One reason they might be wanting to radiate his parotid is because of the extracapsular spread(spread out side of the lymph node). I had stage 3 SCC on the right posterior third of my tongue, they took the whole right side, did a hemiglossectomy. They got clear margins, but they also pulled 40 lymph nodes and found 1 lymph node positive of cancer, but mine didn't have the extracapsular spread, so mine was all contained in the lymph node. But the cancer in my lymph node looked completely different then the cancer in my tongue, so now they are suspecting parotid involvement.