In select patients with castration‐resistant prostate cancer and bone metastases, re‐treatment with radium‐223 offers potential disease control with minimal hematologic toxicity, according to results from a follow-up study (NCT01934790) published in The Prostate.

A total of 44 patients with radiologic or biochemical progression or escalating pain following successful initial radium-223 treatment were re‐challenged with up to 6 additional radium‐223 injections. Per protocol, none received chemotherapy or had visceral metastases in the interim.

Re-treatment was well-tolerated over 2 years with no new safety concerns and favorable effects on disease progression, Oliver Sartor, MD, of Tulane Cancer Center in New Orleans, and colleagues reported. Grade 3 anemia was the sole treatment‐related adverse event during follow-up, described as worsening of pre-existing anemia. Other grade 3 events included single cases of spinal cord compression, arthralgia, and muscle weakness unrelated to treatment. None of the patients had neutropenia or thrombocytopenia.

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Treatment benefits were sustained. Median overall survival was 24.4 months. Radiographic progression or death occurred in 19 of 44 patients, with a median radiographic progression-free survival of 9.9 months. Median time to PSA progression was 2.2 months.

The investigators also observed low rates of bone progression. Radiographic bone progression occurred in 5 of the 44 patients. Median times to first symptomatic skeletal event (SSE) and SSE‐free survival were 16.7 and 12.8 months, respectively. In addition, the median time to progression of total alkaline phosphatase was not reached.

“These results are promising and provide a rationale for further study to more precisely define benefits of re‐treatment with radium‐223,” Dr Sartor’s team stated.

The study was funded by Bayer, which produces radium-223 (Xofigo®).

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Sartor O, Heinrich D, Mariados N, et al. Re‐treatment with radium‐223: 2‐year follow‐up from aninternational, open‐label, phase 1/2 study in patients with castration‐resistant prostate cancer and bone metastases. Prostate. 2019;79:1683-1691. doi:10.1002/pros.23893