Potential use of radiation methods for diagnosing bone metastases of castration-resistant prostate cancer: a literature review

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Introduction

Prostate cancer (PC), one of the most prevalent cancers in men, originates in the glandular epithelium of the prostate [1]. From 2011 to 2021, the incidence of PC in Russia rose by 41.69% [2], making it a socially and economically significant concern. The development of metastatic castration-resistant PC (mCRPC), which is caused by a proliferation of androgen-insensitive cells, makes resistance to androgen deprivation therapy particularly significant [3]. The mean time to hormone therapy resistance is 1.5–2 years, which limits future therapeutic choices. This is complicated by significant variability in tumor morphology, serum prostate-specific antigen (PSA) levels, disease stage, and the risk of relapse [4].

The prognosis worsens with metastatic disease, with only 30% of patients surviving for five years [5]. The incidence of bone metastases in patients with mCRPC can reach 90% [6]. Visceral metastases are most frequently observed when secondary bone lesions are already present, which suggests a poor prognosis [7].

The initial development of bone metastases is determined by an imbalance between bone-resorbing cells (osteoclasts) and bone-forming cells (osteoblasts) resulting from interactions between cancer cells and elements of the internal bone milieu [8, 9].

Diagnostic imaging techniques are essential for the initial assessment of the tumor grade and the number and size of metastases, as well as for monitoring patients with mCRPC during treatment. Each diagnostic radiology technique has its own advantages and limitations. Multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) effectively detect advanced tumors owing to anatomical imaging; however, their application in assessing PC treatment efficacy is restricted. Scintigraphy performs well in screening for bone metastases because of its high sensitivity, but is less effective in evaluating disease progression [10].

For the early detection of local or systemic tumors in PC, hybrid diagnostic techniques like positron emission tomography with computed tomography (PET/CT) and single-photon emission computed tomography with computed tomography (SPECT/CT) with diagnostic radiopharmaceuticals are utilized, taking into account the functional and morphological components of the obtained data [11].

Prostate-specific membrane antigen (PSMA) ligand PET has significantly augmented diagnostic algorithms for patients with PC owing to quantitative data on radiopharmaceutical uptake in the targeted areas. Though there are some unresolved concerns, PSMA PET/CT has demonstrated promising results in predicting the efficacy of cancer treatment [12].

Radionuclide therapy in mCRPC targets PSMA, with subsequent imaging examinations to confirm radionuclide binding [13]. Early relapses, high serum PSMA levels, Gleason scores, and a more aggressive illness are all correlated with PSMA expression [14, 15].

Physiologically, PSMA is also expressed in the lacrimal and salivary glands, proximal renal tubules, liver, spleen, and proximal small intestine [14]. The presence of PSMA activity has been documented in the peripheral ganglia and central nervous system [16].

The most promising and frequently used isotopes for radioligand therapy are ¹⁷⁷Lu and ²²⁵Ac. ¹⁷⁷Lu has unique diagnostic and therapeutic benefits, including the binding of PSMA molecules by β− and γ-emitters ¹⁷⁷Lu-PSMA. ²²⁵Ac exerts a powerful therapeutic effect via binding of PSMA by the α-emitter ²²⁵Ac-PSMA [3]. Prostate tumor cells accumulate ²²⁵Ac- or ¹⁷⁷Lu-labeled PSMA ligands, which damages DNA and eventually results in tumor cell death [17, 18].

Clinicians treating PC should focus on defining objective patient selection parameters for radioligand therapy, as well as on the early detection and imaging assessment of relapses following various PC therapies.

This review examines the potential of various diagnostic radiological modalities in mCRPC patients.

Diagnostic radiology techniques

Radiography is an imaging technique that generates consolidated images of organs, bone structures, and tissues employing the penetrative properties of X-rays. It is a reliable and accessible method for evaluating the structure and location of bone metastases [19]. Kitagawa et al. [20] revealed that radiography exhibits high specificity (80.9%), low sensitivity (45.8%) [due to limited contrast uptake by bone marrow lesions], and an accuracy of 74.8% [20]. If the bone matrix loss is less than 25%–30%, it is difficult to detect bone metastases early by radiography; also, there is limited ability to evaluate medulla alterations [21]. Thus, conventional radiography techniques are more effective for the urgent detection of fractures and postoperative monitoring of surgical hardware and implants [21].

