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Applied Radiation and Isotopes 67 (2009) 1416–1420

Contents lists available at ScienceDirect

Applied Radiation and Isotopes

0969-80

doi:10.1

� Corr

E-m

journal homepage: www.elsevier.com/locate/apradiso

A novel approach to prepare 90Y–EGMP patches for superficial brachytherapy

Sanjay Kumar Saxena a, Ashok K. Pandey b, Pankaj Tandon c, Rubel Chakravarty a, A.V.R. Reddy b,Ashutosh Dash a,�, Meera Venkatesh a

a Radiopharmaceuticals Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, Indiab Radiochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, Indiac Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085, India

a r t i c l e i n f o

Keywords:90Y–EGMP patches

Superficial tumors

Leachability

43/$ - see front matter & 2009 Elsevier Ltd. A

016/j.apradiso.2009.02.059

esponding author. Tel.: +91 22 25595372; fax

ail address: adash@barc.gov.in (A. Dash).

a b s t r a c t

A novel method to prepare 90Y–EGMP patches has been developed for brachytherapy applications.EGMP

films of 1 cm�1 cm size, incorporating �185 MBq of 90Y were prepared and sealed between thin plastic

sheets with uniform distribution of 90Y. The leachability of 90Y from radioactive patches was less than

0.01%. There was no leakage of radioactivity from radioactive patches, when tested in water or saline.

The studies related to establish therapeutic efficacy of these patches are warranted.

& 2009 Elsevier Ltd. All rights reserved.

1. Introduction

Superficial malignancies and in particular skin cancer is oftenfound especially in light skined people. Different modes oftreatment such as surgery (Manternach et al., 2003; Neumannet al., 2006), cryosurgery (Kuflik, 2004), skin graft excision, lasertherapy (Campolmi et al., 2002), chemotherapy (Midena et al.,2000), immunotherapy, photodynamic therapy, radiation therapyetc., are used for management of these cancers. Local destructionand surgery are some of the preferred choices of clinicians, butthese become difficult in case of tumors at sites, which are noteasily accessible. Chemotherapy, in general, is used after surgeryin order to prevent recurrence of disease at a later stage. Suchtumors can be successfully treated by delivering localizedradiation dose to the affected lesion without causing undueradiation dose and injury to the surrounding normal tissues.Radionuclide therapy by intravenous or intra arterial injection andintracavitory instillation of specially formulated radiopharmaceu-ticals is also a preferred method to deliver the radiation doses toselective target tissues (Hoefnagel, 1991). This unique treatmentmodality, which is also an alternative for or adjuvant to externalbeam therapy and chemotherapy, however has not been widelyreported for the management of superficial tumors. Radiotherapywith low energy orthovoltage X-ray machines or megavoltageelectron beam machines has been reported for the treatment ofskin cancers (Shimm and Cassady, 1994). Teletherapy or externalbeam therapy can be given by means of machines located at adistance from the body using kilovoltage X-ray or electron beams.However, in brachytherapy, the radiation dose is delivered by

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: +91 22 25505151.

implanting radioactive source within or close to the cancerouslesion. The therapeutic effect of radiation depends upon the doseof radiation, size of area irradiated and the dose fractionation. Thetotal dose imparted to the tumor, dose to healthy tissues, dose tothe paramedical staff etc., have to be taken into considerationbefore finally deciding for radiation therapy. In order to optimallyutilizing the beneficial effects of radiation therapy, it is desirableto design a radiation source that can deliver adequate radiationdose to the tumor surface uniformly, ensuring minimum dose tothe surrounding normal tissues. It is feasible to have a source ofhigh energy b� radiation that can be applied to the tumor like apatch or bandage for a pre-determined time and that could beremoved easily after the required dose has been imparted to theaffected lesion. Such radioactive patches should be easy to preparein desired shape and size according to the requirement ofoncologists and should also be cost-effective. Mould brachyther-apy using high-energy beta emitters has the advantage overexternal beam therapy, since the former does not need expensivetherapeutic units and the treatment procedure is simple andnoninvasive. The therapeutic application of beta emitting radio-nuclides as brachytherapy sources in the form of 166Ho-patcheshas been reported earlier for the treatment of skin cancers (Leeet al., 1997). Development of radioactive patches incorporatingother beta emitting isotopes, such as 32P, 90Y and 188Re have alsobeen reported by some researchers (Mukherjee et al., 2002; Jeonget al., 2003; Saxena et al., 2007). However, many of the reportedprocedures for source preparation are cumbersome and radio-active patch preparation is difficult and time consuming resultingin poor logistics, specially in case of short lived radionuclides suchas 90Y. In comparison with other beta emitting isotopes, its higherbeta energy is an attractive feature, making it a preferredradionuclide for therapeutic applications. It is a pure beta emitterwith maximum beta energy of �2.27 MeV and its beta emissions

