Clear cell renal cell carcinoma bone metastasis: What should be considered in prognostic evaluation

Differences at diagnosis between long-term survivors and not long-term survivors in metastatic renal cell carcinoma initially treated with TKI

INTRODUCTION

In recent years, significant advancements in the treatment of metastatic renal cell carcinoma (mRCC) have notably extended overall survival (OS) times, particularly with the introduction of tyrosine kinase inhibitors (TKIs) and combination immunotherapy. However, survival outcomes in mRCC remain highly variable.

MATERIALS AND METHODS

This study retrospectively analyzed clinical and demographic factors at diagnosis in patients treated for mRCC to identify predictors of long-term survival (defined as OS ≥ 48 months). Patients were categorized into long-term survivors (LTS) and non-long-term survivors (nLTS).

RESULTS

The analysis revealed that factors such as better Karnofsky Performance Status (KPS), normal baseline laboratory values (e.g., hemoglobin, calcium), and the presence of lung-only metastases were significantly associated with longer survival. Conversely, comorbid conditions like hypertension and dyslipidemia, poorer KPS, and certain adverse laboratory findings were more common in the nLTS group.

CONCLUSION

These findings underscore the importance of baseline prognostic factors in predicting survival outcomes and emphasize the need for personalized treatment strategies in mRCC.

Metastasis directed therapy in recurrent renal cell carcinoma - Retrospective analysis of a ten-year experience

INTRODUCTION

Current guidelines provide a weak recommendation for metastasis directed therapy (MDT) in patients with recurrent renal cell carcinoma (RCC) and is focused on the goal of symptom control and potentially delaying systemic therapy. Especially in light of systemic treatment entailing targeted therapies for metastatic RCC, MDT's role remains undefined. Goal of our study was to evaluate which patients might benefit most from MDT. Our assessed endpoints were time to initiation of systemic therapy and progression-free survival (PFS).

MATERIAL & METHODS

We collected data retrospectively and exclusively at our centre; our study included patients with recurrent RCC after initial partial or radical nephrectomy, who subsequently underwent MDT at the University Hospital Freiburg and whose cases were discussed at our interdisciplinary urogenital tumour board between 2011 and 2021.

RESULTS

A total of 92 patients were included. Median follow up was 57.6 months (IQR 30.9-89.6). Median age was 65.1 (IQR 59.05-72.36) at the time of first MDT. Lung and lymph nodes were the most frequent locations of recurrence (40.2 % and 20.7 %, respectively). Median PFS after the first MDT was 392 days (IQR 100-855). Median time to the initiation of systemic therapy was 534 days (IQR 142-1707). In multivariate regression analysis, a higher T-stage in the initial pathology was associated with shorter PFS (HR 1.64, 95%-CI 0.98-2.66; p = 0.05). Furthermore, older age lowered the risk of progression after MDT (HR 0.97, 95%CI 0.94-1.00; p = 0.04). According to the non-parametrical log-rank test, patients with early recurrence (within 1 year after initial diagnosis) had significant shorter time to initiation of systemic therapy (p = 0.05). However, this effect was not apparent in multivariable regression analysis.

CONCLUSION

We report on a large cohort of patients who underwent MDT for recurrent RCC within the last ten years at our institution. Within the limitations of a retrospective single-centre analysis, our findings support the concept of MDT for recurrent disease in patients presenting a favourable initial tumour stage and rather late recurrence after initial therapy. However, as mRCC is a very heterogeneous disease, more investigation is needed to refine the definition of predictive parameters that facilitate patient-centred decision-making.

