Introduction:

Recent studies have shown survival benefit for patients treated with PD-1 and PDL-1 inhibitors for advanced renal cell carcinoma. Interestingly, response to treatment has not been shown to be consistently related to PDL-1 expression of the tumor.   We hypothesized that kidney tumors may exhibit intra-tumoral heterogeneity of PDL-1 expression, thus leading to variation of tumor staining.

Methods:

All patients who underwent radical nephrectomy for stage T3 renal masses at our institution in the last 6 years were reviewed. Retrospective chart review was performed and tumor specimens were obtained from our pathology tumor bank. Tumors were stained for PD-L1 expression with 2 to 4 samples from each specimen. PDL-1 expression was classified as <1%, 1-5%, or >5%. Highest PD-L1 expression was used to correlate PDL-1 expression with covariables including demographics, tumor stage and grade, recurrence, and survival. 

Results:

We identified 23 patients who underwent radical nephrectomy for T3 tumors and had available tumor specimens. 15 tumors (65%) had positive PDL-1 staining in at least one sample (PDL-1 expression ≥1%). 13 tumors (56%) exhibited variation in PDL-1 expression between samples and 8 (35%) had at least one negative and one positive sample within the same tumor. PDL-1 expression varied based on location within the tumor (Figure 1), with the highest rates of positive expression from the mass involvement of the renal pelvis and the lowest rates of expression from the mass involvement of perirenal fat. PDL-1 expression was not found to be significantly related to age, race, sex, tumor grade, tumor recurrence or survival.

Conclusion:

PDL-1 expression can vary significantly with T3 renal cell carcinoma, based on the area of tissue sampling. Further research is necessary to standardize methods of PDL-1 sampling and determine which patients may benefit from PDL targeted therapy.

Funding: N/A