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have �3.6 mm mean range in soft tissues, with a therapeuticrange of the order of �2.14 mm. Hence, sources made with 90Y canbe effectively used to treat superficial lesions without undueexposure to underlying healthy tissue. We have optimized aprocedure to prepare 90Y–EGMP patch sources in a reproduciblemanner, the details of which are described in this paper.

2. Materials and methods

90Y in desired chemical form was obtained from its parent 90Sr,from an in-house 90Sr–90Y electrochemical generator. Non-radio-active EGMP films were prepared in Radiochemistry Division,BARC. Optical density measurements of exposed GAF-Chromicfilms were carried out with Model-37–443 radiochromic densit-ometer. GAF-Chromic films and radiochromic densitometer bothwere procured from M/s Nuclear Associates (A Division of M/sVictoreen Inc., USA) were used for the measurement of opticaldensity in autoradiography experiments. GM counter and liquidscintillation counter were available in our Division. All otherchemicals used in our work were of GR/AR grade procured fromwell-established manufacturers.

3. Experimental

Experimental conditions for quantitative uptake of 90Y onEGMP films were optimized. Uniformity of 90Y in radioactivepatches was ascertained by autoradiography using GAF-Chromicfilms. Leachability of 90Y in water and saline solutions wasdetermined at ambient temperature. Radioactive 90Y–EGMPpatches were sealed between two plastic sheets and hot waterimmersion leakage and surface contamination tests of encapsu-lated patches were carried out.

3.1. Preparation of EGMP films

The monomer, ethylene glycol methacrylate phosphate (EGMP)along with a cross linker, methylene bis acrylamide (MBA), and anUV initiator (a,a-dimethoxy-a-phenyl acetophenone) were dis-solved in tetrahydrofuran (THF) and dimethylformamide (DMF)mixture. The amounts of cross linker and monomer were adjustedin the polymerization solution to get 5 mol% cross-linking. Theamount of UV initiator was taken as 1 wt%. For grafting of EGMP inthe membrane, the microporous host polypropylene membrane(6 cm�6 cm size, 80% porosity, 0.48mm pore size and 110mmthickness) was soaked in the polymerizing solution and graftingsolution filled membrane was sandwiched between two trans-parent polyester sheets. Sandwiched membrane was exposed to365 nm UV light in a multilamp photoreactor (Heber Scientific,model no. HML-SW-MW-LW-888) for optimized duration. Afterirradiation in the photoreactor, the membrane was washedthoroughly with THF, methanol and distilled water to removethe un-grafted components, and conditioned with 0.25 M NaCl.The membrane sample was dried for 8–10 h under vacuum andweighed to obtain the weight of dry membrane. Dried membranewas cut into 1 cm�1 cm size for studies of uptake of yttrium.

3.2. Elution of 90Y from electrochemical radionuclide generator

An in-house 90Sr–90Y radionuclide generator was used forobtaining 90Y in highly concentrated and desired chemical form.90Y was separated from parent 90Sr by selective electrodepositionof 90Y on a platinum electrode (Chakravarty et al., 2008). Theelectrolysis was carried out in 90Sr(N03)2 feed solution, (pH�2–3)containing �1.85 GBq (50 mCi) of radioactivity by applying a

constant potential of �2.5 V on the cathode, with respect tosaturated calomel electrode. After the first electrolysis, thecathode was removed and transferred to a new cell containing0.003 M nitric acid solution (pH�2–3) and its polarity wasreversed. 90Y was redeposited on a new platinum cathodeadopting the same conditions as above. The 90Y deposited in thecathode after the second electrolysis was dissolved in acetatebuffer (0.6 M, pH�4.75) or 0.1 M HCl or HNO3, to get 90Y indifferent chemical forms that could be directly used for studyingthe incorporation of 90Y in strips of EGMP membrane.

