28th October 2020

An 86-year-old man was treated 20 years ago with radiotherapy for a small carcinoma

An 86-year-old man was treated 20 years ago with radiotherapy for a small carcinoma on the left side of his tongue. He was a heavy smoker and social drinker but has been clean since that diagnosis. He recovered well and was lost to follow up 3 years after. He now presents with pain on the right side of his tongue and right-sided earache. Inspection of his tongue found a hard 2cm nodule extending to the right lateral border of the tongue, with some ulceration on its surface.

Which of the following is the most significant risk factor for his current oral lesion? Select ONE option only.