Renal cell cancer treatment: the Latin American Cooperative Oncology Group (LACOG) and the Latin American Renal Cancer Group (LARCG) surgery-focused consensus update

Renal cell carcinoma (RCC) represents 2.2% of all malignancies worldwide; however, its mortality rate is not negligible. Surgery is the primary treatment for most nonadvanced cases, with its indications and techniques evolving over the years. To provide an update on RCC management in Brazil, focusing on surgery. The Latin American Cooperative Oncology Group-Genitourinary Section and the Latin American Renal Cancer Group gathered a panel of Brazilian urologists and clinical oncologists to vote on and discuss the best management of surgically resectable RCC. The experts compared the results with the literature and graded them according to the level of evidence. For small renal masses (SRMs; less than 4 cm), biopsy is indicated for specific/select cases, and when intervention is needed, partial nephrectomy should be prioritized. Radical nephrectomy and ablative techniques are exceptions for managing SRMs. Patients with small tumors (less than 3 cm), slow tumor growth, or a risk for surgery may benefit from active surveillance. Localized carcinoma up to 7 cm in diameter should be treated preferably with partial nephrectomy. Lymphadenectomy and adrenalectomy should be performed in locally advanced cases if involvement is suspected by imaging exams. Patients with venous tumor thrombi usually require surgical intervention depending on the extent of the thrombus. Neoadjuvant therapy should be considered for unresectable cases. Even in the era of targeted therapy, cytoreductive nephrectomy still has a role in metastatic disease. Metastasectomy is indicated for most patients with resectable disease. This consensus presents recommendations for surgical treatment of RCC based on expert opinions and evidence from the medical literature. Surgery remains the best curative option for nonadvanced cases, and it still has a role for select patients with metastatic disease.

[Pathological fractures of the extremities]

The diagnostics and treatment of pathological fractures of the extremities differ from the approach for conventional fractures. Metastases from breast, bronchial, renal cell and prostate cancer are the predominant cause. Typically, patients present at over 50 years old present after an inadequate trauma. They often report symptoms or swelling in the affected region that already existed before the fracture. An underlying malignant disease is sometimes already known; however, occasionally this is manifested in the form of a fracture. The femur is affected in 74% of cases, followed by the humerus and the tibia. Important indications for the presence of a pathological fracture can even be obtained from conventional radiographs. The diagnostics are supplemented with further modalities depending on the treatment goal. Surgical treatment is the first choice as the fractures do not heal using conservative measures. In this context, a prognosis-stratified approach is recommended.

Therapeutic options for different metastatic sites arising from renal cell carcinoma: A review

Renal cell carcinoma (RCC) stands among the top 10 malignant neoplasms with the highest fatality rates. It exhibits pronounced heterogeneity and robust metastatic behavior. Patients with RCC may present with solitary or multiple metastatic lesions at various anatomical sites, and their prognoses are contingent upon the site of metastasis. When deliberating the optimal therapeutic approach for a patient, thorough evaluation of significant risk factors such as the feasibility of complete resection, the presence of oligometastases, and the patient's functional and physical condition is imperative. Recognizing the nuanced differences in RCC metastasis to distinct organs proves advantageous in contemplating potential treatment modalities aimed at optimizing survival outcomes. Moreover, discerning the metastatic site holds promise for enhancing risk stratification in individuals with metastatic RCC. This review summarizes the recent data pertaining to the current status of different RCC metastatic sites and elucidates their role in informing clinical management strategies across diverse metastatic locales of RCC.

The Musculoskeletal Tumor Society Clinical Practice Guideline on the Management of Metastatic Humeral Disease

Management of Metastatic Humeral Disease is based on a systematic review of published studies surrounding the management of metastatic disease, multiple myeloma, and lymphoma limited to the humerus. This guideline contains seven action statements to assist orthopaedic surgeons, orthopaedic oncologists, physicians, and any other qualified healthcare professionals involved in the surgical management of metastatic disease of the humerus. It is also intended to serve as an information resource for decision makers, researchers, and developers of clinical practice guidelines. In addition to providing pragmatic practice recommendations, this guideline also highlights gaps in the literature and informs areas for future research and quality measure development. This guideline has been endorsed by the American Academy of Orthopaedic Surgeons.

