RT Journal Article
SR Electronic
T1 <sup>177</sup>Lu-PSMA SPECT Quantitation at 6 Weeks (Dose 2) Predicts Short Progression-Free Survival for Patients Undergoing <sup>177</sup>Lu-PSMA-I&amp;T Therapy
JF Journal of Nuclear Medicine
JO J Nucl Med
FD Society of Nuclear Medicine
SP 410
OP 415
DO 10.2967/jnumed.122.264677
VO 64
IS 3
A1 John, Nikeith
A1 Pathmanandavel, Sarennya
A1 Crumbaker, Megan
A1 Counter, William
A1 Ho, Bao
A1 Yam, Andrew O.
A1 Wilson, Peter
A1 Niman, Remy
A1 Ayers, Maria
A1 Poole, Aron
A1 Hickey, Adam
A1 Agrawal, Shikha
A1 Perkins, Gary
A1 Kallinen, Annukka
A1 Eslick, Enid
A1 Stockler, Martin R.
A1 Joshua, Anthony M.
A1 Nguyen, Andrew
A1 Emmett, Louise
YR 2023
UL http://jnm.snmjournals.org/content/64/3/410.abstract
AB 177Lu-PSMA is an effective treatment in metastatic castration-resistant prostate cancer (mCRPC). Our ability to assess response rates and adjust treatment may be improved using predictive tools. This study aimed to evaluate change in 177Lu-PSMA SPECT quantitative parameters to monitor treatment response. Methods: One hundred twenty-seven men with progressive mCRPC previously treated with androgen-signaling inhibition (99%) and chemotherapy (71%) received a median of 3 (interquartile range [IQR], 2–5) 8-GBq (IQR, 8–8.5 GBq) doses of 177Lu-PSMA-I&amp;T. Imaging included 68Ga-PSMA-11 PET/CT (SUVmax &gt; 15 at a single site and &gt; 10 at all sites &gt; 2 cm), diagnostic CT, and 177Lu SPECT/CT from vertex to mid thigh (24 h after treatment). 177Lu SPECT/CT quantitative analysis was undertaken at cycles 1 (baseline) and 2 (week 6) of treatment. Clinical and biochemical results were assessed to evaluate prostate-specific antigen (PSA) progression-free survival (PFS) and overall survival (OS). Results: A PSA reduction of more than 50% was seen in 58% (74/127). The median PSA PFS was 6.1 mo (95% CI, 5.5–6.7), and OS was 16.8 mo (95% CI, 13.5–20.1). At the time of analysis, 41% (52/127) were deceased. At baseline and week 6, 76% (96/127) had analyzable serial 177Lu SPECT/CT imaging. SPECT total tumor volume (TTV) was reduced between baseline and week 6 in 74% (71/96; median, −193; IQR, −486 to −41). Any increase in SPECT TTV between baseline and week 6 was associated with significantly shorter PSA PFS (hazard ratio, 2.5; 95% CI, 1.5–4.2; P = 0.0008) but not OS. Median PSA PFS in those with an increase in SPECT TTV was 3.7 mo (95% CI, 2.8–6.8), compared with 6.7 mo (95% CI, 5.8–10.6) in those with no increase in SPECT TTV. An increase in SPECT TTV greater than 20% was also associated with PSA PFS (hazard ratio, 1.9; 95% CI, 1.2–3.0; P = 0.008) but less significantly than any change in SPECT TTV. There was a significant difference in PSA PFS between patients with both increased PSA and SPECT TTV and patients with reduced SPECT TTV and PSA (median, 2.8 vs. 9.0 mo; P &lt; 0.0001). Conclusion: Increasing PSMA SPECT TTV on quantitative 177Lu SPECT/CT predicts short progression-free survival and may play a future role as an imaging response biomarker, identifying when to cease or intensify 177Lu-PSMA therapy.