18F-FDG PET/CT as a prognostic factor in penile cancer

Current Role of PET CT in Staging and Management of Penile Cancers

Penile cancer (PeCa) is a rare urological malignancy characterized by significant geographical variations in both incidence and mortality rates. Due to its rarity and the consequent lack of randomized trials, current management is based on retrospective studies and small prospective trials. In addition, both the diagnostic pathways and treatment strategies exhibit substantial heterogeneity, differing significantly between less-developed and well-developed countries. The prognosis of PeCas is determined by the presence and extent of regional lymph node (LN) involvement. Therefore, the early detection and treatment of LN metastasis is paramount to ensure better outcomes. In recent decades, overall survival of PeCas has increased, mainly due to advancements in imaging techniques and risk stratification. We aim to provide an overview of the current role of PET CT imaging in the management of patients with PeCa.

The evolution of PET imaging in renal, bladder, upper urinary tract urothelial, testicular and penile carcinoma - Today's impact, tomorrow's potential

INTRODUCTION

The advancement of hybrid PET/CT or PET/MRI imaging for non-prostate genitourinary cancers has not experienced the rapid progress of prostate cancer. Nevertheless, these neoplasms are aggressive and reliable imaging plays a pivotal role in enhancing patients' quality of life and prognosis.

AREAS COVERED

the main evidence regarding [18F]FDG and non-[18F]FDG PET/CT or PET/MRI in non-prostate uro-oncological malignancies are summarized and discussed. Moreover, potential future directions concerning PET imaging in these neoplasms are debated, with the aim to stimulate future research projects covering these fields.

EXPERT OPINION

In Renal Cell Carcinoma (RCC), [18F]FDG PET/CT demonstrates varying efficacy in staging, restaging, and prognostic stratification, but PSMA PET/CT is emerging as a potential game-changer, particularly in advanced, high-grade aggressive clear cell RCC. [18F]FDG PET/CT may see an increased use in N and M-staging of bladder cancer, as well as for detecting recurrence and response to neoadjuvant chemotherapy. Preliminary data regarding [68Ga]-FAPI also looks promising in this context. [18F]FDG PET/MRI could be useful for the T-staging of bladder cancer, while upper tract urothelial carcinoma still lacks of molecular imaging literature reports. In testicular and penile cancer [18F]FDG PET/CT has demonstrated its usefulness in several clinical settings, although experiences with non-[18F]FDG radiotracers are lacking.

Prediction of outcomes in patients with local recurrent nasopharyngeal carcinoma: development and validation of a four-factor prognostic model integrating baseline characteristics and [18F]FDG PET/CT parameters

OBJECTIVES

To investigate the prognostic value of [¹⁸F]FDG PET/CT parameters in local recurrent nasopharyngeal carcinoma (lrNPC) and establish a prognostic tool for lrNPC patients based on these [¹⁸F]FDG PET/CT parameters.

METHODS

A total of 358 lrNPC patients seen from 2010 to 2019 at Sun Yat-sen University Cancer Center with complete baseline characteristics and [¹⁸F]FDG PET/CT data were retrospectively analyzed. Maximal standardized uptake value (SUVmax), SUVmean, SUVpeak, metabolic tumor volume (MTV), total lesion glycolysis (TLG), and heterogeneity index (HI) for recurrent nasopharynx tumors were included. Cox regression analysis was performed to select candidate variables. Subsequently, a nomogram for predicting overall survival (OS) for lrNPC patients was developed and internally validated.

RESULTS

Multivariate Cox analysis results suggested that age ≥ 47 years (hazard ratio (HR), 1.62 (1.18-2.24); p = 0.003)，with smoking history (HR, 1.41 (1.01-1.98); p = 0.046), recurrent T stage {[rT3 vs rT1/2: HR, 1.81 (1.04-3.12); p = 0.037]; [rT4 vs rT1/2: HR, 2.46 (1.32-4.60); p = 0.005]}, and TLG {[37.1-184.3 vs ≤ 37.1: HR, 2.26 (1.49-3.42); p < 0.001]; [>184.3 vs ≤ 37.1: HR, 4.31 (2.50-7.43); p < 0.001]) were independent predictors of OS. A 4-factor nomogram was generated to stratify patients into 3 risk groups. This novel model showed good discrimination with a high C-index (0.752, 95%CI: 0.714-0.790). In addition, the calibration curves showed good agreement between the predicted probabilities and actual observations and decision curve analysis (DCA) suggested that the nomogram was useful for clinical decision-making.

CONCLUSIONS

Our study confirmed that [¹⁸F]FDG PET/CT parameters were valuable in predicting OS and PFS for lrNPC patients. The 4-factor prognostic model combing baseline patient characteristics with [¹⁸F]FDG PET/CT parameters for lrNPC patients had good discrimination, agreement, and clinical application potential.

KEY POINTS

• [¹⁸F]FDG PET/CT parameters were valuable in predicting OS and PFS for lrNPC patients. • The novel 4-factor nomogram for lrNPC patients had good discrimination, agreement, and potential for clinical application.