3.3. Incorporation of 90Y in EGMP films

EGMP films of 1 cm�1 cm size were taken in a small quartzcompartment and solution containing different amounts oftrivalent yttrium ions was added to it. Experiments were carriedout at different pH and the same amount of carrier free 90Y wasadded as radiotracer in all the cases. The total reaction volume inall the experiments was maintained as 1 mL. At the end of eachexperiment, an aliquot of the left over solution was assayed byliquid scintillation counting and subsequently residual radio-activity present in left over solution was estimated. The radio-activity associated with films was calculated indirectly by takingthe difference of originally added activity and left over residualactivity remaining in the solution. Experimental conditions suchas pH, reaction time etc., were optimized for quantitativeincorporation of trivalent yttrium in EGMP films and radioactivesources containing higher amounts of 90Y were prepared bytreating the EGMP films with precalculated amount of 90Y underoptimized experimental conditions. Sources so prepared weresubsequently sealed between two 40mm thick plastic sheets bylamination.

3.4. Uniformity of 90Y in EGMP patches

Uniformity of 90Y in radioactive EGMP films was checked byautoradiography using GAF-Chromic radiosensitive films. Sourcescontaining �37 MBq each of 90Y were prepared under optimizedconditions and were subsequently sealed between two 40mmthick plastic films to make them safer for handling. Such sourceswere used for exposing radiosensitive GAF-Chromic films for aperiod of 5 h. At the end of the experiment, optical density wasmeasured at various points of exposed film. Difference in thevalues of optical density was taken as a measure of variation ofdistribution of 90Y at various points of source.

3.5. Leachability of 90Y–EGMP patches

Leachability of unencapsulated radioactive patches containing�37 MBq of 90Y was determined at ambient temperature in wateras well as saline for a period of 48 h (AERB SS-3 (Rev-1), 2001).90Y–EGMP patches were immersed in test solution and an aliquotof test solution was assayed after the test. Total radioactivityleached out in test solution was subsequently calculated fordetermining the leachability of radioactivity patches.

3.6. Leakage and surface contamination of 90Y–EGMP patches

90Y–EGMP patches containing �37 MBq of radioactivity weresealed within two plastic sheets of 40mm thicknesses. Theencapsulated radioactive patches were subjected to hot waterimmersion test by immersing them in 100 mL of water at 50 1C for5 h. After the test, the radioactivity associated with an aliquot ofthis solution was estimated by liquid scintillation counting. Thevalue of radioactivity associated with aliquot was subsequently

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used to determine the total activity released in entire testsolution. The surface contamination of these patches was alsochecked by taking wet swipes from the surface of radioactivepatches and subsequently counting of the samples in GM counterof known efficiency.

4. Results and discussion

The aim of the present investigation was to develop an easyand reproducible technology for the large scale preparation of 90Yskin patch for brachytherapy applications.

Since, 90Y was required to be incorporated in a solid matrixfilm, polymer was chosen as the basic matrix. An approach inwhich a reactive polymer of desired shape could be kept incontact with a solution containing 90Y to retain the activity on thesurface was considered to be an ideal option to prepare largenumber of sources with uniform activity.

In order to prepare a 90Y patch source, the radionuclide 90Y wasrequired in the solution form with high specific activity and highradioactive concentration. The most suitable mode of obtaininghigh radioactive concentration was to obtain the radionuclde froma radionuclide generator. An electrochemical procedure theseparation of 90Y from 90Sr was successfully developed in ourDivision to obtain high purity 90Y with a very high radiochemicalyield (Chakravarty et al., 2008). The experimental set-up ofelectrochemical generator is shown in Fig. 1. 90Y obtained fromelectrochemical generator was used in preparation of 90Y–EGMPradioactive patches. The two-cycle electrolytic separation techni-que with an overall 90Y yield of 90–93%, corrected for decay wasfound to be the best choice to obtain 90Y with high specificactivity. 90Y so obtained was of high radionuclidic purity(�99.99%), with negligible 90Sr contamination.

D.C.Power

StirrerMagnetic

PP

SE

Parent-daughterElectrolyte

PlatinumPlate

V

Potentiostat

Vent

Fig. 1. Schematic diagram of the electrol

On account of its ability to extract lanthanide ions, EGMPmembrane was selected as base matrix for incorporation of 90Y.The degree of EGMP-grafting in membrane samples was deter-mined from the knowledge of weights of membrane samplebefore (Winitial) and after grafting (Wfinal) using following gravi-metric relation

Degree of grafting ð%Þ ¼ðW final �W initialÞ

ðW initialÞ� 100

The degree of grafting in the films prepared for our experimentswas found to be 450 wt%. When yttrium ions are treated withEGMP, Y+3 ions co-ordinate with two units of EGMP wherein twoPQO groups form co-ordinate bonds, and 3H+ liberated fromOH groups provide electrostatic attraction towards trivalent ions.90Y-patches were prepared by treating EGMP films with 90Ysolution in presence of known amount of carrier. We attempted tooptimize the various process parameters in order to obtain 90Ypatches of desired activity with good reproducibility, suitable fortherapeutic applications.

