Radiotherapy to the target area is given at the max lifetime dose to give best chance of killing the cancer, which is why you can't have it again. Having said that, radiotherapy doesn't often fail in the target area (although it does occasionally happen). When radiotherapy fails, it's more likely to be because there was some cancer already spread somewhere else which wasn't known about. That can often (but not always) still be treated with radiotherapy if suitable treatment paths can be designed which don't take any tissues over their max lifetime dose, usually using SBRT (narrow high power beams), and if there is only a very small number of mets in specific tissues.
If radiotherapy fails and you get recurrence in the prostate (rare), there may still be curative options. Salvage prostatectomy is done in some specialist centres (such as Guys and St.Thomas's). Increasingly, focal therapy is also considered for this, such as HIFU to target the recurrence.
There has been a little talk of redoing radiotherapy in the same area if the original treatment was many years ago. There is some thought that the tissues recover over time and might handle another high dose after many years, but this isn't part of any standard treatment, and I'm not even aware that it's been trialed anywhere. Trialing it might be a difficult sell, because there's clearly a risk of catastrophic side effects (such as overdosing leaving a large chunk of necrotic tissue which can no longer defend itself from infection), when there are effective non-curative treatments such as life-long hormone therapy.
Edited by member 29 Aug 2023 at 20:46
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