Prostate specific membrane antigen (PSMA) avid nonprostatic benign and malignant disease: a pictorial review

Prostate specific membrane antigen (PSMA) positron emission tomography-computed tomography (PET-CT) is revolutionising the management of prostate cancer (PC) in primary staging and assessment of biochemical recurrence (BCR) through its higher diagnostic accuracy compared to both conventional imaging and previously available PET radiopharmaceuticals. PSMA is a transmembrane glycoprotein, highly expressed in prostate cancer, with its extracellular domain the target for PSMA PET radiopharmaceuticals. However, PSMA expression is not prostate specific and resultant PSMA uptake on PET-CT is not restricted to pathologies arising from the prostate gland. The increasing use of PSMA PET-CT has revealed PSMA uptake in a variety of non-prostatic benign and malignant diseases, which adds complexity to PET-CT interpretation and subsequent clinical management. This pictorial review will provide a thorough knowledge and understanding of the comprehensive range of PSMA avid non-prostatic benign and malignant diseases demonstrable on PSMA PET-CT, whilst highlighting the complimentary nature of other imaging modalities.

Setting-up a training programme for intraoperative molecular imaging and sentinel node mapping: how to teach? How to learn?

BACKGROUND

The current expansion of image-guided surgery is closely related to the role played by radio-guided surgery in supporting the sentinel node (SN) procedure during more than three decades. The so-called triple approach (lymphoscintigraphy, gamma probe detection and blue dye) was not only essential in the seminal validation of the SN procedure but also a first collective learning effort based on skill transfer and outcome-related evaluation which laid the fundaments to delineate the field of intraoperative molecular imaging (IMI) based on a similar multimodality approach and multidisciplinary practice.

METHODS

These elements are also becoming valid in the current incorporation of SPECT/CT and PET/CT to existing and new protocols of IMI procedures and SN mapping concerning other clinical applications. On the other hand, there is a growing tendency to combine novel modern technologies in an allied role with gamma guidance in the operating room following the development of hybrid tracers and multimodal detection approaches. Against this background, learning initiatives are required for professionals working in this area.

RESULTS

This objective has led to a group of European practitioners with large experience in SN mapping and IMI applications to give shape to a programme made up out of specific learning modules aimed to be used as a conductive thread in peripherical or centralised training instances concerning the topic.

CONCLUSION

The presented work, written as a tutorial review, is placed in an available prior-art context and is primarily aimed at medical and paramedical practitioners as well as at hardware and software developers.

Distinguishing Physiological Ureter Uptake From an Involved Lymph Node in Staging Prostate-Specific Membrane Antigen (PSMA) Scans: Implications for Radiation Planning

Prostate-specific membrane antigen (PSMA) imaging has become a mainstay diagnostic tool in staging unfavorable primary prostate cancer (PC) and identifying sites of recurrence in previously treated PC. One of the biggest pitfalls of PSMA imaging is rapid radionucleotide excretion in the urine via the​ kidneys, ureters, and bladder.​ The positron-emission tomography (PET) images obtained show increased radiotracer activity in these structures, which can occlude or even mimic true malignant disease. We describe the diagnostic challenges encountered in differentiating benign versus malignant disease with PSMA scans. A 78-year-old male presented ​to our outpatient radiation oncology office ​with high-risk prostate cancer. His medical history was significant for ulcerative colitis (UC). Magnetic resonance imaging (MRI) revealed an enlarged prostate and a Prostate Imaging Reporting and Data System (PI-RADS) class 4 lesion. A subsequent transperineal biopsy confirmed unilateral Gleason 8 adenocarcinoma. A PSMA PET scan was read as increased uptake in the right prostate and a left external iliac node. The patient, having been initially informed of a positive lymph node metastasis, sought a second opinion,​resulting in​​ ​a CT urogram that revealed physiologic ureteral uptake. We were thus able to avoid lymph node radiation and morbidity to the surrounding bowel, already chronically inflamed with ulcerative colitis. This study ​demonstrates the ​potential for misinterpretation of PSMA uptake in the ureter as lymph node metastases. We discuss how peri-uretic activity can hinder accurate visualization of pelvic lymph node metastases. This study highlights the need for careful image interpretation of PSMA uptake patterns in order to avoid diagnostic errors and unnecessary radiation to ​at-risk​​ ​organs in prostate cancer management.

Unusual Sites of Visceral Spread in Prostate Cancer: A Prostate-Specific Membrane Antigen-Based Theranostic Imaging Series

ABSTRACT

Prostate cancer commonly metastasizes to lymphatic and skeletal systems with lesser frequency to visceral organs; however, uncommon visceral sites have also been found and reported as case reports. We present a series of uncommon metastatic visceral spread in prostate cancer on prostate-specific membrane antigen-based diagnostic and posttherapeutic imaging modalities.

Unusual Metastatic Sites of Testis and Rectum in Prostate Cancer Detected by 68 Ga-PSMA-11 PET/CT Imaging at Initial Staging

Imaging plays a pivotal role in defining the extent of disease and deciding therapeutic strategies in recently diagnosed high-risk prostate cancer. Standard-of-care conventional imaging may often miss rare metastatic disease sites. We herein present a unique case of prostate cancer where 68 Ga-PSMA-11 positron emission tomography (PET)/computed tomography (CT) detected two unusual metastatic sites (testis and rectum) in a single patient at initial staging, resulting in an accurate determination of the extent of disease, more tailored multimodal treatment planning, and exploration of the theragnostic potential.

Prostate-Specific Membrane Antigen PET/Computed Tomography: Pearls and Pitfalls

Prostate-specific membrane antigen PET (PSMA-PET) has emerged as a powerful imaging tool for prostate cancer primary staging, biochemical recurrence, and advanced disease assessment. This article offers a concise overview of the benefits and challenges associated with PSMA-PET for prostate cancer evaluation. The article highlights the advantages of PSMA-PET over conventional imaging, such as its higher sensitivity and specificity for detecting metastases, and the potential for guiding personalized treatment decisions. However, it also explores the limitations and potential pitfalls for interpretation. Overall, the article aims to provide valuable insights for clinicians and diagnostic imaging physicians in clinical practice.

A Practical Guide to the Pearls and Pitfalls of PSMA PET Imaging

Prostate-specific membrane antigen (PSMA)-targeted PET agents have revolutionized the care of patients with prostate cancer, supplanting traditional methods of imaging prostate cancer, and improving the selection and delivery of therapies. This has led to a rapid expansion in both the number of PSMA PET scans performed and the imaging specialists required to interpret those scans. To aid those imagers and clinicians who are new to the interpretation of PSMA PET, this review provides an overview of the interpretation of PSMA PET/CT imaging and pearls for overcoming commonly encountered pitfalls. We discuss the physiologic distribution of the clinically available PSMA-targeted radiotracers, the commonly encountered patterns of prostate cancer spread, as well as the benign and malignant mimics of prostate cancer. Additionally, we review the standardized PSMA PET reporting systems and the role of PSMA in selecting appropriate patients for PSMA-targeted therapies.

Inguinal lymph node metastases from prostate cancer: clinical, pathology, and multimodality imaging considerations

Objective

To investigate clinical, pathology, and imaging findings associated with inguinal lymph node (LN) metastases in patients with prostate cancer (PCa).

Materials and Methods

This was a retrospective single-center study of patients with PCa who underwent imaging and inguinal LN biopsy between 2000 and 2023. We assessed the following aspects on multimodality imaging: inguinal LN morphology; extrainguinal lymphadenopathy; the extent of primary and recurrent tumors; and non-nodal metastases. Imaging, clinical, and pathology features were compared between patients with and without metastatic inguinal LNs.

