Rectal Close Margin

[Mandelin Rain]

pT2 pN0 low Rectal AdenoCa with circumferential resection Margin <1mm on APR near a defect in proximal anus.

What say you all?

Technically a positive margin. Recommended to chemorads.

Fields? Technique? Dose?

I'm thinking probably 3D treatment, cover scar, no groins, to 5040 cGy.

Anybody recommend anything different? Been a while since I've treated post APR.

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[elementaryschooleconomics]

pT2 pN0 low Rectal AdenoCa with circumferential resection Margin <1mm on APR near a defect in proximal anus.

What say you all?

Technically a positive margin. Recommended to chemorads.

Fields? Technique? Dose?

I'm thinking probably 3D treatment, cover scar, no groins, to 5040 cGy.

Anybody recommend anything different? Been a while since I've treated post APR.

Definitely no groins, I usually cover traditional fields (no external iliacs for a T2), merge pre-op imaging, look at the clips/where the positive margin is and where the tumor was, boost that area to 5400 cGy (blah blah hypoxic environment and all that).

At the risk of getting eviscerated for saying this, I would consider VMAT to spare bladder (especially if I were doing a sequential boost to 5400), but these are all minor details that I don't feel strongly about.

Curious what our GI friends think - @ramsesthenice et al

 

[Mandelin Rain]

Margin was not anticipated, so might be tough to localize which is why I was thinking less conformal treatment, but definitely understand VMAT urge.

Anyone lower superior border also, given no nodes involved?

 

[ramsesthenice]

Margin was not anticipated, so might be tough to localize which is why I was thinking less conformal treatment, but definitely understand VMAT urge.

Anyone lower superior border also, given no nodes involved?

This whole thing is a little confusing. T2 tumors should rarely be within 1 mm of the CRM. I understand there was a defect but is this a real margin? Personally, it sounds like the only real risk for local recurrence in this case is the close margin. Since the defect was in the anus I am not sure you would gain anything by treating the entire pelvis. If I were to radiate, I might be inclined to do a relatively small field targeting the low pelvis, pelvic floor and perineal scar.

 

[Mandelin Rain]

This whole thing is a little confusing. T2 tumors should rarely be within 1 mm of the CRM. I understand there was a defect but is this a real margin? Personally, it sounds like the only real risk for local recurrence in this case is the close margin. Since the defect was in the anus I am not sure you would gain anything by treating the entire pelvis. If I were to radiate, I might be inclined to do a relatively small field targeting the low pelvis, pelvic floor and perineal scar.

I agree. This was a new one to me. Surgeon was frustrated but path was reviewed and thought to be true margin.

I was also thinking a limited field similar to what you mention.

 

[TheWallnerus]

Wait what. Postop RT for T2 rectal adenoca with close but negative margin? Actually postop chemoRT. Did med onc have any, um, questions.

 

[Mandelin Rain]

<1mm

Wait what. Postop RT for T2 rectal adenoca with close but negative margin? Actually postop chemoRT. Did med onc have any, um, questions.

I think <1mm is considered positive margin in colorectal.

Imagine this is a T2N0 rectal post transanal excision with <1mm margin but couldn't undergo further surgery for whatever reason. What's the recommendation?

 

[TheWallnerus]

I think <1mm is considered positive margin in colorectal.

Well I would have missed that question on OLA

 

[Radonc90]

Probably inexperienced surgeon.
Since the risk is mostly at the perineal scar, I agree with above 3D + chemo, but would modify the upper margin down to S1-S2
to minimize GI toxicity.
No need to go to L5-S1.

 

[Ray D. Ayshun]

<1mm

I think <1mm is considered positive margin in colorectal.

Imagine this is a T2N0 rectal post transanal excision with <1mm margin but couldn't undergo further surgery for whatever reason. What's the recommendation?

I was trained to go to 54 gy if treating definitively, which isn't what you're asking I know. I believe the German rectal study did 55.8 postop. That said, I'd consider 54 in this transanal scenario, and consider it even more after an apr.

