Iodine-125 interstitial brachytherapy for experimental liver cancer

Journal of Medical Colleges of PLA 2007;22(2)

87

Iodine425 interstitial brachytherapy for experimental liver cancer

ZHANC

(s

3, 1, YAN Jian-jun ( @ ) , HUANG Liang ) , LIU Xiang-hua(&mT;iJk) , ZHOU W e i - p i n g ( R % Y ) , YAN Yi-qun' (YLg#)

ZHOU Fei-guo

(

Cai-feng ( $1

8@ ) ,

Department of Heputic Surgery. Eastern Hepatobiliary Hospital, Second Military Medical University, Shanghai 200438, China [Abstract]

Objective: To study the effect of iodine-1 25 interstitial brachytherapy on liver cancer. Meth-

ods : Animal model of human liver cancer was established by injecting SMMC-7721 cells cultivated in vitro subcutaneously into the flank of BALB/c nude mice. Nude mice with tumor of 5 mm in diameter were randomly divided into 2 groups (n=10). One iodine-125 seed of apparent activity 0.8 mCi was implanted into the center of tumor in treatment group, whereas an inactive seed was implanted in control group. The othe r 20 nude mice with tumor reaching 10 mm in diameter were also treated as above. The size of tumor was determined weekly after implantation. and pathological examination and blood routine were taken on the 28"' day. Results: Tumor growth was obviously inhibited in treatment group of tumor of 5 mm in diamet e r , and there was statistically significant difference in tumor volume between treatment and control groups (P
[Key words]

Iodine-125 interstitial brachytherapy is a newly developed radiotherapy for malignant tumor,

Establishment of animal model

BALB/c

nude mice were purchased from Shanghai SLAC

which is characterized by small trauma, high radia-

Laboratory Animal Limited Company. All were

tion dose in target area, lasting effect, mild injury

male, healthy, aged 3 to 4 weeks, and weighed 18

to peripheral normal tissue, and easy radioprotec-

t o 22 g. Cultivated SMMC-7721 cells(in logarith-

tion. This technique has already been used to treat

mic growth phase, 3 X 107/ml density) were sub-

some kinds of solid tumors such as prostate carci-

cutaneously injected into the flank of nude mice.

How ever, up to now, there is

0. 1 ml per mouse. A white nodule of 2 or 3 mm in

little literature on its application to treat primary

diameter grew in the flank about one week after in-

liver cancer. In the present study, we aimed to in-

oculation.

noma very

vestigate

the

effect

iodine-1 25

of

interstitial

brachytherapy on experimental liver cancer.

Implantation of iodine-125 seeds

seeds (model CIAE-6711) were provided by ATB Biomedical Engineering

MATERIALS AND METHODS

Iodine-1 25

Company.

&. Technology Limited

Animals bearing tumor were anes-

SMMC-7721 cell strain was pre-

thetized by intraperitoneal injection of ketamine

sented by professor YTN Zheng-feng, director of

hydrochloride ( 0 . 025 mg/g). First, the assistant

Department of Molecular Oncology of Eastern

pinched the tumor tightly, and rhe operator percu-

Hepatobiliary Hospital.

SMMC-7721 cells were

taneously stabbed into the center of tumor with an

cultivated by means of adherent cell culture in

implanting needle. The needle was subsequently

Cell culture

vit ro

.

connected with a radiation-proof gun loaded with iodine-125 seeds and a seed was gently put into the core of tumor with a needle rod. T h e n , the needle

*

:Corresponding author. E-mail

:

yiqunyan@2lcn. com

was pulled out quickly and the point of puncture

Journal o f Medical Colleges o f PLA 2 0 0 7 ; 2 2 ( 2 )

88

all seeds were retrieved and iodine-125 seeds were

Statistical analysis Data were presented as m e a n f SD. t test was performed for analysis of

preserved in sealed lead pots due to the residual ac-

variance between groups using SAS 8 . 0 software.

pressed for a while. After the experiment finished,

tivity.

