Whole Brain Radiotherapy: Is it valid?

The debate between whole brain radiation therapy and stereotactic radiation is spurious. One thumb rule that determines the “success” of stereotactic radiotherapy is the presence of extracranial disease. If it is still present, whatever lesions are being treated, are all likely to recur.

I strongly feel that motivation for stereotactic came in from higher billable for this modality. It isn’t valid and practical for most scenarios across the world. I am not going in for all defence of whole brain radiation which does have its drawbacks, like affecting the quality of life- but any robust psychometric testing hasn’t reliably quantified this. Likewise, the advantages touted for stereotactic don’t always hold water.

The “researchers” have pushed for statistical mumbo-jumbo with the “expert” committees that jump in to “bring order” to the mess of “confusion”. There is no uniform consensus, still, but it is slowly becoming the norm to push for stereotactic XRT (even for multiple mets) when a whole brain radiation therapy may suffice. I believe that the well was poisoned earlier on by papers pushing for many lesions to be treated via Gamma Knife. Cyberknife has only made things worse.

To top it all, multiple “universities” have overactive public relations department to push for “cutting edge treatment”. I was appalled to note that someone was pushing VMAT, for head and neck, as the “standard”. No Sir. Modulation is still not established on substantial evidence but is being only used for its perceived benefits.

This post was triggered because I had a lengthy discussion with a patient’s family about the use of stereotactic radiation for a solitary lesion versus the whole brain, even though she has an extensive extra-cranial disease. She was arguing from half-baked knowledge because she was concerned about the quality of life. Someone told her that the patient might not be able to do mental calculations. Well, is this reason valid in the socio-cultural context? Nope. Only if people are keen to promote “hippocampal sparing” (which adds to unnecessary complexity to treatment), which ultimately, in my opinion, offers no robust advantage. Likewise, scalp sparing again is fancy vanity metric which I call as intellectual masturbation. Good for the conferences to blow your trumpets but the poor practical application or impacting outcomes.

No, whole brain radiation isn’t out of “fashion”. It has more utility in the face of progressive extracranial disease. Stereotactic radiotherapy may be kept in reserve for recurrence or local failure. Whole brain with concomitant boost might serve the same purpose. I prefer SIB, to be honest, which for me, hasn’t shown any sign of failure.

Always keep some steroids handy, taper them down and patients do well to go to receive definitive chemotherapy. I believe, whole brain XRT will hold more importance in the setting of oligometastatic disease that is likely to impact survival. It is an anecdotal observation- liver Mets have a profound impact on survival. Lung Mets or bone Mets end up with a relatively prolonged course.

Whole brain radiation dose: think about it.

I have always wondered about the tolerance of brain tissue to radiation. Whole brain radiation can be “safely” given up to 54-60 Gy (in the previous protocols for glioblastoma- NO LONGER used). Brainstem dose, in the current QUANTEC era, is not exceeded to 54Gy as a point dose (disregard the 10cc volume for a minute).

The whole brain mean dose is preferably not exceeded beyond a mean dose of 28Gy which we are propagating in the post-hippocampal era (so as to say).

It brings me back to the original question. Why is a focused radiation dose exceeding 60Gy (for example) more injurious than whole brain dose to the same effect? And why brainstem isn’t affected in that scenario?

Another question. If a phased plan is executed, is it sufficient to only add up the mean doses? This is because both the phases have used different calculation subsets; radiation delivery is also going to be markedly different.

Well, no easy answers!