Is there a minimum percentage of sarcomatoid component required to affect outcomes of localised renal cell carcinoma?

Objective To evaluate and compare the outcomes of patients with localised renal cell carcinoma (RCC) with and without sarcomatoid features and the impact of this on cancer recurrence and survival. Material and Methods The Canadian Kidney Cancer information system database was used to identify patients diagnosed with localised RCC between January 2011 and December 2022. Patients with pT1‐T3, n Nx‐N0N1, M0 stage and documented sarcomatoid status were included. Patients with sarcomatoid RCC were categorised according to the sarcomatoid component percentage (%Sarc). Inverse probability of treatment weighting scores were used to balance the groups. Cox proportional hazards models were used to assess the impact of sarcomatoid status and %Sarc on recurrence‐free and overall survival. Results A total of 6660 patients (201 with and 6459 without sarcomatoid features) with non‐metastatic RCC were included. %Sarc data were available in 155 patients, and the median value was 10%. The weighted analysis revealed that the presence of sarcomatoid features was associated with an increased risk of developing metastasis and increased risk of mortality compared to absence of sarcomatoid features. A %Sarc value >10 was associated with an increased risk of developing metastasis and of mortality compared to a %Sarc value ≤10. Conclusions Patients with a %Sarc >10 have an increased risk of recurrence and mortality. These patients may benefit from a more stringent follow‐up and %Sarc could represent an important criterion in the risk assessment for adjuvant therapy.