Results

We evaluated 79 patients, of whom 38 (48.1%) had pathology-proven inguinal LN metastasis. Certain imaging aspects- short-axis diameter, prostate-specific membrane antigen uptake on positron-emission tomography, membranous urethra involvement by the tumor, extra-inguinal lymphadenopathy, and distant metastases-were associated with pathology-proven inguinal LN metastases (p < 0.01 for all). Associations with long-axis diameter, fatty hilum, laterality, and uptake of other tracers on positronemission tomography were not significant (p = 0.09-1.00). The patients with metastatic inguinal LNs had higher prostate-specific antigen levels and more commonly had castration-resistant PCa (p < 0.01), whereas age, histological grade, and treatment type were not significant factors (p = 0.07-0.37). None of the patients had inguinal LN metastasis in the absence of locally advanced disease with membranous urethra involvement or distant metastasis.

Conclusion

Several imaging, clinical, and pathology features are associated with inguinal LN metastases in patients with PCa. Isolated metastasis to inguinal LNs is extremely rare and unlikely to occur in the absence of high-risk imaging, clinical, or pathology features.

Prostate-Specific Membrane Antigen (PSMA) Uptake in the Scrotum and Epididymis on PET-CT: When is it Pathological?

Prostate cancer is the most common solid organ tumor in men and has been reported to metastasize to unusual sites such as the epididymis. The clinical standard for detecting recurrent disease is through positive emission tomography/computed tomography with the radiotracer 18F-DCFPyL binding prostate-specific membrane antigen (PSMA) expressed by cancerous cells. Although PSMA can also be expressed physiologically, metastases are more likely to be intensely PSMA expressing and in a typical distribution depending on the extent of disease burden in the individual patient. A MEDLINE search revealed only three other case reports of isolated epididymal metastases from prostate cancer diagnosed with prostate-specific membrane antigen positron emission tomography-computed tomography. This case series comprising both metastatic and physiological PSMA expression in the epididymis provides a useful framework for the interpreting physician when the possibility of this rare but important finding is encountered in prostate cancer imaging.

Mesorectal nodal metastasis with seminal vesicle invasion in biochemically recurrent prostate cancer

OBJECTIVES

To determine the prevalence and predictors of mesorectal lymph node (MLN) metastases on prostate-specific membrane antigen (PSMA)-based positron emission tomography/computed tomography (PET/CT) in patients with biochemically recurrent prostate cancer (PCa) following radical therapy.

MATERIALS AND METHODS

This was a cross-sectional analysis of all PCa patients with biochemical failure following radical prostatectomy or radiotherapy who underwent an 18 F-DCFPyL-PSMA-PET/CT at the Princess Margaret Cancer Centre between December 2018 and February 2021. Lesions with PSMA scores ≥2 were considered positive for PCa involvement (PROMISE classification). Predictors of MLN metastasis were evaluated using univariable and multivariable logistic regression analyses.

RESULTS

Our cohort consisted of 686 patients. The primary treatment method was radical prostatectomy and radiotherapy in 528 (77.0%) and 158 patients (23.0%), respectively. The median serum PSA level was 1.15 ng/mL. Overall, 384 patients (56.0%) had a positive scan. Seventy-eight patients (11.3%) had MLN metastasis, with 48/78 (61.5%) having MLN involvement as the only site of metastasis. On multivariable analysis, presence of pT3b disease (odds ratio 4.31, 95% confidence interval 1.44-14.2; P = 0.011) was significantly associated with increased odds of MLN metastasis, whereas surgical factors (radical prostatectomy vs radiotherapy; performance/extent of pelvic nodal dissection), surgical margin positivity, and Gleason Grade were not.

CONCLUSIONS

In this study, 11.3% of PCa patients with biochemical failure had MLN metastasis on 18 F-DCFPyL-PET/CT. pT3b disease was associated with 4.31-fold significantly increased odds of MLN metastasis. These findings suggest alternate drainage routes for PCa cells, either via alternate lymphatic drainage from the seminal vesicles themselves or secondary to direct extension from posteriorly located tumours invading the seminal vesicles.

Impact of forced diuresis at two different time points on pelvic imaging in prostatic carcinoma with 68 Ga-PSMA PET/CT

OBJECTIVE

We compared diagnostic quality of 68 Ga-PSMA PET/CT imaging focused on the pelvic structures using two furosemide protocols in two different groups of patients.

MATERIAL AND METHODS

A total of 55 patients with prostate cancer were retrospectively enrolled in the study. Out of 55, 31 patients were in group 1 (median age: 66 years, Range 44-78 years) in which furosemide injection was given after completion of whole-body 68 Ga-PSMA PET/CT scan and 24 patients were in group 2 (median age: 63.5 years, range: 50-82 years) in which it was given along with the 68 Ga-PSMA injection. In both groups, an initial time point scan (T0 scan) and a delayed time point scan (T1scan) were done. The images were analyzed qualitatively as well as quantitatively.

RESULTS

Quantitatively there was no statistically significant difference between the SUVmax and T:B of prostatic lesion and seminal vesicle invasion (SVI) in both the groups at two time points ( P  > 0.05). Early furosemide injection caused a washout of the urinary bladder radiotracer concentration in significantly higher number of patients in group 2 (62.5% vs. 6.45% patients, P  < 0.001). There was significant clearance of radiotracer activity from the ureters in group 2 (SUVmax: 9.28 vs. 3.09, P  = 0.002).

CONCLUSION

The simultaneous furosemide and 68 Ga-PSMA injection can reduce the urinary excretion of the tracer and improve the diagnostic confidence of prostatic lesion, SVI and lymph nodal metastasis, along with reducing the scanning time and radiation burden, making this protocol an effective alternative to the present protocol of delayed furosemide injection.

MRI and PSMA PET/CT of Biochemical Recurrence of Prostate Cancer

Prostate cancer may recur several years after definitive treatment, such as prostatectomy or radiation therapy. A rise in serum prostate-specific antigen (PSA) level is the first sign of disease recurrence, and this is termed biochemical recurrence. Patients with biochemical recurrence have worse survival outcomes. Radiologic localization of recurrent disease helps in directing patient management, which may vary from active surveillance to salvage radiation therapy, androgen-deprivation therapy, or other forms of systemic and local therapy. The likelihood of detecting the site of recurrence increases with higher serum PSA level. MRI provides optimal diagnostic performance for evaluation of the prostatectomy bed. Prostate-specific membrane antigen (PSMA) PET radiotracers currently approved by the U.S. Food and Drug Administration demonstrate physiologic urinary excretion, which can obscure recurrence at the vesicourethral junction. However, MRI and PSMA PET/CT have comparable diagnostic performance for evaluation of local recurrence after external-beam radiation therapy or brachytherapy. PSMA PET/CT outperforms MRI in identifying recurrence involving the lymph nodes and bones. Caveats for use of both PSMA PET/CT and MRI do exist and may cause false-positive or false-negative results. Hence, these techniques have complementary roles and should be interpreted in conjunction with each other, taking the patient history and results of any additional prior imaging studies into account. Novel PSMA agents at various stages of investigation are being developed, and preliminary data show promising results; these agents may revolutionize the landscape of prostate cancer recurrence imaging in the future. ©RSNA, 2023 Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Turkbey in this issue. The slide presentation from the RSNA Annual Meeting is available for this article.

Uptake of 68 Ga-PSMA in Avascular Necrosis of the Femoral Head in a Patient With Prostate Cancer

ABSTRACT

A 69-year-old man with prostate cancer treated with radical prostatectomy underwent 68 Ga-PSMA PET/CT due to biochemical recurrence. Increased radiotracer uptake in the prostate bed suggestive of local recurrence was detected. The right hip also displayed increased 68 Ga-PSMA activity, which was consistent with the avascular necrosis findings on MRI.

