Rose blackspot - cut back rose?

Grajean

A rose we inherited has always had blackspot but this year almost leafless. Its about 12 feet tall flowered earlier, no sign of new buds. Could we cut it back at this time of year to about half? 

Borderline

At 12 ft tall, are they climbers? Summer flowering roses can be cut back if you feel the plant will not gain anymore. If it repeats flower into autumn, your rose may take a bit of time to recover and you may not get further blooms later this year.