Multislice CT (MSCT) is a modern diagnostic radiology technique that uses X-rays to generate cross-sectional images. Because of its high resolution, MSCT produces detailed organ and tissue images. In a meta-analysis examining the diagnostic utility of diagnostic radiology modalities in patients with spinal metastases, the sensitivity and specificity of MSCT were 79.2% and 92.3%, respectively [22–24].

One of the primary benefits of MSCT is the short scan time, which is especially essential in emergency circumstances where patients suddenly develop pain. This technique identifies fractures caused by existing secondary bone lesions and spinal nerve compression [21, 23]. However, due to the limited contrast uptake by soft tissues, MSCT is seldom used as a primary diagnostic tool in PC. It is more typically employed for the detection of distant metastases and for biopsy guidance [19]. This technique determines the structure of the bone metastases and the extent of bone destruction. Additionally, it enables the use of extra image processing techniques for metal artifact reduction in the imaging-based evaluation of surgical hardware [23]. The formation of reactive sclerosis during treatment and the progression of osteoblastic metastases appear to be similar on MSCT scans (by increased lesion density). Because of this characteristic of bone metastases, the RECIST 1.1 criteria categorize these lesions as non-measurable (Fig. 1) [24]. Radiomics facilitate the quantitative assessment of lesions [25].

 

Fig. 1. a, Lumbar spine MSCT, sagittal plane: osteoblastic lesions observed in the S1 and S2 vertebral bodies (white arrow), hemangioma in the L2 vertebral body (orange arrow); b, thoracic spine MSCT, sagittal plane: osteoblastic lesions in thoracic vertebral bodies (white arrow), mixed lesion noted in the Th12 vertebral body (orange arrow).

 

Magnetic resonance imaging is a diagnostic radiological modality that generates images using electromagnetic waves in a constant magnetic field. The advantages of MRI include the lack of ionizing radiation and superior soft tissue imaging. It is one of the most effective techniques for noninvasive bone marrow evaluation (Fig. 2). In addition to anatomical diagnosis, MRI is useful in determining the degree of spinal stenosis and compression, the size and location of lesions, and the extent of vascular supply [23]. The disadvantages include a lengthy scan time and a variety of contraindications, such as the presence of pacemakers and metal implants [26, 27].

 

Fig. 2. a, b, Pelvic MRI, coronal plane, T2WI; c, d, pelvic MRI, coronal plane, T1WI; case follow-up a, c of February 2023 and b, d July 2023: osteoblastic lesions in pelvic bones, increase in lesion size during follow-up (white arrows).

 

A multiparametric approach to the diagnosis of mCRPC involves the evaluation of anatomical T1-weighted images (T1WIs) (scar tissue identification for evidence of replacement fibrosis) and T2WIs (for edema detection) for a detailed examination of the anatomical zones of the prostate and surrounding soft tissues. Short tau inversion recovery sequences, which eliminate the influence of fluid in the resulting images, can be used to differentiate between fat and fluid inclusions in the lesions. Functional diffusion-weighted imaging (DWI) sequences with apparent diffusion coefficient maps may be employed to determine tumor location and aggressiveness. Dynamic contrast-enhanced MRI is utilized for differentiating between inflammatory and benign changes, as well as for ascertaining tumor location and grade [28].

In a prospective study by Perez-Lopez et al. (TOPARP-A) [29], a whole-body DWI MRI was performed in 21 patients with bone metastases at baseline and 12 weeks following treatment. Out of all the bone metastases, five lesions were selected and evaluated. The volume and diameter of the lesions declined 12 weeks after olaparib therapy; the outcomes were inversely proportional to the treatment response. The authors concluded that DWI can play a critical role in assessing the response of bone metastases to mCRPC treatment.

The published results of studies comparing bone scintigraphy and whole-body MRI varies, most likely because different MR scanners are used and there are no established protocols. A meta-analysis revealed that whole-body MRI exhibits a higher sensitivity and specificity (94% and 99%, respectively) than bone scintigraphy (80% and 95%, respectively), indicating that whole-body MRI can be used to verify or rule out bone metastases [30, 31].

