Lose the flab.
Top Line: Ahh, chest wall bolus during post-mastectomy radiation (PMRT).
The Study: Do you use it? What thickness? Do you put it on every day or do you have an elaborate scheme for alternating days? There is a lot of oncolore and limited data supporting how bolus has been used during PMRT. Historically, chest wall bolus was used to replicate the exfoliative effects of Co-60. And while it has been used widely in randomized trials of PMRT and in clinical practice, there is wide variation in bolus practice. Recently, an ESTRO panel was created to generate consensus recommendations for bolus use during PMRT. The big takeaway is that bolus should not be routinely used for everyone receiving PMRT. The reason is that the ESTRO chest wall CTV excludes 3-4 mm below the skin surface in patients without skin involvement. Their physics advisory team indicated that modern treatment planning algorithms are accurate in estimating dose at that depth below surface. Using this logic, bolus should only be applied as a beam modifying device when the 95% isodose line inadequately covers the target 3-4 mm below skin surface. But wait, we’ve seen chest wall recurrences involving the skin. Yes, but a recent study of nearly 2000 patients found that 10-year chest wall recurrences were rare (<2%) after PMRT and that bolus was not associated with reduced local recurrence. With that said, there are obviously cases where bolus is indicated when the CTV includes the skin (tumors approaching or involving the skin or when there is inflammatory breast cancer). In addition, the group did recommend routine bolus use when treating a chest wall recurrence and/or unresectable or fungating breast tumors. When bolus is used, it should be placed at simulation. Also, 3-5 mm bolus is sufficient to provide adequate skin dose as thicker bolus may simply bring supratherapeutic dose to the surface and further increase toxicity. Last, they recommended that when bolus is used, it should be applied daily for the whole treatment course.
TBL: These ESTRO consensus recommendations provide a common sense approach to bolus use during PMRT. | Kaidar-Person, Radiother Oncol 2021