Over recent decades, the use of PET/CT imaging, which integrates functional and anatomic modalities, has increased in PCa. Targeted PSMA-PET is now widely used in imaging diagnostics for PCa, including early diagnosis, staging, advanced metastasis assessment, and detecting biochemical recurrence post-prostatectomy (23). Several PSMA-based radiotracers, such as ⁶⁸Ga-PSMA-11, ¹⁸F-PSMA-1007, ⁹⁹Tcm-PSMA I&S, and ¹⁸F-DCFPyl, have been developed and using in clinical (21–23). A study on biochemically recurrent PCa estimated that PSMA-PET imaging could reduce 75 PCa deaths per 1000 patients, increase life years by 988, and add 824 quality-adjusted life years compared to conventional imaging (4). While PSMA PET/CT with ⁶⁸Ga-PSMA-11 is the most researched and clinically advanced, emerging ¹⁸F-based methods with lower positron energy and longer half-life may offer higher spatial resolution. Potential future applications include tumor localization, treatment stratification, and efficacy monitoring of advanced PCa. Standardizing PSMA ligand PET imaging interpretation is necessary, and efforts are needed to develop user-friendly, side-effect-free diagnostic methods.

Some PCa patients, due to health limitations, cannot undergo surgery and instead rely on innovative treatments like PSMA-RLT, which has shown considerable clinical success (22). The ligand ¹⁷⁷Lu-PSMA-617 binds specifically to PSMA on PCa cells and emits high-energy β and γ particles to kill cancer cells, inducing DNA damage in cancer cells and their surrounding microenvironment. This therapy has been proven to prolong survival and enhance the quality of life in patients with metastatic castration-resistant prostate cancer (mCRPC) (24, 25). PCa exhibits radioresistance, especially in hypoxic conditions. However, α-emitters like ²²⁵Ac-PSMA-617 release potent α-particles unaffected by hypoxia, offering potential benefits for patients with widespread metastases or prior ^177Lu-PSMA-617 treatment failures (26). Adverse effects of PSMA-RLT must be closely monitored. ²²⁵Ac/¹⁷⁷Lu-PSMA-617 therapy results in significant radioactive uptake in salivary glands, potentially causing glandular damage, dry mouth, and reduced taste function, thereby impacting the quality of life (27, 28). Notably, salivary glands act as dose-limiting organs in PSMA-RLT, constraining higher dose administration and impacting therapeutic outcomes. Furthermore, radiotherapy presents challenges such as high costs, reliance on specialized equipment, and the need for trained personnel. Radionuclides are essential in PCa imaging and treatment but pose significant challenges and side effects as mentioned above. Thus, emerging technologies aim to improve diagnostic and therapeutic outcomes with lower costs and fewer side effects, increasing accessibility for patients.

Professor Hongjie Dai is a pioneer in Second Near-Infrared Window (NIR-II) imaging, which extends the range from First Near-Infrared Window (NIR-I, 700-900 nm) to NIR-II (1000-3000 nm), further subdivided into NIR-IIa, NIR-IIb, NIR-IIc, and NIR-IId (29, 30). In vivo fluorescence imaging in living tissues is affected by absorption, scattering, and autofluorescence. Compared to NIR-I, NIR-II fluorescence imaging minimizes light absorption and scattering, reduces autofluorescence, and enables non-invasive imaging with ultra-high resolution, a high signal-to-background ratio (SBR), and centimeter-level tissue penetration (31). This powerful imaging technique complements clinical modalities like MRI, PET, and X-ray. NIR-II imaging overcomes the limited penetration of other optical methods and excels in molecular imaging. In 2009, Dai’s team introduced carbon nanotubes for NIR-II fluorescence imaging, vividly depicting tumor vasculature and paving the way for advanced NIR-II bioimaging technologies (32). The development of NIR-II probes (1050-1350 nm, 1700 nm) enabled breakthroughs in real-time blood flow monitoring and skull imaging, heralding the shift from NIR-I to NIR-II in vivo imaging (33, 34).

