In this second episode of OncChats: Leveraging Endoscopic Ultrasound in Pancreatic Cancer, Toufic A. Kachaamy, MD, Madappa Kundranda, MD, PhD, and Tamas A. Gonda, MD, discuss the techniques used such as endoscopic ultrasound–guided biopsies to collect adequate tissue to perform genomic analyses in pancreatic cancer, and the likelihood for finding actionable mutations in this population.
In this second episode of OncChats: Leveraging Endoscopic Ultrasound in Pancreatic Cancer, Toufic A. Kachaamy, MD, of City of Hope, Madappa Kundranda, MD, PhD, of Banner MD Anderson Cancer Center, and Tamas A. Gonda, MD, of NYU Langone, discuss the techniques used such as endoscopic ultrasound (EUS)–guided biopsies to collect adequate tissue to perform genomic analyses in pancreatic cancer, and the likelihood for finding actionable mutations in this population.
Kachaamy: When you talk about genomic analysis and pancreatic adenocarcinoma, can you elaborate a little bit on the technique needed to ensure tissue adequacy for testing?
Gonda: Yeah, so I think over the past maybe 3 [to] 6 years, biopsy techniques have really evolved from providing a cytologic analysis with a fine needle aspiration; [this] really was a method used to establish very accurate diagnosis of pancreatic cancer and cancer cells. Increasingly, with these advanced molecular and other diagnostic methods, the need emerged to [test] larger volume of tumor, and in many cases, histologically intact tumor samples.Essentially, fine needle biopsy or core needle biopsy methods, which are now pretty much standard and probably can be used in essentially all cases of pancreatic tumor biopsies, have taken a hold. These methods allow us to, with high accuracy, perform any of the currently standard molecular immunohistochemical analysis on these tumor samples.
Kachaamy: So, when you say it has become standard, do you have a special guidance on what gauge needle to use or how many passes to get adequate tissue? We know that molecular testing [results] take time to come back.
Gonda: Right. I think there are essentially a range of sizes and techniques [for obtaining] the specimens and I generally think that there isn’t a huge difference in the safety and the complication rates [when] using these needles. To some extent, ‘the more tissue, the better’ is a reasonable principle to guide sampling. For that reason, what drives the choice of needles, at least in my practice, is technical feasibility and accessibility of the lesion. I think it is very reasonable for most pancreatic tumors to at least use a 22-gauge needle, which is sort of the middle of the road, and if possible, and technically and procedurally feasible, then I think using a 19-gauge needle may provide a slightly greater amount of tissue. It’s usually not necessary to [use the 19-gauge needle; as long as] one of these core needle methods [are used], I think a 22-gauge needle provides a greater than 90% ability to perform all analyses beyond the histology that one would consider at the up-front diagnosis, [at least in my experience.]
Kachaamy: Any thoughts on how often you [will] find an actionable mutation? You have mentioned [that we may see them in] 10% to 20% [of cases]. Was that what you were referring to?
Gonda: Yeah, I think that has been [seen] in several studies, including one that we conducted. That’s the range [in which] we’re currently identifying actionable mutations. Of course, to some extent, this will hopefully evolve, both as we understand more mutations and as more of them are targetable. However, I think at this point, that’s [what we’re seeing.] There are some specific scenarios and some publications that have found [mutations] in a greater number of tumors. Again, you mentioned in the beginning [of our discussion], that we’re focusing on pancreatic adenocarcinoma. Perhaps that number is slightly different when you include neuroendocrine tumors and other cancers; however, for adenocarcinoma, [around] 10% to 15% [of patients] may have an actionable mutation.
Check back on Tuesday for the next episode in this series.