Author: By Lynda Williams, Senior medwireNews Reporter
medwireNews: New unconfirmed bone lesions during enzalutamide treatment may be a form of pseudoprogression for chemotherapy-naïve men who have stable or responding metastatic castration-resistant prostate cancer (mCRPC), analysis suggests.
By contrast, such lesions may predict poor survival in patients who received docetaxel before beginning enzalutamide therapy, report Andrew Armstrong, from Duke University in Durham, North Carolina, USA, and co-authors in JAMA Oncology.
“These findings reinforce the importance of avoiding premature discontinuation of treatment based on new unconfirmed lesions detected on a follow-up bone scan in men with metastatic castration-resistant prostate cancer whose condition is stable or responding to enzalutamide, and the importance of functional imaging for diagnosing bone metastases”, they say.
The post-hoc analysis of the PREVAIL trial of chemotherapy-naïve patients identified new lesions on the first (early) or second (late) bone scan after initiation of enzalutamide 160 mg/day in 27.5% of 643 participants who remained free from prostate-specific antigen (PSA) increase or soft-tissue progression.
Median radiographic progression-free survival (PFS) was unreached in these men and in the 466 participants without new unconfirmed bone lesions, while the corresponding median overall survival (OS) durations were also statistically comparable, at unreached and 32.4 months.
“These results suggest that new unconfirmed lesions detected on follow-up bone scans may represent pseudoprogression in men with mCRPC and are indicative of a favorable treatment response to enzalutamide”, the researchers write.
Overall, 18.1% of the 404 AFFIRM participants who had previously received docetaxel and had achieved stable or responding disease on enzalutamide therapy had new unconfirmed early or late bone lesions. Again, median PFS did not significantly differ between this group and the participants without new bone lesions, at 13.6 and 13.9 months.
However, while median OS was unreached in AFFIRM patients with or without new unconfirmed bone lesions, the hazard ratio for death of 1.94 significantly favoured those without the new lesions.
“These results suggest that newly observed lesions in some men with mCRPC who had received prior docetaxel may more likely reflect the first evidence of true progression”, postulate Andrew Armstrong and co-authors.
The investigators note that both the PREVAIL and AFFIRM studies did not show any difference in quality of life over time between patients with and those without new unconfirmed bone lesions.
They conclude: “Given these findings, we recommend a patient-level decision around the clinical benefits of continuing therapy, based not solely on bone scan findings but also on other disease manifestations, including pain, toxic effects, serum markers such as PSA and alkaline phosphatase levels, and soft-tissue disease as well as patient preference and informed decision-making.”
Armstrong AJ, Al-Adhami M, Lin P, et al. Association between new unconfirmed bone lesions and outcomes in men with metastatic castration-resistant prostate cancer treated with enzalutamide. Secondary analysis of the PREVAIL and AFFIRM randomized clinical trials. JAMA Oncol; Advance online publication 12 December 2019. doi:10.1001/jamaoncol.2019.4636
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