PT  - JOURNAL ARTICLE
AU  - Kumar, Shejil
AU  - Crumbaker, Megan
AU  - Harvey, Christopher
AU  - Pathmanandavel, Sarennya
AU  - John, Nikieth
AU  - Swiha, Mina M.
AU  - McDonald, Michelle M.
AU  - Clifton-Bligh, Roderick
AU  - Lee, Adrian
AU  - Bastick, Patricia
AU  - Counter, William
AU  - Nguyen, Andrew
AU  - Emmett, Louise
TI  - The Tyr Phenomenon: A Hypocalcemic Response in High-Volume Treatment Responders to <sup>177</sup>Lu-Prostate-Specific Membrane Antigen Therapy
AID  - 10.2967/jnumed.123.265759
DP  - 2023 Sep 01
TA  - Journal of Nuclear Medicine
PG  - 1412--1416
VI  - 64
IP  - 9
4099  - http://jnm.snmjournals.org/content/64/9/1412.short
4100  - http://jnm.snmjournals.org/content/64/9/1412.full
SO  - J Nucl Med2023 Sep 01; 64
AB  - 177Lu-prostate-specific membrane antigen (PSMA) is an effective treatment for metastatic castration-resistant prostate cancer. Rarer treatment-related adverse events have not yet been described. Methods: We present case reviews of 2 men with a marked hypocalcemic osteosclerotic response to 177Lu-PSMA-I&T therapy. A clinical dataset of 177Lu-PSMA-I&T therapy was evaluated to estimate the incidence and clinical association with hypocalcemia. Results: Forty-one of the 127 men (32%) had a serum calcium drop, and 6 (5%) developed clinical hypocalcemia during 177Lu-PSMA therapy. The baseline total tumor volume was significantly higher in those who developed hypocalcemia (median, 3,249 cm3 [interquartile range, 1,856–3,852] vs. 465 [interquartile range 135–1,172]; P = 0.002). The mean prostate-specific antigen response in those with hypocalcemia was 78% (SD, 24%). Conclusion: Hypocalcemia may occur in response to 177Lu-PSMA-I&T, particularly with both high-volume bone metastases and a significant prostate-specific antigen response, and may be severe, requiring corticosteroids. Further evaluation of 177Lu-PSMA–induced hypocalcemia is required to better understand mechanisms, optimal treatments, and repercussions from any subsequent osteosclerotic response.