Indocyanine green (ICG), a cyanine-based small molecule fluorescent probe approved by the FDA in 1959, is widely used in various fluorescence-guided surgeries (35). ICG has a high molar extinction coefficient, high fluorescence quantum yield, and good biocompatibility, making it useful in intraoperative angiography, lymphangiography, and tumor resection (36). Research, including animal studies, has demonstrated that ICG’s NIR-II fluorescence imaging outperforms NIR-I imaging, facilitating the clinical translation of NIR-II technology (37). However, as a non-targeted probe, ICG cannot differentiate between benign and malignant tumors, and its accumulation in non-target tissues may result in false-positive tumor diagnoses (38). Consequently, there is a need for NIR dyes with specific targeting capabilities.

Several research groups are currently developing NIR probes with specific targeting. Preclinical animal studies and ex vivo human tissue experiments have shown promising results (39–43). In 2016, Dai’s team used the rapidly excreted NIR-II fluorophore CH1055 to achieve high SBR imaging of the lymphatic system in mice (44). Additionally, new materials have been developed for tumor molecular imaging in the NIR-II region, targeting PD-L1, high endothelial venules (aMECA-79), CD169+ macrophages, and CD3+ T cells in lymph nodes (45–47). These advancements enable non-invasive molecular imaging at the single-cell or vessel level and have also facilitated in vivo imaging of cancer vaccines and immune responses (31). This progress marks a shift from non-specific to specific targeting, offering promising potential for tumor-specific FGS.

In NIR FGS, small molecules, gold particles, rare earth nanoparticles, and carbon nanotubes are being extensively studied as NIR-II fluorescent dyes in clinical and preclinical trials (29, 48). Studies using CD105-targeted molecular imaging probes have achieved a tumor-to-muscle ratio of up to 300, allowing precise tumor visualization and removal of residual cancer cells, ensuring thorough yet conservative resections and setting a benchmark for imaging-guided surgery (49). The gold particle-phosphatidylcholine (Au-PC) probe minimizes interactions with serum proteins, cells, and tissues, enabling accurate lymph node localization. This novel fluorescent technology shows strong potential for clinical application (50). NIR-II molecular imaging excels in deep tissue imaging and shows high clinical translation potential. Advances include new fluorescent probes, preclinical disease models (e.g., cancer, cardiovascular, neural), and clinical applications like perfusion imaging, lymph node localization, immunotherapy, photodynamic therapy, and FGS, paving the way for a novel surgical paradigm. Despite significant progress, most tumor-targeting NIR fluorescent probes remain in preclinical stages. Notably, in 2021, Pafolacianine (OTL38) became the first FDA-approved tumor-targeting fluorescent imaging agent for clinical use, marking a milestone in the field (51).

Following diagnosis, PCa patients frequently undergo radical prostatectomy, with some requiring extended pelvic lymph node dissection (ePLND). Gandaglia et al. reported that combining PSMA-radioguided surgery (PSMA-RGS) with ePLND provides high sensitivity and specificity for identifying lymph nodes during surgery (53). However, the radiation exposure from this surgical method may pose risks to both surgeons and patients, highlighting NIR imaging as a safer and more promising alternative. In NIR imaging, researchers initially developed PSMA-specific fluorescent probes capable of circulating in the body and targeting tumor sites (54, 55). Signals collected under NIR laser (especially in the NIR-II region) enable deep, high-resolution imaging with a high SBR for precise fluorescence-guided tumor resection ( Figure 2A ). For example, the PSMA-targeting fluorescent probe OTL78 was developed by conjugating the high-affinity PSMA ligand DUPA with the commercial NIR dye S0456. This probe achieved a tumor-background ratio (TBR) of 5:1 in vivo, effectively detecting small tumors (56). Despite its good biosafety, the phase II clinical trial also found that OTL78 had low sensitivity for detecting tumor-positive margins (48.6%) and limited ability to identify positive lymph nodes (64.3%) during surgery (57–59). Another NIR probe, Cy-KUE-OA, specific to PSMA and cell membrane phospholipids, was developed and validated in ex vivo imaging studies, showing potential for clinical application in FGS for prostate cancer (60). Current challenges such as probe size, extended circulation times, and the limitation to the NIR-I region (54, 55) underscore an urgent need for the development and clinical application of NIR-II probes specific for PCa in urological surgery.

