Hi CCA9674, - After 2 Cryotherapy treatments and a rising PSA of over 7, I would GUESS that what is meant by "flat", is that the Prostate cells have been architecturally altered by the treatments, so that the Prostate has essentially been destroyed.
There is probably no target left for further localized treatment efforts, which means that the rising PSA is most likely coming from disease that is "systemic", which means it it likely to be circulating in his blood/lymph systems rather than from a localized tumor. IF TRUE, this means that his Prostate Cancer (PCa) can spread to other parts of the body (metastasize), with bones being a favorite target, although it can spread to any other vital organ.
Systemic disease is thought to be incurable so, if applicable, the goal changes from one of attempts to "cure" the PCa, to one of attempting to "control" what has now become a "chronic" disease. Some form of Hormone Therapy (HT) is the usual initial treatment, designed to block the production and reception of testosterone in the body, which is thought to fuel PCa growth.
HT is, usually, quite effective for widely varying time periods, in any individual patient, that are normally measured in years rather than months, so he has a good chance of living out his natural life expectancy, even if my ASSUMPTIONS are correct. There is morbidity (side effects) connected with such treatment, such as possible hot flashes, weight gain and suppressed libido.
Of course, all this is conjecture at this point, with the brief information you have furnished. But it may be worth discussing with the attending Physician who would have the full medical record available and could further clarify his situation. I hope this has helped! - John@newPCa.org (aka) az4peaks