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Introduction

From a clinical perspective, renal cancer encompasses a heterogeneous group of solid malignancies, marked by substantial biological, histological and clinical variability. Although it accounts for a relatively small proportion of all cancers, its clinical relevance is disproportionate, largely due to the frequent diagnosis at advanced stages, the unpredictable disease course and the complexity of therapeutic decision-making. Accordingly, renal cancer is better regarded as a spectrum of tumors with distinct biological behavior and therapeutic implications rather than as a single disease entity^(1-3).

Over the past two decades, advances in the understanding of tumor biology have reshaped the management of renal cancer. The recognition of angiogenesis and hypoxia-related pathways as key drivers of tumor progression provided the rationale for targeted therapies, while the introduction of immune checkpoint inhibitors has translated into meaningful improvements in outcomes for patients with advanced disease. Clinically, these developments have established renal cancer as a paradigmatic solid tumor in which treatment selection and therapeutic sequencing are central to decision-making^(1,3).

Importantly, renal cancer is frequently encountered in patients with chronic kidney disease and cardiovascular comorbidities – factors that directly influence prognosis and may constrain available therapeutic options. For the clinician, this underscores the need for an integrated approach that considers not only tumor-related characteristics, but also renal function, patient comorbidities and treatment-related toxicities⁽¹⁾.

Against this background, the present review aims to provide a concise and clinically oriented overview of renal cancer, focusing on aspects relevant to everyday oncological practice. Particular emphasis is placed on tumor classification and biologically relevant features, clinical presentation and diagnostic strategies, principles of staging and prognostic assessment, current treatment approaches and persisting areas of uncertainty^(1-3).

1. General framework of renal cancer

Renal cancer comprises a group of solid malignancies arising from the renal parenchyma, and it is characte­rized by substantial biological and clinical heterogeneity. From a clinical perspective, this heterogeneity translates into marked variability in disease presentation, natural history and response to treatment. Consequently, renal cancer should be approached as a spectrum of distinct entities rather than as a single pathological condition, with histological and biological classification playing a central role in therapeutic decision-making^(1-3).

In contemporary oncological practice, the conceptual framework of renal cancer is increasingly shaped by the integration of tumor-related characteristics with patient-specific clinical factors. Tumor size, local extension and metastatic spread must be interpreted alongside comorbid conditions – particularly chronic kidney disease and cardiovascular disease – which significantly influence prognosis and treatment feasibility. As a result, the evaluation of renal cancer extends beyond anatomical staging, and requires a global assessment of risks and potential benefits associated with available therapeutic options⁽¹⁾.

1.1. Types of renal cancer

The classification of renal cancer is primarily based on histological criteria, with several major subtypes re­cog­­nized, each associated with distinct biological features and clinical behavior. Clear cell renal cell carcinoma represents the most prevalent subtype, and it is charac­terized by molecular alterations involving hypoxia sig­na­ling and angiogenesis. Other common subtypes include papillary and chromophobe renal cell carcinomas, which exhibit different molecular profiles and generally distinct clinical courses^(2,3).

This histological diversity has direct clinical relevance, influencing both prognosis and therapeutic strategy, particularly in advanced disease. Although the advent of modern systemic therapies has partially reduced outcome disparities between subtypes, clear cell renal cell carcinoma remains the main model for therapeutic development and clinical trials. In contrast, non-clear cell renal cancers continue to pose therapeutic challenges, underscoring the need for individualized treatment approaches and further research^(1-3).

2. Epidemiology and risk factors

Renal cancer accounts for approximately 2-3% of all adult malignancies and predominantly affects older adults, with a peak incidence in the sixth and seventh decades of life, and a clear male predominance. Over recent decades, the incidence of renal cancer has increased steadily, largely as a consequence of the widespread use of cross-sectional imaging and the incidental detection of small renal masses. Despite this trend toward earlier detection, a substantial proportion of patients continue to present with locally advanced or metastatic disease, contributing to the overall disease burden⁽³⁾.

Several risk factors for renal cancer have been consistently identified. Cigarette smoking, obesity and hypertension represent the most important modifiable risk factors, while age and male sex remain key non-modifiable determinants. These factors frequently coexist in patients diagnosed with renal cancer, and are clinically relevant, as they may influence both prognosis and therapeutic decision-making⁽³⁾.

3. Tumor biology

The biological heterogeneity of renal cancer underlies its variable clinical behavior and differential response to treatment. From a pathological standpoint, this heterogeneity is reflected in distinct histological subtypes, each associated with specific molecular alterations and biological pathways. The current classification of renal tumors recognizes these differences as clinically meaningful, rather than merely descriptive, as they influence prognosis and therapeutic sensitivity⁽⁵⁾.

