Patients were considered to have renal cancer if they met either of the following criteria: (i) histologically confirmed renal malignancy based on pathological examination of surgical specimens or biopsy samples; or (ii) a renal mass highly suggestive of malignancy on imaging, defined by contrast-enhanced computed tomography showing a solid renal tumor with characteristic features such as heterogeneous enhancement, irregular margins, necrosis, local invasion, venous extension, or presence of lymph node or distant metastases, in a compatible clinical context (e.g., hematuria, flank pain, or palpable mass).

To minimize misclassification bias, only cases with concordant clinical and radiological findings strongly suggestive of malignancy were included in the absence of histological confirmation. Cases with indeterminate imaging features, cystic lesions without suspicious characteristics (e.g., Bosniak I - II), or insufficient diagnostic data were excluded. Whenever available, histopathological results were used as the reference standard.

This study was conducted in accordance with the principles of the Declaration of Helsinki. Ethical approval was obtained from the Institutional Ethics Committee of the Douala General Hospital and the Laquintinie Hospital of Douala. Administrative authorization to access medical records was granted by the respective hospital authorities.

Given the retrospective design of the study and the use of anonymized patient data, the requirement for informed consent was waived by the ethics committee. Patient confidentiality was strictly maintained throughout the study by de-identifying all data during collection and analysis.

After obtaining ethical clearance, we included all patients managed for primary kidney cancer presenting with a renal tumour suspected of malignancy based on a combination of clinical evidence and/or histological confirmation. We excluded patients treated for secondary renal cancer as well as those with incomplete medical records. Sampling was non-random, consecutive, and exhaustive. The variables studied were epidemiological, clinical, therapeutic, histopathological, and prognostic.

The primary endpoint was overall survival (OS), defined as the time from the date of diagnosis (date of first imaging or histological confirmation of renal cancer, whichever occurred first) to death from any cause. Patients who were alive at the end of the study period (December 31, 2023) or lost to follow-up were censored at the date of last known contact.

Vital status was ascertained through review of hospital records and, where available, follow-up consultations or documented communication. Deaths from causes other than renal cancer were included as events in the analysis, consistent with the definition of overall survival.

Treatment decisions were made in multidisciplinary meetings when feasible, based on tumor stage, resectability, patient performance status, and available resources.

Radical nephrectomy was indicated for localized renal tumors not amenable to nephron-sparing surgery, particularly tumors > 7 cm (≥T2), centrally located masses, or lesions with suspected perirenal fat invasion. Extended radical nephrectomy was performed in cases of locally advanced disease, including tumors with venous extension (renal vein or inferior vena cava), adjacent organ involvement (e.g., adrenal gland), or significant locoregional lymph node enlargement requiring lymphadenectomy.

Systemic treatment was considered for patients with metastatic disease, unresectable tumors, or disease progression after surgery. Targeted therapies (e.g., tyrosine kinase inhibitors such as sunitinib or sorafenib) were preferred when accessible, particularly in patients with suspected or confirmed clear cell carcinoma. Cytotoxic chemotherapy (e.g., platinum- or gemcitabine-based regimens) was used in selected cases, including patients with non-clear cell histology, rapidly progressive disease, or when targeted therapies were unavailable or unaffordable.

Data were entered and analysed using R software version 4.1.2. Comparison tests were performed after verification of their validity criteria, with statistical significance set at p < 0.05. Prognostic factors were determined using Cox regression. Survival was expressed using the Kaplan-Meier method.

Kidney cancer represented 5.1% of the recorded cases, making it the second most frequent urological cancer after prostate cancer (89.8%).

We observed an increase in incidence with a peak in 2022 (9 cases).

The mean age was 49.93 ± 11 years [26 - 69 years]. The most represented age groups were 40 - 50 years and 50 - 60 years; half of the patients were younger than 51 years.

Among the 28 included patients, 18 were men (64.2%) and 10 were women (35.7%), giving a male-to-female ratio of 1.8.

Identified medical histories included hypertension (25%), overweight/obesity (50%), and family predisposition (7.1%).

Symptoms were dominated by flank pain (75%) and hematuria (53.57%). Associated signs included weight loss (28.57%), asthenia (25%), and anorexia (17.86%).

On physical examination, 14 patients had a lumbar mass (50%), 9 had poor general condition (32%), 5 had conjunctival pallor (17.8%), and superficial lymphadenopathy was found in 3.5% of cases. The classical triad (flank pain-hematuria-abdominal mass) was present in 35.7% (10/28).

