With aging, the incidence and prevalence of BCa gradually increase, especially after the age of 60 years, when it reaches its peak (13, 14). Approximately 25% of patients had muscle-invasive or metastatic BCa, while the remaining patients had nonmuscle-invasive BCa (15). However, the prognosis of patients with MIBC was worse than that of patients with NMIBC (16). Not only the depth of tumor invasion but also sex, age, LNM, and other factors affect the prognosis of BCa (17). Over the years, studies showed that patients with BCa having LNM had a worse prognosis compared with patients with negative lymph nodes (18, 19). Also, radical cystectomy combined with extended lymph node dissection could significantly improve the survival rate of patients with BCa (20, 21). To our knowledge, however, no study has explored the factors influencing LNM in patients with T2 BCa. The purpose of this study was to explore the factors affecting LNM so as to individualize the plan of lymph node dissection.
Two previous studies showed that the LNM rate of T2 BCa was 10.5% and 18.3%, respectively (22, 23). However, neither of these studies examined the relationship between LNM and age. The present study, involving 5517 patients with T2 BCa, was novel in investigating the relationship between age and LNM risk. In this study, the LNM rate of T2 BCa was 10.71% and had a correlation with age. The LNM rate was the highest in young patients (20.27%) and the lowest in patients aged 80+ years (6.46%). The results of binary logistic regression models adjusted for different risk factors showed that the correlation between age at diagnosis and LNM was negative. These results suggested that the age at diagnosis should be considered when evaluating the risk of LNM in patients with T2 BCa before radical cystectomy to determine whether the patient needs expanded lymph node dissection. Previous studies have shown that patients with BCa undergoing enlarged lymph node dissection at all ages have a better prognosis (10, 24, 25). Also, a negative correlation exists between age and LNM in other cancers, such as colorectal cancer (26, 27), breast cancer (28), and early gastric cancer (29). Compared with preoperative lymph node evaluation, postoperative lymph node examination is more accurate (30). Hence, it is meaningful to look for risk factors influencing LNM.
In this study, patients with BCa in the age group of 40–49 years classified by other characteristics, including male sex, white ethnicity, tumor size, high grade, metastasis, insurance, and separated, had the highest LNM rates. Previous studies have shown that young patients with BCa have a better prognosis than their old counterparts (31, 32). This may be related to physiological changes. For example, aging can lead to changes in the immune system, which weakens the immune function in the elderly (33-35). In addition, some studies supported age-dependent changes in immunity, including degenerative changes in lymph nodes, lymphatic reduction to lymph nodes, and nodular involution (35-38). However, the association between age and LNM needs to be discussed in the future.
The binary logistic regression results showed that, excepting age, grade and metastasis were statistically significant risk factors (P < 0.001). These results suggest that grade and distant metastasis are also risk factors for LNM. Therefore, it was speculated that age combined with grade and metastasis might better predict LNM. Tumor grade and metastasis were important factors affecting tumor prognosis. The five-year survival rate of patients with a low tumor grade was higher than that of patients with a high tumor grade in BCa (39). The relationship between tumor grade and LNM needs further clarification.
This study had some limitations. First, it was a retrospective study and all the data were retrieved from the SEER database. Therefore, prospective verification of the findings is required. Second, the incidence of BCa is low in young people. Hence, patients younger than 39 years were excluded from our study. Nevertheless, the inclusion of such patients might have been informative. Third, the data on tumors are limited in the SEER database. The risk factors for LNM include lymphatic vessel involvement and tumor budding, but these were not included in this study. Fourth, nonmuscular invasive BCa does not metastasize easily. Only patients with T2 BCa were included in this study. In addition, genetic research could not be conducted. Hence, the potential genetic susceptibility to familial BCa remains largely unknown.