Clear cell renal cell carcinoma, the most common subtype, is characterized by dysregulation of cellular responses to hypoxia, most frequently due to alterations involving the von Hippel-Lindau pathway. This results in increased expression of proangiogenic factors and a highly vascular tumor microenvironment, providing the biological rationale for the use of anti-angiogenic therapies. In contrast, non-clear cell renal cancers exhibit more heterogeneous molecular profiles, with distinct oncogenic drivers and less consistent sensitivity to currently available systemic treatments^(5,6).

Advances in genomic and molecular characterization have further highlighted the complexity of renal cancer biology, revealing substantial intratumoral and intertumoral heterogeneity. These findings help explain the variable clinical course observed even within the same histological subtype and underscore the limitations of a purely morphology-based classification. While molecular profiling has not yet translated into routine biomarker-guided therapy, it has contributed significantly to the conceptual shift toward individualized treatment strategies in renal cancer⁽⁶⁾.

4. Clinical presentation and diagnosis

4.1. Clinical presentation

Renal cancer exhibits a broad spectrum of clinical presentations, ranging from incidental, asymptomatic tumors to advanced disease with systemic manifestations. In contemporary practice, the majority of cases are detected incidentally during imaging performed for unrelated indications, reflecting the increased use of cross-sectional abdominal imaging. Symptomatic presentation is less common, and it is more frequently associated with locally advanced or metastatic disease⁽⁷⁾.

The classic triad of flank pain, gross hematuria and palpable abdominal mass is now rarely encountered and typically reflects advanced tumor stage. In addition, renal cancer may present with paraneoplastic manifestations, including anemia, hypercalcemia, hypertension or constitutional symptoms such as weight loss and fatigue. These systemic features may precede local symptoms and should raise clinical suspicion, particularly in patients with relevant risk factors⁽⁷⁾.

4.2. Diagnosis

The diagnosis of renal cancer is primarily based on imaging, with contrast-enhanced computed tomography representing the cornerstone of initial evaluation. Multiphasic CT allows accurate assessment of tumor size, local extension, vascular involvement and the presence of metastatic disease. Magnetic resonance imaging serves as an alternative in selected cases, particularly in patients with contraindications to iodinated contrast or when venous invasion is suspected⁽⁸⁾.

Histological confirmation is not routinely required prior to surgical management in patients with radiologically typical localized renal masses. However, percutaneous tumor biopsy has an established role in selected clinical scenarios, including indeterminate renal lesions, suspected metastatic disease, or prior to the initiation of systemic therapy. While biopsy can provide valuable diagnostic and prognostic information, its use should be individualized, taking into account potential limitations and the overall clinical context⁽⁸⁾.

5. Staging and prognosis

Accurate staging is essential in renal cancer, as it provides critical prognostic information and directly guides therapeutic decision-making. The TNM staging system remains the standard framework for anatomical staging, incorporating tumor size and local extension, lymph node involvement and the presence of distant metastases. In clinical practice, staging distinguishes localized disease from locally advanced and metastatic forms, a separation that has major implications for treatment strategy and expected outcomes⁽⁹⁾.

Beyond anatomical staging, several clinical and laboratory parameters have been identified as independent prognostic factors, particularly in advanced renal cancer. Performance status, time from diagnosis to treatment initiation, hemoglobin levels, serum calcium and inflammatory markers have all been shown to correlate with survival outcomes. These variables have been integrated into validated prognostic models that allow risk stratification and support therapeutic planning in metastatic disease⁽¹⁰⁾.

Prognostic assessment in renal cancer therefore extends beyond tumor burden alone and requires a multidimensional evaluation that combines anatomical stage with patient-related and disease-related factors. Such an approach is especially relevant in the era of multiple systemic treatment options, where prognostic classification may influence both treatment selection and sequencing^(9,10).

6. Tratament

The management of renal cancer is highly stage-dependent and requires a multidisciplinary approach. Treatment strategies differ substantially between localized and advanced disease, reflecting differences in therapeutic goals, available interventions and expected outcomes. In localized renal cancer, the curative intent is the primary objective, whereas in advanced stages, the systemic therapy plays a central role. Consequently, an accurate assessment of disease extent and patient-related factors is essential for appropriate treatment selection.

6.1. Localized renal cancer

Surgery represents the cornerstone of treatment for localized renal cancer. Whenever feasible, nephron-sparing surgery is preferred, as it provides oncological outcomes comparable to radical nephrectomy while preserving renal function. Partial nephrectomy is therefore recommended for most patients with small and intermediate-sized renal tumors, particularly in those with preexisting renal impairment or increased risk of chronic kidney disease⁽¹⁷⁾.

