This document discusses forward intensity-modulated radiation therapy (IMRT) using the field-in-field (FIF) technique for whole breast irradiation. It begins by introducing the goals of treatment planning to deliver a uniform dose to the target volume while minimizing dose to normal tissues. It then describes how the FIF technique uses multiple subfields in addition to the main tangential fields to improve dose homogeneity. Several studies have shown that improved homogeneity decreases skin toxicities. The document evaluates different methods for generating subfields and finds the alternate subfields method provides the best dose distribution. In summary, the FIF forward planning technique improves dose uniformity in the breast compared to conventional techniques.

1. FORWARD IMRT
DR. AMRITA RAKESH
DNB RESIDENT
DEPT. OF RADIATION ONCOLOGY
BMCHRC,JAIPUR.

2. Introduction
• Prime objective for the planning : to deliver uniform dose
throughout the target volume, with adequate tumour coverage
and minimise dose to normal tissue.
• Evolution of treatment planning : conventional to 3D conformal
to IMRT.
• Most patients with early breast cancer undergo breast-
conserving treatment consisting of wide excision and post-
operative whole-breast radiotherapy. This form of
postoperative radiotherapy reduces the risk of local recurrence
and results in long-term survival similar to that obtained
with mastectomy.
• Thus, postoperative breast therapy is a standard treatment

3. • In recent years, the field-in-field (FIF) technique (i.e.,
Forward IMRT) has become a widely performed
method of administering tangential whole-breast
radiotherapy.
• The use of the FIF technique permits reductions in
the size of the high-dose region and better
homogeneity index.

4. Why homogeneity Matters?
Whole breast irradiation often leads to both acute and
long term toxicities such as :
• moist desquamation
• pain
• breast discomfort
• breast hardness
Many studies shown that toxicities were associated with
dose inhomogeneity (hot spots).

5. • Pignol et al
358 patients were randomized in a multicenter
double-blind clinical trial to either 2-dimentional
treatment planning or IMRT planning with improved
dose homogeneity.
The incidence of moist desquamation in the IMRT
group was 31.2% vs 47.8%, p=0.002
Pignol JP, Olivotto I, Rakovitch E, et al. A multicenter randomized trial of breast intensity-modulated radiation therapy to
reduce acute radiation dermatitis. J Clin Oncol. 2008 May 1;26(13):2085-92.

6. • Donovan et al
306 patients were randomized to 2D or 3D IMRT.
After 5 years 240 patients data was available for
analysis.
The 2D arm patients were 1.7 times more likely to
have changes in breast appearance than IMRT
group
Donovan E, Bleakley N, Denholm E, et al. Randomised trial of standard 2D radiotherapy (RT) versus
intensity modulated radiotherapy (IMRT) in patients prescribed breast radiotherapy. Radiother Oncol. 2007 Mar;82(3):254-
64.

7. Breast V105%
and V110%
were significantly associated
with increase in acute skin toxicity
• V110%
< 200cc: 31% grade >2 skin toxicity
• V110%
> 200cc: 61% grade >2 skin toxicity
Vicini et.al. Int.J. Radiat Oncol Biol Phys 54: 1336-1344; 2002.

8. • The use of IMRT in the treatment of the whole
breast results in a significant decrease in acute
dermatitis, edema, and hyperpigmentation and a
reduction in the development of chronic breast
edema compared with conventional wedge-based
WBRT.
Harsolia et.al. Int.J. Radiat Oncol Biol Phys 68: 1375-1380; 2007

9. • Inverse Planning:
The user specifies the
goals, the computer then
adjusts the beam
parameters to achieve the
desired outcome.
• Forward Planning:
The beam geometry i.e
beam angle, shape,
modifier, weights etc. is
first defined, followed by
calculation of the 3D dose
distribution.

10. IMRT for Breast
Radiotherapy
Many beams with different angles may help with
dose conformality, but will lead to higher doses in
lung, heart and contralateral breast
Tangential beams provide best lung, heart and
contralateral breast sparing.

