adjuvant treatment for undifferentiated pleiomorphic spindle cell

[Kroll2013]

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Dear Colleagues, i would appreciate your opinion :
50-year-old man with a 10 cm high-grade pleomorphic spindle cell sarcoma (FNCLCC G3) of the abdominal wall/cecum (tumor invades into the serosa of the cecum), resected en bloc with ileum and appendix.
Margins negative but deep margin only 1 mm, necrosis present, no lymphovascular invasion, no nodal or distant disease.
- CD117 and CD34: Patchy positivity.
- Desmin, DOG-1, SMA, and S-100: Negative
Seeking advice on adjuvant management (chemo, radiation, or both) after R0 but close-margin resection of a large high-grade sarcoma.

 

[RickyScott]

adjuvant radiation to 50 -60Gy normal tissue tolerance permitting.

 

[OTN]

If you can locate the area of close SM via preop imaging, clips, etc, I would boost to 64 Gy to that area + a generous margin, again if tolerated of course. 2 Gy fx. 50 Gy in 2 Gy fx to a larger field defined by preop imaging, op note, discussion w surgeon etc. No concurrent chemo. Abdominal wall is what’s at risk for recurrence so no need to extend the field too far into the abdominal cavity. I would do a 4D ct sim- If pt is a belly breather then belt compression could help with limitation of movement, even though I usually don’t use it for fractionated treatment.

 

[TheWallnerus]

“abdominal wall/cecum (tumor invades into the serosa of the cecum), resected en bloc with ileum and appendix.”

This sounds like a “big whack”… the 1mm deep margin is thus interesting. I mean he resects a foot of tissue and wow what a coincidence the tumor is 1mm from the margin. Would talk to surgeon and pick his brain for sure. How “close” is this close margin. The pathologists sometimes lack context.

What is the stage group here and does postop RT comport with 2025 NCCN guidelines.

Abdominal wall is what’s at risk for recurrence

Why not a visceral recurrence given cecal invasion.

 

[NotMattSpraker]

“abdominal wall/cecum (tumor invades into the serosa of the cecum), resected en bloc with ileum and appendix.”

This sounds like a “big whack”… the 1mm deep margin is thus interesting. I mean he resects a foot of tissue and wow what a coincidence the tumor is 1mm from the margin. Would talk to surgeon and pick his brain for sure. How “close” is this close margin. The pathologists sometimes lack context.

What is the stage group here and does postop RT comport with 2025 NCCN guidelines.


Why not a visceral recurrence given cecal invasion.

The NCCN guidelines dont really discuss an intra-abdominal sarcoma. I would generally borrow from the RP literature and concepts.

FNCLCC grade 3 sarcoma that is 10 cm is associated with a very high risk of DM. Are they getting chemo? I think they should.

Pos versus negative margin definition in sarcoma has traditionally been tumor on ink, so a "close margin" is very rarely the sole reason I radiate.

If you think you have space to radiate with respect to bowel constraints, Id do it after chemo. If you dont think you can get to 60 Gy safely, Id observe. I dont think giving 64-66 is wrong here but its hard to argue its beneficial with a negative margin.

Its worth explaining this aspect to your surgeon so next time they call you before taking it out. The NCCN would back you up on structuring your service this way.

I've done post op in the abdomen just a handful of times and many were using proton therapy in patients with unusually "good" post op anatomy.

Edit: just to add, if the tumor was large enough to fill the abdominal cavity, its common to have close margins at the posterior abdominal wall. This is the area that is frequently the "high risk" CTV in RP sarcoma.

 

[OTN]

“abdominal wall/cecum (tumor invades into the serosa of the cecum), resected en bloc with ileum and appendix.”

This sounds like a “big whack”… the 1mm deep margin is thus interesting. I mean he resects a foot of tissue and wow what a coincidence the tumor is 1mm from the margin. Would talk to surgeon and pick his brain for sure. How “close” is this close margin. The pathologists sometimes lack context.

What is the stage group here and does postop RT comport with 2025 NCCN guidelines.


Why not a visceral recurrence given cecal invasion.

I was making the assumption the “deep” margin was in the abdominal wall, as it should be easier to get margins in the cecum. Talking with the surgeon key as has been mentioned.

 

[TheWallnerus]

"close margin" is very rarely the sole reason I radiate.

😉😉😉

 

[evilbooyaa]

Pleomorphic spindle cell 10cm size would likely benefit from adjuvant chemo, have him see med onc for at least discussion regarding pros/cons.

Close margin is not positive. What does deep margin mean? At the abdomen? At the intestine? Is a close deep margin like at the peritoneum?

I would either treat to 60 if feasible based on post-op anatomy (is it small bowel or large bowel that is falling into the resection space) vs not irradiate and await recurrence and do pre-op at that time, kinda like a RP sarcoma. Shared decision making with patient.

If I can avoid RT for a 50-year old who needs really high doses, that would be my preference.

If no RT now, let surgeons know in no uncertain terms that a local recurrence needs pre-op, MANDATORY. Some surgeons love to be on their 3rd, 4th, 5th 'oncologic surgery' for these sarcomas before they reach the point of 'maybe we should consider doing pre-op RT'

 

[OTN]

Pleomorphic spindle cell 10cm size would likely benefit from adjuvant chemo, have him see med onc for at least discussion regarding pros/cons.

Close margin is not positive. What does deep margin mean? At the abdomen? At the intestine? Is a close deep margin like at the peritoneum?

I would either treat to 60 if feasible based on post-op anatomy (is it small bowel or large bowel that is falling into the resection space) vs not irradiate and await recurrence and do pre-op at that time, kinda like a RP sarcoma. Shared decision making with patient.

If I can avoid RT for a 50-year old who needs really high doses, that would be my preference.

If no RT now, let surgeons know in no uncertain terms that a local recurrence needs pre-op, MANDATORY. Some surgeons love to be on their 3rd, 4th, 5th 'oncologic surgery' for these sarcomas before they reach the point of 'maybe we should consider doing pre-op RT'

I would follow the patient myself to ensure that when it does recur (I'm pretty pessimistic about this case to be honest, given the high-grade nature and close margins) you as the radonc get to be in the drivers' seat.

 

[evilbooyaa]

I would follow the patient myself to ensure that when it does recur (I'm pretty pessimistic about this case to be honest, given the high-grade nature and close margins) you as the radonc get to be in the drivers' seat.

Very reasonable. I've had similar thoughts on those very high risk prostate cancer patients that end up "choosing" RALP but haven't pulled the trigger on it myself yet...