Radical nephrectomy remains indicated in selected cases, including large or locally advanced tumors not amenable to conservative surgery, or when partial nephrectomy would result in unacceptable morbidity. In carefully selected patients with small renal masses and limited life expectancy or significant comorbidities, active surveillance may represent a reasonable alternative, reflecting the often indolent behavior of some localized renal tumors⁽¹⁷⁾.

Overall, treatment decisions in localized renal cancer should balance oncological control with preservation of renal function and patient quality of life, emphasizing individualized risk assessment rather than a uniform surgical approach⁽¹⁷⁾.

6.2. Advanced and metastatic renal cancer

The treatment of advanced and metastatic renal cancer has undergone a major transformation over the past decade, driven by the introduction of immune checkpoint inhibitors and their combination with targeted agents. Systemic therapy is the cornerstone of management in this setting, with treatment selection guided by prognostic risk stratification, patient comorbidities and anticipated toxicity profiles rather than histology alone in most cases^(11-15).

Combination regimens based on immune checkpoint inhibitors have become standard of care in the first-line treatment of metastatic clear cell renal cancer. Dual immunotherapy as well as combinations of immunotherapy with tyrosine kinase inhibitors have demonstrated significant improvements in overall survival and progression-free survival compared with previous standards. These approaches have shifted the therapeutic goals toward durable disease control and, in selected patients, to long-term remission^(11-14).

Targeted therapies remain an essential component of the therapeutic armamentarium, both as part of combination regimens and in subsequent treatment lines. Agents targeting angiogenic pathways continue to play a central role, particularly in patients who are not candidates for immunotherapy-based combinations or who experience disease progression after initial treatment. Treatment sequencing has therefore emerged as a critical aspect of care, requiring individualized decisions based on prior response, tolerance and evolving disease characteristics^(12-15).

Despite these advances, metastatic renal cancer remains an incurable disease for most patients. The optimal sequencing of available therapies, the management of treatment-related toxicities and the identification of patients most likely to benefit from specific regimens continue to represent major clinical challenges, underscoring the need for personalized treatment strategies and ongoing clinical research^(11-15).

7. Current challenges and grey areas

Despite significant therapeutic advances, several unresolved issues continue to complicate the management of renal cancer. One important challenge relates to disease heterogeneity and variable tumor kinetics, particularly in metastatic settings. A subset of patients exhibits indolent disease behavior, raising questions regarding the optimal timing of systemic treatment initiation. In carefully selected cases, active surveillance has emerged as a potential strategy, allowing postponement of systemic therapy without compromising short-term outcomes⁽¹⁸⁾.

Another major area of uncertainty concerns the management of patients with significant comorbidities, especially chronic kidney disease. Renal cancer frequently arises in patients with impaired renal function, either preexisting or treatment-related, which may limit therapeutic options and increase the risk of toxicity. Preservation of renal function therefore represents a critical consideration throughout the disease course, particularly in the context of repeated lines of systemic therapy^(19,20).

Treatment-related renal toxicity remains an important clinical issue, especially with targeted therapies that interfere with angiogenic pathways. Hypertension, proteinuria and progressive decline in renal function may complicate the long-term treatment and necessitate dose modifications or treatment discontinuation. These challenges underscore the need for close interdisciplinary collaboration and highlight the limitations of a purely tumor-centered approach in the management of renal cancer^(19,20).

Conclusions

Renal cancer represents a biologically and clinically heterogeneous group of malignancies that require an individualized, stage-adapted management strategy. In recent years, advances in tumor biology have translated into substantial progress in systemic treatment, particularly through the integration of immunotherapy and targeted agents, fundamentally reshaping the therapeutic landscape of advanced disease.

However, despite these achievements, renal cancer continues to pose significant clinical challenges. Optimal treatment sequencing, the management of comorbidities and the preservation of renal function throughout the disease course remain critical issues in daily practice. These considerations highlight the importance of a multidisciplinary approach that balances oncological efficacy with patient-centered priorities.

Looking ahead, further progress in renal cancer management will depend on improved risk stratification, the identification of clinically meaningful biomarkers and the refinement of personalized treatment strategies. Such developments are essential to maximize long-term outcomes while minimizing treatment-related toxicity, particularly in an increasingly complex and comorbid patient population.   

Corresponding author: Constantin Verzan E-mail: cverzan@gmail.com

Conflict of interest: none declared.

Financial support: none declared.

This work is permanently accessible online free of charge and published under the CC-BY licence.