12. FIELD-IN-FIELD
TECHNIQUE
• Comprises of two tangential open fields and multiple
subfields to achieve desired homogeneity.
• An open beam configuration is first calculated
and evaluated.
• 4+ subfields per gantry angle are used to produce an
optimal breast plan.
• No wedges.
FORWARD PLANNING

13. Subfields
• Generally have 1 lung block and 3 additional subfields per
gantry angle.
• Lung block is formed by fitting the MLC’s to the shape of
the lung. Aids in lateral hot spots.
• Additional subfields are generated by manually fitting
MLC’s to “hot” areas. Ex. 115%, 110%, etc…

14. • Lung block
• manual fitting of MLC’s to “hot” areas

15. Weighting of Subfields
• Generally, the open beam portion receives ~ 80%
of the dose while the subfields contribute ~20%.
• This makes FP IMRT similar to conventional
treatment .
• Minimizes effects of patient movement on target
coverage.
• Conventional breast plans are generally normalized
to 97% .
• Normalization for IMRT plans are based on
coverage.

16. Determination of the optimal method for the field-in-field
technique in breast tangential radiotherapy
Hidekazu Tanaka, Shinya Hayashi, and Hiroaki Hoshi
J Radiat Res. 2014 Jul; 55(4): 769–773.
• Several studies have reported the usefulness of the
field-in-field (FIF) technique in breast radiotherapy.
However, the methods for the FIF technique used in
these studies vary.
• There were no reports of comparisons among FIF
techniques.

17. • This study, classified the methods used for the FIF technique
into three categories :
• The single pair of subfields method -
• In the SSM, each main field was copied as a pair of subfields.
• The MLCs were manipulated to shield the areas of the breast
receiving any dose (mainly at 105–107% of the prescription
dose).
• The dose to shield the MLCs was determined such that the
isodose cloud disappears.
• This method was composed of four fields, including the main
fields.

18. • The multiple pairs of subfields method -
• Three pairs of subfields were generated.
• The MLCs were set to block the dose level at 1–
2% lower than the maximum dose (Dmax), and
this was followed by a 3–5% dose reduction
(mainly at 102–105% of the prescription dose).
• This method comprised eight fields, including the
main fields.

19. • The alternate subfields method -
• First, the medial main field was copied as the first
subfield.
• The MLCs were set to block the dose level at 1–2%
lower than the Dmax.
• Dose calculation was performed. The beam weight
of this subfield was added until the dose cloud
disappeared.

20. • Second, the lateral main field was copied as the
second subfield.
• The MLCs were set to block the dose level at 2–
3% lower than the dose blocked at the first
subfield.
• Dose calculation was performed again, and the
beam weight of this subfield was added until the
dose cloud disappeared.

21. • Finally, the medial main field was copied again as the
third subfield.
• The MLCs were set to block the dose level at 2–3%
lower than the dose blocked at the second subfield.
• After recalculation, the beam weight of this subfield
was added until the dose cloud disappeared.
• This method was comprised of five fields, including
the main fields.

23. Beam's eye view for typical
subfield. The subfield was
manipulated to shield the
areas of the breast receiving
any dose cloud.

24. • The Dmax to the PTV and the volumes of the PTV
receiving 100% and 95% of the prescription dose
(V100% and V95%, respectively) were calculated.
• The homogeneity index (HI) was calculated.

25. • RESULTS:
• This planning study included 51 patients with early
stage breast cancer: 20 with right-sided breast
cancer and 31 with left-sided breast cancer.
• The median age of the patients was 53 years
(range, 26–76 years).

26. Table
Average of dose parameters of PTV for each method
SSM (± SD) MSM (± SD) ASM (± SD)
Dmax 52.5 (± 0.7)52.2 (± 0.6)52.2 (± 0.7)
V100% 52.6 (± 16.7) 48.7 (± 14.9) 60.3 (± 14.2)
V95% 93.7 (± 4.2)93.2 (± 4.1)94.1 (± 3.5)
• The average V100% with ASM was
significantly higher than that with SSM and
MSM

27. • The ASM outperformed the SSM and MSM for two
possible reasons:
• First is that the number of subfields used is more
suitable for the population under study. When the
number of subfields is large, the dose to the PTV decreases, but
when the number of subfields is small, the full range of
advantages of the FIF cannot be fully obtained.
• The biggest advantage of the ASM is its ability to
perform dose calculation each time a subfield is
added.