Padhani et al. [32] developed and presented guidelines (MET-RADS-P) for whole-body MRI efficacy criteria to assess lesions in patients with advanced PC. According to the authors, accurate assessment of the response to treatment will facilitate the future development of targeted therapy [27].

Due to radiopharmaceutical absorption, hybrid diagnosis techniques are more successful in determining the functional state of lesions than anatomical imaging and bone metastasis follow-up using MSCT and MRI [26].

Bone scintigraphy is a radionuclide imaging technique that utilizes diphosphonate complexes to examine bone lesions. The technique entails assessing the radiopharmaceutical uptake involved in bone metabolism at active bone formation sites, which are linked to benign and malignant abnormalities, as well as physiological processes [24]. In posttraumatic, neoplastic, and infectious alterations, radiopharmaceutical uptake is correlated with local blood flow and osteoblast/osteoclast activity [33].

When activity is identified in the scintigrams of patients with bone metastases, the 2 + 2 rule is used to account for the flare phenomenon detected during osteoblast activation and sclerotic transformation of lesions in the early treatment period [34]. The emergence of two new lesions at a follow-up imaging test six weeks or more after the initial diagnosis is considered progression. An increase in the size of the lesions detected on bone scintigraphy is not regarded as a sign of disease progression [35]. Since this phenomenon is identified within the first three months following chemotherapy and hormone therapy, it may resemble disease progression [36].

Of significance are the scintigram quantitative assessment parameters, such as the bone scan index (BSI) and bone scan lesion area (BSLA).

BSI is the sum of individual bone areas multiplied by the percentage of each bone’s involvement in metastasis. Processing BSI values manually or semiautomatically is time-consuming and subjective. Therefore, scintigram assessment techniques using aBSI automated computer analysis were developed [37, 38], which significantly increase the reproducibility of quantitative assessment to 10 s as opposed to 5–30 minutes with manual assessment [39]. When combined with the diagnostic evaluation of anatomical images, aBSI parameters can be utilized as prognostic biomarkers.

Dennis et al. [40, 41] assessed preliminary data and discovered that BSI changes during treatment were closely correlated with overall survival in patients receiving chemotherapy. The evaluation was carried out three to six months following treatment. The authors concluded that a twofold increase in BSI during treatment results in a 1.9-fold increased risk of death.

Bone scintigraphy enables the detection of early metabolic changes, frequently several weeks or months before they are detected by radiography. Given that the sensitivity and specificity of this technique for detecting bone metastases in PC are 74.5%–83% [42–44] and 62%–82%, respectively, the use of complementary anatomical imaging approaches, such as radiography, MSCT, MRI, or hybrid methods (SPECT/CT and PET/CT) is required [34].

After comparing bone scintigraphy and MRI findings [44], the authors concluded that bone scintigraphy is a rapid and cost-effective technique for the early detection of bone metastases. However, there are several limitations, including the accumulation of radiopharmaceutical agents in inflammatory lesions and regions of intensive bone formation. Lytic bone lesion imaging is challenging due to the lack of bone remodeling and the presence of a soft tissue component where radiopharmaceutical uptake is not feasible [12].

This method can be supplemented by SPECT/CT findings. An additional benefit is the use of BSI as a prognostic marker. The limitations of bone scintigraphy include reduced potential for imaging of lytic lesions (only lesions with radiopharmaceutical uptake can be assessed), lengthy scan time, lower sensitivity compared to CT and MRI, and the flare phenomenon in response to treatment [27, 33].

An additional SPECT/CT can help avoid these limitations.

Single-photon emission computed tomography with computed tomography is a hybrid diagnostic radiology technique that generates 3D images using a gamma chamber and a multislice CT scanner. After computer processing, maps with functional information on metabolic processes in various organs and tissues were matched with anatomical CT images [45]. This approach reduces the disadvantages of each method and improves the diagnostic value.