PSMA-PET detected port site recurrence of prostate cancer following minimally invasive radical prostatectomy and utilisation of hookwire localisation for excision

Biochemical recurrence following prostate cancer treatment is well-known, with predictable sites typically observed in the prostate bed, lymph nodes, or skeleton. The emergence of PSMA-PET scans has revealed the potential for early recurrence in non-conventional sites, including port site metastases. Our report presents a rare case of abdominal wall metastasis detected 97 months post-prostatectomy. The excision of this subcutaneous lesion using image-guided hookwire techniques showed promise in minimising morbidity while providing successful oncologic outcomes. Further investigation is needed to establish the efficacy of PSMA-PET-guided interventions on long-term patient outcomes in treating prostate cancer port site metastases.

Lymphotropic Pattern of Prostate-specific Membrane Antigen-detected Metastases Among Biochemically Recurrent Radical Prostatectomy Patients with Cribriform Disease

BACKGROUND

Cribriform morphology portends worse oncologic outcomes, and has unique cellular intrinsic pathway alterations and tumor microenvironments that may impact metastatic spread patterns.

OBJECTIVE

To determine whether the presence of cribriform morphology in prostatectomy specimens of patients with biochemical recurrence after radical prostatectomy (RP) is associated with the presence of metastasis on prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) and a distinct pattern of spread.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional analysis was conducted of all prostate cancer patients with biochemical recurrence after RP undergoing 18F-DCFPyL-PET/CT between December 2018 and February 2021 at the Princess Margaret Cancer Centre.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Outcomes were presence of any metastasis in the overall cohort and lymphatic versus bone/visceral metastases among patients with metastatic disease. The associations between the presence of intraductal (IDC) and/or invasive cribriform (ICC) carcinoma on the RP specimen and study outcomes were evaluated using logistic regression analyses.

RESULTS AND LIMITATIONS

The cohort included 176 patients. IDC and ICC were observed in 77 (43.8%) and 80 (45.5%) RP specimens, respectively. The median time from RP to PSMA-PET/CT was 5.0 yr. The median serum prostate-specific antigen level at PSMA-PET/CT was 1.12 ng/ml. Overall, metastasis was observed in 77 patients, of whom 58 were had lymphatic-only metastasis. On a multivariable analysis, presence of IDC on RP was associated with increased odds of overall metastasis (odds ratio [OR]: 2.17; 95% confidence interval [CI]: 1.07-4.45; p = 0.033). Presence of ICC on RP was associated with significantly increased odds of lymphatic versus bone/visceral metastases (OR: 3.13; 95% CI: 1.09-21.7; p = 0.004).

CONCLUSIONS

Presence of cribriform morphology on RP specimens of patients with biochemical failure after RP is associated with increased odds of PSMA-PET/CT-detected metastases with a lymphatic predominant pattern of spread. These findings have implications for the design and evaluation of post-RP salvage therapies.

PATIENT SUMMARY

We found that microscopic cribriform appearance correlates with disease spread on imaging in prostate cancer patients with recurrence and has a predilection for spread to lymph nodes, as opposed to bone or visceral organs.

Asthma as an Inflammatory Reason of Tracheobronchial PSMA Uptake

ABSTRACT

A 53-year-old man with persisting increased serum prostate-specific antigen level (9.53 ng/mL) and repeated negative prostate biopsies was referred for a PET/CT with 68 Ga-PSMA-11. The PET/CT revealed focal uptake in the prostate suggestive of localized prostate cancer. Incidentally, it also showed a diffuse uptake in the tracheobronchial tree suspicious for a benign etiology. Because of the clinical history of asthma exacerbation in the previous week, further supplementary studies were performed showing a pathological fractional exhaled nitric oxide level (92 ppb; reference values, <25 ppb) and mild airway obstruction in the spirometry. These findings confirmed asthma as an inflammatory etiology of the tracheobronchial PSMA uptake.

Re-defining 18 F-DCFPyl prostate-specific membrane antigen positron emission tomography detected local recurrence from radical prostatectomy histopathology

OBJECTIVE

To assess topographic concordance between the histopathological features of patients' radical prostatectomy (RP) specimens and the location of the prostate-specific membrane antigen positron emission tomography (PSMA PET) local recurrences, qualitatively and quantitatively.

PATIENTS AND METHODS

Our cohort was selected from the 100 men who received a 18 F-DCFPyL PET scan in the IMPPORT trial (Australian New Zealand Clinical Trials Registry Number: ACTRN12618001530213), a prospective non-randomised study completed by GenesisCare Victoria. Eligibility included patients with a rising prostate-specific antigen (PSA) level (>0.2 ng/mL) after RP and PSMA PET detected local recurrence. Histopathological parameters collated included the location of tumour, extraprostatic extension (EPE), and positive margins. Criteria for the location and 'concordance' between histopathological features and local recurrences were pre-defined.

RESULTS

A total of 24 patients were eligible; the median age was 71 years, the median PSA level was 0.37 ng/mL, and the time between RP and PSMA PET was 2.6 years. In all, 15 patients had recurrences within the vesicourethral anastomotic region and nine within the lateral surgical margins. There was 100% concordance in the left-right plane between tumour location and local recurrence, with 79% of these lesions concordant three-dimensionally; across craniocaudal, left-right, and anterior-posterior planes. In all, 10 of the 16 (63%) patients with EPE and five of the nine patients with positive margins had three-dimensional concordance between their pathology and their local recurrence. In quantitative assessment, 17 of the 24 patients, had local recurrences that correlated with the location of their original tumour in the craniocaudal plane.

CONCLUSION

Local recurrence is highly concordant with the position of the tumour within the prostate. Predicting the location of local recurrence using the location of the EPE and positive margins is less helpful. Further investigation into this field, could impact surgical technique and salvage radiotherapy clinical target volume.

Biochemically recurrent prostate cancer: rationalisation of the approach to imaging

AIM

To assess the utility of magnetic resonance imaging (MRI) in addition to the additive benefit of the conventional imaging techniques, computed tomography (CT) and nuclear medicine (NM) bone scintigraphy, for investigation of biochemical recurrence (BCR) post-prostatectomy where access to prostate specific membrane antigen (PSMA) positron-emission tomography (PET)-CT is challenging.

MATERIALS AND METHODS

Relevant imaging over a 5-year period was reviewed. Ethical approval was granted by the internal review board. All patients with suspected BCR, defined as a PSA ≥0.2 ng/ml on two separate occasions, underwent a retrospective imaging review. This was performed on PACS archive search database in a single centre using search terms "PSA" and "prostatectomy" in the three imaging methods; MRI, CT, and NM bone scintigraphy. All PSMA PET CT performed were recorded.

RESULTS

One hundred and eighty-five patients were identified. Patients with an MRI pelvis that demonstrated distant metastases (i.e., pelvic bone metastases or lymph node involvement more cranial to the bifurcation of the common iliac arteries) were more likely to have a positive CT and/or NM bone scintigraphy. The Pearson correlation coefficient between the findings of M1 disease at MRI pelvis and the presence of distant metastases at CT thorax, abdomen, pelvis and NM bone scintigraphy was calculated at 0.81 (p<0.01) and 0.91 (p<0.01) respectively.

CONCLUSION

An imaging strategy based on risk stratification and technique-specific selection criteria leads to more appropriate use of resources, and in turn, increases the yield of conventional imaging methods. MRI prostate findings can be used to predict the additive value of CT/NM bone scintigraphy allowing a more streamlined approach to their use.

Dose outside of the prostate is associated with improved outcomes for high-risk prostate cancer patients treated with brachytherapy boost

Background

One in three high-risk prostate cancer patients treated with radiotherapy recur. Detection of lymph node metastasis and microscopic disease spread using conventional imaging is poor, and many patients are under-treated due to suboptimal seminal vesicle or lymph node irradiation. We use Image Based Data Mining (IBDM) to investigate association between dose distributions, and prognostic variables and biochemical recurrence (BCR) in prostate cancer patients treated with radiotherapy. We further test whether including dose information in risk-stratification models improves performance.