Recent developments in the diagnosis and management of N1 penile cancer

PURPOSE OF REVIEW

This article presents a critical review of the current literature to provide a brief update on the contemporary advances in diagnosing and managing N1 penile cancer.

RECENT FINDINGS

Penile squamous cell carcinoma (pSCC) has evolved from being an orphan field for cancer innovation. Advances in the understanding tumour biology have enabled sophisticated diagnostics and predictive modelling to better characterize inguinal disease. Minimally invasive inguinal lymph node dissection is emerging as a technique that reduces morbidity while maintaining oncological safety. Furthermore, robust clinical trials are underway ,which will provide level one evidence to guide treatment decisions. Exciting advances in the field of immune-oncology offer promise as adjuvant therapies. International collaboration and centralisation of care will be essential to driving translational research and equitable evidence-based care.

SUMMARY

Improving outcomes for men with pSCC remains a global challenge. Radical inguinal lymph node dissection remains the gold standard for diagnosing and curing N1 disease. Although many promising developments are on the horizon, high-level evidence is required to guide therapy.

An update on treatment of penile cancer

Penile cancer is a rare malignancy, particularly in industrialized nations. In the United States, rates are approximately less than 1 per 100,000 men per year with just over 2000 new cases per year. However, there is significantly increased prevalence in developing nations, with limited treatment expertise and reduced access to care, further driving an unmet clinical need. The most noteworthy risk factor for penile cancer is the association with human papillomavirus infection, which may be present in up to 50% of all penile carcinomas. In addition to local primary tumor approaches, multimodality treatment strategies are vital to patients with clinical regional nodal disease, locally advanced disease. Presence and degree of lymph node involvement remains the most important prognostic factor and patients may benefit from multiple treatment strategies. Interim analysis data from the first randomized clinical trial is expected to yield results in mid/late 2024–early 2025. These treatment approaches include neoadjuvant chemotherapy, adjuvant therapy, including chemotherapy and radiation. Systemic therapy for distant recurrent or metastatic disease is primarily a platinum-based chemotherapy, however with poor overall response. As poor outcomes remain high, particularly in indigent populations, there remains an unmet need for these patients, particularly for high level randomized trials and novel therapeutics. In this review, we will highlight treatment updates for penile cancer. In addition to standard of care, we will review novel lines of therapies including immunotherapies and targeted therapies as well as sequencing approaches.

FDG PET/CT in a Patient With Syphilis Suspected of Having Penile Cancer

ABSTRACT

A 58-year-old man with large penile wound and enlarged regional lymph node was suspected of having disseminated penile cancer. FDG PET/CT for primary staging showed high FDG uptake on penis and in several enlarged lymph nodes. However, biopsies revealed no signs of malignancy, but ulceration, inflammation, fibrosis, and spirochetes. Furthermore, Wassermann test was positive. The patient was then treated for syphilis. To our knowledge, this is the first report on FDG PET/CT in a patient suspected of having penile cancer that turned out to be syphilis. Thus, syphilis can be added to the list of benign pitfalls in FDG PET/CT.

Imaging for the Initial Staging and Post-Treatment Surveillance of Penile Squamous Cell Carcinoma

Although relatively rare in the United States, penile squamous cell carcinoma is encountered worldwide at a higher rate. Initial diagnosis is often made on clinical exam, as almost all of these lesions are externally visible and amenable to biopsy. In distinction to other types of malignancies, penile cancer relies heavily on clinical nodal staging of the inguinal lymph node chains. As with all cancers, imaging plays a role in the initial staging, restaging, and surveillance of these patients. The aim of this manuscript is to highlight the applications, advantages, and limitations of different imaging modalities in the evaluation of penile cancer, including ultrasound, computed tomography, magnetic resonance imaging, and positron emission tomography.

Impact of Examined Lymph Node Count and Lymph Node Density on Overall Survival of Penile Cancer

BACKGROUND

Few studies have explored the optimal examined lymph node count and lymph node density cutoff values that could be used to predict the survival of patients with penile cancer. We further clarify the prognostic value of lymph node density and examined lymph node count in penile cancer.

METHODS

The Surveillance, Epidemiology, and End Results (SEER) database was explored to recruit penile cancer patients from 2010 to 2015. A retrospective analysis of penile cancer patients' data from the First Affiliated Hospital of Anhui Medical University was performed for verification (2006-2016). The cutoff values of examined lymph node count and lymph node density were performed according to the ROC curve. Kaplan-Meier survival analysis was used to compare survival differences among different groups. Univariate and multivariate Cox proportional hazard regression analyses were used to determine the significant variables. On the basis of Cox proportional hazards regression model, a nomogram was established and validated by calibration plot diagrams and concordance index (C-index).