28. Key note :
• Radiotherapy planning with SSM required a relatively short
time, because only a few subfields need to be generated.
• Because SSM is the simplest of the three methods, it
should be the method of choice for patients with small
breasts.
• The method most commonly reported is the one in which
multiple pairs of subfields are used. This method was
classified as MSM. The planning time is longer for this
method because of the high number of subfields.

29. • MD Anderson Cancer Centre group introduced in terms
of number of subfields, fewer subfields than MSM but
more than SSM. This method was classified as ASM.
• The most significant feature of this method is the
recalculation each time when creating subfields, and the
addition of subfields alternately.
• Of note, patients in the thin breast group derived similar
benefit with ASM and SSM.
• ASM resulted in better dose distribution regardless of
the breast size.

30. Nagoya J. Med. Sci. 77. 339 ~ 345, 2015
Evaluation of the field-in-field technique with lung blocks
for breast tangential radiotherapy
Hidekazu Tanaka et al.
• This study evaluated the FIF technique with lung
blocks for breast tangential radiotherapy.
• Compared to irradiation with physical wedges
(PWs), the use of the FIF technique permits
reductions in the size of the high-dose region.
• The impact of respiratory motion is smaller with the
use of the FIF technique than with the use of PWs.

31. • Several authors reported the advantages of lung-
blocked subfields, which help to reduce the dose
received by the lungs.
• However, the use of multileaf collimators (MLCs) to
block the lungs also results in blockade of some
parts of the planning target volume (PTV). This
could decrease the doses delivered to the PTV.
• In this study,16 patients with early-stage breast
cancer, including 9 patients with right-sided cancer
and 7 patients with left-sided breast cancer.

32. • Two opposed tangential fields were created without
PWs.
• The open field was copied as the subfields & on the
beam’s eye view, the MLCs were set to block the
hotspots.
• Then, dose calculation was performed. The beam
weight of this subfield was increased until the dose
cloud disappeared.

35. • The volumes of the ipsilateral lung receiving 20, 30,
and 40 Gy (V20Gy, V30Gy, and V40Gy,
respectively) were calculated.
• The volumes of the PTV receiving 100 and 95% of
the prescription dose (V100% and V95%,
respectively) and the mean dose (Dmean) to the
PTV were also calculated.
• The amounts of change in the FIF plan and PWs
were evaluated.

36. • In this study, lung blocks were useful for reducing
the dose delivered to the lungs, but a simultaneous
decrease in the PTV was observed.
• FIF plan was advantageous over the use of physical
wedges.

38. ique by comparing it with the electronic compensator, varian enh

40. (a) Main field without multileaf collimator (MLC) blocking.
(b)drawing MLCs to block 112 % isodose cloud
(c) drawing MLCs to block out 106 % (d) drawing MLCs to block out 102%

41. FIF gave favourable results for all aspects
when compared with other plans.

42. The “skin flash” problem in
Inverse Problem
• Conventional : margin added
to field edge to allow for
uncertainties.
• IMRT : intensity remains
“zero” outside PTV. No skin
flash

43. • So, previously tissue equivalent material where
added during planning over the breast, and then
plan were made. So, in actual setup, when MLCs
opened up, actual PTV used to be in air.

44. • But now, after forward planning, MLCs are opened
to desired width in air, to allow “skin flash”.

46. • To sum up:
• Conformality adaptions are limited
• Tangential beams are used for main field , as increasing number
of beams will increase lung dose.
• As main field is copied and subfields created to adjust beam
parameters,and then we do dose calculation- so, it is forward
planning.
• Dose homogeneity is improved.
• Less time taking.
• Simple planning.

47. THANK YOU…
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