Method

Planning CTs, dose distributions and clinical information were collected for 612 high-risk prostate cancer patients treated with conformal hypo-fractionated radiotherapy, intensity modulated radiotherapy (IMRT), or IMRT plus a single fraction high dose rate (HDR) brachytherapy boost. Dose distributions (including HDR boost) of all studied patients were mapped to a reference anatomy using the prostate delineations. Regions where dose distributions significantly differed between patients that did and did-not experience BCR were assessed voxel-wise using 1) a binary endpoint of BCR at four-years (dose only) and 2) Cox-IBDM (dose and prognostic variables). Regions where dose was associated with outcome were identified. Cox proportional-hazard models with and without region dose information were produced and the Akaike Information Criterion (AIC) was used to assess model performance.

Results

No significant regions were observed for patients treated with hypo-fractionated radiotherapy or IMRT. Regions outside the target where higher dose was associated with lower BCR were observed for patients treated with brachytherapy boost. Cox-IBDM revealed that dose response was influenced by age and T-stage. A region at the seminal vesicle tips was identified in binary- and Cox-IBDM. Including the mean dose in this region in a risk-stratification model (hazard ratio=0.84, p=0.005) significantly reduced AIC values (p=0.019), indicating superior performance, compared with prognostic variables only. The region dose was lower in the brachytherapy boost patients compared with the external beam cohorts supporting the occurrence of marginal misses.

Conclusion

Association was identified between BCR and dose outside of the target region in high-risk prostate cancer patients treated with IMRT plus brachytherapy boost. We show, for the first-time, that the importance of irradiating this region is linked to prognostic variables.

Staging Prostate Cancer with 68Ga-PSMA-11 PET/CT in the Elderly: Is Preimaging Biopsy Imperative?

Although prostate-specific membrane antigen (PSMA) PET/CT has been shown valuable for staging biopsy-proven [B(+)] high-risk prostate cancer, elderly patients are occasionally referred for PSMA PET/CT without a preimaging confirming biopsy [B(-)]. The current study evaluated the rate, clinical characteristics, and PET-based stage of elderly B(-) patients and explored whether biopsy status affects therapeutic approach. Methods: One hundred consecutive patients at least 80 y old who underwent staging ⁶⁸Ga-PSMA-11 PET/CT were included. For each patient, we documented whether preimaging biopsy was performed, the clinical parameters, the PET-based staging parameters, and the primary therapy received. Results: Thirty-four (34%) of the elderly patients included in the study had no preimaging biopsy. Compared with B(+) patients, B(-) patients were older (median age, 87 vs. 82 y; P < 0.01), with worse performance status (P < 0.01) and higher prostate-specific antigen (PSA) levels (median, 57 vs. 15.4 ng/mL; P < 0.01). On ⁶⁸Ga-PSMA-11 PET/CT, all B(-) patients had avid disease, with trends toward higher rates of bone metastases (47.1% vs. 28.8%) and overall advanced disease (50% vs. 33.3%) than in B(+) patients. Among patients with localized (n = 36) or locally advanced (n = 25) disease, B(-) patients were less commonly referred than B(+) patients for definitive therapies (P < 0.01). However, higher age, Eastern Cooperative Oncology Group performance status, and PSA were other probable factors determining their therapeutic approach. Among 39 patients with advanced disease, 38 received hormonal therapy irrespective of their biopsy status. Among B(-) patients with advanced disease who were referred for hormonal therapy, 12 of 13 with follow-up data showed a biochemical or imaging-based response. Conclusion: Real-life experience with ⁶⁸Ga-PSMA-11 PET/CT indicates that around one third of elderly patients are referred for imaging without a preimaging confirming biopsy. These patients are likely to be older, with a worse clinical status and higher PSA levels. Advanced disease might be more likely to be identified on their ⁶⁸Ga-PSMA-11 PET/CT images, and if it is, their biopsy status does not preclude them from receiving hormonal therapy.

Imaging Recommendations for Theranostic PET-CT in Oncology

We in this article have presented a review of the guideline recommendations on theranostic positron emission tomography-computed tomography (PET-CT) imaging which will be helpful to assist practitioners in providing appropriate patient care. Multiple guidelines by different societies and medical associations provide standards for diagnosis, imaging, and treatment of cancer patients. They have generated a number of recommendations related to 68Ga-DOTATATE and 68Ga-PSMA-11 PET-CT, which are the classical examples of theranostic PET-CT imaging in current practice.

Prostate Cancer-PET Imaging Update

Prostate cancer is the most common non-dermatologic cancer in men, and one of the leading causes of cancer-related mortality. The incidence of prostate cancer increases precipitously after the age of 65 and demonstrates variable aggressiveness, depending on its grade and stage at diagnosis. Despite recent advancements in prostate cancer treatment, recurrence is seen in 25% of patients. Advancements in prostate cancer Positron Emission Tomography (PET) molecular imaging and recent United States Food and Drug Administration (FDA) approvals have led to several new options for evaluating prostate cancer. This manuscript will review the commonly used molecular imaging agents, with an emphasis on Fluorine-18 fluciclovine (Axumin) and PSMA-ligand agents, including their protocols, imaging interpretation, and pitfalls.

Prostate-specific Membrane Antigen Positron Emission Tomography/Computed Tomography-based Lymph Node Atlas for Salvage Radiotherapy in Patients with Recurrent Prostate Cancer: A Validation of the New NRG Oncology 2020 guideline

BACKGROUND

Approximately 20-40% of patients with prostate cancer (PC) who undergo radical prostatectomy (RP) experience relapse, with the majority of these cases developing pelvic lymph node (LN) metastases. Taking new data from the prostate-specific membrane antigen (PSMA) positron emission tomography (PET) era into account, the Radiation Therapy Oncology Group (RTOG) 2009 contouring guideline for the pelvic LNs from 2009 was updated by the NRG Oncology group in 2020 (NRG 2020).

OBJECTIVE

To evaluate and validate the updated NRG 2020 guideline with our established LN atlas.

DESIGN, SETTING, AND PARTICIPANTS

We screened 1653 PSMA PET/computed tomography (CT) data sets for patients with biochemical relapse who underwent a PET scan between November 2012 and November 2017. After screening, we developed an LN atlas using data from 233 patients.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

We evaluated LN overlap (OL) with the RTOG 2009 and NRG 2020 contouring guidelines. OL was defined as within (>90%), partly within (10-90%), or outside (<10%).

RESULTS AND LIMITATIONS

In comparison to the RTOG 2009 guideline, 403 (52%), 134 (17%), and 241 (31%) of the LNs were not, were partly, or were fully covered within the overall group, respectively. By contrast, using the NRG 2020 guideline, 302 (39%), 190 (24%), and 286 (37%) of the LNs were not, were partly, or were fully covered, respectively (p < 0.001). Limitations include the retrospective design with missing data and no histopathological confirmation of the PET results.

CONCLUSIONS

The updated NRG 2020 contouring guideline improves coverage of the pelvic LNs in patients undergoing salvage radiation therapy. However, PET/CT should be considered whenever possible to ensure coverage of untypical LN spread.

PATIENT SUMMARY

We compared the 2009 and 2020 guidelines on the radiation area for the pelvis for patients with recurrent prostate cancer that has spread to lymph nodes. The newer guideline provides better coverage of pelvic lymph nodes than the older one and is useful in planning radiation therapy. However, a scan of the pelvis using the newest technique should be considered for individual patients to ensure coverage of untypical lymph nodes.

