Editing Management of Localized and Locally Advanced Disease (section)

=== Thermal ablation (TA) ===

==== <span style="color:#ff0000">Options (2):</span> ====
# '''<span style="color:#ff0000">Radiofrequency ablation (RFA)</span>''' 
#'''<span style="color:#ff0000">Cryoablation</span>'''
#*'''Experience with renal cryosurgery predates that of RFA and has been more extensive'''
#* No randomized trials directly compare cryoablation to RFA
#* Meta-analyses have shown no significant differences between cryoablation and RFA in outcomes as defined by complications, metastatic progression, or cancer-specific survival.

==== Advantages/Disadvantages ====
*'''<span style="color:#ff0000">Advantages (2):</span>'''
*# '''Low morbidity'''
*#* In the Agency for Healthcare Research and Quality (AHRQ) analysis, TA had the most favorable perioperative outcome profile and a similar low risk of harms when compared to other strategies
*# '''Comparable cancer-specific and overall survival outcomes to partial nephrectomy, in select patients'''
* '''<span style="color:#ff0000">Disadvantage</span>'''
*# '''<span style="color:#ff0000">Risk of local recurrence after primary treatment is higher with TA</span>''' (3-10% cryoablation and 5-20% RFA) '''<span style="color:#ff0000">than partial</span>''' (0-3%) '''<span style="color:#ff0000">or radical nephrectomy</span>''' (0%)
*#* '''<span style="color:#ff0000">Local recurrence after TA can be salvaged with repeat TA.</span>'''
*#** '''<span style="color:#ff0000">Patients should be informed of higher risk of requiring secondary procedure</span>''', compared to partial nephrectomy
*#** '''<span style="color:#ff0000">Allowing for second treatment, risk of local recurrence of TA not significantly different than partial nephrectomy.</span>'''
*#* Observational study comparing partial nephrectomy to TA
*#** Design: retrospective cohort study
*#** Population: 1424 cT1a patients managed with partial nephrectomy or TA
*#** Results:
*#*** 26% of RFA and 7% of cryoablation patients did not undergo biopsy
*#*** 3-year local recurrence-free survival rates were 98% for partial nephrectomy, RFA, and cryoablation.
*#** [https://pubmed.ncbi.nlm.nih.gov/25108580/ Thompson, R. Houston, et al. "Comparison of partial nephrectomy and percutaneous ablation for cT1 renal masses." ''European urology'' 67.2 (2015): 252-259.]
*#* Reported rates of local recurrence after TA may represent underestimates because ≈20% of small renal masses are benign rather than RCC, and a pretreatment biopsy has not always been performed.

==== <span style="color:#ff0000">Indications</span> ====
* '''<span style="color:#ff0000">Alternative approach for management of cT1a solid renal masses <3cm</span>'''
** '''Current technology does not allow for reliable treatment of lesions >4.0 cm, and success rates appear to be highest for tumors <2.5-3.0 cm'''
* '''Relative (4):'''
*# '''Advanced age'''
*# '''Significant comorbidities'''
*# '''Local recurrence after previous nephron-sparing surgery'''
*# '''Hereditary renal cancer who present with multifocal lesions for which multiple PNs might be cumbersome'''
* '''<span style="color:#ff0000">2021 AUA[https://www.auanet.org/guidelines/renal-cancer-renal-mass-and-localized-renal-cancer-guideline]</span>'''
** '''<span style="color:#ff0000">Alternative approach for management of cT1a solid renal masses <3cm</span>'''
*** Patients should be informed about the increased risk of tumor persistence or local recurrence after primary TA, compared to surgical excision, which may be treated with repeat ablation.
***PN seems preferred over TA for cT1a: "PN should be prioritized in the management of patients with clinical T1a renal mass".

==== Contraindications ====
* '''Absolute'''
** '''Inaccessible tumour'''
** Large tumour
* '''Relative'''
** Completely intrarenal lesions or those immediately adjacent to the sinus or hilum are more difficult to treat effectively by TA