 

[Palex80]

I am confused. Review of the path is crucial here.
This is a pT2 tumor, so technically this is within the muscularis and not invading beyond. An APR was done, meaning rectum & anus are gone.
Could the margin be in the direction of the anus that was resected separately, for instance because APR was not planned all along but was performed after the surgeon saw he could not perform a low anterior resection? In that case, the "close margin" would be neighboring the now removed anus?
The other option would be that the close margin is a CRM, which probably means that quality of the resection was bad. The pathologist can have a look at the macroscopy and estimate the quality of the TME. If there is hardly any serosa in the lower parts of the rectum then that would explain the close CRM despite the pT2, perhaps the surgeon actually cut into the muscularis. That would indeed be a problem and associated with a higher risk for local recurrence.

Now, concerning fields:
Depending on the amount of nodes resected and the quality of the TME, one could indeed opt for a local treatment only, targetting the lower parts of the rectum, the anus and the scar. I do not see a necessity in covering lymphatics, provided nodes were actually removed and the TME quality is not nbad, since the only indication for RT at all is the close margin. A close margin does not influence the risk of nodal involvement, it influences solely the risk of a local recurrence in pT2 tumors.

You can actually think of the more common situation we sometimes face in breast cancer.
pT2 (25mm) pN0 (0/3;sn) G2 ER+ PR+ Her2- L0 V0 R1 in a postmenopausal lady, she has a subcutaneous mastectomy. Positive margin was superficial, probably in subcutaneous remaining breast tissue. Surgeon says, she does not want resection in order to not endanger the cosmetic result. Tumor breast says postoperative RT & letrozole (oncotype is intermediate).
Would you treat lymphatics too or just the chest wall?


Indication for chemotherapy depends on your view. If you view R0 (1mm) = R1, then you would have an argument for chemo, if not, I'd skip it.
Dose for: 27 x 2 Gy = 54 Gy

 

[madchemist89]

Great post on reviewing the pathology!

 

[elementaryschooleconomics]

I am confused. Review of the path is crucial here.
This is a pT2 tumor, so technically this is within the muscularis and not invading beyond. An APR was done, meaning rectum & anus are gone.
Could the margin be in the direction of the anus that was resected separately, for instance because APR was not planned all along but was performed after the surgeon saw he could not perform a low anterior resection? In that case, the "close margin" would be neighboring the now removed anus?
The other option would be that the close margin is a CRM, which probably means that quality of the resection was bad. The pathologist can have a look at the macroscopy and estimate the quality of the TME. If there is hardly any serosa in the lower parts of the rectum then that would explain the close CRM despite the pT2, perhaps the surgeon actually cut into the muscularis. That would indeed be a problem and associated with a higher risk for local recurrence.

Now, concerning fields:
Depending on the amount of nodes resected and the quality of the TME, one could indeed opt for a local treatment only, targetting the lower parts of the rectum, the anus and the scar. I do not see a necessity in covering lymphatics, provided nodes were actually removed and the TME quality is not nbad, since the only indication for RT at all is the close margin. A close margin does not influence the risk of nodal involvement, it influences solely the risk of a local recurrence in pT2 tumors.

You can actually think of the more common situation we sometimes face in breast cancer.
pT2 (25mm) pN0 (0/3;sn) G2 ER+ PR+ Her2- L0 V0 R1 in a postmenopausal lady, she has a subcutaneous mastectomy. Positive margin was superficial, probably in subcutaneous remaining breast tissue. Surgeon says, she does not want resection in order to not endanger the cosmetic result. Tumor breast says postoperative RT & letrozole (oncotype is intermediate).
Would you treat lymphatics too or just the chest wall?


Indication for chemotherapy depends on your view. If you view R0 (1mm) = R1, then you would have an argument for chemo, if not, I'd skip it.
Dose for: 27 x 2 Gy = 54 Gy

I can literally feel Palex thinking "stupid Americans, let me write the dose in a way they'll understand"

 

[TheWallnerus]

I can literally feel Palex thinking "stupid Americans, let me write the dose in a way they'll understand"

He's learning.

 

[Radonc90]

Also,

In my book, a cT2N0 lesion that is:
- mid and upper: no need for preop chemoRT.
- low (0-1 cm from upper edge of anus) is a clear indication for chemoRT to avoid APR.

This is probably a rookie surgeon (no offense) that does not know the chemoRT data well.

