Recurrence
- Medulloblastoma is a very aggressive tumor.
- Chances of tumor recurrence are high, usually occurring within the first two years following treatment.
- Most recurrences occur at the primary tumor site in the posterior fossa.
- Relapse within the craniospinal axis may also occur.
- Systemic metastases are rare but may occur even when there is no shunt in place. Bone and bone marrow are the most common sites of these metastases.
- Recurrence 3 years after therapy is unusual, but late recurrences can occur.
Prognostic Factors
The chance of disease free survival depends on several factors:
Patient-related
- Young patients, less than 5 years old, tend to have a worse outcome.
- This may be due in part to the high incidence of the less aggressive desmoplastic variant of medulloblastoma in older children and adults.
Tumor-related factors remain somewhat controversial.
However, a new consensus classification based on Molecular Classification has recently been developed.
- While tumor size was previously correlated with patient prognosis, the extent of disease is more relevant than the size of the tumor itself.
- Localized disease has a much better prognosis than disseminated disease – roughly 70 to 80% chance of 5 year survival after therapy for localized disease.
- Initial metastatic disease to the cord is associated with a significantly increased risk of relapse after therapy – roughly 60% chance of 5 year survival after aggressive therapy.
- Pathology:
- Anaplastic and large cell variant associated with worse outcome
- Desmoplastic variant – better prognostic group than standard pathology
Treatment related factors also play a role in the prognosis of the disease.
- There are many retroactive studies that indicate a greater survival rate after complete surgical resection rather than a biopsy.
- A dose of greater than 50 Gy to posterior fossa improves local control of the tumor.
- The placement of shunts is thought to be associated with a somewhat increased risk of metastatic disease to distant sites.
- Investigators have shown that poor/inaccurate RT planning leads to an increased risk of relapse (if RT field does not adequately cover the cribriform plate, there is an increased risk of relapse in this area).
Effect of prognostic factors on patient outcome:
|
Factors |
|
Effect on Outcome |
Patient |
Patient age |
Patients under 3 years of age have a worse prognosis |
Tumour |
Extent of disease |
Localized disease has better prognosis |
Spinal cord metastases |
Much harder to ablate all disease and higher risk of recurrence after therapy. These patients have a significantly worse outcome |
|
Histologic grade |
Nodularity is associated with a better prognosis
Anaplasia is associated with a worse prognosis |
|
Genetics |
||
Treatment |
Surgery |
Complete resection is associated with a better prognosis
The placement of shunts may be associated with the spread of metastatic disease (medulloblastoma can disseminate to the peritoneal cavity via a VP shunt). |
