RT is an important part of therapy for these tumors in children older than 3 - 5 years.
These tumors are radiosensitive (evidence from retrospective studies).
RT is generally used in children older than 3 years of age17
- Treatment to large volumes of the developing brain to a moderately high dose is likely to result in severe long-term neurocognitive problems.
There is debate about the dose, timing and target volume, but the current recommendations for RT in children over 3 years old are:
- Combination of 24 Gy to 36 Gy to the entire craniospinal axis (CSA RT) plus a boost to the site of the primary tumor to a total dose of 54 Gy17,18
HIT Trials:
Some important knowledge regarding the role of RT in supratentorial PNET treatment comes from the German HIT 88/89 and HIT 91 trials13.
HIT 88/89 trial:
- Patients were treated postoperatively with pre-RT chemotherapy (ifosfamide, etoposide, methotrexate, cisplatin, cytarabine)
- Chemotherapy was given starting 14 days after surgery
- External beam RT then followed 4 weeks after chemotherapy
HIT 91 trial:
- RT given 3 weeks following surgery
- Maintenance chemotherapy (cisplatin, vincristine, lomustine) given 6 weeks after finishing RT
All patients were treated with fractionated RT to the CSA (3520 cGy to CSA with additional boost to the supratentorial tumor of 20 Gy).
Results of HIT trial:
Immediate RT followed by maintenance chemotherapy was better than delaying RT with pre-RT chemotherapy (with an increased rate of early progression 22% in the pre-chemo RT group versus 4% in the immediate RT group).
Dose and volume of RT significant prognostic factor:
- Progression free survival decreased if there were major protocol violations in the way RT as given23
- Protocol violations were defined as:
- CSA RT dose less than 35 Gy
- Local tumor boost dose less than 54 Gy
- No CSA RT was given
- No RT was performed
Effectiveness of RT16:
Study of 15 children under18 years old with non-pineal supratentorial PNETs
Initial treatment with surgery and chemotherapy was given to all patients
RT delivered as follows:
- Up front (initial) RT in 5 patients
- RT given at time of progression in 5 patients
- No RT in 5 patients
All patients receiving upfront RT were alive without any evidence of disease at a follow up averaging 4 years
Another retrospective SIOP/UKSSCG PNET-3 study looked at the effectiveness of RT alone compared to pre-RT chemotherapy (alternating cycles of vincristine, etoposide, carboplatin and vincristine, etoposide and cyclophosphamide) for adjuvant treatment
RT was delivered in standard fractionated format
CSA RT dose of 35 Gy in 21 daily fractions, followed by a boost of 20 Gy to the primary tumor in 12 fractions (total dose was 55 Gy to the primary tumor)18
Results:
- No significant improvement for event free survival
- This study supports the importance of RT in the treatment of supratentorial PNETs.
