Testing and BRAF Mutations in Melanoma

Axel Hauschild, MD, PhD: The crucial question for all of us in tumor boards is if you have a BRAF-mutated patient. We are only discussing patients once the BRAF-mutation status is available, correct?

Dirk Schadendorf, MD: Yes, that’s correct. For some time, it has also been that the German guidelines have recommended to test the odds of patients who have no metastatic disease for BRAF mutation, definitely in stage III. For example, for years now, this could have therapeutic consequences. If you have thick primary tumors or other risk criteria, it’s strongly recommended to do the BRAF testing on the primary tumor.

Axel Hauschild, MD, PhD: That’s very important to say because if you have a tiny micrometastasis on the sentinel node, you might not be able to test for BRAF mutation, so you need to go back to the primary tumor. We are also expecting to have clinical trials in stage II. Mainly, there are 2 trials in Germany right now, or it was 2 trials that were open, and it is now only 1 trial open for recruitment.

There is also 1 clinical trial in progress in the planning phase for 2021 that is using BRAF and MEK inhibitors. Therefore, we eventually need to test from stage IIA onward. Do you think it’s difficult to make this a routine procedure in the German dermatologic oncology environment?

Dirk Schadendorf, MD: Testing thin tumors is challenging not only in Germany, it’s also challenging across the board, because testing for BRAF mutation is also dependent on the amount of tumor in your sample in your primary tumor. If you have thin tumors, 1 mm or a little bit more than 1 mm, enriching for tumor cells is not trivial because all the molecular methodology is dependent on a certain percentage of tumor cells in your sample in order to be correctly positive or negative. The chance that you have false negative results is obviously a risk in very thin tumors.

Axel Hauschild, MD, PhD: Can you give a brief comment to us about whether immunohistochemistry would be an alternative, yes or no? Which test is used as a PCR [polymerase chain reaction] test to detect V600 mutations in your center?

Dirk Schadendorf, MD: Yes. For stage III and stage IV disease, most of the larger centers use NGS [next-generation sequencing] gene panels, which are larger panels that include not just the BRAF mutation.

Axel Hauschild, MD, PhD: NGS standing for next-generation sequencing.

Dirk Schadendorf, MD: Yes, it’s next-generation sequencing. For BRAF testing only, PCR technology is sufficient, and it’s the cheapest way to do it. We then have immunohistochemistry techniques available, which are based on antibodies that are usually specific for V600E mutations of the BRAF gene and only that.

You have some countries and some centers that are doing that, a prescreen with immunohistology and the antibody. If this is negative, only in that case, subsequent molecular testing is done.

One also has to keep in mind that there are some specified molecular tests, like the Cobas test for example, which is detecting only a certain fraction of BRAF V600 mutations. The high-specificity V600E and V600K are a percentage, but other, less frequent mutations like V600M, V600D, and so on are not detected. For that, you need molecular techniques.

Transcript Edited for Clarity