In the present study, we investigated the necessity of PALND for patients with incidentally-detected enlarged PALNs. The results showed that even in patients with no evidence of PALNM on preoperative radiologic examination, pathologic PALNM was identified in a small but non-negligible proportion (2.2%). Patients with pathologic PALNM showed poorer OS than those without pathologic PALNM. However, when R0 resection was achieved, patients with pathologic PALNM had comparable OS to those without pathologic PALNM.
PALNM is a known poor prognostic factor in colorectal cancer patients.(4–7) In cases of liver or lung metastasis, radical resection of the metastatic lesion is known to be beneficial for survival.(10–12) However, there is no established standard treatment for PALNM, which is relatively rarer than liver and lung metastasis.(7, 8, 13) Recently, several studies described that PALND increased survival in patients with PALNM.(6, 7, 13–15) For example, Choi et al. reported that the 5-year OS of the PALND group was significantly higher than that of the control group (53.4% vs 12%, p = 0.045).(6) Ogura et al. reported that the 5-year cancer-specific survival was significantly higher in the R0 resection group than in the control group with palliative resection in patients with extra-regional lymph node metastasis.(16) Gagniere et al. reported the outcome of radical retroperitoneal lymphadenectomy in patients with retroperitoneal nodal metastases from colorectal cancer.(17) They suggested that the 5-year OS of patients who underwent lymphadenectomy was significantly higher than that of patients who treated with non-surgical treatment. However, some authors reported that PALND is not recommended because of its technical difficulties and lack of a survival benefit.(18) Others reported high recurrence rate after PALND even when performed in selective patients with PALNM.(19)
Determining the presence of PALNM through a preoperative imaging study before surgery and establishing an appropriate surgical plan are essential. In this study, radiologic PALNM was identified as a predictive factor for pathologic PALNM in multivariable analysis. Nakai et al. evaluated the diagnostic value of CT and PET-CT in predicting PALNM.(20) When the diagnosis was based on CT combined with PET-CT, the diagnostic ability of PET-CT was 93.8% in patients who had no predictive CT finding. However, in patients with a suspected lesion on CT, the diagnostic ability of PET-CT was decreased to 70.6%. According to a study of Wong et al., among 264 patients suspected of having PALNM on radiologic examination, 118 patients showed positive PALNM on pathology, and the positive predictive value was only 44.7%.(5) Similarly, in the present study, the accuracy of preoperative imaging study in predicting PALNM was 89.7%, whereas the positive predictive value was only 42.4%. Therefore, it is not easy to accurately diagnose PALNM based on preoperative imaging findings.
Surgeons often incidentally detect enlarged PALNs during surgery and deliberate about whether PALND should be performed. However, no standard treatment has been established for the management of incidentally detected enlarged PALNs in colorectal cancer patients. Importantly, in the present study, there were five (2.2%) false-negative cases in which PALNM was not detected on preoperative imaging study but PALND was performed incidentally. In addition, a significant difference in OS was observed between the R0 and R2 resection groups (90.0% vs. 0.0%, p = 0.014). When R0 resection was achieved in patient with PALNM their OS was comparable to that of patients without PALNM (90.0% vs. 82.2%, p = 0.896). Therefore, when an enlarged lymph node is detected during colorectal cancer surgery, we recommend performing PALND for the purpose of R0 resection because it may be beneficial to the prognosis of the patient.
Several studies have reported that retroperitoneal lymph node dissection was related to sexual dysfunction due to hypogastric nerve injury, chylous ascites, and lymphoceles.(21, 22) According to a systematic review by Wong et al.,(5) the postoperative complication rate of PALND ranged from 7.8–33%. We observed a postoperative complication rate of 18.2%, with no postoperative mortality. Because the morbidity rate in the present study was comparable to that of our previous studies (13.9–31.2%) on rectal cancer surgery,(23, 24) PALND can be safely performed with minimal additional surgical complications.
This study had several limitations. First, this study was designed as a retrospective review of data from a single institution. Because PALND decided and performed by four surgeons, the indication for PALND was not standardized, which might have led to a selection bias. Second, as the number of patients with pathologic PALNM was small, the results of multivariate analysis need to be interpreted with caution. Third, we could not evaluate late complications such as ejaculatory dysfunction and reduced quality of life. Despite these limitations, the present study has a strength because very few studies have reported on the probability of pathologic PALNM in patients with incidentally detected PALNs.
In conclusion, the incidence of pathologic PALNM in patients with enlarged PALNs incidentally detected during colorectal cancer surgery was not negligible (2.2%). If R0 resection can be achieved, patients with PALNM can show a relatively good prognosis. Therefore, we recommend performing PALND when an enlarged PALN is incidentally detected during surgery for the purpose of R0 resection.