In principle, you don't need a series resistance with a current source.
But it can't be seen from your diagram, why the circuit shouldn't work. Of course the input common mode range must be kept,
also the zero voltage difference between +ve and -ve input can be only maintained, as long as the output voltage is in the OP's linear
output voltage range. With Cfb of 100 pF and 18 uA current, output saturation is reached within a few 10 us and the input
voltage starts to drift away. Usual slope converters have a factor 100 or 1000 higher feedback capacitance.