Purpose/Objectives
We developed a technique for CSI involving treatment in the prone position with junctions between cranial photon and spinal proton fields. We report acute toxicities and early outcomes of this treatment.
Materials/Methods
From 9/2011 - 8/2013, 16 pediatric MB pts were treated with this CSI technique. Standard-risk (SR) received 23.4 Gy (RBE) CSI and proton boost to tumor bed to 54 Gy (RBE); high-risk (HR) 36 Gy (RBE) and 55.8 Gy (RBE), respectively (2 with spine boosts of 5.4 Gy (RBE) and 12.6 Gy (RBE)). Pts were immobilized in prone position by thermoplastic mask and vacuum bag. Due to field size limitations on proton machines, cranial RT was delivered with 2 opposed lateral 6MV photon fields. Spine RT was delivered with 2-4 double scattered or uniform scanning posterior-anterior proton fields matched at anterior part of the vertebral body and feathered every 5 fractions. Fields were configured in lateral directions using a multileaf collimator and distally by a compensator. Daily IGRT was performed. Toxicities were documented according to CTCAE v4.
Results
Median age was 11 years (range 4.9 - 17.4), 9 pts were female, 10 required anesthesia during RT, and 81% were SR; 7 tumors were classical, 2 desmoplastic/nodular, 7 NOS. Median time from surgery to start of RT was 31 days (range 28-72). Delay >31 days was often due to transfer of care between institutions; the only delay >40 days was for an international patient. Median time from simulation to RT start was 15.5 days (range 6-21). All pts received weekly concurrent vincristine and 1 received additional daily carboplatin. Chemo was initiated prior to RT for 1 pt due to medical delays. Most common acute toxicities were nausea/vomiting and anorexia (table). Mean weight loss was 2.3 kg (range 0-5.8). Bone marrow toxicity was ≤ grade 2 for all pts receiving standard weekly vincristine; 1 pt receiving daily carboplatin developed grade 4 neutropenia and grade 3 thrombocytopenia; 1 pt receiving pre-RT chemo developed grade 3 neutropenia. At a median follow up of 13.6 months (range 3.8-24.5), 13 are alive with no evidence of disease, 1 is alive with recurrence in the cerebellum and thecal sac, 1 is alive with ventricular recurrence, and 1 is lost to follow up.
Conclusions
This review suggests that this CSI technique is safe and well-tolerated; it may decrease GI and bone marrow toxicity depending on chemotherapy regimen. Planning is feasible in a 2 week period, allowing treatment to be initiated within 31 days of surgery, although referral to proton center from outside institutions must be initiated rapidly.
Acute toxicities experienced during photon/proton CSI with concurrent weekly vincristine in MB pts
Grade None 1 2 3 4
Fatigue (n=16) 4 (25%) 9 (56.25%) 3 (18.75%) 0 0
Nausea/vomiting (n=16) 1 (6.25%) 7 (43.75%) 6 (37.5%) 2 (12.5%) 0
Diarrhea (n=16) 14 (87.5%) 2 (12.5%) 0 0 0
Anorexia (n=16) 1 (6.25%) 4 (25%) 3 (18.75%) 8 (50%) 0
Weight loss (n=16) 6 (37.5%) 7 (43.75%) 3 (18.75%) 0 0
Dermatitis (n=16) 3 (18.75%) 12 (75%) 1 (6.25%) 0 0
Decreased Hemoglobin (n=15) 2 (13.3%) 4 (26.7%) 7 (46.7%) 2 (13.3%) 0
Decreased WBC (n=15) 0 3 (20%) 10 (66.7%) 1* (6.7%)*Patient given pre-RT chemotherapy 1** (6.7%)**Patient received daily carboplatin
Decreased Platelets (n=15) 13 (86.7%) 1 (6.7%) 0 1** (6.7%)**Patient received daily carboplatin 0
Hollander, A,
Acute Toxicities and Treatment Outcomes of a Novel Combined Photon/Proton Craniospinal Irradiation (CSI) Technique for Medulloblastoma (MB) Patients. Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL.
http://archive.rsna.org/2014/14041503.html
