hepatocellular carcinoma ( hcc ) is the fifth most common tumour worldwide and even ranks second in terms of mortality [ 1 , 2 ] . moreover , only a small number of cases are eligible to curative treatments , such as resection or transplantation . for the rest , a wide range of palliative treatments can be proposed , among which are chemoembolisation and radioembolisation with lipiodol [ 36 ] . lipiodol is an oily medium which has shown to be selectively retained in tumour when administered intra - arterially . lipiodol has been labelled with iodine-131 [ 8 , 9 ] , rhenium-188 [ 10 , 11 ] , yttrium-90 [ 12 , 13 ] , holmium-166 , and lutetium-177 . some early trials with phosphorus-32 have also been described . however , to date , only the first two have been used in man , the iodine-131-labelled lipiodol ( lipiocis ) having a market authorisation . relabelled lipiodol seems the most promising one , being able to circumvent the major drawbacks of iodine-131 ( long half - life , medium beta energy , strong gamma energy , and cost ) . indeed , rhenium-188 has ideal properties for molecular radiotherapy ( emax = 2.1  mev with a maximum tissue penetration of 11  mm , e = 155  kev ( 15% ) , t1/2 = 17  h ) and has the added advantage of being available on a cost - effective day - to - day basis thanks to its generator mode of production . first attempts to label lipiodol with radioisotopes other than iodine-131 were done with a covalently bond chelate , with disappointing results [ 12 , 20 ] . it was thus postulated that solubilisation of a lipophilic chelate into lipiodol would make a suitable  radiolabelling  . it is in that context that the centre eugne marquis and the ecole nationale suprieure de chimie de rennes ( enscr ) decided to combine respectively their experience on radioembolisation of hcc with i - lipiodol [ 9 , 2427 ] and knowledge of technetium and rhenium coordination chemistry [ 2831 ] , to label lipiodol with a rechelate of their own design . previous studies at the enscr led to the preparation of a new class of complexes with perthiobenzoate and dithiobenzoate moieties [ m ( phcs3)2 ( phcs2 ) ] which structure is given in figure 1 , both with rhenium   and with technetium-99 . these complexes were nicknamed sss , standing for  super - six sulphur  , because the metal core is coordinated by six sulphur atoms . one of the interests of these complexes is that the metal is at the oxidation state + iii , which is more stable than + v and they are , in addition , susceptible to bifunctional approach to design target - specific agents [ 31 , 34 ] . the sss complex was subsequently prepared with technetium-99  m , using a freeze - dried kit method ( containing 0.75  mg tin chloride , 75  mg calcium gluconate , and 25  mg sodium chloride , diluted 1/10 ) , initially in a view of lymphocytes labelling . the complex was obtained , according to procedure shown in figure 2 , with good yield and good radiochemical purity ( > 95% ) . moreover , it proved to be very stable and to be quite lipophilic ( log  p = 3.33 ) . the method previously described by jeong et al .   was used , that is , once the complex is synthesised , 2 - 3  ml of lipiodol ultra - fluide ( simply called lipiodol ) is added . the mixture is shaken then centrifuged at 2200  g for 10  min , and the phases are carefully collected . tc - sss / lipiodol is thus obtained with a 96  2.8% yield and a final rcp of 92.5  2.6% . rhenium-188 is obtained in the form of perrhenate by elution of a w / re generator , similar to the mo / tc generator . the major difference lies in the necessity of postelution concentration to obtain high - volumic activity ( up to 20  gbq / ml with a 37  gbq generator ) , due to the lower specific activity of w compared to mo , necessitating a bigger alumina column ( see figure 3 ) . indeed , rhenium-188 , though its chemistry is very close to that of technetium-99  m , is much harder to reduce and tends to reoxidise very quickly . volume , ph , heating temperature , and reaction time were also modulated . eventually , the solution came with the adjunction of potassium oxalate , which eases the reduction of perrhenate by expanding its coordination sphere , as shown by boschi et al . . finally , the optimal procedure was determined as kit formulation : 0.8  mg sncl22h2o ( dissolved in 0.1  ml hcl 1  m ) , 7.5  mg sodium gluconate , 30  mg ascorbic acid , and 40  mg potassium oxalate . this freeze - dried kit is reconstituted in 0.5  ml saline , and the perrhenate ( 0.5  ml of saline ) is then added . after 15  min at room temperature , 20  mg of sodium dithiobenzoate is added , and the solution is heated for 30  min at 100c , to provide the re - sss complex , as a precipitate . 