==== Technology ====
* '''RFA'''
** Utilizes high frequency alternating current (460-500 kHz) to induce ion agitation and frictional heating in adjacent tissue
*** Can be achieved through 2 types of radiofrequency generator systems:
***# Temperature-based system: drives the current to reach a target temperature
***# Impedance-based systems: continue ablation until a predetermined impedance level is reached.
* '''Cryoablation'''
** Generates lethal temperatures below -20 to -40 °C, resulting in coagulative tissue necrosis
** '''Volume of lethal temperature generated during cryoablation is regulated by (4):'''
**# '''Duration of freezing'''
**# '''Number of freeze cycles'''
**#* '''<span style="color:#ff0000">Double freeze results in larger volumes of renal tissue necrosis, compared to single freeze</span>'''
**# '''Size and number of cryoprobes'''
**# '''Local tissue interactions'''
** '''<span style="color:#ff0000">Complete treatment of a tumour requires that the iceball extend beyond the tumor</span>''' because the peripheral leading edge of the iceball is at sub-lethal temperatures
*** Lethal temperatures are reached approximately 5 mm from the periphery of the iceball; '''<span style="color:#ff0000">the ice-ball is usually extended ≈1 cm beyond the edge of the tumor</span>'''
*'''Both radiofrequency ablation and cryoablation may be offered as options[https://pubmed.ncbi.nlm.nih.gov/28479239/]'''
*Other new technologies, such as high-intensity focused ultrasound and image-guided radiosurgical treatments (SBRT), are under development and may allow extracorporeal treatment of small renal tumors in the future

==== Technique ====
* TA for cystic lesions requires further investigation.
* '''<span style="color:#ff0000">Biopsy should be performed prior to (preferred) or at the time of ablation</span>''' to provide pathologic diagnosis and guide subsequent surveillance.'''[https://pubmed.ncbi.nlm.nih.gov/28479239/]'''
* Percutaneous approach is preferred over a surgical approach whenever feasible to minimize morbidity.
** Percutaneous displacement techniques such as the use of fluid (hydro-dissection), carbon dioxide, or spacer balloons frequently enable separation of adjacent structures from the anticipated zone of ablation, rendering many cases suitable for percutaneous TA.
** A laparoscopic approach is seldom needed except for occasional cases in which adhesions prevent displacement of adjacent structures or when the collecting system is at risk for serious injury even with thermo-protective maneuvers such as pyeloperfusion.

==== Complications ====
* '''Cryoablation:'''
*# '''Renal fracture'''
*#* Higher risk when treating tumours >3cm
*# '''Hemorrhage'''
*# '''Adjacent organ injury'''
*# '''Ileus'''
*# '''Wound infection'''
* '''RFA (uncommon):'''
*# '''Acute renal failure'''
*# '''Stricture of the ureteropelvic junction'''
*# '''Necrotizing pancreatitis'''
*# '''Lumbar radiculopathy'''

==== Post-treatment imaging ====
* Immediate post-procedural imaging of the ablated tumor generally shows the treatment bed to be larger than the pre-treatment tumor size for RFA due to ablation of a peripheral margin of normal tissue, and for cryoablation due to extension of the iceball beyond the original tumor margin.
* '''<span style="color:#ff0000">Renal tumours successfully treated with</span>'''
** '''<span style="color:#ff0000">RFA demonstrate no contrast enhancement. However, they do not regress significantly in size.</span>'''
*** '''Residual enhancement is considered suggestive of residual or recurrent disease'''
** '''<span style="color:#ff0000">Cryoablation may demonstrate reduction in size or complete resolution or scar formation</span>'''
* On MRI, the imaging hallmark of successful renal tumor ablation is lack of tumor enhancement with gadolinium-enhanced imaging.
* Rim enhancement, believed to represent reactive change, may occasionally be seen at early postprocedural MR scanning after RFA or cryoablation, which later resolves.

==== Recurrence following treatment ====
* '''Diagnosis of local recurrence after TA can be challenging''' because evolving fibrosis within the tumor bed can be difficult to differentiate from residual cancer.
* '''<span style="color:#ff0000">Findings suggestive of local recurrence (5):</span>'''
*# '''<span style="color:#ff0000">Enhancement within the tumor bed beyond 6 months</span>'''
*# '''<span style="color:#ff0000">Progressive increase in size of an ablated neoplasm</span>'''
*# '''<span style="color:#ff0000">New nodularity in or around the treated zone</span>'''
*# '''<span style="color:#ff0000">Failure of the treated lesion to regress over time</span>'''
*# '''<span style="color:#ff0000">Satellite or port site lesions</span>'''
* '''<span style="color:#ff0000">Most local recurrences can be salvaged with repeat ablation</span>'''
** Some patients with progressive disease eventually require conventional surgery.
*** PN and minimally invasive approaches are occasionally precluded in this setting because of the extensive fibrotic reaction induced by TA, necessitating RN.