Animal grouping

Twenty nude mice with tu-

mor of 5 mm in diameter were randomly divided in-

RESULTS Tumor growth

Tumors of 4 to 6 mm in di-

to 2 groups (n=10 ) . One iodine-125 seed with ap-

ameter grew in the flank of nude mice about 2

parent activity 0. 8 mCi was implanted into the core

weeks after subcutaneous inoculation of SMMC-

of tumor in treatment group, whereas an inactive

7721 cell suspension ( 0 . 1 m l , 3 X 107/ml density).

seed was implanted in control group. T h e other 20

T h e size of tumor reached 8 t o 10 mm in diameter

animals bearing tumor reaching 10 mm in diameter

about 5 weeks after inoculation. T h e rate of tumor

were also treated as above. In treatment group,

forming was 98 %.

animals were caged individually, with 40 to 50 cm

outward protuberance and good activity were char-

distance between two cages. Nude mice in control

acteristics of the tumors.

group were caged together, 5 per cage.

Irregularly globular shape,

Based on the outward

Changes of tumor volume after implantation After implantation of iodine-125 seed of appar-

protuberance and good activity of the tumor, the

ent activity 0. 8 mCi (29. 6 M B q ) , tumor growth

experimenter could pinch it with his fingers and

was inhibited in treatment group of tumor of 5 mm

measure its diameter with a straight ruler directly.

in diameter. Tumor volume did not notably in-

After implantation, maximum diameter ( A 1 and

crease in the former 2 weeks and began decreasing

minimum diameter ( B ) were measured weekly.

in the latter two weeks.

And the formula 0. 5 X A X B2was used to roughly

group, tumors continued to grow and tumor vol-

calculate the tumor volume. All animals were sac-

ume obviously increased week after week. There

rificed 4 weeks after implantation. At first, fast

was very significantly statistical difference in tu-

cardiac puncture exsanguinated and blood routine

mor volume between treatment and control groups

were taken. T h e n , the tumor was resected com-

on the 71h,141h,21thand 281h days after implantation

pletely and split across the core of tumor to assess intratumoral necrosis. Pathological examination of

(P
tumor was done, and other organs including the

of 10 mm in diameter. T u m o r volume increased in

heart, lung, liver, kidney and spleen were also ex-

both t w o groups every week and no significant dif-

amined.

ference was found (P>O. 05, T a b 2).

Results acquirement

However, in control

Tab 1 Changes of tumor volume after implantation in tumor of 5 mm in diameter (n=10, m e a n f S D , m m 3 ) T i m e after implantation ( d )

Group Treatment Control

“
0

39.25+ 14. 63 41.33+15.27

7 44. 50+17. 15b 75.75125.22

14 45. 2 5 f 1 7 . 38b 172.00k54.38

21 37. 35+-14. 86b 476.90k12.70

28 31. 05+14. 27b 1082. 80*246.73

01 us control group

Tab 2 Changes of tumor volume after implantation in tumor of 10 mm in diameter (n=10, m e a n f S D . mm3) Group Treatment Control

T i m e after implantation ( d ) 0 185.24f66.58 179.56i64.37

7 526. 9 5 1 1 8 1 . 3 3 5 0 4 . 2 5 5 1 6 7 . 78

14

1 043.10k219.71 1 204.135289.41

21 1 447.081161.38 1 660.87Tt313.36

28 2 041.62k379.99 2 173.35f363.02

Journal of Medicul Colleges of P L A 2007 ;22(2)

Pathological results

89

O n the 28Ih day after

ring in tissue around the seed, but relatively, the

treatment in tumor of 5 mm in diameter, it was

scope of necrosis was tiny. Similar result was not

found that tumor tissue around the iodine-125 seed

found in control group.

revealed marked necrosis and softening.

