Good point gmcraft.

To my knowledge, In order to kill squamous cell carcinoma it takes over 50Gy, but is more like 60-70Gy to the primary tumor and involved lymph nodes, and lesser for uninvolved lymph nodes. I understand there is really no maximum amount of radiation that can be given, except exposure to workers. but it's more limited to the toxicity level of the organ and nearby structures like carotid artery, brain stem, brachial plexus, etc. I've had radiation 5 times, over 200Gy to the same left neck area, which were able to be fit in by different radiation modalities, safely, although my risks were and still are higher in certain aspects.

According to the NCCN Guidelines Principles of Radiation, page 19, for oral cancer, it shows the flow chart for radiation, which either IMRT or 3D conformal radiation is recommended. There is shows 66-70Gy in different fractions, even to 81.6Gy in hyper-fractions.

Brachytherapy, either Low Dose or High Dose, in select cases, can be used, but can be more than 70Gy when combined with external beam radiation such as IMRT. If used as sole therapy, 60-70Gy LDR, 45-60Gy HDR. I've had High Dose Rate IORT.

Proton Radiation, which I had, is not mentioned. It's a very precise form of targeted radiation that limits toxicities to nearby structures, and has no exit wound due to the Bragg Peak. The concentration of radiation is to the tumor. Several years ago when I had it, it was usually used in patients that failed prior radiation therapy. but can be used in clinical trials as primary treatment. It's radiation target is not as broad area, but with pencil beam proton radiation, they can fine tune the range, and sometimes combining it with other forms of radiation like I did.

I know for oropharyngeal cancer, they are avoiding level 1 lymph nodes, and other structures to limit side effects, in certain cases, and deintensification with some oropharyngeal related HPV, which is very responsive to radiation, but HPV involved in other areas. like oral mouth, larynx etc. to not have the same benefit.

The radiation is like a target with the cancer being the bullseye, but it also effects the surrounding areas lets say like a ring, they have different names, GTV, CTV, PTV. Maybe that can be lessened, but certain parts need to be strictly adhered to, and with IMRT the delivery can be dose painted.