As shown in Table 1, uptake of yttrium was found to be pHdependent and most favorable in the pH range of 2.5–4.5.Incorporation of yttrium in EGMP films was found to beindependent of the chemical form of Y3+ ions and hence theuptake of yttrium in acetate as well as in nitrate form was almostcomparable. The incorporation of yttrium in EGMP was favorableand hence quantitative uptake of trivalent yttrium ions wasnoticed even at ambient temperature. Adequate amount ofyttrium could be incorporated in EGMP films of 1 cm�1 cm sizeand when the reaction of 90Y was carried out at ambienttemperature in presence of varying amounts of carrier inactiveyttrium ions, �99.1% of 90Y could be incorporated in presence of�100mg of yttrium carrier. The effect of amount of carrier onpercentage uptake of yttrium is shown in Table 2.

Argon GasCylinder

latinumlate

CE Referencelectrode

Inert GasBubbling

ysis cell used for 90Sr–90Y generator.

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Table 1Effect of pH on uptake of yttrium.

S. no. pH (%) Uptake mean7SD

1 2.0 83.974.6

2 2.5 94.771.9

3 3.0 97.172.1

4 3.5 98.370.4

5 4.0 99.170.2

6 4.5 98.470.6

7 5.5 85.871.6

n ¼ 3; reaction volume—1.0 mL; temperature-ambient; carrier—100mg.

Table 2Effect of carrier on uptake of yttrium.

S. no. Amount of carrier (mg) (%) Uptake mean7SD

1 50 98.371.2

2 100 99.170.4

3 150 96.372.1

4 200 94.971.7

5 250 93.670.6

6 300 92.871.5

7 350 91.571.3

n ¼ 3; reaction volume—1.0 mL; temperature-ambient; pH—3.5–4.0.

Fig. 2. Autoradiograph of 90Y–EGMP patch.

Table 3Variation of optical density.

Position no. Optical density (OD) (%) Variation from Mean OD

1. 2.87 1.7

2. 2.88 1.37

3. 2.96 1.37

4. 2.94 0.68

5. 2.96 1.37

Time of exposure-5 h; source activity—37 MBq.

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In order to ascertain uniform distribution of 90Y on the film,autoradiography examination was carried out. The autoradiographobtained by exposing GAF-Chromic film with 90Y–EGMP patch isshown in the Fig. 2. The variation of optical density at variouspoints of exposed GAF-Chromic film revealed that the distributionof yttrium in radioactive patches was uniform within71.7%variation as shown in Table 3. Leachability of 90Y from radioactivepatches in saline as well as in water after immersion in theseliquids for 48 h was found to be less than 0.01% of source activity,

indicating that the patches can be used for therapeutic applica-tions safely. Lamination of the flexible EGMP membrane film inproportion to the shape of the patch was carried out withpolyethylene film to behave like a sealed source. It acts as a barrierto prevent the leaching of activity from the source. The flexibilityof sources could be maintained even after sealing them withintwo plastic sheets of 40mm thicknesses. The dose reduction due toby such encapsulation was found to o1.5%. The leakage andsurface contamination tests revealed that the total release ofradioactivity in both these tests was almost negligible and far lessthan the permissible level of maximum 185 Bq.

The efficacy of 90Y skin patches for skin cancers therapy hasbeen demonstrated by our group (Mukherjee et al., 2002) andtherefore animal experiments were not pursued further. In orderto evaluate the effectiveness of the 90Y–EGMP membrane and toinsure maximum patient safety, quality-control procedures werecarried out.

The radiolabeled membrane could be placed on the skin cancerlesion for treatment. Each patch containing different activitycontent prescribed by the dermatologic surgeon and the radiationoncologist could be prepared at the hospital premises by adjustingthe ratio of active and inactive yttrium in the feed. The size andshape of the 90Y patches could be easily adjusted according to thesize and shape of the tumors to be treated. The radiationemanating from the opposite side of 90Y patches could be shieldedby covering the patches with aluminum foils of appropriatethickness. Use of 90Y would be a cost-effective proposition sincethe 90Y is obtained from a 90Sr–90Y generator system, and theparent 90Sr has a long half life.

