Prognostic impact of FAN score in patients receiving nivolumab plus ipilimumab for metastatic renal cell carcinoma

FAN score is reportedly associated with prognostic outcomes in patients with urothelial carcinoma being treated with immune check point inhibitors. However, the prognostic impact of pre-treatment FAN score in patients with metastatic renal cell carcinoma (RCC) treated with nivolumab plus ipilimumab remains unclear. We retrospectively evaluated the association between pre-treatment FAN score and prognostic outcomes in 154 patients with metastatic RCC treated with nivolumab plus ipilimumab. The pre-treatment FAN score was ‘0’ in 56 patients (36%), ‘1’ in 60 patients (40%), ‘2’ in 37 patients (24%) and ‘3’ in one patient (1%). Progression-free survival was not significantly different between patients with different FAN scores, but second progression-free survival (PFS2), cancer-specific survival (CSS) and overall survival (OS) were significantly different. In multivariable Cox proportional hazard analyses, FAN score ≥ 2 was a significant predictor of poor PFS2 (vs. FAN score 0, HR: 2.43, 95% CI 1.21–4.87, P = 0.01), poor CSS (vs. FAN score 0, HR: 2.71, 95% CI 1.13–6.47, P = 0.02) and poor OS (vs. FAN score 0, HR: 2.42, 95% CI 1.11–5.25, P = 0.02). High pre-treatment FAN score could be a significant independent predictor of poor prognosis in patients receiving nivolumab plus ipilimumab for metastatic RCC.


Patients
We retrospectively reviewed the medical records of consecutive patients who received nivolumab plus ipilimumab treatment for metastatic RCC at eight institutions (our hospital and seven collaborating hospitals) between October 2015 and May 2022.Of 173 patients, this study included the 154 patients whose pre-treatment FAN score could be calculated.

Data collection
Patient characteristics, including laboratory data at the time of drug administration, were retrospectively collected.The collected clinical features were age, gender, body mass index, IMDC risk classification, complete blood cell counts, serum C-reactive protein (CRP) level, serum albumin level, serum bilirubin level, serum aspartate aminotransferase (AST) level and serum alanine aminotransferase (ALT) level.We also collected tumor characteristics including prior resection of the primary site, histologic subtype, sarcomatoid features, metastatic sites and the number of metastatic organs.Fib-4 index was calculated using the following formula 11 : ALBI score was calculated using the following formula 12 : NLR was calculated as neutrophil count divided by lymphocyte count.The pre-treatment FAN score was defined as the total number of Fib-4 > 3.5, ALBI score ≥ 2.6 and NLR > 5.0, in accordance with the original study 10 .
The response of tumors to the treatment was evaluated by using Response Evaluation Criteria in Solid Tumors version 1.1 13 .The objective response rate (ORR) was defined as the rate of patients with complete response or partial response.The disease control rate was defined as the rate of patients with complete response, partial response or stable disease.PFS was defined as the time from the introduction of nivolumab plus ipilimumab treatment to either radiological and clinical disease progression or to death.Second progression-free survival (PFS2) was defined as the time from the introduction of nivolumab plus ipilimumab treatment to radiological and clinical disease progression on second-line treatment or death 14 .Cancer-specific survival (CSS) was defined as the time from the introduction of nivolumab plus ipilimumab treatment to death from RCC or to the patient's last follow-up visit.OS was defined as the time from the introduction of nivolumab plus ipilimumab treatment to either death from any cause or to the patient's last follow-up visit.

Treatment
Patients were treated with nivolumab 3 mg/kg plus ipilimumab 1 mg/kg every three weeks for up to four cycles, then with nivolumab monotherapy, and they continued to receive the treatment until either disease progression or to the presentation of unacceptable adverse events.After the discontinuation of nivolumab plus ipilimumab, the patients were treated with subsequent drugs according to the policy of each physician.

Statistical analysis
All statistical analyses were performed by using JMP Pro 16.Kaplan-Meier method was used to determine PFS, PFS2, CSS and OS rates.Log rank tests were performed to compare them between patients with different FAN scores.Univariable and multivariable Cox proportional regression analyses were performed to identify predictors of PFS, PFS2, CSS and OS.In addition to the FAN score, the factors considered to influence patients' prognoses, such as age, serum CRP level, prior resection of primary site, histologic subtype, IMDC risk classification, and

Association between FAN score and treatment response
The association between pre-treatment FAN score and treatment response is shown in Fig. 1.ORR was 46%, 45% and 39% in patients with FAN score 0, 1 and ≥ 2, respectively (P = 0.78).Disease control rate was significantly different between the three groups: 82%, 67% and 61% in patients with FAN scores of 0, 1 and ≥ 2, respectively (P = 0.04).