18F-DCFPyL PET/CT for Initially Diagnosed and Biochemically Recurrent Prostate Cancer: Prospective Trial with Pathologic Confirmation

Background Prostate-specific membrane antigen (PSMA) PET is standard for newly diagnosed high-risk and biochemically recurrent (BCR) prostate cancer. Although studies suggest high specificity of 2-(3-{1-carboxy-5-[(6-[(18)F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (DCFPyL) for targeting PSMA, false-positive findings have been identified and most studies lack histologic confirmation of malignancy. Purpose To estimate the positive predictive value (PPV) of DCFPyL PET/CT by providing histopathologic proof for DCFPyL-avid lesions suspected of being distant metastases at initial diagnosis and recurrence in BCR prostate cancer. Materials and Methods In this prospective trial, men with newly diagnosed high-risk prostate cancer (sample 1) or BCR prostate cancer and negative findings at conventional CT and/or bone scanning (sample 2) were enrolled between January and December 2021. All men underwent DCFPyL PET/CT. Suspected distant metastases and/or recurrences were biopsied. PPV was calculated. Results A total of 92 men with newly diagnosed prostate cancer (median age, 70 years; IQR, 64-75 years) (sample 1) and 92 men with BCR prostate cancer (median age, 71 years; IQR, 66-75 years) (sample 2) were enrolled. In sample 1, 25 of the 92 men (27%) demonstrated DCFPyL-avid lesions suspicious for distant metastases. Biopsy was performed in 23 of the 25 men (92%), with 17 of the 23 (74%) biopsies positive for malignancy and six (26%) benign. Of the six benign biopsies, three were solitary rib foci and three were solitary pelvic bone foci. In sample 2, 57 of the 92 men (62%) demonstrated DCFPyL-avid lesions suspicious for recurrence. Biopsy was performed in 37 of the 57 men (65%), with 33 of the 37 (89%) biopsies positive for malignancy and four (11%) benign. Of the four benign biopsies, two were subcentimeter pelvic nodes and/or nodules, one was a rib, and one was a pelvic bone focus. Conclusion PET/CT with 2-(3-{1-carboxy-5-[(6-[(18)F]fluoro-pyridine-3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (DCFPyL) had a high biopsy-proven positive predictive value for distant metastases in newly diagnosed prostate cancer (74%) and for recurrence sites in men with biochemical recurrence (89%). However, there were DCFPyL-avid false-positive findings (particularly in ribs and pelvic bones). Solitary DCFPyL avidity in these locations should not be presumed as malignant. Biopsy may still be needed prior to therapy decisions. ClinicalTrials.gov registration no. NCT04700332 © RSNA, 2022 See also the editorial by Zukotynski and Kuo in this issue.

PSMA PET-CT in the Diagnosis and Staging of Prostate Cancer

Prostate cancer is the most common cancer and the second leading cause of cancer death in men. The imaging assessment and treatment of prostate cancer has vastly improved over the past decade. The introduction of PSMA PET-CT has improved the detection of loco-regional and metastatic disease. PSMA PET-CT also has a role in the primary diagnosis and staging, in detecting biochemical recurrence after curative treatment and in metastasis-directed therapy. In this paper we review the role of PSMA PET-CT in prostate cancer.

Longitudinal Changes and Predictive Value of Multiparametric MRI Features for Prostate Cancer Patients Treated with MRI-Guided Lattice Extreme Ablative Dose (LEAD) Boost Radiotherapy

We investigated the longitudinal changes in multiparametric MRI (mpMRI) (T2-weighted, Apparent Diffusion Coefficient (ADC), and Dynamic Contrast Enhanced (DCE-)MRI) of prostate cancer patients receiving Lattice Extreme Ablative Dose (LEAD) radiotherapy (RT) and the capability of their imaging features to predict RT outcome based on endpoint biopsies. Ninety-five mpMRI exams from 25 patients, acquired pre-RT and at 3-, 9-, and 24-months post-RT were analyzed. MRI/Ultrasound-fused biopsies were acquired pre- and at two-years post-RT (endpoint). Five regions of interest (ROIs) were analyzed: Gross tumor volume (GTV), normally-appearing tissue (NAT) and peritumoral volume in both peripheral (PZ) and transition (TZ) zones. Diffusion and perfusion radiomics features were extracted from mpMRI and compared before and after RT using two-tailed Student t-tests. Selected features at the four scan points and their differences (Δ radiomics) were used in multivariate logistic regression models to predict the endpoint biopsy positivity. Baseline ADC values were significantly different between GTV, NAT-PZ, and NAT-TZ (p-values < 0.005). Pharmaco-kinetic features changed significantly in the GTV at 3-month post-RT compared to baseline. Several radiomics features at baseline and three-months post-RT were significantly associated with endpoint biopsy positivity and were used to build models with high predictive power of this endpoint (AUC = 0.98 and 0.89, respectively). Our study characterized the RT-induced changes in perfusion and diffusion. Quantitative imaging features from mpMRI show promise as being predictive of endpoint biopsy positivity.

Importance of tumor subtypes in cancer imaging

Cancer therapy has evolved from being broadly directed towards tumor types, to highly specific treatment protocols that target individual molecular subtypes of tumors. With the ever-increasing data on imaging characteristics of tumor subtypes and advancements in imaging techniques, it is now often possible for radiologists to differentiate tumor subtypes on imaging. Armed with this knowledge, radiologists may be able to provide specific information that can obviate the need for invasive methods to identify tumor subtypes. Different tumor subtypes also differ in their patterns of metastatic spread. Awareness of these differences can direct radiologists to relevant anatomical sites to screen for early metastases that may otherwise be difficult to detect during cursory inspection. Likewise, this knowledge will help radiologists to interpret indeterminate findings in a more specific manner.

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Tumor subtypes can be identified based on their different imaging characteristics.

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Awareness of tumor subtype can help radiologists chose the appropriate modality for additional imaging workup.

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Awareness of differences in metastatic pattern between tumor subtypes can be helpful to identify early metastases.

Robotic Salvage Seminal Vesiculectomy for radio-recurrent prostate cancer post LDR brachytherapy following multiple negative trans-perineal biopsies

Multi-parametric Magnetic Resonance Imaging (mp-MRI) and prostate membrane specific antigen positron emission tomography (PSMA-PET) CT scan in prostate cancer has led to enhanced detection of local and metastatic recurrence post-radiotherapy. A 59-year-old man presented with biochemical relapse following low dose rate brachytherapy for ISUP 2 T1cN0M0 prostate cancer (PCa). Despite strong biochemical and radiological evidence of radio-recurrent PCa in his right seminal vesicle, serial transperineal biopsies revealed benign tissue. He proceeded to Robot Assisted Salvage Seminal Vesiculectomy (RSSV) as a diagnostic procedure without complication. Histo-pathology confirmed a 23 × 17 × 13mm focus of Gleason 4 + 4 adenocarcinoma in the SV with clear surgical margins.

Characterization of Immune-Based Molecular Subtypes and Prognostic Model in Prostate Adenocarcinoma

Prostate adenocarcinoma (PRAD), also named prostate cancer, the most common visceral malignancy, is diagnosed in male individuals. Herein, in order to obtain immune-based subtypes, we performed an integrative analysis to characterize molecular subtypes based on immune-related genes, and further discuss the potential features and differences between identified subtypes. Simultaneously, we also construct an immune-based risk model to assess cancer prognosis. Our findings showed that the two subtypes, C1 and C2, could be characterized, and the two subtypes showed different characteristics that could clearly describe the heterogeneity of immune microenvironments. The C2 subtype presented a better survival rate than that in the C1 subtype. Further, we constructed an immune-based prognostic model based on four screened abnormally expressed genes, and they were selected as predictors of the robust prognostic model (AUC = 0.968). Our studies provide reference for characterization of molecular subtypes and immunotherapeutic agents against prostate cancer, and the developed robust and useful immune-based prognostic model can contribute to cancer prognosis and provide reference for the individualized treatment plan and health resource utilization. These findings further promote the development and application of precision medicine in prostate cancer.

