I am thinking I had read about have extra treatments in a trial study to see if it would help prevent recurrence. Could this be the reason?

Husband diagnosed Oct '11 Cancer of the vocal cord Nov '11 removed right vocal cord. Neck Dissection, cancer in one node, .2, very small & contained) Jan '12 Radiation and Cisplatin, 6 doses. June '12 & Dec '12 clear Pet scan. April '13 Celebrating 1 year cancer free since treatment ended.