In the

Radiation injury

Counts of total white blood

residual tissue, loose arrangement of tumor cells,

cells, neutrophile granulocytes and lymphocytes in

intracellular karyopyknosis and reduced plasma,

treatment group were lower than those in control

and diffused distribution of a deal of cell debris

group, and the difference between t w o groups was

were shown clearly under light microscope. N o

statistically significant (P
visible necrotic zone was found in tumor in control

significant difference in counts of red blood cells

group. Furthermore, oncocytes around the inac-

and platelets, and hemoglobin quantities between

tive seed were still in the condition of active

treatment and control groups. T h e results were

growth, e. g. tight contact with each o t h e r , un-

recorded in Table 3 and Table 4. Appearance and

clear cell boundary, with karyomegaly , anachro-

pathology of t h e heart, lung, liver, kidney and

masis and many karyomitotic figures inside cell nu-

spleen in treatment group were basically normal,

clei. Four weeks after treatment in tumor of 10

with no radiation injury.

m m in diameter, there was a little necrosis occur-

Tab 3

Blood routine on the 28thday after implantation in tumor of 5 mm in diameter

Groups

RBC (X 10“ /L)

HGB (g/L)

Treatment

9. 80+0. 61

136. 9 0 1 1 0 . 51

Control

9.78i-0. 55

135. 6 0 3 ~ 1 0 . 1 2 989. 9 0 k 1 5 7 . 40

PLT

WBC

( x1 o 9 / ~ )

( x109/~) 970. 2 0 f 1 4 1 . 8 6

NEU

( x109/~)

LYM

(x 1 0 9 / ~ )

3.37$-0.133~

0.19+0.07~

0.

4. 6 9 i 0 . 5 1

0.47+0.10

0.57k0.11

Ogb

‘P
Tab 4

Blood routine on the 28Ihday after implantation in tumor of 10 mm in diameter (n=lO, m e a n i S I ) )

RBC

HCB

( X lO’*/L)

(g/L)

9. 80t0.54

138. 301-9. 20

9.81*0.

136. 7 0 f 1 0 . 31

Groups

Treatment Control

69

WBC

PLT

( x1 0 9 / ~ )

( x 1091~)

1 015. 70+101. 97 986. 6 0 k 1 0 8 . 3 4

NEU

( x1 0 9 / ~ )

LYM

(

x 109/~)

3.17k-O. 6Eib

0 . 1 7 k O . 07‘

0. 1 6 1 0 . 0 7 h

4. 4 8 f 0 . 55

0.47-&0.10

0.45+0. 09

‘P
DISCUSSION

pared with traditional external beam radiotherapy, interstitial brachytherapy has many features : ( 1 )

Interstitial brachytherapy with implantation of

Radioactive seeds are implanted directly into the

radioactive seeds is a kind of radiotherapy, which

interior of t u m o r , thus the lethal effect on target

is used t o treat malignant tumor by permanently

tissue is strong; ( 2 ) Biological reactions are obvi-

implanting radioactive seeds into tumor o r tissue

ously enhanced by continuous irradiation, with no

invaded by t u m o r , and gradually killing target tis-

interval ; ( 3 ) Because of Low activity and short ef-

sue with rays emitted consistently from the seeds.

fective distance of radioactive sources, the injury

Recently. this technology has developed rapidly

to surrounding normal tissue is slight.

due t o successful preparation of secure radioactive

Iodine-125 interstitial brachytherapy is indi-

nuclides such a s iodine-125 and palladium-103

cated to treat isolated o r countable solid tumors. It

which emit low energy rays, technical progress in

has been reported in the literature that the thera-

ultrasound and C T imaging, and production of

peutic effects on prostate carcinoma and brain tu-

computed 3D treatment planning systemc3’. Com-

mor a r e definitec””. In addition, some researchers

Journal of Medical Colleges of P L A 2007;22(2)

90

think that local recurrence of non-small cell lung

histocompatibility. It is easy to implant seeds into

cancer can be controlled by implanting seeds into

tissue and after implantation, seeds are not easy to

residual tumor during

displace.

