223 Ra-Dichloride in castration-resistant metastatic prostate cancer: improving outcomes and identifying predictors of survival in clinical practice

Abstract

Purpose

We first assessed whether the pattern of referrals to a nuclear medicine clinic improved as experience with ²²³Ra-dichloride increased, and whether referral patterns affected patient outcomes, and second assessed the value of bone scintigraphy, total alkaline phosphatase (tALP) and lymphadenopathy as prognostic factors in patients receiving ²²³Ra-dichloride.

Methods

A total of 57 patients eligible to receive ²²³Ra-dichloride over a 2-year period (March 2014 to March 2016) were retrospectively assessed and prospectively followed (median follow up 298 days). ²²³Ra-Dichloride was administered at 4-week intervals for a maximum of six injections. The numbers of patients in years 1 and 2 referred in relation to extent of bone disease (EOBD) category and overall survival (OS) were determined. The prognostic factors EOBD category, baseline tALP (tALP_BL), tALP response, greatest percentage reduction in tALP from baseline in any treatment cycle (ALP_max; among patients with elevated ALP_BL), and the presence of lymphadenopathy were assessed as predictors of OS.

Results

The proportion of patients with EOBD1 was higher in year 2 than in year 1 (29% and 4%, respectively), and in year 2 there was a lower rate of symptomatic skeleton-related events, a higher proportion of patients completing six cycles, and longer (albeit nonsignificant) OS (p = 0.55). There were significant differences in OS between EOBD4 patients and those in all other groups and between EOBD1 and EOBD3 patients (p < 0.05). OS was longer in patients with normal tALP_BL than in those with elevated tALP_BL (p = 0.01), in ALP responders than in nonresponders (p < 0.05), and in patients without lymphadenopathy than in those with lymphadenopathy (p = 0.29). OS was correlated with ALP_max (r² = 0.24).

Conclusion

A collaborative multidisciplinary referrals pathway, together with increased experience with ²²³Ra-dichloride, led to improved outcomes. In patients with elevated tALP_BL, tALP dynamics may be useful for monitoring response and predicting OS. Imaging and prognostic markers may therefore be of value for individualizing ²²³Ra-dichloride treatment and planning retreatment; however, further studies are required.

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