Radiating the prostate bed in relapsed oligometastatic prostate cancer: How comprehensive should we be?

PURPOSE

A subset of patients with high-risk pathological features at radical prostatectomy recur with oligometastatic disease. The aim of this study is to investigate the rate of prostate bed recurrence, with or without history of prostate bed irradiation (PBRT), in oligometastatic prostate cancer (OMPC) patients after metastasis-directed therapy (MDT).

METHODS

We performed a retrospective analysis of hormone-sensitive OMPC patients treated initially with curative-intent radical prostatectomy followed by disease recurrence and metastasis-directed stereotactic ablative radiotherapy (SABR) at our institution. Prostate bed recurrence rates were compared between patients who had PBRT at any point (i.e., before oligometastatic diagnosis or concurrently with MDT) versus those with no history of PBRT.

RESULTS

Seventy-seven patients were included, and 68.8% had received PBRT. There were no significant differences in baseline characteristics between those who had received and had not received PBRT. There were five prostate bed recurrences following MDT, specifically with a 24-month cumulative incidence of 30.4% in patients who did not have PBRT and 2.4% in those who did (p = 0.03). Three of the five recurrences were isolated to the prostate bed at time of recurrence.

CONCLUSIONS

Relapsed oligometastatic prostate cancer patients who have not received maximal local consolidative therapy to the prostate bed may have higher rates of local failure. Prospective studies are warranted investigating when prostate bed irradiation should be considered for patients after radical prostatectomy who ultimately have oligometastatic prostate cancer.

Non-prostate cancer tumours: incidence on 18F-DCFPyL PSMA PET/CT and uptake characteristics in 1445 patients

Purpose

With increasing use of PSMA PET/CT in the staging and restaging of prostate cancer (PCa), the identification of non-prostate cancer tumours (NPCaT) has become an increasing clinical dilemma. Atypical presentations of PSMA expression in prostate cancer and expression in NPCaT are not well established. Understanding the normal and abnormal distribution of PSMA expression is essential in preparing clinically relevant reports and in guiding multidisciplinary discussion and decisions.

Methods

Retrospective review of 1445 consecutive ¹⁸F-DCFPyL PSMA PET/CT studies by experienced radiologists and nuclear medicine physicians. Lesions indeterminate for PCa were identified. Correlation was made with patient records, biopsy results, and dedicated imaging. Lesions were then categorized into four groups: 1. Confirmed prostate cancer, metastases, 2. NPCaT 3. Benign, and 4. Indeterminate lesions.

Results

68/1445 patients had lesions atypical for prostate cancer metastases. These comprised 8/68 (11.8%) atypical prostate cancer metastases, 17/68 (25.0%) NPCaT, 29/68 (42.6%) indeterminate, and 14/68 (20.6%) benign. In the context of the entire cohort, these are adjusted to 8/1445 (0.6%), 17/1445 (1.2%), 29/1445 (2.0%), and 14/1445 (1.0%) respectively. With the exception of Renal Cell Carcinoma (RCC), NPCaT demonstrated no or low PSMA expression. A similar trend was also observed for indeterminate and benign lesions. Conversely, most atypical PCa metastases demonstrated intermediate or high PSMA expression.

Conclusion

¹⁸F-DCFPyL PSMA PET/CT detection of NPCaT is low. Lesions demonstrating intermediate to high PSMA expression were exclusively prostate cancer metastases, aside from RCC, and lesions detected in organs with high background expression.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00259-022-05721-z.

Narrative Review of the Post-Operative Management of Prostate Cancer Patients: Is It Really the End of Adjuvant Radiotherapy?

Simple Summary

Among patients with prostate cancer who have been operated on, a subset harboring high-risk features will present with a biochemical recurrence (BCR). Adjuvant radiotherapy (aRT) was proven to significantly reduce the risk of BCR when compared to salvage radiotherapy (SRT) but suffered from several limitations: a lack of patient selection criteria, a higher treatment-related morbidity and an uncertain benefit for long-term clinical endpoints. In the same clinical setting, early SRT (eSRT) appears as non-inferior to aRT with a lower morbidity, replacing aRT as the preferred option. In this review, we insist on the need for multidisciplinary discussions to fully comprehend the individual characteristics of each patient and propose the best treatment strategy for every patient.

Abstract

Despite three randomized trials indicating a significant reduction in biochemical recurrence (BCR) in high-risk patients, adjuvant radiotherapy (aRT) was rarely performed, even in patients harboring high-risk features. aRT is associated with a higher risk of urinary incontinence and is often criticized for the lack of patient selection criteria. With a BCR rate reaching 30–70% in high-risk patients, a consensus between urologists and radiation oncologists was needed, leading to three different randomized trials challenging aRT with early salvage radiotherapy (eSRT). In these three different randomized trials with event-free survival as the primary outcome and a planned meta-analysis, eSRT appeared as non-inferior to aRT, answering, for some, this never-ending question. For many, however, the debate persists; these results raised several questions among urologists and radiation oncologists. BCR is thought to be a surrogate for clinically meaningful endpoints such as overall survival and cancer-specific survival but may be poorly efficient in comparison with metastasis-free survival. Imaging of rising prostate-specific antigen (PSA), post-operative persistent PSA and BCR was revolutionized by the broader use of MRI and nuclear imaging such as PET-PSMA; these imaging modalities were not analyzed in the previous randomized trials. A sub-group of very high-risk patients could possibly benefit from an adjuvant radiotherapy; but their usual risk factors such as high Gleason score or invaded surgical margins mean they are unable to be selected. More precise biomarkers of early BCR or even metastatic-relapse were developed in this setting and could be useful for the patients’ stratification. In this review, we insist on the need for multidisciplinary discussions to fully comprehend the individual characteristics of each patient and propose the best treatment strategy for every patient.

Personalized Medicine for Prostate Cancer: Is Targeting Metabolism a Reality?

Prostate cancer invokes major shifts in gene transcription and metabolic signaling to mediate alterations in nutrient acquisition and metabolic substrate selection when compared to normal tissues. Exploiting such metabolic reprogramming is proposed to enable the development of targeted therapies for prostate cancer, yet there are several challenges to overcome before this becomes a reality. Herein, we outline the role of several nutrients known to contribute to prostate tumorigenesis, including fatty acids, glucose, lactate and glutamine, and discuss the major factors contributing to variability in prostate cancer metabolism, including cellular heterogeneity, genetic drivers and mutations, as well as complexity in the tumor microenvironment. The review draws from original studies employing immortalized prostate cancer cells, as well as more complex experimental models, including animals and humans, that more accurately reflect the complexity of the in vivo tumor microenvironment. In synthesizing this information, we consider the feasibility and potential limitations of implementing metabolic therapies for prostate cancer management.

Frequency and intensity of [18F]-PSMA-1007 uptake after COVID-19 vaccination in clinical PET

Objectives:

To assess the frequency and intensity of [18F]-PSMA-1007 axillary uptake in lymph nodes ipsilateral to COVID-19 vaccination with BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna) in patients with prostate cancer referred for oncological [18F]-PSMA PET/CT or PET/MR imaging.

Methods:

One hundred twenty six patients undergoing [18F]-PSMA PET/CT or PET/MR imaging were retrospectively included. [18F]-PSMA activity (SUVmax) of ipsilateral axillary lymph nodes was measured and compared with the non-vaccinated contralateral side-and with a non-vaccinated negative control group. [18F]-PSMA active lymph node metastases were measured to serve as quantitative reference.