5. Conclusion

90Y could be successfully incorporated in EGMP polymer filmsand sources containing �185 MBq/cm2 could be prepared withextremely good reproducibility. These patches with desiredflexibility, were prepared by initially adjusting the percentagegrafting of EGMP during the preparation of polymer films. Qualityevaluation of 90Y–EGMP patches suggests that these can befurther evaluated for accessing their clinical utility in superficialbrachytheapy.

Acknowledgments

Authors wish to thank Dr. V. Venugopal, Director, Radio-chemistry & Isotope Group for his encouragement and continuedsupport. We gratefully acknowledge the help provided by HealthPhysicist of our Division during counting of radioactive samples.We also thank Mr. Pritam Bansode, Radiopharmaceuticals Divisionfor preparing necessary engineering drawings required for thework.

References

AERB SS-3 (Rev-1), 2001, Testing and Classification of Sealed Radioactive Sources.Campolmi, P., Brazzini, B., Urso, C., Ghersetich, I., Mavilia, L., Hercogova, J., Lotti, T.,

2002. Superpulsed CO2 laser treatment of basal cell carcinoma withintraoperatory histopathologic and cytologic examination. Dermatol. Surg. 28(10), 909–912.

Chakravarty, R., Pandey, U., Manolkar, R.B., Dash, A., Venkatesh, M., AmbikalmajanPillai, M.R., 2008. Development of an electrochemical 90Sr–90Y generator forseparation of 90Y suitable for targeted therapy. Nucl. Med. Biol. 35, 245–253.

Hoefnagel, C.A., 1991. Radionuclide therapy revisited. Eur. J. Nucl. Med. 18,408–431.

Jeong, J.M., Lee, Y.J., Kim, E.H., Chang, Y.S., Kim, Y.J., Son, M., Lee, D.S., Chung, J.K.,Lee, M.C., 2003. Preparation of 188Re-labeled paper for treating skin cancer.Appl. Radiat. Isot. 58, 551–555.

ARTICLE IN PRESS

S.K. Saxena et al. / Applied Radiation and Isotopes 67 (2009) 1416–14201420

Kuflik, E.G., 2004. Cryosurgery for skin cancer: 30-year experience and cure rates.Dermatol. Surg. 30 (2), 297–300.

Lee, J.D., Park, K.K., Lee, M.G., Kim, E.H., Rhim, K.J., Lee, J.T., Yoo, H.S., Kim, Y.M., Park,K.B., Kim, J.R., 1997. Radionuclide therapy of skin cancers and Bowens diseaseusing a specially designed skin patch. J. Nucl. Med. 38, 697–702.

Manternach, T., Housman, T.S., Williford, P.M., Teuschler, H., Fleischer, A.B.,Feldman, S.R., John chen, G., 2003. Surgical treatment of nonmelanomaskin cancer in the medicare population. Dermatol. Surg. 29 (12),1167–1169.

Midena, E., Angeli, C.D., Valenti, M., de Belvis, V., Boccato, P., 2000. Treatment ofconjunctival squamous cell carcinoma with topical 5-fluorouracil. Br. J.Ophthalmol. 84, 268–272.

Mukherjee, A., Pandey, U., Sharma, H.D., Pillai, M.R.A., Venkatesh, M., 2002.Preparation and evaluation of 90Y skin patches for therapy of superficialtumours in mice. Nucl. Med. Commun. 23, 243–247.

Neumann, H.A.M., Krekels, G.A.M., Verhaegh, M.E.J.M., 2006. Treatment of 208extensive basal cell carcinomas with Mohs micrographic surgery. J. Eur. Acad.Dermatol. Venereol. 6 (3), 217–225.

Saxena, S.K., Ram, R., Shinde, S.N., Tandon, P., Dash, A., Venkatesh, M., 2007. A facilemethod to prepare 32P-patches for the treatment of superficial cancers, In:Proceedings of Nuclear and Radiochemistry Symposium (NUCAR), pp. 549–550.

Shimm, D.S., Cassady, J.R., 1994. The skin. In: Cox, J.D. (Ed.), Moss’ RadiationOncology: Rationale, Technique and Results, seventh ed. Mosby-Year Book Inc.,St. Louis, pp. 99–118.