Development of a nomogram to predict the prognosis of patients with secondary bone tumors in the intensive care unit: a retrospective analysis based on the MIMIC IV database

PURPOSE

The present study aimed to develop a nomogram to predict the prognosis of patients with secondary bone tumors in the intensive care unit to facilitate risk stratification and treatment planning.

METHODS

We used the MIMIC IV 2.0 (the Medical Information Mart for Intensive Care IV) to retrieve patients with secondary bone tumors as a study cohort. To evaluate the predictive ability of each characteristic on patient mortality, stepwise Cox regression was used to screen variables, and the selected variables were included in the final Cox proportional hazard model. Finally, the performance of the model was tested using the decision curve, calibration curve, and receiver operating characteristic (ROC) curve.

RESULTS

A total of 1028 patients were enrolled after excluding cases with missing information. In the training cohort, albumin, APSIII (Acute Physiology Score III), chemotherapy, lactate, chloride, hepatic metastases, respiratory failure, SAPSII (Simplified Acute Physiology Score II), and total protein were identified as independent risk factors for patient death and then incorporated into the final model. The model showed good and robust prediction performance.

CONCLUSION

We developed a nomogram prognostic model for patients with secondary bone tumors in the intensive care unit, which provides effective survival prediction information.

Efficacy and safety of nivolumab in bone metastases from renal cell carcinoma: Results of the GETUG-AFU26-NIVOREN multicentre phase II study

INTRODUCTION

Bone metastases (BM) in renal cell carcinoma (RCC) are associated with a poor prognosis based on retrospective studies evaluating antiangiogenic agents. Few data are available regarding immune checkpoint inhibitors (ICI) in patients with bone metastatic RCC. NIVOREN is a multicentre prospective study in which patients were treated with nivolumab after the failure of antiangiogenic agents. We aim to assess the impact of BM on prognosis, and the efficacy and safety of nivolumab in patients enrolled in the NIVOREN trial.

MATERIALS AND METHODS

All patients with BM at inclusion were included in our study. The primary endpoint was overall survival (OS). Secondary endpoints were progression-free survival (PFS), objective response rate (ORR), safety, and skeletal-related events (SRE).

RESULTS

Among 720 patients treated with nivolumab, 194 presented BM at inclusion. The median follow-up was 23.9 months. Median OS was 17.9 months in patients with BM versus 26.1 months in patients without BM (p = 0.0023). The difference was not statistically significant after adjustment (p = 0.0707). The median PFS was shorter in patients with BM even after adjustment (2.8 versus 4.6 months, p = 0.0045), as well as the ORR (14.8% versus 23.3%). SRE occurred for 36% of patients with BM. A post-hoc analysis evaluating the impact of bone-targeting agents (BTA) on SRE incidence showed a significant benefit of BTA on the incidence of SRE (OR = 0.367, CI95% [0.151-0.895]).

CONCLUSION

Nivolumab is associated with shorter PFS, and lower ORR in RCC patients with BM. Our study suggests that BTA in association with immunotherapy decreases the incidence of SRE.

Bone metastasis risk and prognosis assessment models for kidney cancer based on machine learning

Background

Bone metastasis is a common adverse event in kidney cancer, often resulting in poor survival. However, tools for predicting KCBM and assessing survival after KCBM have not performed well.

Methods

The study uses machine learning to build models for assessing kidney cancer bone metastasis risk, prognosis, and performance evaluation. We selected 71,414 kidney cancer patients from SEER database between 2010 and 2016. Additionally, 963 patients with kidney cancer from an independent medical center were chosen to validate the performance. In the next step, eight different machine learning methods were applied to develop KCBM diagnosis and prognosis models while the risk factors were identified from univariate and multivariate logistic regression and the prognosis factors were analyzed through Kaplan-Meier survival curve and Cox proportional hazards regression. The performance of the models was compared with current models, including the logistic regression model and the AJCC TNM staging model, applying receiver operating characteristics, decision curve analysis, and the calculation of accuracy and sensitivity in both internal and independent external cohorts.

