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It is important to note that treatment protocols differ geographically. In Europe the Société Internationale d’Oncologie Pédiatrique approach is dominant and in Canada and the United States the NWTSG protocols predominate.

 

The goal of both these groups is to increase the cure rates while minimising morbidity; however, there are important differences. In the SIOP protocols, treatment is based on initial imaging studies and chemotherapy is started prior to surgery and defi nitive tissue diagnosis. In the NWTSG protocols, tissue diagnosis, primary nephrectomy and surgical staging is performed first followed by adjuvant therapy.

 

Six per cent of patients with Wilms’s tumour present with stage V (bilateral) disease. Partial nephrectomy is indicated in those with a solitary kidney but also in those with bilateral Wilms’s tumour. Partial nephrectomy for small polar tumours with no evidence of spread, is practised in some centres, especially in Italy. Chemotherapy agents used include dactinomycin, vincristine and doxorubicin. A skeletal survey and bone scan are not required in all patients with Wilms’s tumour but should be routine investigations in those with clear cell sarcoma because of the high metastatic potential of this tumour.

 

In the SIOP studies the therapeutic approach has focused on developing stage specific strategies after prenephrectomy therapy. Stage classification and histopathological diagnosis are delayed until after surgery. It is thought that the use of prenephrectomy chemotherapy facilitates surgical resection and minimises complications. Children under 6 months of age undergo primary nephrectomy unless there is evidence of metastases at presentation. Therefore, patients in the SIOP trial with chemotherapy-induced tumour shrinkage result in a different stage distribution to those patients in the North American National Wilms’ Tumour Study Group (NWTSG).

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OPERATIVE THERAPY

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Goals:

• Perform en bloc excision of the tumor with radical nephrectomy.

• For an upper pole Wilms tumor, include the adrenal gland in the specimen if it is adherent to the tumor.

• Dissect the ureter distally and ligate it as close to the bladder cuff as possible.

• Achieve safe tumor excision with minimal blood loss.

• Ligate the vascular supply either before or after tumor mobilization, depending on the tumor size and renal hilar anatomy.

• Avoid tumor rupture during the operation.

• Perform accurate staging at laparotomy.

• Inspect the peritoneal cavity for:

  • Tumor implants

  • Distant lesions

  • Evidence of preoperative rupture

• Perform retroperitoneal lymph node sampling.

• Excise any grossly enlarged lymph nodes.

• Even if no obvious lymphadenopathy is present, sample nodes from the periaortic and aortocaval regions.

• Use titanium clips to mark:

  • Any area of residual tumor

  • Any area of tumor rupture

• Place a port-a-cath under the same anesthetic for administration of adjuvant chemotherapy.

 

Unilateral Tumors

• Wide abdominal exposure, resection of surrounding Gerota’s Fat and fascia to remove potential sites of lymphatic spread and early control of renal vessels.

• Lymphnode sampling is crucial for accurate staging

• A transverse abdominal or a thoracoabdominal incision (which is best if tumor large tumors, to optimize visualization of the plane between the tumor and the diaphragm to avoid rupture from excessive traction of the tumor.

• Early examination of the liver, renal veins or the IVC or peritoneal surfaces is important

• If studies suggest possible contralateral lesion, the contralateral kidney should be formally explored prior to nephrectomy.

• Ladd and Gross stressed the need for early vascular ligation prior to the development of chemotherapy. This is no longer practiced because of the risk of injury to the vessels, particularly to the superior mesenteric artery in large left-sided tu-mors. The tumor should be mobilized by opening the lateral peritoneal reflection and reflecting the colon and its mesentery off the anterior surface of the kidney. For right-sided tumors, a Kocher procedure is also helpful. When ligat-ing the renal pedicle, it is best to ligate the renal artery first if it can be safely identified., to avoid increasing the venous pressure within the tumor, which can result in rupture of the capsule. Vascular control in most cases is best completed after the tumor is fully mobilized. The renal vein should be palpated prior to ligation to be certain there is no venous extension of the tumor. The adrenal gland may be left in place if it is not abutting the tumor; but, if the mass arises in the upper pole of the kidney, the adrenal gland should be removed with the neoplasm. The ureter is ligated and divided as low as possible. The tumor and kidney should be handled gently throughout the operation to avoid rupture which will increase the intensity of therapy and risk for local recurrence.

• Pathological assessment of hilar and regional lymph nodes is critical to accurately stage a child with renal tumor  routine lymphnode sampling from renal hilum, the pericaval or paraaortic areas must be perfomed.

• WTs tend to displace rather than invade the surrounding vessels; when actual invasion is identified, radical en bloc resection (eg partial hepatectomy or colectomy) is not warranted as primary therapy. WTs are very chemosensitive and in these cases prior chemotherapy is warranted.

• Priamary resection of Liver Metastasis prior to adjuvant therapy is not currently recommended.

 

Spill

• Spill refers to a break in the tumor capsule during operative removal.

• Studies have shown a higher risk of recurrence in patients who had tumor spill or rupture, irrespective of the cause and extent of soiling.

• Spill is also considered to have occurred if the renal vein or ureter is transected where they contain the tumor.

• In COG protocol, spill is also considered to have occurred if a preoperative or intraoperative needle/open biopsy was performed. This is not the case in SIOP protocol: Fine needle or trucut biopsies are allowed however incision biopsies are considered as ruptures, automatically stage III, and are contraindicated.

