I have no medical training, but will share some thoughts, partly in backward order.

I also had a "resectable" PDAC tumor in the head of my pancreas and no evidence of spread; did 6 months of chemo (mFolfirinox) followed by Whipple at a center of excellence with clear margins and 22/22 lymph nodes clean. My cancer was back at the original tumor site (head of pancreas) in 3.5 months.

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With that said, the more you cut out, the less chance there is of cancer remaining. Invisible cancer at the margins can kill. The pathology they do during surgery is far from perfect/definitive. In my case, the surgeon's first slice still had malignant cells visible, so he sliced off some more, which came back clean, and then sewed me back up.

When the cancer came back, it was right at the "anastomosis" where he rejoined my remaining pancreas to the jejunum. We don't know for sure if there were other malignant cells at the margin that weren't detected in pathology, if there were malignant cells slightly farther inside from the slice that couldn't be examined, or if cells in the remaining pancreas simply turned malignant after the surgery. I was not receiving adjuvant chemo, and whatever was waiting grew back really fast: It was not visible on MRI a month after surgery, and was not detected by ctDNA tests, but had grown to almost 2 cm 2.5 months after the first MRI and metastasized before we were able to begin treatment.

Since the tumor first reappeared on imaging at the original surgical site, and the mets were distant (not physically touching the tumor site) rather than local, it's very unlikely malignant cells hiding elsewhere made their way back to the original site; far more likely that malignant cells were either missed at the original site, or that other cells turned malignant in that non-chemo period after surgery.

I have a germline ATM mutation, which increased my chance of developing pancreas cancer. I assume that also includes risk of developing new cancer in whatever remaining pancreas was clean upon completion of the Whipple. In hindsight, understanding the imperfect pathology and the increased risk from ATM, I would have requested a TOTAL pancreatectomy instead of just a Whipple.

In your case, I don't know if you've had the genetic tests to evaluate germline risks and tumor somatic characteristics, but those should play a part in discussions with your surgical and medical oncologists.

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Regarding your case, since you mention Whipple, I assume the cancer is in or near the head of your pancreas. I don't know if it has invaded the main pancreatic duct, and I don't know if the surgeon can just "take out the obvious cancer" near the duct and still maintain structural integrity of the duct itself, but you could ask. I'm guessing one piece of the Whipple they've learned from experience is how to cut the right shapes in order to best reconnect the plumbing, whether it's as perpendicular as possible to the pancreas or its duct, or at some optimal angle. Taking a surgical approach they don't normally take might increase the chance of complications like leakage. Again, I don't know, but it's something to ask the surgeon.

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Three days after my recurrence was detected on MRI, I returned to the same center of excellence for an EUS biopsy, which came back negative for malignant cells. The surgeon was absolutely sure if cancer was present, his procedure would have gotten malignant samples. I think this highlights the imperfect lab pathology and the risk of cutting too conservatively during surgery. Just my opinion, but now that I'm Stage-4, it's a hard opinion to shake.

Many in the oncology field believe that even when cancer is first detected and declared resectable, it has already spread somewhere. Part of the push for neoadjuvant chemotherapy (before surgery) is to see which patients will have no detectable spread during chemo, and spare them from surgery metastases pop up and are not controllable with chemo.

I have trouble with that approach, also based on my experience with 6 months of Folfirinox not getting much of a response. It felt like wasted time. I'm in the camp of preferring to take out the cancer you know is there with an approach that you know will work, rather than first treating cancer that *might* be elsewhere with a therapy that *might* kill it. The professionals are still studying and debating both sides, and I'm just a sample of one, but my outcome has uncontrollably biased my position to the former. And when it comes to the cuts, I'm thinking, "In for a dime, in for a dollar... Get it ALL!"

There are the issues of insulin production and enzyme production to consider. You might become an insulin-dependent diabetic if more pancreas is taken out, and you might need digestive enzymes like creon if more pancreas is taken out. But you might also experience those just due to a failing pancreas as well, as I was with insulin before Whipple, and am now with enzymes after. I would gladly go get the rest of my pancreas and spleen removed now if that removed all the tumors from my body, but there others elsewhere in my abdomen that render it moot.