Results

Our prognosis model achieved an AUC of 0.8269 (95%CI: 0.8083-0.8425) in the internal validation cohort and 0.9123 (95%CI: 0.8979-0.9261) in the external validation cohort. In addition, we tested the performance of the extreme gradient boosting model through decision curve analysis curve, Precision-Recall curve, and Brier score and two models exhibited excellent performance.

Conclusion

Our developed models can accurately predict the risk and prognosis of KCBM and contribute to helping improve decision-making.

Role of metastasectomy in the management of renal cell carcinoma

Treatment of metastatic renal cell carcinoma (mRCC) has evolved with the development of a variety of systemic agents; however, these therapies alone rarely lead to a complete response. Complete consolidative surgery with surgical metastasectomy has been associated with improved survival outcomes in well-selected patients in previous reports. No randomized control trial exists to determine the effectiveness of metastasectomy. Therefore, reviewing observational studies is important to best determine which patients are most appropriate for metastasectomy for mRCC and if such treatment continues to be effective with the development of new systemic therapies such as immunotherapy. In this narrative review, we discuss the indications for metastasectomies, outcomes, factors associated with improved survival, and special considerations such as location of metastasis, number of metastases, synchronous metastases, and use of systemic therapy. Additionally, alternative treatment options and trials involving metastasectomy will be reviewed.

Risk Factors, Prognostic Factors, and Nomograms for Bone Metastasis in Patients with Newly Diagnosed Clear Cell Renal Cell Carcinoma: A Large Population-Based Study

Background

This study aimed to investigate risk factors and prognostic factors in patients with clear cell renal cell carcinoma (ccRCC) with bone metastasis (BM) and establish nomograms to provide a quantitative prediction of the risk of BM and survival probability.

Methods

The clinicopathological characteristics of patients with ccRCC between January 2010 and December 2015 were obtained from the Surveillance, Epidemiology and End Results (SEER) database. Independent factors for BM in ccRCC patients were identified using univariate and multivariate logistic regression analyses. Prognostic factors for predicting cancer-specific death were evaluated using univariate and multivariate analyses based on a competing risk regression model. We then constructed a diagnostic nomogram and a prognostic nomogram. The two nomograms were evaluated using calibration curves, receiver operating characteristic curves, and decision curve analysis.

Results

Our study included 34,659 patients diagnosed with ccRCC in the SEER database, with 1,415 patients who presented with bone metastasis. Risk factors for BM in patients with ccRCC included age, stage T, stage N, brain metastasis, liver metastasis, lung metastasis, tumor size, and laterality. Independent prognostic factors for patients with ccRCC patients with BM were Fuhrman grade, tumor size, T stage, N stage, brain metastases, lung metastasis, and surgery. For the diagnostic nomogram, the area under the curve values in the training and testing cohorts were 0.863 (95% CI, 0.851–0.875) and 0.859 (95% CI, 0.839–0.878), respectively. In the prognostic cohort, the area under the curve values for 1-, 2-, and 3-year cancer-specific survival rates in the training cohort were 0.747, 0.774, and 0.780, respectively, and 0.671, 0.706, and 0.696, respectively, in the testing cohort. Through calibration curves and decision curve analyses, the nomograms displayed excellent performance.

Conclusions

Several factors related to the development and prognosis of BM in patients with ccRCC were identified. The nomograms constructed in this study are expected to become effective and precise tools for clinicians to improve cancer management.

Development and Validation of a Predictive Model to Evaluate the Risk of Bone Metastasis in Kidney Cancer

Background

Bone is a common target of metastasis in kidney cancer, and accurately predicting the risk of bone metastases (BMs) facilitates risk stratification and precision medicine in kidney cancer.