In our study population, 27 over 28 patients underwent CT urography. The tumour was located in the right kidney in 60.71% of cases. The most frequent locations were the upper pole (25%) and lower pole (21.4%). Necrosis was found in 7.1% of cases. The mean tumour size was 111.73 mm [17 - 232 mm], and 50% (13 patients) had tumours measuring between 94 mm and 232 mm.

Localised tumours (T1 - T2: n = 19; 67.8%) predominated over locoregionally advanced tumors (T3 - T4: n = 9; 32.1%). Venous extension most commonly involved the renal vein and the infra-diaphragmatic inferior vena cava (T3b). An exceptional extension to the pulmonary arteries was observed.

Approximately one tumour in four showed local extension (8 cases), including 7 tumours extending into perirenal fat (T3a: 25%) and 1 tumor extending to the adrenal gland (T4: 3.5%).

There was a high proportion of lymph node involvement (n = 18; 64.2%). The most frequent lymph nodes involved were mesenteric (32.1%) and celiac (21.4%). Distant metastases were found in 8 patients (28.5%), involving the liver, lungs, and bones.

Most patients were diagnosed at an advanced stage (stage III - IV: 71.4%, 20/28), while early-stage disease (stage I - II) accounted for 28.6% (8/28).

Histopathological data were available for 19 patients, among whom clear cell carcinoma was the most frequent subtype (63.2%, 12/19), followed by tubulo-papillary carcinoma (n = 5; 26.31%). The Fuhrman grade was reported in only one case and was grade IV.

Overall, 18 patients (64.2%) underwent locoregional treatment consisting of total nephrectomy (n = 8; 44.4%) and extended radical nephrectomy (n = 10; 55.5%).

In parallel, 8 patients (28.5%) received systemic treatment, among whom 37.5% received targeted therapies (sorafenib, sunitinib) and 62.5% received chemotherapy (cisplatin, gemcitabine).

Three patients (10.71%) developed postoperative complications: grade II (severe anemia in 2 patients) and grade III (parietal suppuration) according to the Clavien-Dindo classification. Six patients (21.42%) experienced complications related to systemic treatment.

In the overall study population, 5-year overall survival was 12.5% with a mean survival of 25 months. Among the 28 patients, 12 (42.85%) survived.

The survival curve showed a survival probability of 92.5% at 1 year and 50% at 3 years. Median survival was 32 months.

Sex-specific overall survival was 61.1% for men (11 alive) and 50% for women (5 alive).

3.7.1. Age and Sex

There was no significant difference in mean age between survivors and deceased patients (p = 0.83). Survival between men and women was not significantly different (p = 0.70).

3.7.2. Medical History

Analysis (Table 2) showed none of these variables were statistically associated with mortality (p > 0.05), and survival probabilities between groups were not significantly different.

3.7.3. Tumor Location, Stage, and Therapeutic Modality

In univariate analysis, left kidney involvement was significantly associated with better survival (p = 7 × 10⁻⁴), particularly after the 12th month (Figure 1). Tumor stage was not significantly associated with overall survival (p = 0.59). Treatment modalities were also not significantly associated with overall survival.

Table 2. Distribution of kidney cancer predisposing factors and mortality.

CKD: Chronic Kidney Disease.

Figure 1. Survival rate according to kidney laterality.

3.7.4. Multivariate Analysis

In multivariate analysis, right kidney involvement (reference: left kidney) was independently associated with worse overall survival (HR = 6.25; 95% CI: [1.4 - 27.8]; p = 0.018), with an instantaneous risk of death of approximately 84% (HR = 0.16) (Table 3). The overall model was statistically significant (likelihood ratio test p = 0.00036), indicating tumor location as a prognostic factor associated with survival.

Table 3. Factors associated to survival rate (Cox’s regression).

We collected 623 cases of urological cancers, among which 30 patients had complete follow-up records, while 2 patients had died from causes other than kidney cancer. A total of 28 patients were retained, corresponding to a prevalence of 5.1%. This result is higher than that reported in the 2021 Cancer Report of MINSANTE [14], which found a prevalence of 3.6% among adults, and considerably higher than that reported by Mohamed et al. in 2022 [12] on renal carcinoma characteristics in Somalia, where a prevalence of 0.7% was observed. This statistical difference could be explained by the fact that our sample was not sufficiently representative of the general population compared to theirs, as it was derived from data collected in only two hospitals.

The mean age of our population was 49.93 ± 11 years. These results are similar to those of the 2021 MINSANTE Cancer Report, which found a mean age of 50 years [14], and to those of Ndiath et al. in 2020 in Dakar, Senegal, who reported a mean age of 49.5 years [15]. However, our findings differ from those of Doehn et al. (2020) in Germany, who reported a mean age of 68 years in men and 71 years in women [16], and Dudani et al. in the United States, who reported a mean age of 60 years [17]. This disparity could be explained by differences in age distribution, with a higher proportion of elderly individuals in Western countries compared to Africa [18].

