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Muttin et al. Mini-invasive Surg 2019;3:10 I http://dx.doi.org/10.20517/2574-1225.2018.005 Page 3 of 5

Table 1. Factors favoring active surveillance
Patient-related Tumor-related
Elderly Tumor size < 3 cm
Life expectancy < 5 years Tumor growth < 5 mm/year
High comorbidities Non-infiltrative on imaging
Excessive perioperative risk Low complexity
Frailty (poor functional status) Favorable histology (if RTB is performed)
Patient preference for AS
Marginal renal function
RTB: renal tumor biopsy; AS: active surveillance

carcinoma, with relatively indolent biologic and clinical behavior [9,10] . Indeed, most of SRM grow slowly,
[7]
with a median linear growth rate (LGR) of 0.22 cm/year for cT1a tumors . Conversely, although benign
tumors may grow significantly, high median LGR (0.37 cm/year) has been associated with a progression to
metastasis and may be mirror more aggressive cancers [7,9,11,12] .

Elderly and comorbid patients with SRM have a relative low risk of CSM but a significant risk of OCM,
thus questioning their eligibility for surgery, which may also expose the patient to a greater risk of post-
operative morbidity [13-17] . In comparative retrospective and prospective analyses, although patients in the
AS arm were older with greater comorbidity and smaller tumors with respect to the surgical counterpart,
no statistically significant difference in OS and CSS were observed once adjusted for patients and tumor
characteristics [10,13,18,19] .

Triggers for AS cessation and commencement of treatment are poorly understood and include tumor
volume doubling time < 12 months, LGR > 0.5 cm/year, tumor maximal diameter at risk of systemic
dissemination (3-4 cm), malignant RTB results, new onset of tumor-related symptoms and/or patient’s
preference [11,20] . Up to one-third of patients in AS cross over to treatment and most of them within the
[1,2]
first 2-3 years . For the 1%-26% of cT1a tumors undergoing surgical DT, the median LGR has been found
[7]
0.62 cm/year . Furthermore, increasing growth kinetics at the first follow-up imaging appear to be
associated with higher treatment crossing over but not with OS, which suggests that rapidly growing masses
[12]
early in AS may not necessarily require immediate treatment .

The optimal follow-up schedule for patients in AS is still unknown and therefore hasn’t been standardized.
Current recommendations suggest imaging at relatively frequent intervals initially, which may increase
as the stability of the lesion is demonstrated: cross-sectional imaging every 3-4 months for the first year,
followed by cross-sectional imaging or ultrasound every 4-6 months for the second year and every 6-12 months
[20]
thereafter .

Nephron-sparing surgery
Although AS and ablative therapies have been regarded as attractive treatment modalities, partial nephrectomy
(PN) represents the standard of care for the management of SRMs [1,15,21-23] . Indeed, PN has demonstrated
comparable cancer control [24-26] but a lower incidence of chronic kidney disease [27-30] , cardiovascular events [31,32] ,
overall and competing-cause mortality [31,33-35] when compared to radical nephrectomy.

According to a surgeon’s experience and preference, a PN can be performed with open (OPN), laparoscopic
[1]
(LPN) or robot-assisted (RAPN) approach . Specifically, RAPN provides non-inferior oncological and
functional outcomes and an improved morbidity profile with respect to OPN [36,37] . Moreover, RAPN is now
considered the preferable minimally invasive approach to PN because it eliminates the technical issues of
LPN and reduces the surgical learning curve [38-40] .