Iodine-125

Apparent activity of iodine-1 25 seeds

brachytherapy has already been utilized in several

which

are

clinically

applied

to

interstitial

domestic hospitals in recent

However,

brachytherapy for malignant tumor usually ranges

there is very little published information about its

from 0 . 1 to 1. 0 mCi(3. 7-37 MBq) , with the dose

application to treating primary liver cancer. Liver

rate from 8 t o 10 cGy/h. Although both activity

cancer is very common in our country, and surgical

and dose rate are not high, via continuous irradia-

resection is the major method for curing liver can-

tion of gammar rays, iodine-125 seeds can effec-

cer. Unfortunately, i t is noticed that there are

tively kill tumor cells in target area. Considering

many patients who have no chance of getting any

the effective scope of a single seed might be small,

operation. The main reasons are that tumors lie in

we therefore used iodine-125 seeds of slightly high

the depth of liver parenchyma, that tumors are

activity ( 0 . 8 mCi) and selected tumors in a little

near to important introhepatic structure, or that

short diameter (5 m m , 10 mrn) to study the effect

patients have severe liver cirrhosis or suffers liver

of iodine-125 seeds on tumor growth by means of

malfunction at the same time. In the light of the

implanting seeds into the center of tumors, one

advantages such as small trauma, high dosage in

seed per tumor.

target area and minor injury t o normal tissue, io-

T o our knowledge, only when oncocytes in a

dine-1 25 interstitial brachytherapy may be theoret-

certain site of tumor obtain essential therapeutic

ically suitable for these patients. In order t o deter-

dose, the cells will gradually come to damage and

mine whether iodine-125 brachytherapy has thera-

death; and when oncocytes in most sites of tumor

peutic effect on liver cancer, we conducted the pre-

receive therapeutic dose, the tumor will cease to

liminary empirical research in animals.

growth. After an iodine-125 seed is implanted into

SMMC-7721 cell strain and nude mice were

tumor, it actually acts as an immovable miniature

selected to establish the animal model of human

radiation source.

Following the inverse square

liver cancer. SMMC-7721 cell strain was originat-

law, the intensity of radiation declines rapidly a-

ed from human primary hepatocellular carcinoma,

long with the increasing distance away from the

so the autoploidy was very strong. Nude mice, as

seed, that is, the dose distribution of a single seed

experimental animals, were liable to develop solid

is unequal, According to this property, the effica-

neoplasm after subcutaneous inoculation of tumor

cy of iodine-125 brachytherapy should be linked to

cells due to congenital immunodeficiency. More-

the size of tumor on condition that category of tu-

over, as they lay on body surface, it was very con-

mor, activity of seed and action time are given. In

venient t o observe tumor growth and perform some

our study, after the two groups of liver cancer of

operations on them. In our experiment, one week

different size were treated with iodine-125 seeds of

after subcutaneous injection of SMMC-7721 cells,

activity 0. 8 mCi, tissue necrosis and cell damage

macroscopic nodules grew in the flank of nude

around the seeds were detected in both two

mice. The rate of tumor forming was rather high,

groups.

near t o 100%.

seeds have lethal effect on liver cancer.

These findings indicate that iodine-125 After

The features of iodine-125 nuclide include

treatment, the growth of liver cancer of 5 mm in

short half-life time (59. 6 d ) , low energy of gam-

diameter was obviously inhibited, whereas the

mar rays (35. 5 k e V ) , and short penetrating dis-

growth of liver cancer of 10 mrn in diameter was

tance of rays (approximately 1. 7 cm). The shape

not affected. T h e results demonstrate that the effi-

of iodine-125 seed is like a short rod, with 0. 8 mm

cacy of a single iodine-125 seed is related to the

4.5 mm in length. Its sealed outer

size of tumor. It is also implied that the seed has a

coating is made of titanium alloy, which has good

certain scope of lethal effect. When a tumor is

in diameter and

91

Journal o f Medical Colleges of P L A 2 0 0 7 ; 2 2 ( 2 ) within the scope, damaged and died oncocytes may increase continuously, and soon after the tumor may stop growing. O n the contrary, when a tumor is beyond the scope, all tissues outside the scope

may not suffer from lethal dose radiation and a great quantity of tumor cells may survive and multiply,

thus leading to the ongoing of

tumor

growth. From our results, it can be inferred that the effective semi-diameter of a single iodine-125 seed of activity 0. 8 mCi on liver cancer may be about 2 . 5 mm.

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( 2 ) : 122. (Received 2006-09-25, revised 2007-03-25) (Editor LI Dan-yang)