In our study, 64.29% of patients were male and 35.71% were female, giving a male-to-female ratio of 1.8:1. This result is similar to those of Mohamed et al. in Somalia [12] and Avakoudjo et al. in Cotonou, Benin [19], who reported sex ratios of 2:1 and 1.6:1, respectively. However, it differs from those of Bafadni et al. in Sudan [13], Harir et al. in Dakar [1], and Dudani et al. in the United States [17], who reported sex ratios of 1.2:1, 1.3:1, and 2.6:1, respectively. These differences may be explained by variations in study sample sizes (N = 57; 189; 10,105), while our study had the smallest sample (N = 28).

In our study, the classic symptomatic triad (flank pain-hematuria-lumbar mass) was present in 35.7% of cases. Stages III and IV were found in 71.4% of patients (39.2% and 32.1%, respectively). These findings are comparable to those of Avakoudjo et al. in Cotonou [19] and Bafadni et al. in Sudan [13], who reported the symptomatic triad in 79.3% and 53% of cases, and advanced stages in 95% and 82.5%, respectively.

However, our results differ from those of Vasudev et al. in the United Kingdom [20], who reported incidental diagnosis in 60% of cases and stage Ia tumors in 87%, compared to only 36% for stages III and IV. These differences may be explained, on the one hand, by public and physician awareness campaigns regarding kidney cancer and, on the other hand, by widespread access to screening methods within resilient healthcare systems in the United Kingdom, leading to improved early diagnosis rates. In contrast, in our country, the relative rarity of kidney cancer makes it a lower public health priority, resulting in limited awareness campaigns.

The preferred tumor location in our series was the right kidney (60.1%), similar to findings by Salako et al. in Nigeria [21] (58.8%) and Avakoudjo et al. [19] (58%). However, this differs from Bafadni et al. in Sudan [13] and Mohamed et al. in Somalia [12], who reported preferential involvement of the left kidney in 52% and 57% of cases, respectively.

According to the literature, the most common histological type of renal cancer is clear cell carcinoma, accounting for approximately 85% of cases [1]. In our study, clear cell carcinoma was also the most frequent type (63.2%) among tested patients (n = 19). However, this proportion is lower than that reported by Bafadni et al. (73.5%) and Ndiath et al. (68%). This difference may be explained by the difficulty in obtaining histological confirmation in our context, often leading clinicians to rely on a combination of clinical and radiological arguments.

The main surgical procedure performed was open radical nephrectomy. Systemic treatment was administered in 28.5% of cases, with targeted therapy used in 10.7% and chemotherapy in 17.8% of systemic treatment cases.

These findings are similar to those of Bafadni et al. and Salako et al., who reported radical nephrectomy rates of 66.7% and 78.4%, respectively, with targeted therapy administered in 0% and 7.3% of cases. However, they differ from Mohamed et al., who reported radical nephrectomy in 32% and partial nephrectomy in 13% of cases.

These differences may be explained by limited technical resources and the high cost of systemic therapies, which restrict access, particularly in a context where 37.8% of the population lives on less than 813 CFA francs per day [22].

Radical nephrectomy was predominant in our series because the tumours were large, with a mean size of 11.1 cm compared to 6.34 cm in Mohamed et al. [12]. In accordance with the literature, although partial nephrectomy can be performed for T1 - T3 tumours, it is primarily recommended for localised T1 tumours [23].

The 5-year overall survival probability in our study was 12.5%, with a median survival of 32 months. These results are comparable to those of Bafadni et al., who reported a 40% survival probability and a median survival of 24 months [13].

However, they differ significantly from Mohamed et al., who reported a 5-year survival probability of 60.8% [12], and from Siegel et al. in the United States, who reported a 5-year overall survival of 77% [5].

This disparity may be explained by two main factors:

i) In our context, most cases are diagnosed at an advanced stage;

ii) The high cost of management makes optimal treatment inaccessible for many patients due to limited economic resources.

Right-sided tumor location was associated with worse survival in our cohort. However, this finding should be interpreted with caution given the small sample size and the absence of similar observations in the literature. This may be explained by the anatomical proximity of the right kidney to critical structures such as the liver and the inferior vena cava, potentially facilitating rapid locoregional and metastatic spread.

The main limitation of our study was the difficulty in accessing medical records, which prevented us from achieving a larger sample size and conducting more in-depth analyses. Therefore, these results cannot be generalized to the entire Cameroonian population.

The strength of this study lies in its inclusion of all histological types of renal cancer over 10 years in first- and second-category hospitals, providing valuable data for these central healthcare structures.