(UroToday.com) The 2026 ASTRO Multidisciplinary Radiopharmaceutical Therapy Symposium featured a plenary session and a presentation by Dr. Daniel Rosen discussing hematologic toxicity outcomes of Lu-PSMA-617 in patients previously treated with external beam radiotherapy for oligometastatic disease. Hematologic toxicities of Lu-PSMA-617 treatment can occur in patients and may limit further cycles. In fact, in the VISION trial,1 hematological toxicity was the most common adverse event leading to Lu-PSMA-617 treatment discontinuation:
External beam radiation therapy can also cause radiation induced lymphopenia, anemia, and thrombocytopenia. Factors associated with cytopenia include (i) field size, (ii) dose, (iii) location of disease, (iv) pretreatment regimen, and (v) age, amongst other factors. As radiation therapy for oligometastatic disease becomes standard of care, more patients will have had multiple courses of external beam radiation therapy directed at bony metastases prior to progressing to metastatic castration resistant prostate cancer (mCRPC) and Lu-PSMA-617 treatment. At the 2026 ASTRO Multidisciplinary Radiopharmaceutical Therapy Symposium, Dr. Rosen and colleagues evaluated if external beam radiation therapy to bony oligometastases prior to delivery of Lu-PSMA-617 impacted hematologic toxicities and outcomes.
Patients who received Lu-PSMA-617 for mCRPC at the Dana-Farber Cancer Center and who received prior external beam radiation therapy for bony oligometastases were identified via retrospective review (June 1, 2022 – June 1, 2025). Hematologic adverse events were identified at pre-cycle blood draws according to the VISION trial and CTCAE guidelines.
There were 70 patients that received external beam radiation therapy for bony metastases prior to Lu-PSMA-617 administration, with a median interval time of 32 months (IQR 18-56 months):
The median number of external beam radiation therapy courses prior to Lu-PSMA-617 was 2, with 39 patients receiving 2 or more prior courses. Overall, 24/70 patients (34.3%) did not receive the full 6 courses of Lu-PSMA-617, with 10 patients discontinuing due to disease progression, and 2 patients secondary to adverse events (neither of which was due to hematologic toxicities). There was no grade 3 or greater hematologic toxicities in the cohort, and grade 1 or 2 anemia was 16/70 (22.9%), thrombocytopenia 23/70 (32.9%), and leukopenia 17/70 (24.3%):
Compared to the VISION trial,1 there were higher rates of thrombocytopenia and leukopenia in this cohort, but a lower rate of non-completion of 6 rounds of Lu-PSMA-617:
When dichotomizing by 1 versus 2 or more prior courses of external beam radiation therapy, there was no statistically significant difference regarding anemia (32.3% versus 15.4%, p = 0.15), thrombocytopenia (32.3% versus 33.3%, p > 0.99), leukopenia (22.6% versus 25.6%, p > 0.99), or completion of all 6 cycles (70.1% versus 69.1%, p > 0.99):
Dr. Rosen concluded his presentation discussing hematologic toxicity outcomes of Lu-PSMA-617 in patients previously treated with external beam radiotherapy for oligometastatic disease with the following take-home points and future directions:
- Metastasis-directed external beam radiotherapy (ie. stereotactic body radiotherapy) prior to Lu-PSMA-617 is well tolerated with:
- Future studies of synchronous Lu-PSMA-617 and external beam radiation therapy may be warranted
Presented by: Daniel Rosen, MD, PhD, Brigham and Women’s, Dana-Farber Cancer Center, Harvard Medical School, Boston, MA
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Wellstar MCG Health, @zklaassen_md on Twitter during the 2026 American Society for Radiation Oncology (ASTRO) Multidisciplinary Radiopharmaceutical Therapy Symposium, Palm Desert, CA, Tues, Feb 17 – Wed, Feb 18, 2026.
Reference:
- Sartor O, de Bono J, Chi KN et al. Lutetium-177-PSMA-617 for Metastatic Castration-Resistant Prostate Cancer. N Engl J Med. 2021 Sep 16;385(12):1091-1103.