• Rupture refers to either the spontaneous or post traumatic rupture of the tumor preoperatively with the result that tumor cells disseminate throughout the peritoneal or retroperitoneal space.

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Unresectable tumors

• Primary nephrectomy is contraindicated (1) There is extension of the tumor thrombus above the level of the hepatic veins (2) The tumor involves contiguous structures, where the only means or removing the kidney tumor requires removal of other structures (spleen, pancreas, and colon but excluding the adrenal gland) (3) B/L tumors (4) Solitary Kidney (5) There is pulmonary compromise resulting from extensive pulmonary metastasis (5) tumor associated with a syndrome that increases risk for future metachronous tumors,.

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Special Considerations

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Management of Tumor extension in the renal vein, IVC and atrium

• 4-11%

• Usually detected preoperatively but renal vein extension detection might only be possible peroperatively so palpation of the renal vein before mobilizing is important because it might dislodge the thrombus.

• Preoperative chemotherapy will shrink the thrombus

• If the thrombus extension is below the level of the liver, the tumor and the thrombus can in most cases, be removed en bloc with the kidney.

• Control of renal veins and cava above and below the tumor with vessel loops is necessary, using standard vascular surgery techniques. The tumor should not be transected, if possible, because this will result in spill and upstaging of the patient. In some cases, the tumor may be adherent to the vessel wall. A similar technique used for removing plaque for a carotid endarterectomy is helpful to lift the tumor off the vein wall. It must be stated in the operative report if the intravascular tumor extension was removed en bloc or if tumor was transected, as well as if the tumor thrombus is removed completely and if there is evidence of either adherence to or invasion of the vein wall. If, after preoperative chemotherapy, the tumor still extends above the hepatic veins, cardiopulmonary bypass is generally needed to remove the vascular extension of the tumor.

 

Ureteral extension

• Only 2%

• If extension of the tumor into the ureter is detected or suspected, the ureter should be resected with clear margins

 

 

Horseshoe Kidney, Single Kidney and Nonfunctioning Kidney

• Children with tumors with a horseshoe kidney are treated as unilateral tumors NOT as bilateral tumors

• The blood supply of a horseshoe kidney is variable and should be imaged prior to surgery.

• The side of the kidney containing the tumor, the isthmus, and the ipsilateral ureter are resected. As with the other unilateral procedures, the lymph nodes are sampled for staging purposes.

• Children with a single kidney, or a situation where a tumor occurs in one kidney but the second kidney is nonfunctioning, should be managed using a renal sparing approach, with preoperative chemotherapy to facilitate surgery and preserve more renal tissue.

 

Patients with Wilms Tumor Treated Only with Surgery

• Favourable histology with lymphnodes biopsies

• Specimen weight less than 550g

• <2 years of age.

 

Neonatal Tumors

• 50% tumors are congenital mesoblastic nephroma

• Wilms Tumor

• Rhabdoid Tumor of the Kidney

• Clear Cell Sarcoma of the Kidney

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After three months of age:

• CMN

• WT

• Rhabdoid Tumor (Most likely presents with mets)

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ACQUIRED WONWILLEBRAND DISEASE WITH WILMS TUMOR

Presents with Mucocutaneous Disease with WT, Clinical Features: Epistaxis, Hematuria, Gingival Bleeding,

• Proloned BT

• Decreased vWF, decreased F8 and activity of ristocetin cofactor activity.

• Might require multiple transfusions of F8, FFP, cryoprecipitate

• Immediately after ligation of the renal vessels, all abnormal bleeding stops, with normalization of F8 and wWF activity.

  • Absorption of  wWF by the tumor

  • wWF inhibitors

  • Rapid abnormal clearance of vWF

  • Coagulopathy related with to elevated levels of hyaluronic acid.

• Initial Signs are increased PTT

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BILATERAL WILMS TUMOR

• 4-13%

• More likely to present with renal failure.

  • Intrinsic Progressive renal disease  Genetic Predisposition

  • Inadequate renal parenchyma

  • Nephrotoxic effects of chemotherapy and radiation

  • Hyperfiltration Injury

• Most important risk factor is B/L WT

• Denys Dash Syndrome

• Metachronous Tumors

• Radiation

• If bilateral lesions do not respond radiographically to therapy, it is critical to establish whether this is due to anaplasia or mature histology (rhabdomyomatous or differentiated stromal elements) in which complete resection is required.

• In SIOP9 patients with unilateral tumors received chemotherapy for 4-8 weeks of dactinomycin and vincristine (with an average of 48% reduction in tumor size)

• The two principle aims of COG BWT study are to improve the 4 year survival and to prevent complete removal of at least one kidney in 50% of patients with BWT by using preoperative chemotherapy. This is a response based therapy followed by evaluation at 6 and 12 weeks.

• Initial regimen consists of Vincristine, Dactinomycin and Doxorubacin

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CHEMOTHERAPY

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In the SIOP model, first presenters that are unilateral and have no evidence of metastasis are given 2 drugs for 4 weeks. In patients who have B/L disease, have evidence of metastasis are given 3 drugs for 6 weeks. 

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Post operative chemotherapeutic regimen in COG is as follows: