Skip to content
How It Works
Explore
Resources Ask a Question
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 18 peer-reviewed journal articles Updated
Pediatric Oncology

Treatment Protocols and Staging (COG vs SIOP)

At a Glance

Treatment for Wilms tumor typically follows the COG protocol (surgery first) or the SIOP protocol (chemotherapy first). Both approaches achieve high survival rates using a combination of surgery and chemotherapy, with treatment tailored to the tumor's specific stage to minimize side effects.

When your child is diagnosed with a Wilms tumor, the medical team will follow a standardized “playbook” to determine the best treatment. Globally, there are two main approaches used to manage this disease, and while they differ in timing, both have achieved the same exceptionally high survival rates [1][2].

Two Global Philosophies: COG vs. SIOP

Depending on where your child is being treated, they will likely follow one of two major clinical protocols:

  • COG (Children’s Oncology Group): Most common in North America. This approach usually starts with a nephrectomy (surgery to remove the tumor) as the very first step [3][4]. Doctors use the surgery to immediately “stage” the tumor and determine how much chemotherapy is needed afterward [1].
  • SIOP (International Society of Pediatric Oncology): Most common in Europe and elsewhere. This approach starts with 4 to 6 weeks of chemotherapy before surgery [5]. The goal is to shrink the tumor, making the surgery safer and reducing the risk of the tumor breaking (rupturing) during the procedure [3][6].

The Staging System (Stages I–V)

Staging describes how far the tumor has spread. Your child’s stage is determined by the surgeon’s findings and the pathologist’s report [4][5].

  • Stage I: The tumor is limited to the kidney and was completely removed during surgery [7].
  • Stage II: The tumor grew beyond the kidney (into nearby fat or blood vessels) but was still completely removed [7].
  • Stage III: The tumor cannot be completely removed, has spread to nearby lymph nodes, or has ruptured [7][8].
  • Stage IV: The tumor has spread to distant organs, most commonly the lungs or liver [7].
  • Stage V: Tumors are present in both kidneys at the time of diagnosis (also called bilateral disease) [9][10].

The Impact of Tumor Rupture

A critical factor in staging is whether the tumor stays intact. If a tumor rupture occurs—meaning the tumor breaks and spills cells into the abdomen either before or during surgery—the case is automatically classified as Stage III [8][11]. This is a significant turning point because it necessitates more intensive chemotherapy and requires the use of abdominal radiation to target any spilled cells [8].

Modern Treatment Goals: Less is More

While the goal is always to cure the cancer, modern medicine is now focused on risk stratification—tailoring treatment to be as “light” as possible while still being effective [2][12].

  • Standard Chemotherapy: Most children receive a two-drug combination of Vincristine and Actinomycin-D [13]. While highly effective, these drugs can cause acute side effects during treatment, such as peripheral neuropathy (tingling or weakness in the hands and feet) and constipation from Vincristine, as well as nausea, vomiting, or hair loss from Actinomycin-D [14][2].
  • The “Third Drug”: Doxorubicin is added for higher-stage or higher-risk tumors. However, doctors try to avoid it when possible because it can cause cardiotoxicity (long-term damage to the heart) [2][15].
  • Radiation Therapy: Used for Stage III and IV cases, and some high-risk early stages (such as Stage I or II tumors with diffuse anaplasia). Like doxorubicin, radiation is used selectively to avoid long-term side effects, such as the risk of developing secondary cancers later in life [2][16].

What to Expect: The Treatment Timeline

While every child’s journey is unique, active treatment for Wilms tumor typically ranges from 3 to 6 months for early stages (Stage I or II with favorable histology), up to 9 to 12 months for more advanced stages or high-risk tumors requiring prolonged chemotherapy and radiation [12][2].

For children with Stage V (bilateral) disease, the focus is on nephron-sparing surgery, which aims to remove the tumors while saving as much healthy kidney tissue as possible to preserve long-term kidney function [17][18].

Back to Home

Common questions in this guide

What is the difference between the COG and SIOP treatment protocols?
The COG protocol, common in North America, starts with surgery to remove and stage the tumor before chemotherapy. The SIOP protocol, common in Europe, starts with chemotherapy to shrink the tumor before surgery. Both approaches have excellent survival rates.
What happens if a Wilms tumor ruptures during surgery?
If a tumor breaks or spills cells into the abdomen, it is automatically classified as Stage III. This means your child will need more intensive chemotherapy and abdominal radiation to target any spilled cells.
Why do doctors try to avoid using doxorubicin if possible?
Doxorubicin is a powerful chemotherapy drug used for higher-stage or high-risk tumors. However, doctors limit its use when possible because it carries a risk of cardiotoxicity, which is long-term damage to the heart.
How is bilateral Wilms tumor (Stage V) treated?
When tumors are present in both kidneys, surgeons use a technique called nephron-sparing surgery. The goal is to safely remove the tumors while leaving behind as much healthy kidney tissue as possible to protect long-term kidney function.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Is my child being treated under the COG protocol (surgery first) or the SIOP protocol (chemotherapy first)?
  2. 2.Based on the surgical findings, what is my child's stage (I through V)?
  3. 3.Was there any tumor rupture or spillage during the surgery, and how does that affect the treatment plan?
  4. 4.Will my child's chemotherapy regimen include doxorubicin? If so, how will we monitor their heart health?
  5. 5.Is radiation therapy recommended for my child? If so, what are the specific target areas?
  6. 6.For Stage V cases, is nephron-sparing surgery possible to preserve kidney function?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (18)
  1. 1

    Many faces of Wilms Tumor: Recent advances and future directions.

    Bhutani N, Kajal P, Sharma U

    Annals of medicine and surgery (2012) 2021; (64()):102202 doi:10.1016/j.amsu.2021.102202.

