title: Management of bilateral Wilms tumor over three decades: The perspective of a single center.
abstract: BACKGROUND
  Outcomes of Wilms tumor improved in last 50 years and excellent survival rates can be achieved especially in case of non-metastatic disease and favorable histology. Nevertheless, bilateral cases still stand as a therapeutic challenge. Prognosis of bilateral Wilms tumor (BWT) is not as good as the unilateral tumors of similar stage and histology in terms of survival and renal function.
  
  
  OBJECTIVE
  Management of BWT is constantly evolving and still stands as a therapeutic challenge. This study is designed to review and share our experiences on this topic from a surgical standpoint.
  
  
  METHODS
  The records of patients treated in our clinic between 1980 and 2013 according to Turkish Pediatric Group of Oncology protocol were analyzed retrospectively and clinical data, surgical details, pathology results, long term outcomes were analyzed.
  
  
  RESULTS
  Thirteen girls and 7 boys with a mean age of 2,5 years were treated. There were 2 patients with Wilms tumor-Aniridia-Growth Retardation complex and one with isolated hemihypertrophy. Metastasis were detected in lungs of 4 patients; liver of 2 and in the cranium of one. All patients except one with the presumptive diagnosis of unilateral Wilms tumor were given preoperative chemotherapy. To sum up; 19 nephroureterectomies, 8 partial nephrectomies and 13 enucleations were performed to 36 kidneys without any major early or late postoperative complications. Pathologic results revealed positive surgical margins in 2 lesions with enucleation and in 2 with partial nephrectomies and anaplasia in 4 patients. Two patients were not operated due to parental disapproval. Two patients had the need of dialysis; one was anephric and the others' renal functions recovered over a year. Seven patients received radiotherapy for pulmonary metastasis, positive surgical margins or local recurrences. Overall, 13 patients survived and 7 died due to metastasis, recurrences, and complication of dialysis and refusal of surgical treatment. Survival among all patients was 65% and 72.2% among operated ones. Of the 7 patients with the partial nephrectomy, 2 died and 5 survived. Among enucleation group, 8 out of 10 survived and 2 died. Survival was slightly higher among enucleation group (80% vs 71.4%). Median time of follow-up for survivors of disease is 5.8 years (min: 6 months and max: 14 years).
  
  
  CONCLUSIONS
  Outcomes of BWT management have changed dramatically during the last few decades from only survival, to a long life expectancy without the need of renal replacement therapy owing to improvements in treatment options. We argue that positive surgical margins do not necessarily lead to local recurrence. For this reason it may be wiser to favor on more nephron sparing surgery than to achieve negative surgical margins. Adjuvant chemotherapy and radiotherapy may be adequate to prevent local recurrence. Also, survival did not differ significantly between different ways of nephron sparing surgeries, so it may be wiser to choose enucleation over partial nephrectomy which preserves more nephrons. Nephron-sparing surgery should have utmost importance despite the risk of positive margins. On the other hand, there is not enough data to interpret if positive surgical margins have role on distant metastases or not. Presence of metastasis and recurrence seems to be an important determinant of prognosis given the fact that none of the survivors had any metastasis or recurrence.
  
  
  CONCLUSIONS
  Nephron preservation should be the aim while taking positive surgical margin risk on nephron sparing surgery side relying on postoperative chemotherapy and carefully planned radiotherapy to avoid recurrence. However, there is significant diversity on the management BWT in different centers and a certain validated guideline or protocol to provide the optimal treatment is still lacking.
authors.affiliation: Department of Pediatric Surgery, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: I R
authors.initials: IR
authors.lastname: User
authors.affiliation: Department of Pediatric Surgery, Hacettepe University Faculty of Medicine, Ankara, Turkey. Electronic address: sekinci@hacettepe.edu.tr.
authors.forename: S
authors.initials: S
authors.lastname: Ekinci
authors.affiliation: Pediatric Pathology Unit, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: G
authors.initials: G
authors.lastname: Kale
authors.affiliation: Pediatric Oncology Unit, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: C
authors.initials: C
authors.lastname: Akyüz
authors.affiliation: Pediatric Oncology Unit, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: M
authors.initials: M
authors.lastname: Büyükpamukçu
authors.affiliation: Department of Pediatric Surgery, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: I
authors.initials: I
authors.lastname: Karnak
authors.affiliation: Department of Pediatric Surgery, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: A Ö
authors.initials: AÖ
authors.lastname: Çiftçi
authors.affiliation: Department of Pediatric Surgery, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: F C
authors.initials: FC
authors.lastname: Tanyel
authors.affiliation: Department of Pediatric Surgery, Hacettepe University Faculty of Medicine, Ankara, Turkey.
authors.forename: M E
authors.initials: ME
authors.lastname: Şenocak
mesh_terms: D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007680:Kidney Neoplasms / Q000401:mortality / Q000473:pathology / Q000601:surgery*; D008297:Male; D009392:Nephrectomy; D012189:Retrospective Studies; D016896:Treatment Outcome; D014421:Turkey; D009396:Wilms Tumor / Q000401:mortality / Q000473:pathology / Q000601:surgery*
keywords: Bilateral; Child; Renal salvage surgery; Survival; Wilms tumor