DOES RENAL DAMAGE OCCUR AFTER THE ADMINISTRATION OF P-32 FOR PALLIATION OF PAIN FROM SKELETAL METASTASES

In normal adults, the maintenance of phosphate balance involves the re absorption of 85-90% of filtered phosphate by the proximal tubule. Al a glomerular filtration rate (GFR) of 125 ml min(-1) and a plasma phos phate concentration of 1.3 mmol l(-1), the filtered phosphate is appro ximately 235 mmol day(-1). Following intravenous administration 25-50% of P-32 is excreted over 4-6 days in normal subjects. In spite of suc h extensive renal handling of phosphate and, therefore, of P-32, there are no data in the literature concerning possible P-32-related nephro toxicity. Adult dosimetry values for the kidney after P-32 are reporte d as 4.8 rad mCi(-1) h(-1) (0.048 mSev 37 MBq(-1) h(-1)). The entry cr iteria for P-32 therapy insist on a normal serum creatinine value, ref lecting awareness of potential renal damage. To answer the fundamental question of whether there is demonstrable renal damage after P-32, We undertook serial measurements of GFR in patients given P-32 for treat ment of pain from skeletal metastases. Twenty-one patients who had nor mal pre-treatment renal function as shown by normal serum creatinine v alues were administered P-32 orally in doses ranging from 277.5 to 466 .2 MBq, with a mean of 425.5 MBq. Pre-treatment, GFR was estimated wit h Tc-99(m)-diethylenetriamine pentaacetate renography using the Gates protocol. Post-treatment, GFR was estimated serially as far as possibl e, at weeks 1, 2, 3 and 4 and then every 4 weeks for another 3 months, at which Feint follow-up ceased. Serum creatinine was assessed pre-tr eatment and every 2 weeks until the end of follow-up, in addition to a ll other parameters and a clinical evaluation. Mean pro-treatment GFR was 87.5 ml min(-1), with a range of 48.7-110 ml min(-1). Not all pati ents could fulfil the entire follow-up schedule as designed, but we ob tained a minimum of four follow-up tests, two before and two after 4 w eeks post-treatment. GFR fell to 72% of the pre-therapy value during t he first 4 weeks following therapy By the sixteenth week, however, the mean value had returned to or exceeded the pre-treatment value. There was no change in serum creatinine values. At a time when multiple the rapies are being considered, this early depression of GFR may be of im portance. A closer assessment of altered renal function may be warrant ed and other sensitive tests of renal damage like microalbuminuria cou ld be used. ((C) 1998 Lippincott-Raven Publishers).