Results:

There was a significant difference in SUVmax in ipsilateral and compared to contralateral axillary lymph nodes in the vaccination group (n = 63, p < 0.001) and no such difference in the non-vaccinated control group (n = 63, p = 0.379). Vaccinated patients showed mildly increased axillary lymph node [18F]-PSMA uptake as compared to non-vaccinated patients (p = 0.03). [18F]-PSMA activity of of lymph node metastases was significantly higher (p < 0.001) compared to axillary lymph nodes of vaccinated patients.

Conclusions:

Our data suggest mildly increased [18F]-PSMA uptake after COVID-19 vaccination in ipsilateral axillary lymph nodes. However, given the significantly higher [18F]-PSMA uptake of prostatic lymph node metastases compared to “reactive” nodes after COVID-19 vaccination, no therapeutic and diagnostic dilemma is to be expected.

Advances in knowledge:

No specific preparations or precautions (e.g., adaption of vaccination scheduling) need to be undertaken in patients undergoing [18F]-PSMA PET imaging after COVID-19 vaccination.

Patterns of Prostate Cancer Recurrence After Brachytherapy Determined by Prostate-Specific Membrane Antigen-Positron Emission Tomography and Computed Tomography Imaging

PURPOSE

The aim of this study was to characterize the patterns of prostate cancer recurrence after brachytherapy (BT) using 2-(3-[1-carboxy-5-([6-¹⁸F-fluoropyridine-3-carbonyl]-amino)-pentyl]-ureido)-pentanedioic acid ([¹⁸F]DCFPyL) prostate-specific membrane antigen (PSMA) positron emission tomography (PET) and computed tomography (CT) imaging.

METHODS AND MATERIALS

Patients were selected from an ongoing prospective institutional trial investigating the use of [¹⁸F]DCFPyL PSMA PET and CT in recurrent prostate cancer (NCT02899312). This report included patients who underwent BT (either monotherapy or boost) and experienced a biochemical failure (BF) defined by the Phoenix definition (prostate-specific antigen [PSA] > 2 ng/mL above nadir).

RESULTS

Between March 2017 and April 2020, 670 patients underwent [¹⁸F]DCFPyL PSMA PET and CT imaging. Of these 670 patients, 93 were treated with BT; 73 underwent monotherapy, and 20 underwent BT boost (19 low-dose rate and 1 high-dose rate). To report on patterns of recurrence outcomes, 86 patients (median prescan PSA 6.0) with a positive [¹⁸F]DCFPyL PSMA PET and CT scan and true BF were included. The most common location of relapse was local; 62.8% had a component of local failure (defined as prostate and/or seminal vesicles), and 46.5% had isolated local failure only, with no other sites of involvement. Regional failure occurred in 40.7% of patients, and 36.0% had metastatic failure. Isolated local recurrence was seen in 54.3% of monotherapy patients versus only in 12.5% of boost patients. Metastatic failure was seen in 28.6% of monotherapy patients versus 68.8% of the boost patients. Local recurrences (69.0%) were found within the same prostate biopsy sextant involved with the tumor at diagnosis, and 76.0% of patients with seminal vesicle recurrences had prostate-base involvement at diagnosis.

CONCLUSIONS

Contrary to previous evidence, our study suggests that in prostate BT patients with biochemical recurrence, the most common site of failure is local for the patients treated with monotherapy and metastatic for patients treated with a combination of external beam radiation and BT boost.

68Ga-PSMA-11 PET/CT in Isolated Bilateral Adrenal Metastases From Prostate Adenocarcinoma

ABSTRACT

A 65-year-old man with treated prostate adenocarcinoma underwent 68Ga-PSMA-11 PET/CT scan for restaging due to significantly increased serum PSA levels. PET/CT showed bilateral adrenal masses with high 68Ga-PSMA-11 uptake. There was no other lesion suspicious for metastasis. The laboratory and imaging findings were consisted with isolated bilateral adrenal metastases from prostate adenocarcinoma. The patient received docetaxel chemotherapy in combination with androgen deprivation therapy. PSA levels gradually decreased during chemotherapy. Follow-up MRI showed the bilateral adrenal masses significantly decreased in size. This case demonstrates the usefulness of 68Ga-PSMA-11 PET/CT in identifying atypical metastasis from prostate adenocarcinoma.

Post-Operative Radiotherapy in Prostate Cancer: Is It Time for a Belt and Braces Approach?

Approximately 30% of patients treated with radical prostatectomy (RP) for prostate cancers experience biochemical recurrence (BCR). Post-operative radiation therapy (RT) can be either offered immediately after the surgery in case of aggressive pathological features or proposed early if BCR occurs. Until recently, little data were available regarding the optimal RT timing, protocol, volumes to treat, and the benefit of adding androgen deprivation therapies to post-operative RT. In this review, we aim to pragmatically discuss current literature data on these points. Early salvage RT appears to be the optimal post-operative approach, improving oncological outcomes especially with low prostate-specific antigen (PSA) levels, as well as sparing several unnecessary adjuvant treatments. The standard RT dose is still 64–66 Gy to the prostate bed in conventional fractionation, but hypofractionation protocols are emerging pending on late toxicity data. Several scientific societies have published contouring atlases, even though they are heterogeneous and deserve future consensus. During salvage RT, the inclusion of pelvic lymph nodes is also controversial, but preliminary data show a possible benefit for PSA > 0.34 ng/ml at the cost of increased hematological side effects. Concomitant ADT and its duration are also discussed, possibly advantageous (at least in terms of metastasis-free survival) for PSA rates over 0.6 ng/ml, taking into account life expectancy and cardiovascular comorbidities. Intensified regimens, for instance, with new-generation hormone therapies, could further improve outcomes in carefully selected patients. Finally, recent advances in molecular imaging, as well as upcoming breakthroughs in genomics and artificial intelligence tools, could soon reshuffle the cards of the current therapeutic strategy.

18F-Fluciclovine Avid Axillary Lymph Nodes After COVID-19 Vaccination on PET/CT for Suspected Recurrence of Prostate Cancer

Abnormally increased ¹⁸F-FDG avidity of axillary lymph nodes has become a frequent diagnostic dilemma on PET/CT in the current climate of global vaccinations directed against severe acute respiratory syndrome coronavirus 2. This avidity is due to the inflammatory response evoked by vaccines and the nonspecific nature of ¹⁸F-FDG uptake, which is increased in both malignant and inflammatory processes. Similarly, ¹⁸F-fluciclovine, an amino acid analog indicated for the assessment of biochemical recurrence of prostate cancer, may also demonstrate nonspecific inflammatory uptake. We report a case of ¹⁸F-fluciclovine PET/CT obtained for concern about prostate cancer. In this case, isolated avid lymph nodes were seen in the left axilla. A screening questionnaire revealed that the patient had recently received the second dose of the Pfizer-BioNTech coronavirus disease 2019 vaccine in his left shoulder, and hence, the uptake was determined to be reactive.

Incidental Serous Cystadenoma Presenting as a Photopenic Pancreatic Defect on 18F-Fluciclovine PET/CT

ABSTRACT

18F-fluciclovine (Axumin) PET/CT has been widely used for the evaluation of biochemically recurrent prostate cancer following prior treatment. While lymph node and visceral organ metastases typically show increased radiotracer uptake, altered patterns of normal physiologic activity may also provide insight into other disease processes. We present a case of an incidental pancreatic head mass presenting as a photopenic defect on a staging 18F-fluciclovine PET/CT, which was subsequently confirmed to be a benign serous cystadenoma using multisequence MRI.

