Quick Nasopharynx question

[Reaganite]

For nasopharynx, are you guys taking bilateral Ib-V (including II to jug foramen) + RPLNs to 59.4 in all cases?

I'll admit I've always found these nodal coverage recommendations a little strange, as this seems to be the only site where the bilateral neck is taken to 59.4 and where you always treat level II to jug foramen even if node negative. I hear the term "parotid-sparing" associated with nasopharynx IMRT, but how can you spare the parotids if you're taking bilateral level II all the way to BOS to 59.4? Am I misreading the protocols?

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[Gfunk6]

This came up when we were studying for oral boards last year.

70 Gy in 33 fractions to the primary.
59.4 Gy in 33 fractions to the "high risk" neck.
54 Gy in 33 fractions to the "low risk" neck.

This is supported by RTOG 0225, Section 6.2.2:

Three different CTV's will be defined, namely CTV70 for the gross tumor volume, CTV59.4 for the high risk nodal regions, and CTV50.4 for the low risk nodal regions.

It is also supported by RTOG 0616, Section 6.1:

6.1.1 PTV70 (CTV70 + margin) will receive 70 Gy in 33 fractions at 2.12 Gy per fraction.
6.1.2 PTV59.4 (CTV59.4 + margin) will receive 59.4 Gy in 33 fractions at 1.8 Gy per fraction.

At the discretion of the treating physician, the dose to the high-risk subclinical region will be 59.4 Gy. If the treating physician would like to treat all sites: primary, upper and lower neck with a single 3D-CRT or IMRT plan, the low neck will receive 54 Gy at 1.64 Gy per fraction. This is known as PTV54 (CTV54 + margin).

Unfortunately, these protocols are relatively silent on what constitutes "high risk" and "low risk." For my patients, I generally treat the ipsilateral neck to 59.4 Gy and the contralateral neck to 54 Gy (obviously gross LNs are treated to 70 Gy). If you have an unfortunate patient with bilateral neck disease, you may be forced to treat both necks to 59.4 Gy

 

[Palex80]

I don't perform elective nodal irradiation to doses higher than 50/2 in cN0-patients.

If the patient has cN+ disease, I generally push the dose higher and treat positive nodes to 70 Gy, while the next level usually gets 60 Gy anyways.


That's just our institutional guideline however, so feel free to correct me. I am not sure, if there's any evidence out there, showing increased nodes of isolated neck failures in areas electively treated with 50 Gy.

 

[medgator]

For nasopharynx, are you guys taking bilateral Ib-V (including II to jug foramen) + RPLNs to 59.4 in all cases?

I'll admit I've always found these nodal coverage recommendations a little strange, as this seems to be the only site where the bilateral neck is taken to 59.4 and where you always treat level II to jug foramen even if node negative. I hear the term "parotid-sparing" associated with nasopharynx IMRT, but how can you spare the parotids if you're taking bilateral level II all the way to BOS to 59.4? Am I misreading the protocols?

Sometimes, you just can't spare the parotids and still deliver the right treatment. IMRT in NPC isn't just for saving the parotids, like it is in many other H&N cancers. In fact, I would argue that isn't the primary purpose at all.

You also have other things to deal with like optic nerve/chiasm tolerance, cord/brainstem/brain tolerance, etc and this is what you're really worried about when you are using IMRT in these patients. Compared to the INT 0099 experience, IMRT has definitely allowed for better tumor coverage and a corresponding improvement in LC. And yes, better xerostomia outcomes.

(RTOG 0225 experience: http://jco.ascopubs.org/content/27/22/3684.full)

 

[deleted4401]

Yeah, it always seemed to high for me for a cN0 neck, but the long term outcomes with UCSF and 0225 lead me to believe that there is no reason to deviate from protocol. The only thing you could maybe consider is if level IV is negative, lower the dose to the SCV, as they allow, which doesn't help you with the 'rotids. And, as everyone else has said, the primary goal is not parotid sparing, but seems to be a nice benefit according to the data.

 

[TarHeelRadOnc]

Yeah, it always seemed to high for me for a cN0 neck, but the long term outcomes with UCSF and 0225 lead me to believe that there is no reason to deviate from protocol. The only thing you could maybe consider is if level IV is negative, lower the dose to the SCV, as they allow, which doesn't help you with the 'rotids. And, as everyone else has said, the primary goal is not parotid sparing, but seems to be a nice benefit according to the data.