Methods

Patients diagnosed with kidney cancer were extracted from the Surveillance, Epidemiology, and End Results (SEER) database to comprise the training group from 2010 to 2017, and the validation group was drawn from our academic medical center. Univariate and multivariate logistic regression analyses explored the statistical relationships between the included variables and BM. Statistically significant risk factors were applied to develop a nomogram. Calibration plots, receiver operating characteristic (ROC) curves, probability density functions (PDF), and clinical utility curves (CUC) were used to verify the predictive performance. Kaplan-Meier (KM) curves demonstrated survival differences between two subgroups of kidney cancer with and without BMs. A convenient web calculator was provided for users via “shiny” package.

Results

A total of 43,503 patients were recruited in this study, of which 42,650 were training group cases and 853 validation group cases. The variables included in the nomogram were sex, pathological grade, T-stage, N-stage, sequence number, brain metastases, liver metastasis, pulmonary metastasis, histological type, primary site, and laterality. The calibration plots confirmed good agreement between the prediction model and the actual results. The area under the curve (AUC) values in the training and validation groups were 0.952 (95% CI, 0.950–0.954) and 0.836 (95% CI, 0.809–0.860), respectively. Based on CUC, we recommend a threshold probability of 5% to guide the diagnosis of BMs.

Conclusions

The comprehensive predictive tool consisting of nomogram and web calculator contributes to risk stratification which helped clinicians identify high-risk cases and provide personalized treatment options.

Metastasectomy in kidney cancer: current indications and treatment approaches

PURPOSE OF REVIEW

Although systemic agents for the treatment of metastatic renal cell carcinoma (mRCC) have improved survival, remission and cure for mRCC remains rare with systemic therapy alone. However, there is a body of observational evidence supporting a survival benefit in mRCC among patients who undergo complete surgical consolidation including resection of the primary tumor and all metastatic deposits. In this review, we aim to synthesize recent evidence regarding metastasectomy (MTS), with or without concurrent systemic therapy, in mRCC.

RECENT FINDINGS

MTS is a critical component of mRCC patient care, alongside modern systemic therapy. Presently, there is a robust body of observational data supporting the association between surgical MTS and improved oncologic outcomes, especially when complete MTS is feasible.

SUMMARY

Among a retrospective, observational body of literature, MTS is associated with improved oncologic outcomes. However, it is impossible to discern to what degree these findings are biased by favorable tumor biology and patient selection, as opposed to being related to surgical MTS itself.

Shoulder pain in a patient with renal cell carcinoma? Suprascapular neuropathy caused by bone metastasis of renal cell carcinoma: A case report

BACKGROUND

Pain management is crucial in palliative care for patients with advanced cancer. Here, we report a case of shoulder pain in a patient with renal cell carcinoma.

CASE PRESENTATION

A 36-year-old male diagnosed metastatic renal cell carcinoma presented with pain and weakness on left shoulder for more than 6 months. Physical examination showed limited range of motion and atrophic changes on supraspinatus and infraspinatus muscles. Weakness in shoulder abduction and external rotation was also noted.

POSSIBLE COURSES OF ACTION

In this case, suprascapular neuropathy, adhesive capsulitis of shoulder and metastatic lesions involving shoulder joint were suspected.

FORMULATION OF A PLAN

We planned imaging studies including X-ray, bone scan, magnetic resonance imaging, and electrodiagnostic studies.

OUTCOME

Imaging and electrodiagnostic studies showed suprascapular neuropathy by bone metastasis. Conservative treatment including injection and rehabilitation therapy reduced the patient's pain and improved the range of motion limitation.

LESSONS FROM THE CASE

Clinicians should be aware that bone metastasis in patients with advanced cancer can cause suprascapular neuropathy, shoulder pain and shoulder dysfunction.

VIEW ON RESEARCH PROBLEMS, OBJECTIVES, OR QUESTIONS GENERATED BY THE CASE

More research is expected on development of an early surveillance model, barriers to cancer pain management, communication from patients' perspectives.

