Acute Lymphopenia and Recovery With Prophylactic Pelvic Nodal Radiotherapy in Oligometastatic Prostate Cancer: Interim Results From the Prospective PROLONG2 Cohort
Xin Qi, Hewei Wang, Huan Zhang, Xueying Ren, Mingwei Ma, Xiaoying Li, Wanqi Zhang, Zhisong He, Yi Song, Cheng Shen, Wei Yu, Yu Fan, Xianshu Gao, Hongzhen LiABSTRACT
Background
Prophylactic pelvic nodal radiotherapy (PRT) aims to eradicate occult pelvic nodal disease in oligometastatic prostate cancer but increases lymphocyte exposure. Its early hematologic safety and lymphocyte recovery when added to radiotherapy to the prostate/prostate region and all imaging‐visible metastases remain uncertain.
Methods
PROLONG2 is an ongoing, single‐center, prospective, nonrandomized, two‐arm cohort study. This interim analysis included 133 patients who completed radiotherapy: 86 with PRT and 47 without PRT (NPRT). The key safety endpoint was acute grade ≥ 3 lymphopenia. Other assessments included lymphocyte status at 6–12 months and acute hematologic and genitourinary/gastrointestinal toxicities. The association was estimated by multivariable logistic regression adjusted for age, clinical N stage, and hormone‐sensitivity status. Survival analysis was exploratory.
Results
Acute grade ≥ 3 lymphopenia occurred in 43/86 PRT patients (50.0%) and 8/47 NPRT patients (17.0%). PRT remained associated with acute grade ≥ 3 lymphopenia after adjustment (OR, 4.03; 95% CI, 1.55–11.54; p = 0.006). At 6–12 months, grade ≥ 2 lymphopenia occurred in 18.2% versus 16.7%, and grade ≥ 3 lymphopenia in 1.3% versus 2.4%, respectively. Among evaluable PRT patients with acute grade ≥ 3 lymphopenia, 25/38 (65.8%) recovered to grade 0–1. No acute grade ≥ 3 genitourinary/gastrointestinal toxicity occurred. Progression‐free survival data remained immature, with only eight events reported.
Conclusions
PRT was associated with markedly more acute lymphopenia, but persistent severe lymphopenia was uncommon and the between‐group difference was substantially attenuated at 6–12 months. Continued prospective hematologic surveillance and mature survival data are needed to determine PRT's benefit–risk profile.
Trial Registration
Chinese Clinical Trial Registry: ChiCTR2400083776