Physical Models For Time Dose & Fractionation Strandqvist Plot Cohen’s Formula Fowler Concepts NSD Model TDF model Target Theory L Q model BED calculation of different fractionation regimen

1. PHYSICAL MODELS FOR
TIME DOSE & FRACTIONATION

5. TIME DOSE MODELS
• Strandquist was 1st to device scientific
approach for correlating Dose to OTT to
produce an equivalent biological isoeffect
(Isoeffect Curve)

16. Radiation Induced Cell Death

22. c

26. 35# of 2 Gy/# once a day for 5 days/ week, for an overall
treatment time of 7 weeks; that is, 35F 2 Gy/7 weeks
Treatment: conventional

27. hyperfractionation more effective
for tumor control (84vs.89.8Gy10),&
also better for late effects (116.7 vs.
111.4 Gy3)
CLINICAL PRACTICE

29. concomitant boost is hotter than
conventional schedule (6 WEEKS)
for both early(84.4Gy vs72Gy) and
late effects(113.4Gy vs100 Gy)
Compared with hyperfractionation,
however, this concomitant boost is
almost the same for late
effects(113.4Gy vs 111.4Gy) but less
effective for early effects including
tumor control(84.4 Gy vs89.8Gy)

31. • Direct comparison of CHART with the previous examples in terms of Gy10 and
Gy3 is meaningless because CHART has an overall time of only 12 days
compared with 6 or 7 weeks for the other schedules

37. MARCH META-ANALYSIS
2006
2010
2017
The Lancet, Volume 368, Issue 9538, Pages 843 - 854, 2 September 2006

38. 15 Randomized Trials of Varied Fractionation (1970-1998)
PATIENT CHARACTERISTICS
7073 patients
Tumours sites: mostly oropharynx and
larynx
hyper fractionated
accelerated
accelerated with
total dose reduction
Overall survival was
the main endpoint
median follow up:6 yr

39. benefit Conventional vs Altered Hyper fractionation vs
Accelerated fractionation
1. Locoregional
control
Loco regional control
6.4 %times higher
benefit was higher with hyper
fractionated radiotherapy
( OS 8% at 5 years) than with
accelerated radiotherapy
2. Survival benefit absolute benefit of 3·4% at
5 years with altered
fractionated radiotherapy,

40. UPDATE (2017)

44. THANKYOU