From the details you provided I can't get to a definite conclusion whether the present problem is cancer therapy related or not.
Please provide some more details like
-What kind of a surgical resection was done ?
-What was the chemotherapy
regimen you took and for how long ?
Some more medical history would be useful too. Like
-Do you smoke ?
-Do you take alcohol regularly ?
-What is your occupational status ?
And from nature of complaint I am of the opinion that you are having Tinnitus
which can be the symptom of damage to the cochlea(hearing apparatus in ear). The damage could be due to drugs you took or some other unrelated condition.
Please visit an ENT specialist
and get your hearing checked and also try to do a High Frequency Pure Tone Audiogram.
Hope I have clarified some of your concerns.
Please revert with any further queries.