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Table 1 Normal tissue dose tolerance limits for 4-fraction stereotactic body radiation therapy

From: Dosimetric feasibility of stereotactic body radiation therapy as an alternative to brachytherapy for definitive treatment of medically inoperable early stage endometrial cancer

Site

4-fraction SBRT

Data point

Reference

Reference limit

Reference BED (α/β = 10)

Current BED (α/β = 10)

Volume

Threshold dose (Gy) per fx

Bladder

       
 

<1 cc

8.93

1 cc

RTOG 0938

<105% Rx

67

67.6

 

<2 cc

4.60

2 cc

Institutional*

4.8 Gy × 4

--

--

 

<15 cc

4.50

15 cc

TG-101

5.6 Gy × 3

26.2

26.1

 

90%

7.65

D10%

RTOG 0938

<90% Rx

53.9

54.0

 

50%

4.25

D50%

RTOG 0938

<50% Rx

24.7

24.2

Rectum

       
 

<1 cc

8.93

1 cc

RTOG 0938

<105% Rx

67

67.6

 

<2 cc

4.60

2 cc

Institutional*

4.8 Gy × 4

--

--

 

<3 cc

8.08

3 cc

RTOG 0938

<95% Rx

58.1

58.4

 

<20 cc

6.50

20 cc

TG-101

8 Gy × 3

43.2

42.9

 

90%

7.65

D10%

RTOG 0938

<90% Rx

53.9

54.0

 

80%

6.80

D20%

RTOG 0938

<80% Rx

45.8

45.7

 

50%

4.25

D50%

RTOG 0938

<50% Rx

24.7

24.2

Sigmoid colon

       
 

<2 cc

4.80

2 cc

Institutional*

4.8 Gy × 4

--

--

 

<20 cc

6.50

20 cc

TG-101

8 Gy × 3

43.2

42.9

Other bowel

       

Small bowel

<5 cc

4.75

5 cc

TG-101

5.9 Gy × 3

28.1

28.0

Large bowel

<20 cc

6.50

20 cc

TG-101

8 Gy × 3

43.2

42.9

Femoral Heads

       
 

Point

6.89

Max

RTOG 0938

<81% Rx

46.6

46.5

 

<10 cc

4.59

10 cc

RTOG 0938

<54% Rx

27.2

26.8

  1. These are proposed guidelines that were used as constraints in the current study. References for each parameter are listed.
  2. * In accordance with our institutional per-fraction brachytherapy policy.
  3. Abbreviations: SBRT stereotactic body radiation therapy, fx fraction, BED biological effective dose, Rx prescription dose, D(x)% dose to x percent of the volume, RTOG Radiation Therapy Oncology Group, TG-101 stereotactic body radiation therapy Task Group 101.