SPECT/CT results are used to semi-quantitatively assess lesions using the standardized uptake value body weight (SUVbw), a parameter based on body weight. The following formula is used for differentiating between degenerative changes and metastatic lesions:

$SUVbw=\frac{A\times B}{\text{C}},$

where A = local activity concentration, B = body weight, and C = administered activity. SUV_bw values in bone metastases are significantly higher than in degenerative changes; the sensitivity and specificity in differential diagnosis are 73.8% and 85.4%, respectively [46, 47].

The diagnostic utility of scintigraphy with ¹⁷⁷Lu-PSMA was assessed in patients with PC with elevated PSA levels and negative findings on conventional imaging examinations (MSCT, MRI) [48]. The analysis included 26 patients with PSA failure after curative therapy; ¹⁷⁷Lu-PSMA was administered, and SPECT/CT and whole-body planar scintigraphy were then performed. According to SPECT/CT findings, the total metastasis detection rate was 38.5%, with secondary lesions being most frequently detected in the lungs, abdominal lymph nodes, and mediastinum. When PET/CT with ⁶⁸Ga-PSMA is unavailable, SPECT/CT with ¹⁷⁷Lu-PSMA can detect secondary lesions in more than one-third of patients, making it a valuable diagnostic tool in mCRPC patients (Fig. 3).

 

Fig. 3. a, Whole-body scintigraphy with ¹⁷⁷Lu-PSMА, anterior view; b, posterior view of December 2021: diffuse-plus-focal radiopharmaceutical hyper uptake of differing intensity, multiple PSMA-positive bone lesions; c: whole-body scintigraphy with ¹⁷⁷Lu-PSMА, anterior view; d, posterior view of April 2022: reduced radiopharmaceutical uptake in the lesions, absence of new areas of radiopharmaceutical hyper uptake.

 

Several authors have conducted comparative studies of SPECT/CT and MRI. When assessing the potential of SPECT/CT and whole-body MRI in patients with bone metastases, the sensitivity, specificity, and precision of both methods were found to be 94.4%, 75%, and 92.3%, respectively, indicating that these modalities are complementary (Table 1) [23, 49, 50].

 

Table 1. Comparison of the diagnostic criteria for bone lesion detection employing diagnostic radiological techniques
Diagnostic method	Study (publication)	Patients/studies, n	Sensitivity, %	Specificity, %
Radiography	Kitagawa et al., 2018 [20]	129	45.8	80.9
MSCT	Liu et al., 2017 [22]	183 (3)	79.2	92.3
MRI	Liu et al., 2017 [22]	381 (7)	94.1	94.2
	Sun et al., 2020 [31]	1939 (15)	94	99
SPECT/CT	Sun et al., 2020 [31]	1939 (15)	80	95
	Sheikhbahaei et al., 2019 [42]	507 (14)	79	62
	Shen et al., 2014 [43]	901 (12)	83	82
ОФЭКТ/КТ	Liu et al., 2017 [22]	343 (4)	90.3	86
	Mohd Rohani et al., 2020 [46]	34	73.8	85.4
ПЭТ/КТ	Liu et al., 2017 [22]	403 (5)	89.8	63.3

 

Positron emission tomography with CT is a hybrid radionuclide diagnostic method that makes use of a three-dimensional distribution of radio-emitting indicators labeled with positron (β⁺) emitters. This enables the noninvasive assessment of the body’s biochemical and functional processes [45]. PET/CT uses radiopharmaceuticals such as ¹⁸F-FDG (fluorodeoxyglucose) and amino acid-based agents to detect diverse molecular and cellular mechanisms of tumor metabolism [45].

Semiquantitative measurements and the standardized uptake value (SUV) allow for the differentiation of malignant and benign lesions [51].

The use of ¹⁸F-FDG PET/CT in the initial assessment and PC staging is restricted. This approach is not recommended for detecting bone metastases in patients with PC. Low bone tissue glucose consumption and inadequate ¹⁸F-FDG uptake make it difficult to identify osteoblastic lesions. Moreover, this approach does not distinguish between primary and secondary lesions, particularly for small lesions [45].

¹⁸F-NaF (sodium fluoride) is a positron emitter that binds to osteoblasts during osteogenesis, producing positive findings in both benign and malignant lesions [51].

