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BackTable / Urology / Article
Ablation vs. Excision: Where Do We Draw the Line on Renal Tumor Size?
Evangeline Adjei-Danquah • Updated Oct 31, 2025 • 35 hits
The management of small renal masses has evolved dramatically over the past few decades, moving from radical nephrectomy as the default to a more nuanced approach that now includes ablation, partial nephrectomy, and even active surveillance. Central to this shift is the question of tumor size and how it dictates treatment choice. While ablation has proven highly effective for very small lesions under 2 cm, its durability decreases as tumors grow, leaving a gray zone between 3 to 4 cm where outcomes become less predictable. Beyond this threshold, surgery continues to stand as the gold standard for long-term oncologic control. Drawing on expert insights and clinical experience, this article explores where ablation ends, where surgery begins, and how physicians and patients navigate the delicate balance between efficacy, risk, and quality of life.
This article features excerpts from the BackTable ENT Podcast. We’ve provided the highlight reel in this article, but you can listen to the full podcast below.
The BackTable Urology Brief
• Ablation is highly effective for tumors <2 cm, offering outcomes comparable to surgery with lower invasiveness, especially valuable for older or comorbid patients.
• Efficacy declines as tumor size increases, with outcomes dropping after 3 cm, where recurrence risks and need for repeat ablations become more likely.
• The 3–4 cm range represents a gray zone, where shared decision-making is critical—balancing patient goals, comorbidities, and preferences against recurrence risk.
• Surgery remains more effective for tumors >4 cm, offering the most durable oncologic control through partial or radical nephrectomy.
• Patient-centered management is essential, with size, tumor biology, growth kinetics, and individual risk tolerance guiding whether ablation, surgery, or surveillance is most appropriate.
Table of Contents
(1) Tumor Size & Ablation Efficacy
(2) The Gray Zone Between 3 to 4 cm
(3) Surgery is More Effective for Larger Lesions
Tumor Size & Ablation Efficacy
For very small renal tumors, particularly those under 2 centimeters, ablation is consistently effective and can achieve cure rates comparable to surgery. Its minimally invasive nature makes it an appealing option for patients with significant comorbidities or those who wish to avoid operative intervention. As tumor size increases, however, the effectiveness of ablation begins to decline. Clinical outcomes remain favorable up to approximately 3 centimeters, but beyond this point, success rates fall as recurrence and retreatment become more common. Larger lesions present greater challenges in achieving complete thermal coverage, which can compromise long-term control. Tumor location is equally important in determining success. Peripheral or exophytic lesions are easier to access and ablate thoroughly, while central or hilar tumors are more technically demanding and carry a higher risk of incomplete treatment.
[Dr. Aditya Bagrodia]
Assuming in a healthy person, is there a size cutoff where you're more inclined to start the conversation about we're likely going to be treating this versus a size criteria where we'll likely start off with observation and we're going to get to biopsies at some point, which is the focus of this talk?
[Dr. Christopher Anderson]
I don't know. I think it varies a little bit based on age, comorbidity, and so forth. I certainly have patients who are in their mid-80s who are ill who have 6-centimeter tumors that we've been watching for years. Likewise, there's patients who are very young who may not tolerate surveillance for even very small tumors. I do think it's very individualized. I don't think I have a specific cut point, but the bigger they are in general, the higher the risk of an aggressive pathology.
Certainly, there's the patient anxiety that comes into play too. As much as you try to reassure people, knowing that you have a 5-centimeter tumor on your kidney makes you anxious. Some people may or may not want to monitor things depending on how their health is otherwise.
[Dr. Aditya Bagrodia]
I promised myself I'd refrain from any type of generalization than sticking my foot in my mouth. I don't know, this is my gestalt. If it's less than 2 centimeters, I have a hard time signing that person up for any intervention. This, of course, is broad strokes. I think the downside of interval imaging in four to six months, a biopsy is so low. Your likelihood of a missed opportunity of a window for a cure is so low that this is broad strokes. Of course, I want to get your opinion.
Then in a healthy person, 50s, 60s, maybe like hypertension, really as we start getting above 3 centimeters, I'll still try to keep the anxiety level super-duper low. This is extremely manageable. I don't love watching tumors bigger than that. The broad strokes just throwing it out there.
