To determine the proportion of cancer patients who survived, we first need to find the fraction of cancer patients who survived, and then convert it to a proportion.
Step 1: Find the fraction of cancer patients who survived.
Fraction of cancer patients who survived = Number of cancer patients who survived / Total number of cancer patients
Fraction of cancer patients who survived = 105 / 125 = 21 / 25
Step 2: Convert the fraction to a proportion.
To convert a fraction to a proportion, we divide the numerator by the denominator and multiply by 100 to get a percentage.
Proportion of cancer patients who survived = (21 / 25) * 100% = 84%
\boxed{84\%} of the cancer patients survived.