In PC, proliferating tumor cell membranes contain ¹⁸F-CH (fluorocholine) [52]. ¹⁸F-CH exhibits a longer half-life than ¹¹С-choline (up to 109.8 minutes vs. 20.4 minutes), making it appropriate for PET centers without a cyclotron and increasing its availability. Compared to ¹⁸F-FDG, this agent was reported to be more successful in detecting metastases in PC because of greater radiopharmaceutical uptake in bone lesions [53].

When analyzing the PET/CT findings in patients with bone metastases, ¹⁸F-CH and ¹⁸F-NaF demonstrated comparable sensitivity of 91%. However, the specificity of PET/CT with ¹⁸F-CH and ⁸F-NaF was 89% and 83%, respectively [54].

PET/CT identifies metabolic changes before the detection of morphological changes by MSCT. ¹⁸F-CH PET/CT is comparable to whole-body MRI and superior to bone scintigraphy and MSCT. However, it is linked to disadvantages such as the flare phenomenon, inadequate liver and urinary tract imaging, and inconsistent detection of small lesions at low serum PSA levels [27].

The effectiveness of antineoplastic treatment can be predicted using quantitative data on radiopharmaceutical uptake provided by PSMA PET.

The FDA approved ⁶⁸Ga-PSMA and ¹⁸F-PSMA in 2020 and 2021, respectively, as the first and second PSMA PET indicators for patients with PSA failure [55].

According to the working group guidelines (PCWG3, 2016), the evaluation of baseline data and follow-up in patients with PC must be based on diagnostic radiological findings [43]. The RECIST 1.1 criteria for anatomical imaging must be used to solid tumors identified by MSCT and MRI [56], whereas the response criteria (PERCIST) must be used to evaluate PET/CT results [57].

Anatomical imaging methods along with serum PSA measurement are used to evaluate therapy response for solid tumors in PC patients based on the RECIST criteria [58].

According to the PERCIST criteria, the response to treatment is assessed qualitatively (e.g., based on the presence/absence of lesion activity) and quantitatively, where the initial and follow-up imaging parameters must be identical. The standardized uptake value normalized by lean body mass (SUL) is used for measurements. The results are presented as a percentage of the peak SUL for the lesion exhibiting the highest activity [59].

Maffey-Steffan et al. [58] compared the findings of ⁶⁸Ga-PSMA PET/CT (interpreted using modified PERCIST criteria, with a semiquantitative SUVmax analysis) and whole-body ¹⁷⁷Lu-PSMA scintigraphy performed 24 hours after treatment, using the tumor-to-background ratio. Progression was defined as the emergence of new lesions and/or increased radiopharmaceutical uptake, partial remission as the elimination of one or more lesions and/or decreased radiopharmaceutical uptake, and stable disease as no changes in the number of lesions and radiopharmaceutical uptake. A mixed response was characterized by the elimination of some lesions and/or their decreased radiopharmaceutical uptake, with the emergence of new lesions. The results matched the visual perception of various imaging methods. The interpretation of 24-hour SPECT/CT findings is sufficiently accurate, and the technique is simple and cost-effective. Follow-up PET/CT is time-consuming, making examinations in patients with pain syndrome challenging. For monitoring patients, the PSA level must be measured and 24-hour SPECT/CT findings must be analyzed, whereas PET/CT should be utilized for patient selection and treatment efficacy assessment [59].

The LifeX software was used for assessing ⁶⁸Ga-PSMA PET/CT images, including the analysis of PSMA levels and their expression in the tumor, with a prespecified SUV threshold of 3.0 (based on software settings) and 45% (based on published findings of previous studies). The resulting data were manually updated. A decline in tumor volume and PSMA expression after treatment was reported in 63% and 74% of patients, respectively; moreover, there were significant differences in SUV_max values before and after treatment. The authors concluded that a quantitative analysis of the molecular volume and PSMA expression in the tumor can be employed to assess the response to ¹⁷⁷Lu-PSMA therapy [57, 60].