Determining tumor boundaries during surgery remains challenging. Rapid pathological testing provides a diagnosis within 30 minutes but is limited by the morphological similarity of tumor cells in HE staining, leading to potential misdiagnoses and complications. Immunohistochemical staining (IHC) supports diagnosis but requires 2–3 hours, limiting intraoperative utility and risking missed small lesions (61). NIR-specific probes have shown promise in preclinical and clinical studies for visualizing tumor boundaries in ex vivo tissues, including lung, osteosarcoma, and colorectal cancers (41, 43, 62). In PCa, incubating preoperative needle biopsy strips with probes enables visualization of tumor tissues while sparing normal tissues, offering a potential diagnostic tool. Imaging intraoperative specimens can delineate tumor boundaries, aiding surgical and prognostic assessments ( Figure 2B ). Probes’ incubation times range from minutes to hours, with shorter times being clinically advantageous. PSMA-N064 solution and Cy-KUE-OA have demonstrated effective tumor visualization in PCa but require further development to match rapid pathological testing (60, 63). NIR-I imaging devices have achieved clinical maturity and are widely utilized. In contrast, NIR-II imaging systems and dyes offer the potential for enhanced image clarity. The adoption of NIR-II technology in clinical settings could herald a revolutionary advance in clinical imaging (48, 64).

Photothermal therapy (PTT) is an advanced technique that uses NIR light of specific wavelengths to activate photosensitive nanomaterials, converting light energy into heat to kill tumor cells or induce apoptosis, thus inhibiting tumor growth. PTT allows precise temperature control by adjusting laser power. The temperature increase to 41–43°C induces hyperthermia, which does not directly kill tumors but enhances the effects of radiotherapy and chemotherapy. Higher temperatures, including subcoagulation (43–55°C) and coagulation (55–100°C), cause rapid cell death by protein denaturation and cell membrane damage (67). NIR light in PTT penetrates tissues deeply while minimizing damage to normal tissues. Compared to traditional methods, PTT is minimally invasive, efficient, precise, and effective in inhibiting tumor metastasis (68). Pathological and biochemical recurrences frequently occur after PCa surgery. Combining mitochondrial-targeted NIR-II FGS with intraoperative PTT significantly reduces recurrence rates (69). PSMA-targeted PTT probes hold significant potential for further development, leveraging imaging for therapeutic applications.

Photodynamic therapy (PDT) is an important phototherapy method. Upon absorbing incident light, photosensitizer (PS) molecules transition from the ground state to a short-lived excited singlet state (~ns), followed by a more stable excited triplet state (~ms). From the triplet state, PS molecules can return to the ground state via Type I or Type II photodynamic reactions. Type I reactions involve electron transfer from activated PS to substrates, generating reactive oxygen species (ROS). In Type II reactions, energy is transferred directly to ground-state molecular oxygen, producing highly reactive singlet oxygen (¹O₂). These reactive species trigger various downstream biological events, such as cytotoxicity, inflammation, and vascular damage. Due to the limited diffusion range of ROS, targeted PDT can provide precise treatment for solid tumors (65). Researchers have synthesized PSMA-N064, a targeted photosensitizer IRDye700DX, which generates reactive oxygen under laser irradiation, inducing tumor cell apoptosis, delaying growth, and improving survival in PSMA-positive tumor mice (63). In fresh ex vivo human PCa tissue, PSMA-PDT treatment significantly increased cell apoptosis compared to untreated controls (63). PDT is limited by the hypoxic nature of solid tumors, while PTT carries the risk of off-target damage. The combination of PDT and PTT, whether applied simultaneously or sequentially, optimizes the benefits of both approaches while mitigating their individual limitations. PCa, traditionally considered a “cold tumor,” may be converted into a “hot tumor” through activation by PTT or PDT. Additionally, PSMA-targeted NIR phototherapy can be integrated with ADT and chemoradiotherapy to improve therapeutic outcomes.