Sorry to hear, Phrannie.
I was treated with radiation 5x to the same left side neck with IMRT 2x, IORT 2x, and Proton Therapy, some with surgery or with chemo for 7 recurrences, so reirridation is possible with select patients by experienced doctors, and cancer centers. The lymph nodes near the collar bone sounds like level V in the lymph chain, which I had too, so additional radiation, along with chemo or targeted therapy or even immune therapy these days, may be recommend depending on surgical biopsies.
A concern with reirridation to level V, depending on prior radiation to that area, is Brachial Plexopathy.
I also did Cisplatin/Taxotere/5-FU before, so my two other chemo's/targeted therapy were
Erbitux/Taxotere, and then Carboplatin another time.
If you have any questions, just ask, and good luck.