From the Guidelines
For the initial diagnosis of renal masses, contrast-enhanced CT remains the standard first-line imaging technique, while PET/CT is not a standard investigation in the diagnosis and staging of clear-cell RCC, but may be considered in specific cases such as papillary RCC or for staging, restaging, and monitoring treatment response. The choice between PET-CT and CT for diagnosing Renal Cell Carcinoma (RCC) depends on the specific clinical scenario and the subtype of RCC. According to the european association of urology guidelines on renal cell carcinoma: the 2022 update 1, CT, ultrasound, and magnetic resonance imaging (MRI) are the imaging modalities used to detect and characterize renal masses.
For solid renal masses, the most important criterion for malignant lesions is the presence of contrast enhancement or restriction. However, CT and MRI cannot reliably distinguish oncocytoma and fat-free angiomyolipoma from malignant renal neoplasms. Positron emission tomography (PET) is increasingly being used in papillary RCC, but PET is currently not a standard investigation in patients with clear-cell RCC.
The use of PET/CT in RCC is still evolving, and its role is being investigated, especially with newer radiotracers like PSMA. As stated in the renal cell carcinoma: esmo clinical practice guidelines for diagnosis, treatment and follow-up 1, fluorodeoxyglucose positron emission tomography (FDG-PET) is not a standard investigation in the diagnosis and staging of ccRCC and should not be used.
In terms of staging, chest CT is the most accurate investigation for diagnosing lung metastases or enlarged mediastinal lymph nodes, and is strongly recommended except in cT1a renal tumors, for which the probability of positive chest CT is low 1. The guidelines also recommend that bone or brain imaging is performed if indicated, with the exception of patients with metastatic RCC, for whom brain imaging is recommended.
The renal mass and localized renal cancer: evaluation, management, and follow-up: aua guideline: part ii 1 suggests that patients undergoing follow-up for treated malignant renal masses should only undergo bone scan if one or more of the following is present: clinical symptoms such as bone pain, elevated alkaline phosphatase, or radiographic findings suggestive of a bony neoplasm.
Overall, while PET/CT has its advantages, including higher sensitivity for detecting distant metastases, its use should be tailored to clinical scenarios where the additional information will impact management decisions, due to its higher radiation dose and cost compared to CT alone.
From the Research
Difference between PET-CT and CT for Diagnosing Renal Cell Carcinoma (RCC)
- PET-CT is a functional imaging modality that provides information on the metabolic activity of tissues, whereas CT is an anatomical imaging modality that provides information on the structure of tissues 2, 3.
- CT is widely used for the diagnosis and staging of RCC, and is considered a reliable and effective method for detecting renal tumors and evaluating their extent 4, 5.
- PET-CT, on the other hand, has limited application in the diagnosis of RCC due to the physiological excretion of FDG from the kidneys, which can decrease contrast between renal lesions and normal tissue 3.
- However, PET-CT can be useful in certain situations, such as:
- Postoperative surveillance and restaging of RCC, where it has high sensitivity, specificity, and accuracy 3.
- Detecting metastasis to the bone, where it has higher sensitivity and accuracy compared to bone scan 3.
- Monitoring the efficacy of new target therapies, such as tyrosine kinase inhibitors, where change in FDG uptake can be a strong indicator of biological response to treatment 3.
- Recent developments in targeted PET-CT imaging using radiolabeled antibodies, such as girentuximab, have shown promise in detecting clear cell RCC and differentiating it from other renal tumors 6.
- The use of PET-CT in RCC is still evolving, and further research is needed to fully establish its role in the diagnosis and management of the disease 2, 6.