[Dr. Christopher Anderson]
I agree. I think going back to what I was saying earlier, there's a lot we can learn still about how much is size relevant. Is that the only relevant factor? That's something that we can see, we quantify, we follow that. For patients on surveillance, we've learned that rapid growth is bad. Stable growth does not rule out malignancy. How much should we be worried about size alone? I think that's where we probably can get more information on these patients.
There's different ways we can do that. Biopsy is certainly one of them. I think we can probably move towards a smarter algorithm to try to better risk stratify patients compared to looking at your CAT scan and telling you whether or not you should have surgery or surveillance alone.
[Dr. Aditya Bagrodia]
Totally. Totally. Size is obviously variable. There can be periods of no growth and then exponential growth or linear growth. It's impossible to know that with serial scans, but it does impact treatment efficacy, particularly for some of our ablative options.
[Dr. Christopher Anderson]
Absolutely. Yes. Small tumors, usually very, very well suited for ablation depending on the location of the tumor. As they get bigger, ablation is just less effective.
[Dr. Aditya Bagrodia]
Do you have a number in your head where, once they start crossing thresholds, you're like–
[Dr. Christopher Anderson]
Yes. Certainly, the 2 centimeters and less, just like you said, I think that's a great size that's well suited for a successful ablation. There has been effectiveness for larger tumors than that, but very small ones, less than 2 centimeters, almost always effectively ablated.
[Dr. Aditya Bagrodia]
I trained at UT Southwestern and Jeff Cadeddu was a pioneer on RFA. It always seemed that the data suggested after 3 centimeters, you saw a substantial drop-off. That's not like a 90% efficacy versus 50%. It was low 90s down to the 70s. Honestly, that's a little bit tricky. As they started approaching, in my mind, 3 centimeters, do you pull the trigger? Do you continue to watch? Is repeat ablation really that big of a deal? Any thoughts on that, Chris?
[Dr. Christopher Anderson]
That's one of the things that I talk to patients about where we're headed toward some sort of treatment and it's like, "Do I want a surgery? Do I want to avoid surgery with ablation if that's appropriate?" I do tell them that, if you compare surgery compared to ablation, the ability to cure cancers is about the same, although that might require a second ablation in a handful of patients. Some people are very happy to avoid surgery at all costs, even if that means two ablations. Although, for people who want that one-and-done treatment, then surgery probably makes the most sense for them.
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The Gray Zone Between 3 to 4 cm
Tumors measuring between 3 and 4 centimeters fall into one of the most complex areas of small renal mass management. Ablation within this range is possible but carries a higher chance of incomplete treatment or recurrence, sometimes requiring additional procedures. For patients with medical comorbidities or limited surgical tolerance, accepting these risks may be worthwhile if it avoids the challenges of surgery. Others may prioritize the reliability of surgical removal, which offers a higher single-procedure cure rate and longer-term control. The decision depends on an individualized assessment that considers patient age, tumor growth patterns, imaging findings, and comfort with active surveillance. In this intermediate zone, shared decision-making is particularly critical. Physicians can help patients weigh the advantages and drawbacks of less invasive but potentially less durable ablation against the more definitive nature of surgery
[Dr. Aditya Bagrodia]
It's kind of wild that, once upon a time, kidney cancer was the internist dilemma because there's all these paraneoplastic syndromes, funky manifestations, flank masses, hematuria, and all that kind of stuff. Now it's like everybody and their brother are getting a CT scan. Just baseline, what are we talking here in numbers; common, uncommon, roughly? What's the incidence of kidney cancer, kidney tumors, maybe even smaller kidney tumors?
[Dr. Christopher Anderson]
Fairly common. About 80,000 people a year are diagnosed with renal cell carcinoma. That's based on the most recent SEER statistics for the United States. At least 1 in 40 to 1 in 70 adults will be diagnosed with a kidney cancer during their lifetime, so that's not insignificant. We've seen a substantial increase in incidents of kidney cancer, particularly over the last 30 years. If you look at the curves, there's been this dramatic increase. There's a couple of thoughts about why that is, but probably, for what you've already talked about is that we're doing a lot of cross-sectional imaging.
