit from specific treatments after surgery? Is that right?

Dr. Brian Wojciechowski: Yeah. In the case of Oncotype, they test 21 genes. And based on that testing, they come up with a score. And depending on what your score is, that would determine if you would benefit from chemotherapy. It also gives you prognostic information. So, it tells you what the prognosis is — the higher the score, the worse prognosis. Or another way to say it is, the higher the chance that the cancer would come back, and therefore, the higher the benefit of chemotherapy.

Jamie DePolo: Okay. And I believe there are a couple other genomic tests for breast cancer. And I'm assuming, say, each specific type of cancer may have different genomic tests — and I'm going to forget all the different names — but isn't there one that tells you how likely distant recurrence is, like metastatic recurrence? Am I remembering that correctly?

Dr. Brian Wojciechowski: I think they all contribute to the distant metastatic recurrence risk to a certain extent.

Jamie DePolo: Oh, okay. Oh, I know what is. I'm sorry. It's a late recurrence. So, I believe one is used to say, “Okay, you've taken five years of hormonal therapy for hormone receptor-positive disease, would you benefit from taking five more years for a total of 10 years?” I think that's right.

Dr. Brian Wojciechowski: Yeah, that's exactly right. And that's for just hormonal therapy, not chemotherapy.

Jamie DePolo: Okay. And so, all these tests are different. So for you, as an oncologist treating somebody, how do you decide if a genomic test is right for somebody and then which genomic test?

Dr. Brian Wojciechowski: So, you have to consider first of all, what is…oh, and I think the test you were referring to was the Breast Cancer Index, maybe?

Jamie DePolo: Okay, that sounds familiar. Yeah.

Dr. Brian Wojciechowski: Yeah. Yeah. So, when I'm considering a genomic test, the first thing I ask myself is, “Is it going to change my recommendation?” If a woman says to me, “I'm 80 years old, there's no way I would do chemotherapy,” then I'm not going to run a genomic test that costs $3,000 to give me information about her, whether she would benefit from chemo if she's going to refuse chemo anyway. So that's the first thing is, is it actually going to, you know, change our course of action.

The other thing you think about for genomic tests is that they're based on the ER/PR status. So, for example, the Oncotype test is really only for ER/PR-positive, HER2-negative patients, whereas another genomic test called the MammaPrint can actually be used for triple-negative, as well. So, those are the main considerations that I take into account. I would say the most common test I've used is the Oncotype, and I think I've used the MammaPrint a handful of times, as well.

Jamie DePolo: Okay. Okay. And then, when you're talking to your patients, and you present this information, it's still kind of a choice. Like you can say, “Here's what the genomic test results show. Here's what I'd recommend. What are your preferences?” I mean, the patient still has input into all this.

Dr. Brian Wojciechowski: That's right. There's always a choice all along the way.

Jamie DePolo: Okay. Do you ever recommend more than one genomic test? Is that ever appropriate for one person?

Dr. Brian Wojciechowski: That would be a very uncommon and unique scenario. I would say 99% of the time, just one or the other is appropriate.

Jamie DePolo: Okay. Okay. And then, if somebody has been diagnosed with early-stage disease — I'm going to kind of stick with that one — and their doctor hasn't mentioned genomic testing, does it make sense to at least bring it up and talk about why somebody is or isn't a good candidate?

Dr. Brian Wojciechowski: I think in medicine, you always have to be your own advocate. Doctors are human beings just like anyone else, and we're not infallible. So, it's possible, you know, that maybe your provider forgot about it or didn't consider it.

In most cases, in breast cancer, you want to be at a place where there's a multidisciplinary team, a group of the various specialists — the chemo doc, the radiation doc, the surgeon, the genetic specialists — so that everything is, you know, so that they cover all the bases. But yeah, I think it makes total sense to bring it up if it has not been brought up. And I think that also applies for genetic testing, as well. Bring it up if it has not been brought up. Like I said, the criteria for genetic testing is always changing, and it seems we're moving in the direction of doing more genetic testing and not less.

Jamie DePolo: Okay, and kind of to make it parallel, in your mind, how common is genomic testing for people who've been diagnosed with breast cancer? Is it really common or is it not so common?

Dr. Brian Wojciechowski: I think it's very common. Yeah, I think it's very common. I think anyone who has early-stage breast cancer, who's ER/PR-positive, probably 75% are going to have some kind of genomic testing.

The ones that will not get genomic testing are probably the ones who are elderly, or for some reason or another are not candidates for chemotherapy, like chemotherapy would do more harm than good. And the other group who would probably not get genomic testing is the person with a very advanced, locally advanced, non-metastatic breast cancer, say, with more than three positive lymph nodes, inflammatory breast cancer, you know — those are the cases where you give chemo no matter what, and you really don't need the genomic test in that case. Another example would be very early stage. So, you know, a node-negative half-centimeter tumor is probably not going to get genomic testing, but there are exceptions.

Jamie DePolo: Okay. And one last question. For the Breast Cancer Index test, I believe that was the one that kind of helps you make a decision about five more years of hormonal therapy. That sounds to me like something that you would do, as the completion of the first five years are coming up. Is that correct, or do people do that closer to diagnosis to sort of make that decision then, or do you take the five years and then do the test?

Dr. Brian Wojciechowski: Yeah, I think the best thing to do is wait a little while and see how someone tolerates the first several years. Some women just sail right through it, and they're eager to continue on to 10. No problem. You know, if she develops osteoporosis, that's another thing that goes into the calculation. But yeah, I think for the most part, you're waiting several years before doing that test.

Jamie DePolo: Okay. And if someone, say, was having very bad side effects from hormonal therapy, that also plays into your decision-making process, too?

Dr. Brian Wojciechowski: It does. Because she might say, “Look, no matter what this test shows, I'm not going to go to 10 years, I'm stopping at five,” or, “I have really bad osteoporosis, and I had a hip fracture, and there's just no way I can go further.” In that case, you're not really going to do the tests, because again, you know, it costs a lot of money, and out-of-pocket expenses can be an issue, and why go through all that if the test is not going to impact your decision making in the end?

Jamie DePolo: Okay. Well, thank you very much, Brian. This has been very helpful, and hopefully we'll be talking to you again in the future.

Dr. Brian Wojciechowski: I hope so.