    PMID: 33747498
  2. 2

    Wilms tumor.

    Pater L, Melchior P, Rübe C, et al.

    Pediatric blood & cancer 2021; (68 Suppl 2()):e28257 doi:10.1002/pbc.28257.

    PMID: 32893998
  3. 3

    From Wilms to kidney tumors: which ones require a biopsy?

    Brisse HJ, de la Monneraye Y, Cardoen L, Schleiermacher G

    Pediatric radiology 2020; (50(8)):1049-1051 doi:10.1007/s00247-020-04660-x.

    PMID: 32248272
  4. 4

    Imaging of Wilms tumor: an update.

    Servaes SE, Hoffer FA, Smith EA, Khanna G

    Pediatric radiology 2019; (49(11)):1441-1452 doi:10.1007/s00247-019-04423-3.

    PMID: 31620845
  5. 5

    [Paediatric kidney tumours: Update on the challenges of nephroblastoma and other kidney tumours].

    L'Herminé-Coulomb A, Berrebi D

    Annales de pathologie 2026; (46(3)):195-206 doi:10.1016/j.annpat.2026.02.011.

    PMID: 41881740
  6. 6

    How we approach paediatric renal tumour core needle biopsy in the setting of preoperative chemotherapy: A Review from the SIOP Renal Tumour Study Group.

    Jackson TJ, Brisse HJ, Pritchard-Jones K, et al.

    Pediatric blood & cancer 2022; (69(9)):e29702 doi:10.1002/pbc.29702.

    PMID: 35587187
  7. 7

    Wilms Tumor (Nephroblastoma), Version 2.2021, NCCN Clinical Practice Guidelines in Oncology.

    Balis F, Green DM, Anderson C, et al.

    Journal of the National Comprehensive Cancer Network : JNCCN 2021; (19(8)):945-977.

    PMID: 34416707
  8. 8

    Agreement between clinicoradiological signs at diagnosis and radiohistological analysis after neoadjuvant chemotherapy of suspected Wilms tumor rupture: Consequences on therapeutic choices.

    Le Rouzic MA, Mansuy L, Galloy MA, et al.

    Pediatric blood & cancer 2019; (66(6)):e27674 doi:10.1002/pbc.27674.

    PMID: 30773805
  9. 9

    Preoperative Wilms tumor rupture in children.

    Zhang Y, Song HC, Yang YF, et al.

    International urology and nephrology 2021; (53(4)):619-625 doi:10.1007/s11255-020-02706-5.

    PMID: 33245535
  10. 10

    A rare case of fetal bilateral Wilms' tumor in horseshoe kidney: A case report.

    Melis A, Tadesse T, Jemal S, Ketema W

    International journal of surgery case reports 2025; (133()):111619 doi:10.1016/j.ijscr.2025.111619.

    PMID: 40674961
  11. 11

    Surgical treatment of large adnexal masses: a retrospective analysis of 330 consecutive cases.

    Casarin J, Laganà AS, Uccella S, et al.

    Minimally invasive therapy & allied technologies : MITAT : official journal of the Society for Minimally Invasive Therapy 2020; (29(6)):366-374 doi:10.1080/13645706.2019.1649700.

    PMID: 31375049
  12. 12

    Recent advances in the management of Wilms' tumor.

    Lopes RI, Lorenzo A

    F1000Research 2017; (6()):670 doi:10.12688/f1000research.10760.1.

    PMID: 28620463
  13. 13

    Update on Wilms tumor.

    Aldrink JH, Heaton TE, Dasgupta R, et al.

    Journal of pediatric surgery 2019; (54(3)):390-397 doi:10.1016/j.jpedsurg.2018.09.005.

    PMID: 30270120
  14. 14

    Outcome and Prognostic Factors in Stage III Favorable-Histology Wilms Tumor: A Report From the Children's Oncology Group Study AREN0532.

    Fernandez CV, Mullen EA, Chi YY, et al.

    Journal of clinical oncology : official journal of the American Society of Clinical Oncology 2018; (36(3)):254-261 doi:10.1200/JCO.2017.73.7999.

    PMID: 29211618
  15. 15

    Cardiovascular Health Status And Genetic Risk In Survivors of Childhood Neuroblastoma and Nephroblastoma Treated With Doxorubicin: Protocol of the Pharmacogenetic Part of the LESS-Anthra Cross-Sectional Cohort Study.

    Zolk O, von dem Knesebeck A, Graf N, et al.

    JMIR research protocols 2022; (11(2)):e27898 doi:10.2196/27898.

    PMID: 35175211
  16. 16

    Breast Cancer Secondary to Radiation Therapy in a Patient With Wilms Tumor.

    Ramachandran L, Patel G, Fatima S, Khan M

    Cureus 2022; (14(3)):e23597 doi:10.7759/cureus.23597.

    PMID: 35505703
  17. 17

    Overall Survival and Renal Function of Patients With Synchronous Bilateral Wilms Tumor Undergoing Surgery at a Single Institution.

    Davidoff AM, Interiano RB, Wynn L, et al.

    Annals of surgery 2015; (262(4)):570-6 doi:10.1097/SLA.0000000000001451.

    PMID: 26366536
  18. 18

    Nephron-sparing surgery for Wilms tumor.

    Murphy AJ, Davidoff AM

    Frontiers in pediatrics 2023; (11()):1122390 doi:10.3389/fped.2023.1122390.

    PMID: 36743884

This page explains Wilms tumor treatment protocols and staging for educational purposes only. Always consult your pediatric oncologist for specific treatment recommendations and staging interpretation for your child.

Get notified when new evidence is published on Nephroblastoma.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.