hypofractionation

1. Dr. KIRAN SIMON PAUL
SENIOR REGISTRAR

2.  Breast-conserving surgery (BCS) with subsequent
whole breast irradiation (WBI) is considered the
standard of care for the majority of cases with early-
stage breast carcinoma
 Conventional radiotherapy after BCS uses two
tangential fields for doses of 45–50 Gy/ 1.8–2 Gy per
fraction.
 A boost irradiation with electron or photon beams to
deliver a total tumour bed dose of 60–66 Gy is
usually prescribed.

3. Why Hypofractionate
 The α/β of breast cancer is estimated to be
around 4 .
 This assumption suggests that
hypofractionated regimens should be more
effective than conventional fractionation.
 Moreover, the shorter the total treatment time,
the lower the potential of repopulation of
cancer cells, thus improving local control

4.  Multiple trials trials(START A, START B , Whelan,
RMH/GOC) indicated similar rates of loco-regional
relapse comparing the two radiation treatment
arms.
 Evaluation of breast cosmesis at a median follow-
up greater than 10 years was equivalent in both
treatment arms
 It was largely confirmed that a 13–16 fraction
regimen delivered over 3–4 weeks is as safe and
effective as 50 Gy in 25 fractions.

5. Concomitant Boost and dose
 Based on published reports available in
literature, boost doses of 10–16 Gy in 2 Gy/
fraction or 10 Gy in 2.5 Gy/fraction were
considered acceptable.
 But this further increases treatment duration
by one to two weeks

6.  A concurrent boost to the tumour bed delivering a
total dose of 48.0 Gy in 15 fractions with 3.2 Gy
per day would result in an equivalent tumour bed
dose (assuming an alpha beta ratio of 4, and
correcting for proliferation effects) in 2-Gy per
fraction of approximately 63-66 Gy in 2 Gy
fractions.

7. EVIDENCES- 40.05 GY/15# TO WHOLE
BREAST AND 48 GY/15 # BOOST TO
LUMPECTOMY CAVITY
 Scorestti et al (2012)- PhaseI-II study of hypofractionated
simultaneous integrated boost using volumetric modulated
arc therapy for adjuvant radiation therapy in breast cancer
patients : – feasible and was associated with acceptable
acute skin toxicity profile.
 De Rose Et al (2016) - Phase II trial of hypofractionated
VMAT-based treatment for early stage breast cancer: 2-
year toxicity and clinical results - 3-week VMAT-SIB course
as adjuvant treatment after breast-conserving surgery
showed to be well tolerated and was associated with
optimal local control.

8.  NRG RTOG 1005(2022): A Phase III Trial of
Hypo Fractionated Whole Breast Irradiation with
Concurrent Boost vs. Conventional Whole Breast
Irradiation Plus Sequential Boost Following
Lumpectomy for High Risk Early-Stage Breast
Cancer
 Concomitant boost with hypofractionated WBI results
in non-inferior in breast recurrence compared to
sequential boost after Conventional in high-risk
cases and reduces overall treatment time.
 No differences in toxicity or cosmetic outcome for
concomitant v sequential boost or the WBI
fractionation regimen

9. Methods
 Invasive cancer post BCS
 Any systemic therapy was allowed in neo
adjuvant or adjuvant setting allowed
 Patients with Surgical Clips in Lumpectomy cavity
 No of Patients – 30
 Time period – 2022 -23

10. Simulation and contouring
 All patients were set-up in supine position, with both
arms above the head. CT dataset was acquired with 5
mm thick adjacent slices without contrast.
 No respiratory gating was adopted.
 The clinical target volume CTV of the whole breast was
the entire mammary gland.
 CTV of the boost was the surgical bed, defined by adding
1 cm to the surgical clips placed in the lumpectomy
cavity during surgery.
 PTV was created by adding 5 mm to CTV and limiting 5
mm from skin surface and excluding ribs and lung
parenchyma

11. Plan objectives
 The treatment dose was prescribed with SIB as 40.05 Gy to the
PTV_WB and 48.0 Gy to the PTV_boost, in 15 fractions over 3
weeks, delivering 2.7 and 3.2 Gy/ fraction to each PTV Plan.
 At least 95% of the breast PTV will receive at least 95% (38 Gy) of
the whole breast prescribed dose of 40 Gy.
 At least 95% of the Lumpectomy PTV will receive at least 95% (at
least 45.6 Gy) of the boost prescribed dose of 48 Gy.
 Ipsilateral lung should receive mean dose < 10 Gy and V20 less
than 10 %(acceptable upto 20% in RTOG 1005)
 Heart V40Gy less than 3% and V18 less than 5 % (Formenti et al,
2007)
 No specific requests for mean heart dose; minimize contra lateral
lung and breast irradiation; (Formenti et al, 2007)

13. Results(Mean ± SD)
Structure parameter All patients Right left
Lung ipsi Mean 9.84±1.49 9.7±1.4 9.93±1.5
V20 14.9±3.67 15.6±3.4 13.78 ±3.77
V5 56.9±14.02 54.7±13 60.3 ± 14.57
Lung contra Mean 3.43±1.28 3.65±1.12 3.08±1.41
Heart Mean 3.45±1.0 2.89±0.67 4.29±0.83
V18 1.59±2.19 0.11±0.26 3.8±1.93
V40 0±0 0±0 0±0
Breast contra mean 2.67±0.82

14. Skin Toxicities
Grade Toxicity Description Number of cases Percentage of cases
0 No change over
baseline
11/30 36.67
1 Follicular, faint or dull
erythema/epilation/dry
desquamation/decreas
ed sweating
16/30 53.33
2 Tender or bright
erythema, patchy moist
desquamation/moderat
e edema
3/30 10
3 Confluent, moist
desquamation other
than skinfolds,pitting
edema
0/30 0
4 Ulceration,hemorrhage,
necrosis
0/30 0

15.  No Cardiac or Lung toxicities noticed in the follow up
period in any patient, although longer follow up
needed.
 Limitation – Unavailibilty of DIBH/ Respiratory
Gating technques
 We had difficulty in achieving desired dosimetry in
some of the patients with medial quadrant tumours
which led to adoption of sequential Electron boost
rather than concomitant boost

16. Conclusion
Hypofractionation with Whole breast receiving
40.05 Gy in 15 fractions with concomitant boost
to tumour bed to a dose of 48 Gy in 15 fractions
is feasible with respect to dosimetry and early
side effect profile.