Agree with Palex re pathology review: orientation of the specimen is crucial.
Good surgeon is the one that scrubs out and walk into Pathology dept to go over the "difficult" specimen
with the pathologist "live" to discuss, then scrubs back into the case.

Anyway, if path is concerning then do the 3D Tx, then perhaps boost the perineal scar to higher dose, the American way lol...

 

[jondunn]

Dose for: 27 x 2 Gy = 54 Gy

2 gy a fraction is where you lost many Americans! What are you nuts!!?

 

[Ray D. Ayshun]

2 gy a fraction is where you lost many Americans! What are you nuts!!?

I didn't realize 54 divided by 2 would result in a whole number.

 

[Palex80]

I can literally feel Palex thinking "stupid Americans, let me write the dose in a way they'll understand"

Replace "stupid" with "weird".

 

[elementaryschooleconomics]

Replace "stupid" with "weird".

I remember in my first year in residency when I was presenting patients in chart rounds, one of the faculty stopped me because I was "saying the doses wrong" and they were getting confused.

We're a simple people, I guess.

 

[Mandelin Rain]

Also,

In my book, a cT2N0 lesion that is:
- mid and upper: no need for preop chemoRT.
- low (0-1 cm from upper edge of anus) is a clear indication for chemoRT to avoid APR.

This is probably a rookie surgeon (no offense) that does not know the chemoRT data well.

Agree with Palex re pathology review: orientation of the specimen is crucial.
Good surgeon is the one that scrubs out and walk into Pathology dept to go over the "difficult" specimen
with the pathologist "live" to discuss, then scrubs back into the case.

Anyway, if path is concerning then do the 3D Tx, then perhaps boost the perineal scar to higher dose, the American way lol...

Great surgeon. Fellowship trained CR. Peak of career. Has sent me low lying T2N0 multiple times to avoid APR. this one was low enough where not an option/anal involvement on MR. Does great TMEs. All photographed grossly in the OR. Reviewed gross photos compared to sectioning/path extensively in tumor board. All involved very much frustrated.

 

[elementaryschooleconomics]

Great surgeon. Fellowship trained CR. Peak of career. Has sent me low lying T2N0 multiple times to avoid APR. this one was low enough where not an option/anal involvement on MR. Does great TMEs. All photographed grossly in the OR. Reviewed gross photos compared to sectioning/path extensively in tumor board. All involved very much frustrated.

Wow, that does sound like a great surgeon. Sorry y'all are in this situation.

 

[Palex80]

Great surgeon. Fellowship trained CR. Peak of career. Has sent me low lying T2N0 multiple times to avoid APR. this one was low enough where not an option/anal involvement on MR. Does great TMEs. All photographed grossly in the OR. Reviewed gross photos compared to sectioning/path extensively in tumor board. All involved very much frustrated.

Well, in that case (to play the devil's advocate) how about talking to your friend about organ preservation regimes?

A cT2 cN0 rectal cancer stands a good chance to become cT0 cN0 with primary chemorads (not necessarily the full course TNT)...
If I was that patient, I would opt for definitive chemorads and resort to APR in case of residual tumor or recurrence.
Quite a good chance to walk out of this with an intact and functioning rectum.

 

[Mandelin Rain]

Well, in that case (to play the devil's advocate) how about talking to your friend about organ preservation regimes?

A cT2 cN0 rectal cancer stands a good chance to become cT0 cN0 with primary chemorads (not necessarily the full course TNT)...
If I was that patient, I would opt for definitive chemorads and resort to APR in case of residual tumor or recurrence.
Quite a good chance to walk out of this with an intact and functioning rectum.

Done that multiple times as well. The patient was not exactly the doctoring kind. Like
No PCP. Never been screened for anything type person.High risk to lose to follow up.

 

[Mandelin Rain]

I understand the desire to point fingers and blame someone with a less than ideal outcome, but this one can truly be filed under the “**** happens” category.

 

[evilbooyaa]

Tough case. I think argument for local therapy alone (to a broad area given unclear location of margin) is reasonable. Bolus scar, I'd likely plan IMRT similar to a vulvar case, but that's just my preference. Elective coverage of inguinal LNs given anal involvement upfront not unreasonable, not sure that I'd go chasing pelvic LNs assuming remainder of TME was LN negative with pathological evaluation for LNs.