Another study used ¹⁸F-NaF PET/CT and ^99mTc SPECT/CT to assess SUV_max, SUV_peak, SUV_mean, metabolic bone volume, and total bone uptake. The formula SUV_mean×MBV was applied for each lesion with radiopharmaceutical uptake. The preliminary conclusion was that SUV parameters with SPECT/CT were substantially lower than those with PET/CT. However, compared to PET/CT, the radiopharmaceutical uptake with SPECT/CT was significantly higher. The values of metrics calculated for metastatic lesions were significantly higher than those for benign lesions [61].

Vlachostergios et al. [62] compared ⁶⁸Ga-PSMA PET/CT with a quantitative assessment and SPECT/CT with a semiquantitative assessment in ¹⁷⁷Lu-PSMA therapy. Three lesions with the highest radiopharmaceutical uptake in comparison to the liver were evaluated using SPECT/CT results. A five-point scale was used, with 0 denoting no changes, 1 denoting low tumor activity, 2 denoting strong tumor activity but below that of the liver, 3 denoting tumor activity equal to that of the liver, and 4 denoting tumor activity greater than that of the liver. The PET/CT findings were then used to evaluate the average SUV_max for the five lesions with the greatest radiopharmaceutical uptake compared to the SUV_mean of the liver. The following scale was used: 0 = no changes, 1 = SUV_max < SUV_mean of the liver, 2 = SUV_max = 1–2.5 × SUV_mean of the liver, 3 = SUV_max = 2.5–5 × SUV_mean of the liver, and 4 = SUV_max >5 × SUV_mean of the liver. The authors found that semiquantitative PSMA measurements using SPECT/CT and PET/CT can serve as prognostic indicators of overall survival in patients with mCRPC because this parameter represents the metastatic load.

A study [63] assessed the efficacy of radioligand therapy with ¹⁷⁷Lu-PSMA in patients with mCRPC. A technique developed in Germany has shown a significant increase in the overall survival and quality of life. In a multicenter study, 145 patients received one to four rounds of ¹⁷⁷Lu-PSMA treatment, with an overall biochemical response of 45%. For patients with PSA failure, PSMA-based hybrid imaging greatly increases the diagnostic efficacy. PSMA PET/CT can be valuable in radiotherapy planning because it can identify affected lymph nodes and rule out distant metastases, resulting in treatment adjustments in up to 30% of patients. Radionuclide therapy with labeled PSMA analogs enhances the diagnosis and treatment of mCRPC, which needs to be validated in prospective studies.

A multicenter, retrospective study was conducted by a group of researchers [64] to establish a RECIP 1.0-based approach (PSA + RECIP) to standardize the criteria of response to ¹⁷⁷Lu-PSMA therapy based on PET/CT findings for treatment efficacy assessment in mCRPC. This study aimed to formulate an integrated response classification combining laboratory PSA levels and response criteria based on PET/CT findings. This approach incorporated the analysis of the PSMA-positive tumor volume (PSMA VOL) and the detection of new metastases, employing a standardized system to determine the response criteria.

This method yielded four response categories: RECIP-CR for complete response, RECIP-PR for partial response, RECIP-PD for disease progression, and RECIP-SD for stable disease.

The results achieved using the RECIP 1.0 approach (PSA + RECIP) included the following:

• Reduction in PSA levels by ≥50% or RECIP-CR/RECIP-PR;
• Rise in PSA levels by ≥25% or RECIP-PD.

The study assessed the predictive value of RECIP 1.0 in terms of increases in overall survival. However, these findings must be corroborated in prospective studies [64].

Like all diagnostic radiology techniques, PET/CT has limitations, including motion artifacts, which result in incorrect image matching, and truncation artifacts due to differences in the field of view of СT and PET scanners (50 cm vs. 70 cm), especially in patients with excess body weight. Another disadvantage is that when PET shows radiopharmaceutical uptake, no changes are observed on CT. The results of these examinations must be interpreted with caution [45].

Table 2 presents a comparison of diagnostic radiological procedures based on the parameters that indicate the presence of bone metastases in PC (adapted from Isaac et al. [65]).

 

Table 2. Comparison of the diagnostic radiological techniques
Diagnostic radiological technique	Bone tissue morphology	Bone tissue metabolism	Bone marrow lesions	Diffusion	Radiopharmaceutical metabolism
Radiography
MSCT
MRI
Bone scintigraphy
SPECT/CT
PET/CT
Note. Highlighted: the parameter is present; not highlighted: the parameter is absent.

