What are the advantages and disadvantages of concomitant versus sequential boost for treating cancers of the head and neck with IMRT?

When using SIB for HN IMRT there are a few different options for dose levels. In the definitive setting, I typically use 70/63/56 Gy in 2.0/1.8/1.6 Gy/fraction over 35 fractions. The 1.6 Gy/fraction is less than ideal, but the small dose escalation to 56 Gy (rather than 50 Gy in 2 Gy/fraction) makes up for it. An advantage of sequential boost is that the dose/fraciton can remain at 1.8-2.0 Gy/fraction.

I prefer using SIB over sequential boost because I find that sequential boost plans tend to b...

Concomitant boost IMRT requires just one, while sequential requires two plans (disregarding the possible need for adaptive re-planning, which would be the same in both). BED2 doses to the targets and to specified organs are expected to be similar, however, the doses to the non-defined tissues are higher in a sequential plan: it is always less conformal than a concurrent boost plan. A beautiful discussion of these issues, as well as a discussion of the biological consequences of different fractio...

I tend to use Sequential plans for patients receiving radiation alone, as I am somewhat uncomfortable using less than 1.8 Gy daily dose in the absence of chemotherapy. Sequential plans in general result also in better sparing of structures more than ~1 cm away from the high dose target. As the absolute elective nodal dose is less (I use 40-50 Gy depending on the clinical situation and parameters, vs 54-56 for SIB), this results in a lower integral dose to the patient.

SIB plans are logistically ...