 Introduction/Background According to the American Cancer Society, approximately 73,750 new cases of kidney and renal pelvis cancer will be diagnosed in the United States in 2020, and approximately 14,830 people will die of this disease [1]. Renal cell carcinoma (RCC) accounts for 85% of all malignant renal tumors and represents approximately 2% to 3% of all malignancies in adults [2]. RCC is also considered the most lethal of all urologic cancers. Surgical resection with curative intent, including radical nephrectomy (RN) or partial nephrectomy (PN), continues to be the standard of care for clinically localized RCC [2]. Ablative therapies such as radiofrequency ablation, microwave ablation, and cryoablation have been shown to be effective and safe alternatives for the treatment of small localized RCCs [3-7]. In some patients with small localized RCCs, treatment may also be deferred, with management instead consisting of active surveillance protocols [8]. For follow-up of patients with treated or untreated RCC and those with neoplasms suspected to represent RCC, radiologic imaging is the most useful component of surveillance, because most relapses and cases of disease progression are identified when patients are asymptomatic [9,10]. There is currently no consensus regarding surveillance protocols; however, various guidelines and strategies have been developed by international oncologic and urologic societies, such as the National Comprehensive Cancer Network, the American Urological Association, and the European Association of Urology, using both patient- and tumor-specific characteristics [2,9,11,12]. Although imaging is the centerpiece in all of these guidelines, the recommendations vary regarding the timing, frequency, and duration of follow-up, as well as the selection of imaging modalities for follow-up [12,13].
Post Treatment Follow up and Active Surveillance of Renal Cell Carcinoma.  Introduction/Background According to the American Cancer Society, approximately 73,750 new cases of kidney and renal pelvis cancer will be diagnosed in the United States in 2020, and approximately 14,830 people will die of this disease [1]. Renal cell carcinoma (RCC) accounts for 85% of all malignant renal tumors and represents approximately 2% to 3% of all malignancies in adults [2]. RCC is also considered the most lethal of all urologic cancers. Surgical resection with curative intent, including radical nephrectomy (RN) or partial nephrectomy (PN), continues to be the standard of care for clinically localized RCC [2]. Ablative therapies such as radiofrequency ablation, microwave ablation, and cryoablation have been shown to be effective and safe alternatives for the treatment of small localized RCCs [3-7]. In some patients with small localized RCCs, treatment may also be deferred, with management instead consisting of active surveillance protocols [8]. For follow-up of patients with treated or untreated RCC and those with neoplasms suspected to represent RCC, radiologic imaging is the most useful component of surveillance, because most relapses and cases of disease progression are identified when patients are asymptomatic [9,10]. There is currently no consensus regarding surveillance protocols; however, various guidelines and strategies have been developed by international oncologic and urologic societies, such as the National Comprehensive Cancer Network, the American Urological Association, and the European Association of Urology, using both patient- and tumor-specific characteristics [2,9,11,12]. Although imaging is the centerpiece in all of these guidelines, the recommendations vary regarding the timing, frequency, and duration of follow-up, as well as the selection of imaging modalities for follow-up [12,13].