BACKGROUND

Renal tumor biopsies (RTB) have been proposed as a means to diminish overtreatment of small renal masses. A potential concern of RTB is tumor seeding along the biopsy tract leading to worse clinical outcomes.

OBJECTIVES

To evaluate whether RTB was associated with greater upstaging to pT3a compared to patients without a biopsy and to determine if pathologic upstaging affects the risk of recurrence.

DESIGN, SETTING AND PARTICIPANTS: The Canadian Kidney Cancer information system was used to identify patients who underwent radical or partial nephrectomy for malignant renal tumors ≤ 4cm (cT1a) between January 1, 2011 and July 2, 2019.

INTERVENTION

RTB prior to nephrectomy or nephrectomy without biopsy.

OUTCOMES MEASUREMENTS AND STATISTICAL ANALYSIS

Upstaging to pT3a and cancer recurrence were compared between subjects that had a RTB compared to those who did not. A multivariable analysis was used to evaluate factors associated with disease upstaging and recurrence.

RESULTS AND LIMITATIONS

The cohort consisted of 1993 cT1a patients, followed for a median of 17.5 months. Of these patients, 502 (25%) had a preoperative RTB. There was no difference in the proportion with tumor upstaging to pT3a between patients that had RTB compared to those who did not (7.2% vs. 6.3%; P = 0.5). On multivariable analysis, RTB was not associated with pathological upstaging (Odds Ratio 0.90; 95% Confidence Interval 0.61-1.34) or recurrence (Odds Ratio 1.04; 95% Confidence Interval 0.57-1.89). The main limitation is that the study is underpowered to detect small differences between groups.

CONCLUSIONS

In this large, multi-institution cohort, RTB was not associated with increased risk of tumor upstaging or recurrence. Hence, tumor tract seeding, although possible, should not be a clinical deterrent to using RTBs as a means of personalizing renal masses management and diminishing overtreatment.

PATIENT SUMMARY

Recent evidence suggests that tumor seeding following RTB may be more common than initially perceived. Our results have demonstrated that RTB was not associated with an increased risk of tumor upstaging or disease recurrence.