In the United States, we do tons of scans. We do probably upwards of 80 million CAT scans a year in the United States. In the Medicare population, just shy of 50% of patients will be at risk for having a CAT scan over the next five years. The more we look at people, the more we find. In fact, there's a lot of incidental findings on a CAT scan or an MRI, and the kidney is one of the major ones. About 2% to 3% of CAT scans or MRIs of the abdomen will find something on the kidney. I think that's really led to this huge increase in incidents.
[Dr. Aditya Bagrodia]
I hear you loud and clear. Clearly, there's some consternation that comes along with it until they meet with somebody and hopefully, some of that anxiety is diffused. Maybe just diving on into it, new patient incidentally discovered small renal mass. Let's just hit the highlights on critical elements of history, physical, if there are any critical physical elements that you run through.
[Dr. Christopher Anderson]
Do a full medical surgical history on every patient as you would for anybody. I think family history is really important to learn about whether the relatives have had any cancers, particularly kidney cancers. You're looking for associations with renal cell carcinoma syndromes. Not terribly common, but good to know about. Most of these are not palpable on exam.
I think reviewing their imaging is of critical importance. I rarely rely on a report that describes some sort of suspicious kidney tumor. I usually always want to look at those pictures myself, determine the size, the location, whether it enhances or not. I think a lot of our counseling is based on exactly what a CAT scan or an MRI says, and perhaps the quality of that imaging as well.
[Dr. Aditya Bagrodia]
Obviously, if they're smoking, I think it's a nice opportunity just to plug them into smoking cessation or any of those types of things as a risk factor in addition to the family history. Review the imaging. I'll admit, I love a CAT scan. I love a pre and post-contrast CAT scan. I could wrap my brain around that fairly easily. Then when I look at the MRIs, I generally try to go for the sequences that look most like a CAT scan first.
[Dr. Christopher Anderson]
I'm right with you.
[Dr. Aditya Bagrodia]
Then I'm looking at DWI and the in and out phases. I guess I say this because, of course, as the surgeon in the front line of the disease, we've got to evolve. I also think having a high-quality MRI program and radiologists that you work with is critical.
[Dr. Christopher Anderson]
Fully agree. In fact, we're ordering more and more MRIs to look at kidney tumors. I think that you get more information out of them, and I think our radiologists are able to give us probably better advice about what they think these things are from a radiographic standpoint. No question. Sometimes it's a little bit difficult for me to interpret as well, but I do think that they're very valuable if they can be done correctly.
[Dr. Aditya Bagrodia]
Yes. I feel like I've been able to wrap my brain around prostate MRIs pretty well over my time in this field, but kidney MRIs, I still think there's some learning to be done for me. All right. You've gotten your history, your physical. They've got a small renal mass, which to me is still a quite broad term, 4 centimeters. Is this what you're talking about, right, Chris, 4 centimeters or less?
[Dr. Christopher Anderson]
Yes.
[Dr. Aditya Bagrodia]
My radar for concern at 4 centimeters is quite different from, say, 1.2 centimeters. Let's hear your spiel, if you will, to the patient when they come in with an incidentally discovered mass.
[Dr. Christopher Anderson]
I think this is definitely worth a conversation. A lot of patients get sent in saying, "You have a cancer. You need to see someone immediately to get this removed." Part of the initial conversation is, "Let's slow down a little bit. Let's backtrack just a tad and talk about what exactly are we looking at here. What are some of the numbers, some of the things that we've already discussed."
One thing I'll tell people is that, "Listen, we are diagnosing tens of thousands of small renal masses a year. We've seen this huge incidence in small renal mass, but really, this has not translated to decreases in kidney cancer mortality. There's a possibility that you are here because you've been overdiagnosed with a small mass. Meaning, you have been found to have something that may or may not impact you for the rest of your life."
That's one way to diffuse the tension just a little bit. I do think that's important when appropriate, but then I also talk to patients about, "What could this be?" There's plenty of papers out there that show us among surgically resected renal masses, what are they? For masses that are less than 4 centimeters, about one in five are benign. There's a whole variety of benign masses they can be, and there's a huge prevalence of what are classified as indolent tumors. Meaning, they are cancerous, usually clear cell, but sometimes very histologies that have very low metastatic potential and are very unlikely to cause any harm if possibly left untreated.
