Table 3. Surveillance strategy and outcomes of delayed intervention. Studies without follow up not shown.
| Study | Imaging modality used | Frequency of imaging | Definition of progression | Indications for intervention | Mean growth rate of SRM on AS (cm/year) | % of SRM on AS showing no growth/ decrease in size |
Intervention rate | Median time to intervention |
Reasons for intervention | Final histology after DI |
|---|---|---|---|---|---|---|---|---|---|---|
| Cleveland Clinic (18) | Not specified | 6-monthly | n/r | n/r | n/r | n/r | n/r | n/r | n/r | n/r |
| University of Toronto (19) | CT/MRI/US according to patient body habitus and physician preference | 6-monthly | n/r | No predefined criteria for intervention |
0.25 | 15% | 14.6% (12/82) | 27 months | 25% (3/12) due to improvement in comorbidities; Patient choice 50% (6/12); Rapid growth 50% (6/12) - mean of 1.07 cm/yr | All found to have RCC |
| DISSRM, 2015 (20) | US preferred. Axial imaging if any discrepancy in tumour size or growth rate, or US poor quality or change in tumour appearance | Initially 4–6-monthly for 2 years, then every 6–12 months | n/r | Growth rate >0.5 cm/yr or Size >4 cm or Patient choice at any time | 0.11* | 10% | 9.4% (21/223) | n/r | Patient preference 46% (15/21) with average GR 0.08cm/yr; 29% (6/21) met progression criteria with average GR 1.1 cm/yr | 67% RCC in patient preference group |
| 83% RCC in DI due to progression group | ||||||||||
| Canada (22) | CT/MRI/US | Initially at 3 and 6 months, then 6-monthly for 3 years, then annually | SRM growth ≥4 cm, or doubling of SRM volume in ≤12 months, or metastases |
Same as progression criteria | 0.13 | 36% | 5% (9/178) (In addition, 16 withdrawn patients also had DI) | n/r | All due to progression | All had RCC who had PN or RN for DI (All 16 withdrawn patients who had DI also had RCC on final histology) |
| Oxford, 2012 (23) | CT / MRI / US | No prospectively established AS protocol Imaging every 3-6 months |
n/r | Recommended to have treatment if size >4 cm or had rapid tumour growth rates | 0.21 | 53% | 19.7% (14/71) | 29 months | Increase in size 64% (9/14); Patient choice 29% (4/14); Change in diagnosis 7% (1/14) | n/r |
| Haifa (25) | CT/MRI in the first year. Alternating CT or MRI with US in second year | 6-monthly | n/r | High growth rate or size >4 cm or patient or doctor preference | 0.17 | 31% | 10% (7/70) | 25.9 months | Not specified | RCC 5/7, Oncocytoma 2/7 |
| University of Michigan, 2016 (26) | Cross-sectional imaging for first 2 years. CT/MRI/US thereafter Modality at discretion of urologist | Institutional protocol for AS: every 5–6 months for 2 years Interval at discretion of urologist 6 to 12-monthly thereafter |
n/r | No defined criteria for delayed intervention initially. Subsequent criteria to include growth, rate >0.5 cm/year, size >4cm | 0.20 | 36% | 24% (28/118) | 24 months | Patient preference 11%; Growth rate ≥5 mm/year 53%; Surgeon recommendation despite not meeting criteria 36% | Not detailed |
| Pusan National University (27) | Abdominal CT or US and chest CT | 6-monthly intervalsThen if no change in size, annual follow up | Predefined criteria: Growth rate >0.5 cm/yr or Size >4 cm or Clinical progression | Progression criteria met or Patient choice | 0.20 | n/r | 8% (3/37) | n/r | 100% (3/3) due to progression of growth rate >0.5 cm/yr | All 3/3 had RCC |
| Tayside (28) | Mostly used CT. A few patients had US follow-up with conversion to CT if US showed growth or poor visualisation | n/r | Tumour growth defined as any increase in size on interval imaging | Surgery offered for solid SRM >4 cm or Patient or surgeon choice when <4 cm or Younger patients with reluctance to follow-up | 0.29 | 53.5% (94% of cystic SRM showed no growth, 36% of solid SRM showed no growth) | 19% (43/226) | n/r | n/r | n/r |
| MD Anderson (30) | CT/MRI | 6-monthly | n/r | Growth rate of SRM >0.5 cm/yr or Size >4 cm or Patient choice | 0.24 (from baseline to 2-year scan) | n/r | 24% (64/272) | n/r | Patient choice 47% (14/30) within first 2 years of AS; Increasing size 61% (19/31) after 2 years of AS |
n/r |
*value is median. AS, active surveillance; CT, computed tomography; DI, delayed intervention; GR, growth rate; MRI, magnetic resonance imaging; PN, partial nephrectomy; RCC, renal cell carcinoma; RN, radical nephrectomy; SRM, small renal mass; US, ultrasound.