BIR/IPEM, London, June 23rd

Usually

• / is assumed to be 10 for early reacting tissues (including tumours ) and 3 for late reacting tissues

• T1/2 is assumed to be 1.5 hours for both

early and late reacting tissues

Using these values the therapeutic gain will be less using HDR compared to LDR (~0.5 Gy/h) (unless a lot of fractions are used in the HDR schedule ~ 33)

BIR/IPEM, London, June 23rd

However….

Review: Stewart and Viswanathan, Cancer 2007

Randomized prospective and retrospective studies

show overall statist

ically equivalent local control,

overall survival, a

nd complication rates between

HDR and LDR.

BIR/IPEM, London, June 23rd

Endpoint T1/2 (h) Source

Erythema, skin 0.35 & 1.2 Turesson & Thames, R&O 1989

Mucositis, H&N 2-4 Bentzen et al, R&O 1996

  0.3 - 0.5 Denham et al, R&O 1995

Skin telangiectasia 0.4 & 3.4 Turesson & Thames, R&O 1989

  3.8 Bentzen et al, R&O 1999

Subcutaneous fibrosis 4.4 Bentzen et al, R&O 1999

Various pelvic complications

1.5-2.5 Fowler, R&O 1997

Published half time of repair

BIR/IPEM, London, June 23rd

Different half time for tumour and OAR

• BEDtumour,LDR= BEDtumour,HDR=

80Gy

• BEDOAR,LDR= BEDOAR,HDR

• /tumour=10 Gy /OAR=3 Gy

• t1/2,tumour = 1.5 h

C. Orton, IJROBP, 2001

HDR: 2Gy in 33 fractions

HDR: 5Gy in 10 fractions

HDR: 7Gy in 7 fractions HDR: 12.5Gy in 3 fractions