Predictive value of FAN score for outcomes
As shown in Table 2, while age and no prior resection of the primary site were independent predictors of poor PFS (P = 0.04 and P = 0.02, respectively), the pre-treatment FAN score was not.On the other hand, FAN score ≥ 2 was an independent predictor of poor PFS2 (P = 0.01) in addition to no prior resection of the primary site (P = 0.02) and multiple metastatic organs (P = 0.02), as shown in Table 3.Moreover, FAN score ≥ 2 was independently associated with poor CSS (P = 0.02) and poor OS (P = 0.02) as well as no prior resection of the primary site (P = 0.01 and P = 0.01) and histologic subtype (P < 0.01 and P < 0.01), as shown in Tables 4 and 5.

Discussion
The potential for FAN score to be used as a prognostic marker in patients with urothelial carcinoma receiving pembrolizumab has been previously reported, but there has not been a proper evaluation of the usefulness of FAN score for predicting prognostic outcomes after ICI treatment in metastatic RCC.To the best of our knowledge, this is the first report on the prognostic impact of-pre-treatment FAN score in patients with RCC receiving nivolumab plus ipilimumab.In this multi-center retrospective study, we examined the association between pre-treatment FAN score and prognostic outcomes in patients treated with nivolumab plus ipilimumab treatment for metastatic RCC.Patients with high pre-treatment FAN scores had lower rates of PFS2, CSS and OS compared with those with low FAN scores.Moreover, FAN score ≥ 2 was a significant independent predictor of poor PFS2, CSS and OS.
The original results of the Checkmate 214 trial showed that nivolumab plus ipilimumab had clinical benefits for patients with untreated IMDC intermediate/poor risk RCC compared with sunitinib 2 .Extended follow-up results of the trial also demonstrated that this combination therapy had durable clinical efficacy 9 .Therefore, while various novel ICI regimens have been approved, nivolumab plus ipilimumab is still recommended as the first-line treatment regimen for patients with IMDC intermediate/poor risk RCC 8 .The IMDC risk classification has been proposed as a prognostic classification for patients receiving molecular targeted drugs and has been widely used in clinical practice, but a prognostic classification for patients receiving ICIs including nivolumab plus ipilimumab has not yet been well established 15 .To select patients suitable for nivolumab plus ipilimumab www.nature.com/scientificreports/for metastatic RCC, development of novel prognostic biomarkers or nomograms which may be easily used in daily practice is highly anticipated.
The FAN score, a focus of the present study, is a novel prognostic scoring system for patients treated with ICIs and based on Fib-4 index, ALBI score and NLR.The Fib-4 index was originally proposed as an indicator of liver fibrosis in patients with viral hepatitis 11 .The cutoff value of 3.5 for Fib-4 index is used as an indicator of liver cirrhosis and is also used to calculate the FAN score 10,16 .ALBI score was originally proposed as a novel indicator of functional liver reserve for patients with hepatocellular carcinoma 17 .The cutoff value of -2.6 for ALBI score is widely accepted, and is also used in the calculation of the FAN score 10,17 .These scoring systems are not just indicators of liver function, they are reportedly associated with prognosis in patients with hepatocellular  carcinoma treated with ICIs, cardiac disease and coronavirus disease [18][19][20][21][22][23][24] .There is reported association between ALBI score and prognosis of patients with various cancers other than hepatocellular carcinoma 25,26 .In addition, pre-treatment ALBI grade was recently reported to be associated with prognosis in patients with lung cancer or urothelial carcinoma treated with ICIs 12,27,28 .The liver is an important organ in relation to protein production and regulation of innate and acquired immunity 29 .Liver dysfunction could affect the interaction between various cytokines and lead to changes of T cell subset repertoires, which might explain why these scoring systems are associated with the prognosis of patients with cancer that are treated with ICIs 30,31 .In addition, these scoring systems could reflect general conditions related to cachexia 10 .Cancer-related cachexia is induced by changes of systemic metabolic environment due to elevation of inflammatory cytokines in tumor cells, hepatocytes and adipose tissue, changes of protein synthesis and degradation in skeletal muscle and insulin resistance.It leads to weight loss, anorexia and decreased systemic function [32][33][34][35][36][37][38][39] .NLR, meanwhile, is widely known to be an indicator of systematic inflammatory responses.The elevation of neutrophil counts induces the secretion of cytokines, such as interleukin-1β and interleukin-12.Tumor necrosis factor-α promotes a chronic inflammation condition and inhibits natural killer cells and effector T-cell-mediated antitumor immunity 40,41 .The prognostic role of NLR in urological cancers including RCC has not been widely reported 42 .Meanwhile, there have been reports of the prognostic role of NLR in patients with metastatic RCC treated with nivolumab plus ipilimumab 43,44 .Our results, that FAN score had a significant impact on the prognosis of metastatic RCC patients receiving nivolumab plus ipilimumab, are thus thought to be reasonable.
Kawashima et al. established FAN score by using the data of 165 patients with metastatic urothelial carcinoma receiving pembrolizumab as a validation cohort 10 .FAN score was significantly associated with both PFS and CSS.Moreover, they also examined the association between FAN score and prognosis in a validation cohort including 103 patients with metastatic urothelial carcinoma treated with pembrolizumab.FAN score was also a significant predictor of PFS and CSS.In our study, pre-treatment FAN score was not significantly associated with PFS, but FAN score ≥ 2 was a significant predictor of poor PFS2 (vs.FAN score 0, HR: 2.43, 95% CI 1.21-4.87,P = 0.01), poor CSS (vs.FAN score 0, HR: 2.71, 95% CI 1.13-6.47,P = 0.02) and poor OS (vs.FAN score 0, HR: 2.42, 95% CI 1.11-5.25,P = 0.02).PFS might not be a surrogate for OS in patients receiving ICI, but ICI could provide delayed benefit 45 , and our results might align with this.Studies on the association between FAN score and prognosis in patients with malignancies receiving ICIs are still limited, so further validation of the prognostic value of FAN score is required.
We found no prior resection of the primary site to also be significantly associated with poor prognostic outcomes.Subgroup analyses of the Checkmate 214 trial reported that nivolumab plus ipilimumab provided survival benefits and volume reduction of the primary site in patients without prior nephrectomy 46 .However, Kato et al. analyzed the real-world data of 72 Japanese patients with metastatic RCC and receiving nivolumab plus ipilimumab; they reported that median OS in patients with prior nephrectomy was better than in those without (not reached vs. 25.3 months, P = 0.028) and that no prior nephrectomy was an independent predictor of poor OS 47 .Stellato et al. also retrospectively evaluated the real-world data of patients with metastatic RCC receiving ICIs.Median OS in patients who underwent previous nephrectomy was better than in those who did not (20.9months vs. 13 months, P = 0.001) and prior nephrectomy was an independent predictor of better outcome in terms of both OS and PFS 48 .Our results were consistent with the results of these previous studies.
The present study has several limitations.First, it is a retrospective study with a limited number of patients, which could lead to a selection bias.However, the number of patients in this study is comparable with that in previous studies which reported the clinical outcomes of nivolumab plus ipilimumab for metastatic RCC in realworld clinical practice.Second, the follow-up duration after the introduction of nivolumab plus ipilimumab was relatively short (median: 21 months).However, the prognosis of patients with IMDC intermediate/poor risk is generally poor and 70 patients (45%) from our cohort died (all causes) during the follow-up duration.Third, although we carefully selected and investigated the patient background and tumor characteristic factors to be collected, there might still be confounding factors which could not be assessed in the present study.Further large-scale studies will seek to verify our results.

