V5 Lung

[Gfunk6]

So I know some of you are doing IMRT for lung and esophagus. You look at the V20 (looks good!), you look at the MLD (looks good!), and you look at the V5 . . .

In some recent thoracic protocols (RTOG 1010 comes to mind) they've asked that the V5 < 55%. Are you guys looking at V5? Do you think it has been sufficiently validated to serve as an endpoint?

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[ShirleyT]

Yes, I always look at lung V5. The only study i am aware of showing its use is from MDACC, where they showed it was the most important predictor:
http://www.ncbi.nlm.nih.gov/pubmed/16997503


i always try to keep lung v5 as low as possible, will accept streaking and hot spots in the plan to allow dosimetry to push the V5. I aim for 60% or lower and if they are esophagus patients and may go to surgery i really like 50% or lower because the same group from MDACC showed lung V10 predicts for postop pulmonary complications in these patients.

 

[Palex80]

If extensive nodal irradiation in breast cancer becomes daily practice again and people start treating these patients with VMAT, RapidArc or Tomotherapy, we may start getting some more firm data on how a high V5 may predict for pneumonitis.

 

[TarHeelRadOnc]

MLD and V20 are far more validated than V5 in my opinion. While V5 is intriguing I don't think you can say its as validated. As such, Iook at the MLD and V20 first and then check the V5 just to see what it is. I haven't run into too many cases where I felt the need to change a plan in light of the V5 with MLD and V20 being met.

Agree that V20, MLD, and even sup-inf location are far more validated than V5.
Currently, I am not altering plans or doses
based on V5.

MDACC paper is a nice contribution to the literature on this topic, but unfortunately has several statistical methodoligic problems: (1) The authors of this study used a Cox proportional hazards model to compare the statistical significants of the covariates (lung volume, GTV, MLD, rV5-rV80, and aV5-aV80) in predicting clinical RP. Unfortunately, for the Cox model to be statistically valid, the covariates have to be independent of one another. MLD, rV5-rV80 and aV5-aV80 are not independent of one another. If the covariates are co-dependent, then the most statistically valid method for multivariate comparison is using Bootstrap modelling... which is very labor intensive. (2) The authors also failed to develop a "test" and "validation" cohort to confirm the statistical validity of their predictors (V5 specifically). Jeff Bradley's group at Wash U used Bootstrap modelling in their study in the Red J a few years ago. They also used a separate "test" cohort - from Wash U- and "validation" cohort- from RTOG 9311. In my opinion, this is the most statistically valid paper on this topic. (3) Finally, the authors of the MDACC/V5 paper failed to include sup-inf location in the Cox model. The Wash U/RTOG 9311 paper identified MLD and sup-inf location as the most significant predictors of pneumonitis (even more than V20). Leaving sup-inf location out further weakens the validity of the conclusions.

 

[Palex80]

In other pneumonitis news...
http://www.ncbi.nlm.nih.gov/pubmed/22682812

Maybe we should start looking less at the V5 and more at what kind of chemo the oncology folks are giving to our patients.

 

[TarHeelRadOnc]

In other pneumonitis news...
http://www.ncbi.nlm.nih.gov/pubmed/22682812

Maybe we should start looking less at the V5 and more at what kind of chemo the oncology folks are giving to our patients.

Yes. I have asked the medical oncologists I work with to give less Carbo/Taxol (and more CDDP/VP-16 or Carbo/Alimpta for adeno) on account of this data. I have certainly noticed an increased risk of pneumonitis in elderly pts receiving Carbo/Taxol

 

[medgator]

Yes. I have asked the medical oncologists I work with to give less Carbo/Taxol (and more CDDP/VP-16 or Carbo/Alimpta for adeno) on account of this data. I have certainly noticed an increased risk of pneumonitis in elderly pts receiving Carbo/Taxol

Not to mention that carbo/taxol is a weaker copout compared to cis/etoposide for patients that can tolerate it. All of the pre-op chemoRT data is done with that, yet I still manage to find med oncs giving carbo/taxol in the community.