RESULTS

A total of 528 patients in the Surveillance, Epidemiology, and End Results cohort and 156 patients in the Chinese cohort were included in this study. Using the ROC curve, we found that the recommended cutoff values of ELN and LND were 13 and 9.3%, respectively (P <0.001). Kaplan-Meier curves suggested the significant differences of overall survival among different examined lymph nodes and lymph node density. Multivariate analysis indicated ELN and LND were independent prognostic factor for OS of penile cancer patients. Nomogram showed the contribution of ELN and LND to predicting OS was large. The C-index at 3-, and 5-year were 0.744 for overall survival (95% CI 0.711-0.777).

CONCLUSIONS

The more lymph nodes examined, the lower the density of lymph nodes, and the higher the long-term survival rate of penile cancer. We recommended 13 examined lymph nodes and lymph node density >9.3% as the cutoff value for evaluating the prognosis of penile cancer patients.

PET/CT limitations and pitfalls in urogenital cancers

Hybrid FDG PET/CT plays a vital role in oncologic imaging and has been widely adopted for the staging and restaging of a variety of malignancies. Its diagnostic value in urogenital malignancies is less well-known, not at least because of the variable FDG avidity of these tumor entities, the sites of these tumors, and technical challenges associated with sequential imaging of CT and PET. PET/CT interpretation thus can be especially challenging and is associated with many pitfalls, which can lead to both false-positive and false-negative diagnoses as well as incorrect assessment of metabolic change following therapy. Currently, FDG PET/CT is not the standard of care for the initial diagnosis or staging of early-stage or low-risk urogenital cancers; however, it can help evaluate distant metastatic disease, response to therapy, and disease recurrence in high-risk patients. Knowledge of imaging features of tumor metabolic avidity and pitfalls is essential for accurate interpretation.

Management of Advanced Penile Cancer

Penile squamous cell carcinoma (PSCC) is a rare cancer, with approximately 2000 new cases in the United States and 35,000 globally every year. Multiple risk factors are involved in PSCC, but most importantly, the high-risk human papillomavirus infection is thought to be present in approximately 50% of cases. Penile squamous cell carcinoma presents as localized or locally advanced disease. Multiple prognostic markers have been explored over the past 3 decades, but lymph node status remains the strongest predictor of clinical outcomes. Surgical decisions are based on the primary tumor pathologic findings, nodal clinical examination, and imaging results. Most patients with high-risk advanced PSCC benefit from a multimodal treatment approach combining chemotherapy with consolidation surgical treatment. The role of neoadjuvant chemotherapy with radiation therapy has not been well explored in PSCC. Prospective clinical studies, like the International Penile Advanced Cancer Trial, have been launched to provide high-level evidence for multimodal treatment. The International Penile Advanced Cancer Trial is the first randomized clinical trial among patients with PSCC and is currently accruing, with the expectation to generate results in 2023. Unfortunately, most patients with high-risk locally advanced PSCC will have relapsed or refractory cancer after cisplatin-based combination chemotherapy. These patients have dismal outcomes with salvage chemotherapy, highlighting the major unmet need to expand our knowledge of the disease's biology and develop clinical trials that use novel systemic agents. This narrative review synthesizes relevant publications retrieved from PubMed. Our aim is to discuss current approaches in the management of PSCC, summarize ongoing efforts to improve care, and identify future areas for enhancing our understanding of the disease.

DaPeCa-7: comparative assessment of fluorodeoxyglucose positron emission tomography/computed tomography (CT) and conventional diagnostic CT in diagnosis of lymph node metastases, distant metastases and incidental findings in patients with invasive penile cancer

OBJECTIVES

To evaluate diagnostic accuracy of ¹⁸ F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) compared to contrast-enhanced CT in assessment of inguinal lymph node (ILN) metastases, distant metastases and synchronous cancers in patients with penile squamous cell carcinoma (pSCC).

PATIENTS AND METHODS

During a 4-year period, patients with pSCC were scheduled for FDG PET/CT prior to surgical treatment at two referral centres that manage all penile cancers in Denmark. The primary endpoint was diagnostic accuracy of FDG PET/CT and of CT alone with histopathology or Response Evaluation Criteria In Solid Tumors (RECIST) as reference.

RESULTS

We evaluated 171 patients for distant metastases and synchronous incident cancers and examined 286 groins in 143 patients for LN metastases by FDG PET/CT. Six groins disclosed false negatives. FDG PET/CT sensitivity was 85.4% per patient. In 135 patients (270 groins), CT images were evaluated separately and 22 groins disclosed false negatives. CT sensitivity was 47.5% per patient. FDG PET/CT detected pSCC distant metastases in seven patients. Distant metastases from other cancers were newly detected in three patients. In eight patients, an incidental synchronous cancer was detected. Seven out of the 18 distant malignancies detected depended on FDG PET information.

CONCLUSION

This study underlines the increased diagnostic accuracy of FDG PET/CT compared to CT alone in the evaluation of ILN status. In patients with palpable LNs, the advantage of FDG PET/CT over CT is less pronounced. FDG PET/CT may play a role in penile cancer evaluation.