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Lu-177 PSMA Therapy Shows Promise in Early-Stage Prostate Cancer: LUNAR Trial Dosimetry Analysis
A secondary analysis of the LUNAR trial reveals that neoadjuvant 177Lu-PSMA-I&T delivers well-tolerated radiation doses while significantly improving progression-free survival in patients with low-volume oligometastatic prostate cancer when combined with stereotactic radiotherapy.
Background
Oligometastatic prostate cancer—disease with limited metastatic spread—presents a unique treatment opportunity. The LUNAR trial investigated combining 177Lu-PSMA-I&T (targeted radiopharmaceutical therapy) with stereotactic body radiotherapy (SBRT). This secondary analysis examines radiation absorption doses to critical organs and tumor lesions.
Key Findings
In 45 patients receiving two cycles of 177Lu-PSMA-I&T (6.8 GBq each), quantitative SPECT/CT imaging revealed:
- Organ safety: Kidney dose 0.35±0.10 Gy/GBq; parotids 0.20±0.10 Gy/GBq; bone marrow 0.005±0.002 Gy/GBq—all within acceptable limits.
- Lesion heterogeneity: 123 tumor lesions showed wide variability (0.01–36.73 Gy range), with lymph node lesions receiving higher median doses than bone or soft tissue lesions.
- Clinical efficacy: Despite low measurable lesion doses, combination therapy improved progression-free survival to 17.6 months versus 7.4 months with SBRT alone (HR 0.37).
Why It Matters
Organs remain protected even in a neoadjuvant setting. The significant survival benefit despite low measured lesion doses suggests 177Lu-PSMA-I&T treats occult micrometastatic disease beyond imaging detectability, supporting this combination in early-stage disease.
Limitations
Secondary analysis of 45 patients at defined imaging time points. Substantial dose heterogeneity suggests opportunity for improved patient selection strategies. Extended follow-up is needed to establish durability of benefit.
Original paper: Dosimetry Analysis of 177Lu-PSMA-I&T in Patients with Low-Volume Oligometastatic Hormone-Sensitive Prostate Cancer: A Secondary Analysis of the LUNAR Trial. — Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 10.2967/jnumed.125.271467