 

[seper]

Carbo/taxol is super easy to give apparently. At my practice, we have 4 medoncs just out of fellowship, and they use Carbo/taxol for everything: lung, esophagus (both SCC and Adeno), gyne, germ cell tumors, H&N. etc.

 

[medgator]

Carbo/taxol is super easy to give apparently. At my practice, we have 4 medoncs just out of fellowship, and they use Carbo/taxol for everything: lung, esophagus (both SCC and Adeno), gyne, germ cell tumors, H&N. etc.

It may be easier to give, but that doesn't mean it's necessarily better for the patient

Once again, we have the chinese to thank for creating an RCT to address this question

http://www.ncbi.nlm.nih.gov/pubmed/22418243
http://clinicaltrials.gov/ct2/show/NCT01494558

 

[SchwettieBalls]

Agree that V20, MLD, and even sup-inf location are far more validated than V5.
Currently, I am not altering plans or doses
based on V5.

MDACC paper is a nice contribution to the literature on this topic, but unfortunately has several statistical methodoligic problems: (1) The authors of this study used a Cox proportional hazards model to compare the statistical significants of the covariates (lung volume, GTV, MLD, rV5-rV80, and aV5-aV80) in predicting clinical RP. Unfortunately, for the Cox model to be statistically valid, the covariates have to be independent of one another. MLD, rV5-rV80 and aV5-aV80 are not independent of one another. If the covariates are co-dependent, then the most statistically valid method for multivariate comparison is using Bootstrap modelling... which is very labor intensive. (2) The authors also failed to develop a "test" and "validation" cohort to confirm the statistical validity of their predictors (V5 specifically). Jeff Bradley's group at Wash U used Bootstrap modelling in their study in the Red J a few years ago. They also used a separate "test" cohort - from Wash U- and "validation" cohort- from RTOG 9311. In my opinion, this is the most statistically valid paper on this topic. (3) Finally, the authors of the MDACC/V5 paper failed to include sup-inf location in the Cox model. The Wash U/RTOG 9311 paper identified MLD and sup-inf location as the most significant predictors of pneumonitis (even more than V20). Leaving sup-inf location out further weakens the validity of the conclusions.

Nice response.

What kind of V5 do you allow when giving whole lung RT to a kid with Ewing's or Wilms?

 

[Mandelin Rain]

Anybody have different thoughts on this V5 topic from years ago?

I've had a run of IIIb NSCLCs with extensive superior-inferior nodal burden. Mainly small nodes, but a lot of the them. Everywhere. The only way to achieve moderately good coverage, cord tolerance, and V20/MLD has been RapidArc, but that leaves me with 90-100% V5s. Static fields have looked terrible in general and not much better on V5. APPA with off cord is essentially palliative treatment with terrible coverage.

Are people treating these big V5s, or is it better to just punt them to chemo only and forego the small chance of long term control?

 

[Burt Radnolds]

I was just having this same discussion with some colleagues. There was a secondary analysis presented of RTOG 0617 at ASTRO last year that demonstrated lower lung V20 and use of IMRT to be the biggest predictors of less pneumonitis.

Furthermore V5 was not predictive of any toxicity endpoint whatsoever. They probably got excellent data for this too as they did not even constrain V5 and some of those 74 Gy IMRT plans probably had V5s of 100%.

I have heard some people say that they feel comfortable completely disregarding V5 at this point (at least in intact definitive lung). This was a non surgical trial so I cant comment on its applicability to preoperative chemo radiation.

 

[medgator]

I'm surprised the IMRT findings aren't getting more press. Most of my IIIA/B plans, especially with a lot of central disease have been getting imrt for a few years now.

Still having to submit crappier 3D plans for comparison for some insurance companies when getting authorization

 

[seper]

I agree that in inoperable stage III NSCLC it is safe to accept V5 to be as high as 70%.

 

[nkmiami]

biggest risk factors in my experience are inferior location (more lung will mover through the field) and taxane