Scintigraphic aspects of the recurrence of treated Paget's disease of bone.

The value of bone scintigraphy in the prediction and detection of a relapse of Paget's disease of bone after treatment, as well as the pattern of such a recurrence, were studied in a group of 40 patients. Thirty of these received a combination of calcitonin and HEDP, ten were treated alternately with calcitonin and HEDP. Scintigraphic deterioration is reliable evidence for a recurrence of Paget's disease of bone; one third of all recurrences was noted first on the bone scintigram. In another third of the cases of recurrence, however, the scintigram showed virtually no signs of deterioration. Scintigraphically a recurrence appears as a diffuse and homogeneous increase in activity in an affected part of the skeleton, or a focal and spotty increase of uptake in a diseased area, or a progression of a lesion beyond its original boundaries into healthy bone. Recurrence is usually not a generalized process occurring throughout the skeleton, but remains restricted to one or several lesions. Recurrence after combined treatment appeared to differ in nature from that seen after the use of calcitonin alone; the former was probably due to local exacerbation of the disease, probably caused by insufficient suppression of the Pagetic cells at these sites. The chance of recurrence could not be predicted on the basis of the pretreatment bone scintigram.