Agree. Have treated 3 NPX pts in past yr, all per 0225 protocol. I have been able to keep mean dose to at least one parotid in 30 Gy range for each case. Not quite 26Gy, but still qualifies as parotid sparing in my book. Agree that 59.4Gy is a high elective dose, but first echelon nodes for NPX are RPs and high level II. So if you believe in dose-painted IMRT utilizing a high risk (intermediate) PTV, then the electively treated region around the parotid will always be included within this intermediate dose in NPX cases. Granted we don't have any trials comparing dose-painted IMRT with 3 prescription dose levels to conventional 50/70Gy sequential tx. That said, many of us were trained using the former and there are supportive large volume single institutional experiences (MSKCC, etc) showing excellent outcomes with this regimen.

 

[Palex80]

I don't want to escalate the discussion, but perhaps these "intermediate" dose level for elective treatment may be a product of the trend to deliver more aggressive therapy with IMRT.

Look at the prostate: Before IMRT arrived few people went above 74-76 Gy for the prostate. And even today, we don't really have prospective randomized evidence pointing out that beyond 74-76 Gy you will get a better biochemical free survival with escalated dose, all randomized trials are 68-70 vs. 78-80 Gy.

Yet with IMRT people are pushing for a higher dose.
Don't get me wrong, you will probably get a better biochemical control with 84 Gy IMRT than you do with 74 Gy 3D, yet you may end up producing the same level of toxicity. Is that the goal of prostate IMRT?

 

[Gfunk6]

Yet with IMRT people are pushing for a higher dose.
Don't get me wrong, you will probably get a better biochemical control with 84 Gy IMRT than you do with 74 Gy 3D, yet you may end up producing the same level of toxicity. Is that the goal of prostate IMRT?

This is a really good point that bears repeating. More and more it seems, Radiation Oncologists use the "because we can" argument for dose escalation.

Higher doses do not always equal better outcomes. The early results of RTOG 0617 are a good example of this. We must not be seduced by technology and marketing reps into performing non-evidence based treatments.

 

[Reaganite]

Agree. Have treated 3 NPX pts in past yr, all per 0225 protocol. I have been able to keep mean dose to at least one parotid in 30 Gy range for each case. Not quite 26Gy, but still qualifies as parotid sparing in my book. Agree that 59.4Gy is a high elective dose, but first echelon nodes for NPX are RPs and high level II. So if you believe in dose-painted IMRT utilizing a high risk (intermediate) PTV, then the electively treated region around the parotid will always be included within this intermediate dose in NPX cases. Granted we don't have any trials comparing dose-painted IMRT with 3 prescription dose levels to conventional 50/70Gy sequential tx. That said, many of us were trained using the former and there are supportive large volume single institutional experiences (MSKCC, etc) showing excellent outcomes with this regimen.

So if you guys have an unknown primary with unilateral adenopathy, and you are covering the nasopharynx in your elective volumes, what do you do about the contralateral neck? I ask this because the recs I have seen (and what we did where I trained) was to treat contralateral II-IV + RPLN, with level II coverage only to the transverse process of C1. But again, the Nancy Lee NPX protocol calls for coverage to base of skull even if node negative.

 

[deleted4401]

Totally logical question about the unknown primary. My thought is that nobody really knows what the answer to that, but because the odds are that it is oropharynx >> nasopharynx ~= larynx >oral cavity, we play the odds on the contralateral side. One could make the argument to go up to BOS if the EBV is positive.

 

[medgator]

One could make the argument to go up to BOS if the EBV is positive.

Yup.... HPV and EBV testing can be very helpful here.

 

[Gfunk6]

I looked at the Ang & Garden H&N Bible (4th edition) to see what their comments on NPx were. They do provide a nice historical perspective which answers the OP's question.

Originally, with conventional setup, all neck nodes, primary disease, and high-risk clinical sites received 50 Gy in 25 fractions. This was followed by a boost to 16 Gy to 20 Gy in 8 to 10 fractions to high-risk/gross disease sites, respectively.

Nowadays, they recommend the usual 60 Gy and 70 Gy in 33-35 fractions to the high-risk/gross disease sites using IMRT. They don't explicitly mention doses to "elective nodes." However, in their case studies many patients are treated with an IMRT plan for the primary, base of skull, and upper neck which is then matched with a low neck AP or AP/PA photon field w/ larynx block. This low neck field gets 50 Gy in 25 fractions.

So I guess if you were trained this way, it is a totally reasonable approach which can potentially spare the patient larynx/brachial plexus morbidity.