We're looking at, among patients with small renal masses, who are the maybe 10% of patients who have aggressive cancers, and could that be you? That's usually where I start the conversation, is to try to diffuse the tension a little bit, give them a little bit more perspective and say, "Listen, most of the time, this is nothing that you need to be urgently worried about."
[Dr. Aditya Bagrodia]
I love that. I'm glad my statistics match with yours. Here's what I do. First day I walk in and say, "You're going to be fine. You're not going to die of kidney cancer. It's not time to get your papers in a fair. You're going to be okay." Then I'll typically say something along the lines of, "If this was 50 years ago, we would've lopped your kidney out. If it was 30 years ago, we would've just removed the spot." These days, we know that so many of these are so benign behaving. I actually borrow a phrase from Scott Eggener's active surveillance counseling, wimpy tumors that almost pose no threat to your life.
Sometimes I'll actually juxtapose it to say, for instance, like pancreatic cancer, esophageal cancer, that are ones that get our attention in a big way. Sometimes tears of joy right there. You can just tell that that was meaningful. I agree. We might get into the incidence of benign tumors in a centimeter, sub-centimeter, 1 to 2 versus 4 centimeters, but 80% of these are going to be cancers. I always say about 90% of those are going to be very benign behaving cancers. I think that math leads to about 10% of these could be real cancer somewhere down the way.
[Dr. Christopher Anderson]
Yes, absolutely.
Surgery is More Effective for Larger Lesions
Surgery remains the most effective and durable treatment option for renal tumors exceeding 4 centimeters. Both partial and radical nephrectomy provide superior oncologic control, achieving reliable cure rates that ablation cannot match as tumor size increases. While ablation remains valuable for smaller and well-localized lesions, its effectiveness declines with larger tumors, leading to higher rates of incomplete treatment and recurrence.
Advances in minimally invasive and robotic approaches have improved surgical precision, shortened recovery times, and lowered perioperative complications. Even so, surgery is not without risk, as patients may experience bleeding, urine leaks, or a reduction in renal function. These potential outcomes make thorough patient counseling an essential part of decision-making. When long-term cure and disease control are the primary goals, surgery continues to be the preferred approach for larger renal masses. The focus remains on balancing oncologic benefit with patient safety and overall quality of life
[Dr. Aditya Bagrodia]
How do you describe what a biopsy is going to be like to the patient?
[Dr. Christopher Anderson]
I would say that it's an outpatient procedure. It's usually done under ultrasound guidance, maybe with some local anesthesia. They're awake. You take usually a coaxial sheath or a thin needle, put it through the skin, and then put another needle through it, similar to the needles we use for prostate biopsies. It's safe. I tell people that there's a low chance of having a complication from a biopsy, but it's usually self-limiting like hematuria or flank pain. It's very uncommon to have any high-grade or bad complication after a kidney biopsy.
The main risks that I talk about are that there's this nagging, persistent risk of non-diagnostic biopsies. I think this is one of the biggest limitations of the kidney biopsy as we do it today, is that anywhere from 10 to 15 of them are just non-diagnostic. Then you went through all this trouble, you had a procedure. Maybe it was a little uncomfortable or maybe you had a complication, and you didn't get the answer you were looking for. I think that's frustrating for patients as well as for doctors, but it's very important to be upfront about the fact that, yes, you may be faced with that non-diagnostic result if we go down this road.
[Dr. Aditya Bagrodia]
I appreciate the coaxial sheath description because patients will often ask, "Is this going to spread the cancer or cause it to misbehave?" and I try to explain how a separate needle comes out and then retracts within the sheath, and that prevents dragging tumor cells across any non-cancerous areas. Non-diagnostic, we'll jump into that in a bit. All right. We're trying to figure out cancer, no cancer, if cancer, what type of cancer, is it dangerous? Cancer, no cancer, what are the performance characteristics of a biopsy? We're talking about 18-gauge, not FNAs, right?
[Dr. Christopher Anderson]
Correct. 18-gauge biopsies, core biopsies, particularly, if possible, multi-quadrant biopsies. If you sample a tumor in a couple of different places, it definitely helps improve biopsy accuracy. That's the type of biopsy we're looking at. How accurate is it? It's actually reasonably accurate. If you get a diagnostic result, it's very good. There's a very high sensitivity for determining cancer versus no cancer. We're talking mid to high 90s. It's highly specific as well.