[Treatment strategies for tumor-related pathological fractures of the extremities]

Pathological fractures of the extremities frequently lead to uncertainty with respect to the treatment strategy and timing. The origin of metastases is typically breast, bronchial, renal and prostate cancer and myelomas. Primary bone tumors play a subordinate role. The majority affect the femur, humerus and occasionally the tibia. Surgery is typically the first line treatment as healing under conservative treatment is unlikely. The most important goal is to relieve pain and the preservation or restoration of function. For correct assessment of indications, analysis of the fracture pattern and oncological aspects including dignity, entity, prognosis, metastatic status and the general condition of the patient need to be taken into consideration. Based on all these aspects the surgical approach can be chosen. Treatment options range from osteosynthetic stabilization and augmentation osteosynthesis up to endoprosthesis replacement. The treatment is carried out in an interdisciplinary procedure as additional measures need to be addressed in addition to the surgical treatment.

Survival nomogram for patients with bone metastatic renal cell carcinoma: A population-based study

Purpose:

Increased attention has been focused on the survival of renal cell carcinoma (RCC) patients with bone metastasis. This study proposed to establish and evaluate a nomogram for predicting the overall survival (OS) and cancer-specific survival (CSS) of RCC patients with bone metastasis.

Materials and Methods:

RCC patients with bone metastasis between 2010 and 2015 were captured from the surveillance, epidemiology and end results (SEER) database. Univariate and multivariate cox regressions were performed to assess the effects of clinical variables on OS and CSS. The nomogram based on the Cox hazards regression model was developed. Concordance index (C-index) and calibration curve were performed to evaluate the accuracy of nomogram models, receiver operating characteristic (ROC) curves and decision curve analysis (DCA) were conducted to assess the predict performance.

Results:

A total of 2.471 eligible patients were enrolled in this study. The patients were assigned to primary (n=1.672) and validation (n=799) cohorts randomly. The 1-, 2-, and 3-year OS and CSS nomogram models were constructed based on age at diagnosis, sex, marital status, pathological grade, T-stage, N-stage, brain/liver/lung metastasis, surgery, radiotherapy and chemotherapy. The c for OS and CSS prediction was 0.730 (95% confidence interval [CI]: 0.719-0.741) and 0.714 (95%CI:0.702-0.726). The calibration curves showed significant agreement between nomogram models and actual observations. ROC and DCA indicated nomograms had better predict performance.

Conclusions:

The nomograms for predicting prognosis provided an accurate prediction of OS and CSS in RCC patients with bone metastasis, and contributed clinicians to optimize individualized treatment plans.

Prognostic Impact of Bone Metastasis on Survival Outcomes in Patients with Metastatic Renal Cell Carcinoma Treated by First Line Tyrosine Kinase Inhibitors: A Propensity-Score Matching Analysis

Purpose: To investigate the effect of bone metastasis (BM) on survival outcomes in patients with metastatic renal cell carcinoma (mRCC) treated with first-line tyrosine kinase inhibitors (TKI) by performing propensity-score matching (PSM) analysis.

Materials & Methods: We retrospectively reviewed 1,151 patients with mRCC who were treated with first-line TKI from December 2006 to September 2016. After excluding 135 patients, 1,016 patients with mRCC were finally analyzed. The primary and secondary end points were overall survival (OS) and progression-free survival (PFS), respectively. After 1:1 PSM analysis, survival outcomes were compared between patients with BM (n=237) and without BM (n=237). Multivariate Cox regression analysis was used to determine predictors of survival.

Results: Among 1,016 total patients, 27.5% (n=279) had BM. Before PSM, patients with BM had worse OS outcomes than those without BM. Even after PSM, OS was significantly poorer in patients with BM compared to those without BM. Of note, the presence of BM was identified as an independent predictor of OS (HR=1.36), in addition to prior nephrectomy, sarcomatoid differentiation, and IMDC risk group. However, there were no differences in PFS according to the presence of BM after PSM. In the subgroup analysis, only intermediate IMDC risk group showed significant differences in OS according to the presence of BM.

Conclusion: Based on PSM analysis, the presence of BM negatively affected OS outcomes in patients with mRCC treated with first-line TKI, particularly in the IMDC intermediate risk group.

