For head and neck cancer radiation requiring boost, do you plan using simultaneous integrated boost technique vs cone down technique?

SIB always provides more conformal dose distributions compared with sequential boost IMRT, as the beam placement and intensity of the sequential boost do not take into account the dose distributions of the first plan. This issue, as well as the lower fraction doses to the normal tissue embedded in the secondary targets in SIB (but not in sequential IMRT), suggest SIB superiority. These issues are nicely discussed in a classical paper by Mohan et al., PMID 10701741.

As always, Dr. @Dr. First Last is correct, this time regarding the superiority of SIB for conformality.

The trade off though is fractionation, since a SIB plan will have varying fraction sizes if you use multiple targets. For most cases, this is acceptable (or even desired). For example, a standard 3 target PORT with 60/57/54 in 30 fx to tumor bed, operative bed, and non-operated elective sites.

However, there are situations where the fractionation (i.e., total dose and dose per fraction) is more important and especially when there is a large gap in the total dose that you want to get to the differing targets, the fractionation may supercede the conformality especially if the conformality need is not critical.

As a cautionary note though, i...

Dr. @Dr. First Last cited this classic paper, "Radiobiological considerations in the design of fractionation strategies for intensity-modulated radiation therapy of head and neck cancers." In it, you can see the genesis of the 56/63/70 Gy in 35 fractions regimen which seems to be the most common SIB (and the authors explicitly called this SIB, which was about the first or second paper to use the exact term, if I recall correctly) regimen now used. The 56/63/70 regimen was 100% derived... the theoretical physicists might call this "figuring things out on paper." The authors of the paper ended their conclusion section thusly:

"IMRT dose distributions are most conformal when designed to be delivered as SIB. Using isoeffect radiobiological relat...

Have moved almost exclusively to sequential plans for a number of reasons.

While Dr. @Dr. First Last is correct that SIB plans are more conformal, particularly within 1 cm of the high dose PTV, OARs beyond 1 cm receive a lower total dose with SEQ plans (secondary to lower total dose to elective PTV). This becomes more important as elective nodal doses are lowered further and further. Currently dosing the elective neck to 4140 cGy/23 fractions. And of course, MSK has published their experience with elective neck at 3000 cGy in HPV+ Oropharyngeal. With these regimens, would be uncomfortable reducing the fraction size to less than 180 cGy.

Second, SEQ plans do make it easier effort-wise to generate an adaptive plan if needed (e.g., no need t...

For patients with a large dose gap between two dose levels (say 50Gy and 70Gy), I now do a sequential plan. The uninvolved neck skin can start the healing process in the last 10 days while boosting gross disease in say, a p16+ OPhx SCC.

This will be consistent with the adoption of bigger dose changes between elective volumes and gross disease (say, 30Gy elective, while maintaining 70Gy to gross disease, as per MSKCC data).

In scenarios where boost plans would be 5 days or shorter (such as 50/60 seq or 50/60/70 seq), the lack of conformality seen with sequential plans plays more of a role for me, and I would prefer dose painting (54/60 or 56/63/70).

I have not personally seen more homogeneity with a sequential H&N plan while maintaining appropr...

We primarily use sequential plans because we deliver 30 Gy elective neck dosing for HPV+ disease and 40 Gy elective neck dosing for HPV- disease (excluding oral cavity cancer). This is based on our institutional experience and RCT. All targets receive 2 Gy per fraction. We also do a lot of adaptive planning and sequential planning makes this easy.

Tsai et al., PMID 35050342

Deschuymer et al., PMID 32044165

Either.