Conclusion
In conclusion, high pre-treatment FAN score could be associated with poor prognosis in patients treated with nivolumab plus ipilimumab.Pre-treatment evaluation of FAN score may be clinically useful for predicting prognosis in patients receiving nivolumab plus ipilimumab treatment.

Figure 1 .
Figure 1.Association between pre-treatment FAN score and treatment response.CR: complete response, PR: partial response, SD: stable disease and PD: progressive disease.

Figure 2 .
Figure 2. Comparison of (a) progression-free survival, (b) second progression-free survival, (c) cancer-specific survival and (d) overall survival between patients with different FAN score.

Table 1 .
Patient characteristics based on FAN score.Continuous variables are shown in "median (IQR)" form.BMI body mass index; CRP C-reactive proten; IMDC International Metastatic RCC Database Consortium.

Table 2 .
Univariable and multivariable analyses of factors associated with progression free survival.BMI body mass index; CRP C-reactive proten; IMDC International Metastatic RCC Database Consortium.

Table 3 .
Univariable and multivariable analyses of factors associated with progression free survival 2. BMI body mass index; CRP C-reactive proten; IMDC International Metastatic RCC Database Consortium.

Table 4 .
Univariable and multivariable analyses of factors associated with cancer-specific survival.BMI body mass index; CRP C-reactive proten; IMDC International Metastatic RCC Database Consortium.

Table 5 .
Univariable and multivariable analyses of factors associated with overall survival.BMI body mass index; CRP C-reactive proten; IMDC International Metastatic RCC Database Consortium.