Brain-sparing holo-cranial radiotherapy: a unique application of helical tomotherapy.
OBJECTIVE
Diffuse and extensive involvement of the scalp/skull by malignancy mandates holo-cranial radiotherapy with the aim to deliver homogeneous doses to the planning target volume (PTV) while minimising the dose to surrounding organs at risk (OARs). Previously described techniques result in significant heterogeneity, suboptimal coverage or poor conformity and need complicated beam matching. Here we report our preliminary experience of planning and delivery of brain-sparing holo-cranial radiotherapy with helical tomotherapy.


METHODS
Three patients with extensive involvement of the scalp/skull by malignancy were planned and treated with image-guided intensity-modulated radiation therapy on helical tomotherapy. The plan evaluation was carried out using standardised dose metrics.


RESULTS
Helical tomotherapy achieved highly conformal and homogeneous dose distributions with substantial OAR sparing in all three patients. The volume of PTV receiving ≥95% of prescribed dose (V(95%)) was ≥98% in all three patients. The mean (standard deviation) homogeneity index and conformity index was 0.046 (0.006) and 0.783 (0.035), respectively. The mean dose to the brain parenchyma outside the PTV was 17.32 Gy (74%), 28.76 Gy (63.9%) and 26.7 Gy (59.3%) for the three patients. The mean (standard deviation) monitor units and beam-on time was 6939 (985) and 8.10 (1.137) min, respectively. Overall the treatment was very well tolerated with no significant acute toxicity. Early follow-up evaluation revealed a good clinicoradiological response and the absence of local disease progression with no significant sequelae, implying successful application of the treatment paradigm.


CONCLUSIONS
Helical tomotherapy is ideally suited for brain-sparing holo-cranial radiotherapy with its exceptional ability of tangential beam delivery resulting in highly conformal and homogenous dose distribution across large, complex target volumes with substantial OAR sparing.
Gupta
T
T
Department of Radiation Oncology, Advanced Centre for Treatment Research & Education in Cancer (ACTREC), Tata Memorial Centre, Mumbai, India.
Mallik
S
S
Master
Z
Z
Phurailatpam
R
R
Laskar
S
S
D001921:Brain / Q000528:radiation effects; D005260:Female; D006258:Head and Neck Neoplasms / Q000532:radiotherapy*; D006801:Humans; D007223:Infant; D016403:Lymphoma, Large B-Cell, Diffuse / Q000532:radiotherapy; D008297:Male; D008875:Middle Aged; D009447:Neuroblastoma / Q000532:radiotherapy; D058958:Organs at Risk / Q000528:radiation effects; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012535:Scalp; D012878:Skin Neoplasms / Q000532:radiotherapy*; D012888:Skull Neoplasms / Q000532:radiotherapy*; D016896:Treatment Outcome; D055815:Young Adult