One of the criticisms of biopsy has been, well, there's a lot of heterogeneity in these tumors, so what if you're not assessing grade accurately? It's actually reasonably good at that as well. Probably mid-90s in terms of accuracy for grade, especially if you categorize it low versus high grade, meaning grade 1, grade 2 versus grade 3, grade 4. It's pretty good at that. It's also reasonably good at determining type of histology, so if it was cancerous, what type of cancer it is.
[Dr. Aditya Bagrodia]
Perfect. The non-diagnostic rate, sometimes you'll see-- it's interesting, right? For every type of image-guided procedure that I've interacted with over my career, there's a couple of shots of a needle going into whatever is of interest. Sometimes you see this like skiving and you're like, "Huh?"
[Dr. Christopher Anderson]
I'm not sure they got that one.
[Dr. Aditya Bagrodia]
I'm not passing judgment. I recently started doing transperineal prostate biopsies and, in some form or fashion, that was an exercise in humility. My good old-fashioned transrectal approach, there was not a lot of doubt of where I was and what I was doing. I'm not passing judgment, but there is some technical prowess, finesse, familiarity with these, the kidney moves, is the capsule thick, whatever, that can impact this.
[Dr. Christopher Anderson]
Absolutely. What else impacts non-diagnostic rates or when would you maybe think twice about doing a biopsy on somebody who you suspect that it's just going to be futile, they're not going to find anything? If it's very, very small, I think those are ones that are hard to hit. Cystic masses tend to be more likely to be non-diagnostic. Very endophytic tumors, also more non-diagnostic. Then the longer skin-to-tumor distance. If you have very, very large patients, those are much more difficult targets to hit. When you're having that conversation with that patient, you're saying, "Listen, you could have a biopsy, but it's going to be probably pretty tough for you to get that."
[Dr. Aditya Bagrodia]
The cystic masses, I like that you brought that up. I feel like historically it was, "Don't even attempt it." Maybe if they got a decent intramural nodule or something along those lines, then you're considering surveillance because I don't know how you feel about this, but I think it's actually the size of the enhancing nodular component more so than the fact that they have 3-centimeter fluid-filled cyst.
[Dr. Christopher Anderson]
Absolutely. I agree with you. I think that's where really good cross-sectional imaging and perhaps even MRI can help you. A good radiologist will say, "Listen, this is a Bosniak IV cyst, but there's only a 3-millimeter nodular component," or something that maybe perhaps makes you a little bit less worried.
[Dr. Aditya Bagrodia]
What about Albutrix? Percutaneous biopsies, yes, no?
[Dr. Christopher Anderson]
I haven't done a lot of those, but I have ordered several. I think that the concern for the upper tract biopsies has historically been that you're going to seed the tract and you're going to spread the cancer. Not a lot of evidence to support that. Now there's actually evidence to suggest that ureteroscopic biopsies might increase the risk of bladder cancer recurrence or other complications that could be avoided. It's on the map. It's not totally part of the routine standard process yet, but perhaps in the future.
[Dr. Aditya Bagrodia]
Without getting too far off kilter here, I think for infiltrative masses that are into the parenchyma suggestive upper tract, the data suggesting tract seeding is an issue is pretty weak actually. Let's get a biopsy, get on with it, save them an anesthetic, all that, and then some of the considerations in terms of bladder recurrences, so I'm a fan. All right, so, "Negative biopsy. Good luck and goodnight. Check you later," or how does that work?
[Dr. Christopher Anderson]
There's different negatives, right? You have an angiomyolipoma, you have an oncocytoma. That's negative for cancer. I don't think I would ever discharge those patients from clinic, but they're basically, at least in my mind, put on an access surveillance protocol where you might monitor them, but you would adjust the frequency and intensity of monitoring based on what you find in the biopsy.
The non-diagnostic biopsies are a different dilemma. I think that that's either where you're thinking about repeating a biopsy in some cases, which usually if you do it twice, if it's an appropriate tumor, you'll get a result, or empirically treating. That's currently what we do. Those could be frustrating results at times.
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Cite This Podcast
BackTable, LLC (Producer). (2023, November 3). Ep. 134 – The Role of Renal Mass Biopsy in Modern Urology [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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