Invited Commentary: A Team Approach—Contemporary Diagnosis and Management of Renal Cell Carcinoma

See also the article by Abou Elkassem et al in this issue.

In the article “Role of Imaging in Renal Cell Carcinoma: A Multidisciplinary Perspective,” Abou Elkassem et al (1) undertake the ambitious goal of reviewing the many roles of imaging in the characterization and staging of renal cell carcinoma (RCC), as well as the roles of imaging in treatment planning, postprocedural evaluation, and assessment of advanced disease. As radiologists, we are well aware of the important role that multidisciplinary tumor boards play in guiding patient management. For instance, tumor board discussion has been shown to change treatment plans for genitourinary tumors in 18%–46% of patients (2). With an increasing recognition that traditional management approaches lead to overtreatment of indolent malignant renal neoplasms and sometimes benign neoplasms (3), management has shifted to a more deliberately calculated weighing of the risks and benefits of various therapeutic efforts (4). This nuanced approach relies heavily on the combined expertise of multidisciplinary specialists, which is reflected by the list of authors for this article, a team composed of radiologists, urologists, oncologists, and radiation oncologists.

Abou Elkassem et al (1) begin their review by describing imaging findings for the indeterminate renal mass, including descriptions of CT and MRI protocols and suggestions regarding how to report imaging findings. The authors do not delve into how to differentiate benign from malignant lesions or how to characterize the different types of RCC. However, the authors do describe the American Joint Commission on Cancer TNM staging system and emphasize the key distinction between T2 tumors and T3a tumors; namely, invasion into the renal vein or perinephric tissues or the central sinus, including the collecting system. This distinction has been one in which imaging has struggled. As the authors state, findings such as perinephric stranding and enhancing nodules have been reported to indicate perinephric spread (1). However, stranding is nonspecific, and nodules, although they have a high positive-predictive value, are uncommon.

Other imaging findings investigated to distinguish these T stages include tumor necrosis, tumor edge extending to the renal sinus or perirenal fascia, irregularity of tumor contour, accentuated perinephric septa, thickening of the perirenal fascia, increased perinephric vascularity, and calcification. However, most of these findings suffer from poor interobserver agreement (5). Nevertheless, the distinction between these tumor types is important, as the recurrence-free survival rate with pathologic T3a tumors is approximately 70%–80% at 5 years, which is considerably lower than the rate with organ-confined neoplasms. Research has shown that approximately 5%–15% of tumors that have been staged as T1–T2 on the basis of clinical and imaging findings are upstaged at pathologic analysis to T3a, and this phenomenon has been correlated with reduced recurrence-free survival, cancer-free survival, and overall survival (6).

As Abou Elkassem et al (1) point out, management of RCC has increasingly moved to a less aggressive approach, with a larger role for minimally invasive and percutaneous therapies and active surveillance. Anatomic considerations, indications and contraindications, and posttreatment imaging follow-up vary among these management approaches. The increasing use of partial nephrectomy (PN) in tumors up to 7 cm in size (T1b) has been advocated, as PN in these cases has been found to lead to outcomes similar to those with radical nephrectomy (RN). However, studies have demonstrated conflicting findings regarding whether outcomes are worse after PN than after RN in patients with T3a disease. The most recent American Urological Association guidelines recognize the significance of renal functional decline after RN or PN (7) and stress the importance of preserving functioning parenchyma. As more than 25% of patients with localized RCC have preexisting chronic kidney disease, which is often unrecognized, patients will benefit from optimized renal function after PN. This will minimize the risk of progression to renal failure and the accompanying increase in mortality rate.

Abou Elkassem et al (1) also address the use of percutaneous tumor ablation, which has been practiced for more than 20 years and demonstrates outcomes that are nearly identical to those found with PN for localized tumors that are smaller than 4 cm (T1a). Xing et al (8) used propensity score matching to assess outcomes in more than 10 000 patients in the Surveillance, Epidemiology, and End Results–Medicare-linked database and found that for older patients with T1a tumors, percutaneous ablation demonstrates outcomes equivalent to those seen with PN (9-year cancer-specific survival rates of 96.3% for ablation and 96.4% for PN).

Other management approaches for RCC include transarterial embolization and stereotactic body radiation therapy. Transarterial embolization is an infrequently used approach that has shown mixed results in patients with RCC, whereas stereotactic body radiation therapy may be considered an emerging approach to be used in specific circumstances. For instance, this approach may be used to achieve local control in patients who are poor surgical or ablation candidates or in patients with a small number of metastatic lesions.

With increasing recognition that many patients die with RCC rather than from RCC, the use of active surveillance of renal masses has increased, especially in patients with significant comorbidities. Multiple studies have evaluated the competing risks of death in patients with RCC and have found that the risk of death from comorbidities greatly outweighs the risk of death from a T1a RCC. For example, a nomogram developed by Kutikov et al (9) predicts that an 80-year-old Black man with a history of myocardial infarction who has moderate renal insufficiency and a 4-cm renal tumor is expected to have a 5-year mortality rate of 5% from RCC compared with a rate of 48% from other causes.

Abou Elkassem et al (1) also review the pros and cons of stringent and less-stringent surveillance for local recurrence and metastases after RCC treatment in asymptomatic patients. An important point to consider is the radiation exposure and cost related to surveillance imaging. For example, radiation exposure can vary from 0 mSv to 102 mSv for posttreatment surveillance of a 3-cm clear cell carcinoma, depending on the follow-up protocol performed (10).

Finally, the authors discuss the complex topic of advanced RCC and the role of systemic therapy (1). Although details regarding these treatments are beyond the scope of their article, the authors summarize the different classes of agents and conveniently list the associated complications in Table 5. The authors emphasize that targeted antiangiogenic agents are cytostatic rather than cytotoxic, and thus cause devascularization, leading to modest size decreases with decreasing enhancement in responding tumors, as manifested by lower attenuation on portal venous phase CT images. They also review the concept of pseudoprogression after immunotherapy, which involves increased tumor size and the appearance of new lesions, a pitfall in detecting disease progression in these patients. The authors point out that commonly used metrics such as Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 are limited in assessing these newer classes of agents used for advanced RCC, and they discuss the development of newer biomarkers.

In summary, Abou Elkassem et al (1) synthesize the many aspects of imaging as applied to patients with RCC and broadly summarize the key points related to renal mass reporting, staging of RCC, and management approaches and imaging correlates. This review is an excellent starting point for understanding the contemporary management of RCC and the increasingly complex and evolving approach “toward more rational treatment” (4). This rational treatment requires a multilayered evaluation and treatment plan best implemented by a diverse care team.