Ashish Kamat: Hello, everyone. Welcome to UroToday's Bladder Cancer Center of Excellence. I'm Ashish Kamat, urologic oncologist in Houston, Texas, and it's a pleasure to welcome Wei Shen Tan back to the forum. Welcome, Shen.

Wei Shen Tan: Thanks so much, Dr. Kamat, as well as UroToday for the opportunity to speak on our recent review that we just published. So the title of this review is on partial cystectomy for muscle-invasive bladder cancer, and in this review we discuss patient selection, the techniques and outcomes following partial cystectomy. So this is the review that we published in Cancers. In the next couple of slides, I'll just talk you through and summarize what we discussed within the review. So radical cystectomy remains the standard of care for muscle-invasive bladder cancer, although it does have a high morbidity rate, so there's a high complication rate, as well as a small but significant risk of mortality. Efforts such as minimally invasive cystectomy have been popularized in our efforts to try to minimize morbidity, although it still remains a fairly morbid procedure. There are significant impacts to patients' quality of life following cystectomy such as physical, cognitive, emotional, urinary, as well as sexual function. And partial cystectomy in very selective cases would offer shorter length of stay, lower morbidity, as well as mortality. And the aim would be to try to preserve—to maintain oncological outcomes.

So partial cystectomy remains fairly underutilized despite it being in the NCCN guidelines. As you can see here, it is an option in highly selected patients with solitary lesions in a suitable location without CIS. And also, when patients who undergo bladder preservation in the form of chemoradiation, if there is recurrence, they may be a candidate depending on location and some of these other features that we'll discuss shortly. In terms of indications for partial cystectomy, urachal cancers as well as diverticular tumors are established indications that would benefit from partial cystectomy, although in patients with muscle-invasive bladder cancer, approximately just 5% to 10% of patients may be suitable. This table here summarizes the different guidelines and their recommendations. As you can see, the AUA guidelines, EAU guidelines, which do recommend partial cystectomy, NCCN guidelines and the IBCG guidelines.

And if you pull together some of the indications and selection criteria, location is key. So ideally, in the dome or an area where the tumor can be resected very safely with negative margins. Tumor should be solitary, small T2, and less than 3 cm. It should have absence of CIS and no multifocal disease. And in the IBCG, the recommendation was in the absence of variant histology because some of the diseases with variant histology would be quite aggressive. And these represent a very selective group of patients, and it's important to appreciate that partial cystectomy is not standard of care for muscle-invasive bladder cancer. In terms of the workup, patients should have preoperative labs to look at renal function, make sure their urine culture is negative, staging cross-sectional imaging, and also CT urogram will be quite useful to delineate their ureteric anatomy in patients where ureteric reimplantation may be necessary, and also to confirm the absence of metastatic disease.

Patients should have a radical TURBT to minimize tumor spillage, to debulk as much tumor as possible and clear the disease prior to partial cystectomy. Mapping biopsies or enhanced cystoscopy like blue-light cystoscopy would be very useful to rule out the presence of CIS. And the goals for this are to exclude metastatic disease, minimize tumor spillage, and confirm that there's no evidence of CIS within the bladder. Key points: it's important to appreciate that the role of neoadjuvant systemic therapy for muscle-invasive bladder cancer still remains. So whether you're doing partial cystectomy or radical cystectomy, patients should have neoadjuvant chemotherapy. Lymph node dissection is also recommended even in patients with partial cystectomy, and cystoscopy surveillance as well as urinary cytology would be based on high-risk non-muscle-invasive bladder cancer guidelines. So again, typically three-monthly urinary cytology and cystoscopy for the first two years, followed by six-monthly for the next two years, and then annually for life.

Surgical techniques. Key points: you could do it open versus robotic, appreciating some surgeons do not feel that partial cystectomy should be performed robotically, but key features, key points are important to minimize risk if performing it robotically. You could localize the tumor using flexible cystoscopy to ensure that you can excise exactly where the tumor is. Placing stay sutures at the time of robotic cystectomy can be useful to allow the bladder to distend and allow full-thickness excision. The bladder should be drained prior to excision, and in cases where the tumor is not at the dome but at the posterior or lateral wall and deemed still suitable for partial cystectomy, the bladder would need to be mobilized. The vas should be divided to free up space, and likewise, the bladder pedicles as well, to ensure that the whole tumor with negative margins can be safely excised.