Metatarsal metastasis from clear cell renal cell carcinoma: a case report and literature review

Background

Bone metastasis is known to occur in some patients with cancer, usually in the spine, pelvis or ribs, and less than 0.01% of patients have metastases in the foot bone, so metatarsal metastasis is quite rare. The initial symptoms of osseous metastases are swelling, pain, or both.

Case presentation

We report a 68-year-old man with solitary metatarsal metastasis 26 months after a diagnosis of renal clear cell carcinoma. The patient suffered intermittent swelling of his right foot and pain for one year due to trauma and was not treated. The doctor attributed the symptoms to trauma, administering massage therapy and a plaster cast to the patient at the local clinic. After reviewing the medical records, we found that this patient had a history of clear cell renal cell carcinoma. The patient underwent radiological examination and open biopsy of the first metatarsal bone of the right foot. These findings confirmed that the patient had a metatarsal metastasis from clear cell renal cell carcinoma. The patient subsequently underwent right foot amputation. No local recurrence or distant metastasis was found after a 6-month follow-up.

Conclusion

Clinicians should be aware of a history of renal cell carcinoma (RCC) and fully understand the patient’s past medical history. When treating patients with clear cell renal cell carcinoma who have unresolving bony pain or swelling, clinicians should always keep in mind the possibility of bone metastasis of RCC.

[Clinical and pathological analysis of small renal cell carcinoma]

OBJECTIVE

To analyze the clinical and pathological features of small renal cell carcinoma (RCC), especially of those with diameter less than 4 cm and to understand the characteristics and factors related to recurrence and progression.

METHODS

A total of 200 patients with RCC were stratifiedly selected for retrospective analysis. Their baseline demographic features, tumor-specific clinical features, pathological features of renal lesions, especially microscopic features were collected. The patients were divided according to the largest diameter of renal tumor lesions. Univariate analysis was used to compare the differences between tumor staging and microscopic pathological features between the groups. Binary multivariate Logistic regression was used to investigate factors related to tumor progression and prognosis in the patients with small RCC.

RESULTS

The tumor diameters of 127 RCC patients were less than 4 cm and most of them had clear cell renal cell carcinoma (ccRCC). The increase in tumor diameter resulted in significantly higher T stage (P<0.01), higher WHO/International Society of Urological Pathology (ISUP) grade (P<0.05) and increasing chance of lymph node metastasis (P<0.01). Even when the tumor diameter was less than 4 cm, the patients might still have perirenal fat invasion, renal sinus invasion and greater elevated tumor grade (greater than grade 3) and synchronous lung metastasis. The incidences of intravascular thrombus (9.3% vs. 0) and tumor necrosis (27.8% vs. 5.5%) in the patients with RCC between 4-7 cm were significantly higher than those with RCC less than 4 cm (P<0.01). Sub-group analysis of small RCC (less than 4 cm) indicated that the patients with RCC between 2-4 cm were more likely to have intratumoral hemorrhage (44.7% vs. 23%, P<0.05) and necrosis than those with RCC less than 2 cm (8.2% vs. 0, P=0.095). Logistic regression analysis of small RCC showed that the incidence of tumor invasion to renal capsule was higher in ccRCC (OR=5.15, 95%CI: 1.36-19.52). Necrosis was closely related to the formation of peritumor pseudocapsule in small RCC (OR=14.90, 95%CI: 1.41-157.50). Increase in the tumor diameter was related to higher tumor grade (greater than grade 3) (OR=3.49, 95%CI: 1.11- 10.93).

CONCLUSION

The tumor stage and grade of small RCC (less than 4 cm) are low, but extra-renal invasion and synchronous distant metastasis may occur. Internal hemorrhage and necrosis in tumor, ccRCC subtype, along with microscopic features, such as the renal capsule invasion and perirenal pseudocapsule formation are relevant factors of malignant behavior of small RCC and could be considered in prognosis evaluation.