 

Thus, available evidence demonstrates the heterogeneity of data regarding the diagnostic utility and potential of diagnostic radiological techniques, which are essential for the noninvasive assessment of mCRPC.

Conclusion

There are multiple diagnostic radiological techniques and associated approaches for the quantitative assessment of mCRPC. These techniques are widely employed in mCRPC diagnosis and staging, as well as in treatment strategy selection and efficacy assessment. The advantages and disadvantages of imaging examinations in this patient population are considered complementary because of their differing sensitivity and specificity; thus, an integrated use of these techniques is recommended.

A review of published evidence suggests that radionuclide diagnosis and therapy with ¹⁷⁷Lu-PSMA and ²²⁵Ac-PSMA can be a promising strategy. These radiopharmaceuticals offer unique opportunities for targeted therapy and quantitative assessment of ¹⁷⁷Lu-PSMA therapy efficacy through diagnostic radiological techniques.

Further development of quantitative efficacy assessment tools for mCRPC therapy and the identification of prognostic biomarkers using radionuclide imaging techniques will help select the optimal treatment strategy, thereby improving overall survival.

Additional information

Funding source. This article was not supported by any external sources of funding.

Competing interests. The authors declare that they have no competing interests.

Authors’ contribution. All authors made a substantial contribution to the conception of the work, acquisition, analysis, interpretation of data for the work, drafting and revising the work, final approval of the version to be published and agree to be accountable for all aspects of the work. The contribution is distributed as follows: A.A. Karpova— data collection and processing, data analysis, writing of the text; N.I. Sergeev — preparation and editing of the text, involvement in scientific design, data analysis and interpretation; O.A. Borisova — preparation and editing of the text, involvement in scientific design; P.A. Nikitin — preparation and editing of the text, data analysis and interpretation; D.K. Fomin — preparation and editing of the text, approval of the final version of the article; V.A. Solodkiy — study concept and design, approval of the final version of the article.

About the authors

Anastasia A. Karpova

Pulmonology Scientific Research Institute

Author for correspondence.
Email: karpovaaadoc@yandex.ru
ORCID iD: 0000-0002-0251-254X
SPIN-code: 9993-5553

MD, Radiologist 

Russian Federation, Moscow

Nikolay I. Sergeev

Russian Scientific Center of Roentgenoradiology

Email: sergeevnickolay@yandex.ru
ORCID iD: 0000-0003-4147-1928
SPIN-code: 2408-6502

MD, Dr. Sci. (Medicine), Head of  Laboratory of  Roentgenoradiology of the Complex Diagnostics of Diseases and Radiotherapy department

Russian Federation, Moscow

Olga A. Borisova

Russian Scientific Center of Roentgenoradiology

Email: olga250578@yandex.ru
ORCID iD: 0009-0003-7809-0130
SPIN-code: 2416-1885

MD, Cand. Sci. (Medicine), Radiologist, Head of the Radionuclide Diagnostics Department

Russian Federation, Moscow

Pavel A. Nikitin

Pulmonology Scientific Research Institute

Email: paul2003@mail.ru
ORCID iD: 0000-0003-1809-6330
SPIN-code: 6257-2399

MD, Cand. Sci. (Medicine), head of X-ray department - radiologist

Russian Federation, Moscow

Dmitriy K. Fomin

Russian Scientific Center of Roentgenoradiology

Email: dkfomin@yandex.ru
ORCID iD: 0000-0002-7316-3519
SPIN-code: 4593-1292

MD, Dr. Sci. (Medicine), Professor of the Russian Academy of Sciences, Head of the Nuclear Medicine Clinic

Russian Federation, Moscow

Vladimir A. Solodkiy

Russian Scientific Center of Roentgenoradiology

Email: director@rncrr.ru
ORCID iD: 0000-0002-1641-6452
SPIN-code: 9556-6556

MD, Dr. Sci. (Medicine), Professor, Academician of the Russian Academy of Sciences

Russian Federation, Moscow

References

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