Recently, NLR had been shown to be an independent prognostic risk factor for certain solid malignancies [6,7,8,9,10]. Only one study comparing the NLR and the prognosis of ACC has been reported—by Bagante et al. . They found that an NLR > 5.0 was associated with a poorer disease-specific survival and progression-free survival in ACC. No other reports have investigated the effectiveness of NLR in detecting the malignancy of an adrenal tumor. In the present study, we found that a higher NLR in adrenal tumors was associated with a higher incidence of malignancy. These findings might contribute to the prediction of malignant disease for differentiating incidentaloma.
Among incidental adrenal tumors, ACC is difficult to diagnose using preoperative imaging findings. A tumor size >4 cm is a well-known imaging finding for differentiating malignant tumors, with a sensitivity of 81% . A previous report showed that 16% of adrenal tumors with diameters of <5 cm were ACCs .
Due to the marked increase in the rate of imaging analyses being performed at medical check-ups, small ACC would be increased. So, differentiated diagnosis except tumor size would be needed.
Irregular margins are usually seen in ACC, but some benign adrenal tumors also showed irregular margins . Computed tomography (CT) shows a finding of a low Hounsfield unit value (< 10) with 98% specificity. Chemical-shift imaging with magnetic resonance imaging (MRI) has also been reported to be useful for detecting adrenal adenomas . However, the specific imaging findings indicative of ACC remain unclear. The NLR can be easily calculated during a daily clinical examination. The combination of imaging findings on CT and/or MRI and the NLR may support the preoperative diagnosis of adrenal tumor.
Previous reports have shown that an NLR > 5.0 indicates a poor prognosis in pancreas cancer and liver metastatic rectal cancer [15, 16]. Our previous study showed that an NLR > 2.4 was associated with a high risk of prostate cancer in patients with a PSA of 4–10 ng/mL . However, due to the small number of patients, that study could not detect an adequate NLR cut-off point. In the present study, we found that an NLR cut-off point of 5.0 was adequate for predicting the prognosis of ACC. The cut-off NLR of 5.0 was the same as a previous report and was the median value in this study. The cut-off NLR of 5.0 was relatively high in comparison to other studies, which indicated the aggressive nature of ACC in comparison to other types of cancer. Further studies are needed to validate the clinical utility of this parameter.
In this study, the multivariate analysis revealed that the tumor size and NLR were found to be independent predictors of malignant disease. The combination of the NLR and imaging findings might support the preoperative diagnosis and detection of malignant adrenal tumors, including ACC and malignant lymphoma, as well as benign adrenal tumors, helping in the planning of an adequate surgical approach.
This study showed that an NLR of 5.0 was a candidate cut-off point for predicting the prognosis in ACC. In localized ACC, the surgical margin was confirmed to be the most important prognostic factor. The 5-year overall survival in completely surgically resected patients ranges from 40 to 50%, while the median overall survival in unresectable case is <1 year . In cases preoperatively predicted to have a poor outcome, a preoperative surgical plan with extended resection might be suggested in order to obtain a negative surgical margin.
This study was limited by its small sample size and retrospective nature, both due to the rarity of ACC. Further study is needed to confirm the usefulness of NLR in ACC to confirm the sensitivity and specificity.