ptjunkie t1_ivnstho wrote on November 9, 2022 at 8:36 AM

Reply to comment by ReasonablyBadass in Experimental “FLASH” cancer treatment aces first human trial by tonymmorley

They do, but typically the delivery nozzle of the machine rotates around the patient to get other angles.

ReasonablyBadass t1_ivnt9d7 wrote on November 9, 2022 at 8:42 AM

I meant at the same time, so that you get higher energy in the tumor tissue.

ptjunkie t1_ivntufc wrote on November 9, 2022 at 8:51 AM

I don’t think there is a benefit from doing it all at once. You can just rotate and dynamically collimate the beam to hit it over a longer period of time with the same effect.

Not to mention that multiple angles would require multiple beams, or complicated beam splitters to change the energy levels for the changing depth of tumor from different angles.

In practice, most treatment plans are delivered in fractions anyway, to synchronize the radiation delivery with the cancer cell life cycle.

They aren’t trying to burn the tumor out, they are trying to snuff out the tumor cells as the body heals around it.

st4nkyFatTirebluntz t1_ivnxe2o wrote on November 9, 2022 at 9:44 AM

Listen, I'm high, tired, and didn't even slightly read the underlying study. But, wasn't that the whole point? That they tried maximizing the rate of delivery to the affected area, and that it seems to improve the ratio of therapeutic benefit to harmful side effect?

Spitballing wildly, I'd imagine there's some sort of optimal rate for tumor destruction (obviously dependent on the type of tumor and other specific details), and optimal rates for non-tumor preservation, and you'd be able to optimize between the two by utilizing multiple beams from multiple directions in certain scenarios.

Mounta1nK1ng t1_ivpfm3h wrote on November 9, 2022 at 5:27 PM

You are correct. The whole point is delivering it all at once so you get the FLASH effect. Different radiobiological mechanism than traditional fractionated radiotherapy.

Mounta1nK1ng t1_ivpcbmz wrote on November 9, 2022 at 5:06 PM

The FLASH studies have shown the lower side effects by using a single pulse, so the idea when putting this into clinical practice would be a single shot. Obviously no fractionation, as this isn't relying on the 5 R's. It's relying on a transient radiation-induced hypoxia that affects tumor cells more as they're already hypoxic.

For clinical treatment they would be looking at multiple treatment head gantries so the tumor could be shot from multiple angles at once in a single pulse so that you get the benefit of the FLASH effect that this treatment relies on.