Advantages for partial cystectomy: compared to chemoradiation, with partial cystectomy, you get ideally full-thickness histology. We do know that in patients who achieve pT0 at TURBT, up to 60% of them actually had residual disease at the time of radical cystectomy. So it's important to appreciate there's always a risk of understaging patients who are going to undergo chemoradiation. Partial cystectomy also avoids side effects such as radiation cystitis in patients, allows lymph node dissections to be performed, and also early salvage treatment in the form of completion radical cystectomy for patients with local recurrence can be performed without the presence of radiation effects, which may make the procedure a little bit more challenging post-radiation treatment. In terms of oncological outcomes, all the data with partial cystectomy are generally based on retrospective data. A lot of them are single-center studies. Some of them are comparative studies where propensity score matching and weighting have been performed to try to minimize the risk of confounding factors.

Five-year outcomes can vary quite significantly, and it's important to appreciate that this is not standard of care, but where tumor can be safely excised, it is an option in the absence of CIS. So in terms of the take-home message, just to summarize that partial cystectomy is established for urachal and diverticulum tumors, but it's an option for very selective muscle-invasive bladder cancer cases. Neoadjuvant treatment as well as pelvic lymph node dissection should be performed as standard of care for muscle-invasive bladder cancer, and surveillance would comprise cystoscopy, cytology, as well as cross-sectional imaging. Thank you very much.

Ashish Kamat: Thanks so much, Shen. That was a nice overview of the review that you published. I think one of the key points that we need to make sure the audience takes home is that it is a valid option in a very select group of patients. It's not standard of care. We—and when I say we, I mean me, but I'm sure you too—are not recommending it for every patient with muscle-invasive bladder cancer because I remember the time when we were doing too many partial cystectomies, and then of course there were too few partial cystectomies, so it has to be the right patient at the right time. And as you mentioned, urachal tumors, clearly if you can get negative margins, partial cystectomy should be standard of care. Tell me a little bit more about diverticular tumors, because there are some people that believe that if a tumor is in a diverticulum, it's not really a partial cystectomy, it's a diverticulectomy. So talk a little bit about the difference between diverticulectomy and partial cystectomy for diverticular tumors.

Wei Shen Tan: In a way, a diverticulectomy is removing the diverticulum. We're taking out part of that area of the bladder as well. So either way, we are excising a portion of the bladder. The principles should still—you should adhere to the same principles. Ideally, the tumor should be resected completely to minimize tumor spillage upon entering the bladder. In some cases, you could close the diverticulum itself to minimize spillage of the tumor, and following excision, it also needs to be—in some of these cases, we would have to reimplant the ureter just because of the anatomy, where the ureter travels, and essentially you're taking out part of the bladder itself. So as long as you adhere to the principles, it's a good option.

Ashish Kamat: Yeah, exactly. And I'm glad you made that point because otherwise, there's a misconception that if a tumor is in a diverticulum, you can just excise the diverticulum and not have to worry about the neck of the diverticulum or getting sufficient margin. So a diverticulectomy for cancer should be essentially a partial cystectomy in that area. The other point I'm glad you emphasized is that patients undergoing a partial cystectomy should undergo lymph node dissection, a standard lymph node dissection, and they should also undergo consideration for neoadjuvant chemotherapy or neoadjuvant therapy. It might change from chemo to other agents, but as you would for any muscle-invasive bladder cancer.

You did mention a little bit about robotic versus open. I think the key principle there, and I'm sure you'd agree with me, is oncologic principles. If the tumor is in a location where you would have frank spillage of viable urothelial cells if you did it robotically, don't do it. If you can do it safely without spilling tumor, that's a great option as well for patients. In your review, did you come across studies, and if so, could you comment a little bit on something that I've been doing for many years, which is at the time or right before the partial cystectomy in a patient that has frank tumor, instilling gemcitabine in the bladder? I used to do mitomycin—some people do other agents—to decrease tumor spillage. Did you come across a lot of those in your review?

Wei Shen Tan: I didn't come across that specifically, but that would be recommended. I do that all the time also for patients undergoing nephroureterectomy. We instill gemcitabine within the bladder and drain it before we do the dissection for the bladder cuff. It does make sense. It reduces the risk potentially of seeding, so I would be in agreement with that.

Ashish Kamat: Great. Shen, in conclusion, just because again, we want to highlight for the audience before we close, in maybe 30 seconds or so, the ideal candidate for a partial cystectomy is...

Wei Shen Tan: In patients with muscle-invasive disease, it should be a small tumor, ideally less than 3 cm, solitary tumor, a favorable location, ideally at the dome or in areas that you think that you can get negative margins and minimize tumor spillage—that's key. And the patients should have no evidence of CIS. So those are the key inclusion criteria for patients suitable for partial cystectomy for muscle-invasive disease.

Ashish Kamat: Great. Well summarized. Thank you so much, Shen. Always a pleasure having you.

Wei Shen Tan: Great. Thanks so much, Dr. Kamat.