PET Imaging for Prostate Cancer

The role of PET imaging with ¹¹C-choline and ¹⁸F-fluciclovine in evaluating patients with prostate cancer (PCa) has become more important over the years and has been incorporated into the NCCN guidelines. A new generation of PET radiotracers targeting the prostate-specific membrane antigen (PSMA) is widely used outside the United States to evaluate patients with primary PCa and PCa recurrence. PET imaging influences treatment planning and demonstrates a significantly higher disease detection rate than conventional imaging such as computed tomography and MR imaging. Early data indicate that using PET radiotracers such as ¹⁸F-fluciclovine and PSMA improves patient outcomes. 68-Ga-PSMA-11 and 18F-DCFPyL-PET/CT were recently approved by the US Food & Drug Administration (FDA) for clinical use. Other PSMA radiotracers, including fluorinated variants, will likely gain FDA approval in the not-too-distant future.

Atypical Metastases in the Abdomen and Pelvis From Biochemically Recurrent Prostate Cancer: 11C-Choline PET/CT Imaging With Multimodality Correlation

PET imaging with targeted radiotracers has become integral for mapping the location and burden of recurrent disease in patients with biochemical recurrence (BCR) of prostate cancer (PCa). PET with 11C-choline is part of the National Comprehensive Cancer Network and European Association of Urology guidelines for evaluation of BCR. With advances in PET technology, increasing use of targeted radiotracers, and improved survival of patients with BCR due to novel therapeutics, atypical sites of metastases are being increasingly encountered, challenging the conventional view that PCa rarely metastasizes beyond bones or lymph nodes. We describe such atypical metastases in the abdomen and pelvis on 11C-choline PET (including in the liver, pancreas, genital tract, urinary tract, peritoneum, and abdominal wall, as well as perineural spread), presenting multimodality imaging features and relevant imaging pitfalls. Given atypical metastases' inconsistent relationship with serum PSA and non-specific presenting symptoms, they are often first detected on imaging. Awareness of their imaging features is important as their detection impacts clinical management, patient counseling, prognosis, and clinical trial eligibility. Such awareness is particularly critical as the role of radiologists in the imaging and management of BCR will continue to increase given the expanding regulatory approvals of other targeted and theranostic radiotracers.

Theranostics in Nuclear Medicine: Emerging and Re-emerging Integrated Imaging and Therapies in the Era of Precision Oncology

Theranostics refers to the pairing of diagnostic biomarkers with therapeutic agents that share a specific target in diseased cells or tissues. Nuclear medicine, particularly with regard to applications in oncology, is currently one of the greatest components of the theranostic concept in clinical and research scenarios. Theranostics in nuclear medicine, or nuclear theranostics, refers to the use of radioactive compounds to image biologic phenomena by means of expression of specific disease targets such as cell surface receptors or membrane transporters, and then to use specifically designed agents to deliver ionizing radiation to the tissues that express these targets. The nuclear theranostic approach has sparked increasing interest and gained importance in parallel to the growth in molecular imaging and personalized medicine, helping to provide customized management for various diseases; improving patient selection, prediction of response and toxicity, and determination of prognosis; and avoiding futile and costly diagnostic examinations and treatment of many diseases. The authors provide an overview of theranostic approaches in nuclear medicine, starting with a review of the main concepts and unique features of nuclear theranostics and aided by a retrospective discussion of the progress of theranostic agents since early applications, with illustrative cases emphasizing the imaging features. Advanced concepts regarding the role of fluorine 18-fluorodeoxyglucose PET in theranostics, as well as developments in and future directions of theranostics, are discussed. ^©RSNA, 2020 See discussion on this article by Greenspan and Jadvar.

Diagnostic performance and clinical impact of 68Ga-PSMA-11 imaging in early relapsed prostate cancer after radical therapy: a prospective multicenter study (IAEA-PSMA study)

Biochemical recurrence (BCR) is a clinical challenge in prostate cancer (PCa) patients, as recurrence localization guides subsequent therapies. The use of PET with prostate-specific membrane antigen (PSMA) provides better accuracy than conventional imaging practice. This prospective, multicenter, international study was performed to evaluate the diagnostic performance and clinical impact of PSMA PET/CT for evaluating BCR in PCa patients in a worldwide scenario. Methods: Patients were recruited from 17 centers in 15 countries. Inclusion criteria were histopathologically proven prostate adenocarcinoma, previous primary treatment, clinically established BCR, and negative conventional imaging (CT plus bone scintigraphy) and MRI results for patients with PSA levels of 4–10 ng/mL. All patients underwent PET/CT scanning with ⁶⁸Ga-PSMA-11. Images and data were centrally reviewed. Multivariate logistic regression analysis was applied to identify the independent predictors of PSMA-positive results. Variables were selected for this regression model on the basis of significant associations in the univariate analysis and previous clinical knowledge: Gleason score, the PSA level at the time of the PET scan, PSA doubling time, and primary treatment strategy. All patients were monitored for a minimum of 6 mo. Results: From a total of 1,004 patients, 77.7% were treated initially with radical prostatectomy and 22.3% were treated with radiotherapy. Overall, 65.1% had positive PSMA PET/CT results. PSMA PET/CT positivity was correlated with the Gleason score, PSA level at the time of the PET scan, PSA doubling time, and radiotherapy as the primary treatment (P < 0.001). Treatment was modified on the basis of PSMA PET/CT results in 56.8% of patients. PSMA PET/CT positivity rates were consistent and not statistically different among countries with different incomes. Conclusion: This multicenter, international, prospective trial of PSMA PET/CT confirmed its capability for detecting local and metastatic recurrence in most PCa patients in the setting of BCR. PSMA PET/CT positivity was correlated with the Gleason score, PSA level at the time of the PET scan, PSA doubling time, and radiotherapy as the primary treatment. PSMA PET/CT results led to changes in therapeutic management in more than half of the cohort. The study demonstrated the reliability and worldwide feasibility of PSMA PET/CT in the workup of PCa patients with BCR.

General Concepts in Theranostics

Theranostics describes the pairing of diagnostic biomarkers and therapeutic agents with common specific targets. Nuclear medicine is the greatest theranostics protagonist, relying on radioactive tracers for imaging biologic phenomena and delivering ionizing radiation to the tissues that take up those tracers. The concept has gained importance with the growth of personalized medicine, allowing customized management for diseases, refining patient selection, better predicting responses, reducing toxicity, and estimating prognosis. This work provides an overview of the general concepts of the theranostics approach in nuclear medicine discussing its background, features, and future directions in imaging and therapy.

Isolated peritoneal carcinomatosis in prostate cancer: from a successful hormonal management to a review of the literature

Metastases from prostate cancer involve mainly the bone compartment. However, visceral metastases are found in up to 49% of metastatic patients, occurring mainly in late stages of the disease, and are correlated with poor outcome. Peritoneal carcinomatosis is rarely described in literature, particularly when not associated with other distant metastatic lesions. We present the management of a patient with prostate cancer progressing on androgen deprivation therapy with description of omental involvement on ⁶⁸Ga PSMA-PET. There was no ascite or other distant lesion, reflecting thus a specific tropism of the cancer in this patient who had no history of prostate surgery. Abiraterone acetate resulted in a long-lasting complete response. We also present a review focusing on this entity.

Prostate-specific Membrane Antigen PET in Prostate Cancer

Prostate-specific membrane antigen (PSMA)-targeted radiopharmaceuticals are playing a large role at the time of initial staging and biochemical recurrence for localizing prostate cancer, as well as in other emerging clinical settings. PSMA PET has demonstrated increased detection rate compared with conventional imaging and has been shown to change management plans in a substantial percentage of cases. The aims of this narrative review are to highlight the development and clinical impact of PSMA PET radiopharmaceuticals, to compare PSMA to other agents such as fluorine 18 fluciclovine and carbon 11 choline, and to highlight some of the individual PSMA PET agents that have contributed to the advancement of prostate cancer imaging.