2 - 3 ml of lipiodol is added to the mixture , which is then centrifuged , as previously described with technetium-99  m.re-sss/lipiodol was obtained with a 87  9.1% yield and a final rcp of 93  3.4% . labelling was further optimised to reach 97.3  2.1% yield and a final rcp of 94.1  1.7% . a new efficient and stable labelling of lipiodol was described . however , for activities above 1850  mbq ( therapeutic activities ) , the labelling yield decreased dramatically . consequently , the synthesis had to be further improved , in view of hcc treatment . kit formulation was tuned , and reaction conditions were slightly modified . a freeze - dried kit ( 4  mg sncl22h2o ( dissolved in 0.1  ml hcl 1  m ) , 30  mg sodium gluconate , 30  mg ascorbic acid , 40  mg potassium oxalate ) is reconstituted in 0.5  ml saline , and the perrhenate ( 0.5  ml of saline ) is then added . after 15  min at room temperature , 40  mg of sodium dithiobenzoate is added , and the solution is heated for 15  min at 100c , to provide the re - sss complex , as a precipitate . 2 - 3 ml of lipiodol is added to the mixture , which is then stirred with a vortex . after 10  min of centrifugation ( 2200  g ) , both phases are separated , and the lower phase ( radiolabelled lipiodol ) is carefully recovered . re - sss / lipiodol is obtained with a 98.56  1.2% yield and a final rcp of 92.52  2.3% and is stable for at least 7 days . having to handle high activities of re to prepare therapeutic doses can result in an excessive radiation exposure to the operator , and particularly at the finger tips . the authors have thus developed an automated procedure to limit the radiation exposure to the personnel , as well as to have a reproducible synthesis , in view of clinical trials . the remote - controlled system employed is a taddeo module ( comecer , castel bolognese , italy ) and is displayed in figure 4 . the main change was the substitution of the centrifugation step and the use of solid - phase extraction cartridges to purify the product . the final yield is somewhat lower than with manual preparation ( 52.68  9.6% ) , due to the loss of activity in the tubing and the vessels ( figure 5 ) . impact of the automation was studied with thermoluminescent dosimeters ( tld ) fixed at the finger tips , and , respectively , 80 and 58% decreases in the right - hand and left - hand doses were shown . personal dose equivalents  measured with continuously readable epd dosimeters  were reduced by 38 and 43% for hp ( 10 ) and hp ( 0.07 ) , respectively . mean dose equivalents ( msv / gbq ) for both hands are displayed in figure 6 . good targeting and stability of radiolabelled lipiodol were investigated in vivo , in healthy pigs , then in hepatoma - bearing rats . the radiotracer was injected through the hepatic artery , and biodistribution was checked by scintigraphy and ex vivo countings . autoradiography was also done , to assess more precisely the fixation of the radiotracer . 
 tc - sss / lipiodol could be useful for carrying pretherapeutic dosimetry studies , as is performed with tc - maa for y - labelled microspheres . it was injected into the hepatic artery of healthy pigs and showed a biodistribution pattern similar to that of i - labelled lipiodol in human . fixation was stable and showed only mild digestive elimination 24  h after injection . scintigraphic scans ( figure 8) and ex vivo countings ( figure 9 ) show the quasiexclusive hepatic fixation , with a slight pulmonary uptake ( not visible on scintigraphy ) . the fixation also proved to be stable with a very weak urinary and intestinal elimination . at the microscopic level , the radioactivity is mainly  and rapidly  located in the sinusoids ( figure 10 ) , as lipiodol alone , where it is retained . unfortunately , no porcine model of hepatocarcinoma was described , and attempts to develop one with human hepatocarcinoma cells in immunodepressed pigs with cyclosporine gave no results . on the contrary , it was thus decided to investigate the tumour uptake of re - sss / lipiodol in rats inoculated with n1s1 hepatocarcinoma cell line . our team , in collaboration with j. p. benoit 's team in angers , developed a new technique for the tumoral inoculation as well as the intra - arterial injection . results showed preferential hepatic uptake , with a weak to moderate pulmonary uptake , and , most importantly a good tumour retention ( figure 11 ) . the tumour - to - liver ratio increases from 2.9  1.5 to 4.1  0.7 between 1  h and 48  h. however , this model has its limitations , notably the fact that a single small tumour in a rat is probably too small for rhenium-188 to be truly effective . indeed , when compared to i - lipiodol , the latter proved to be more effective . to assess the safety of the radiotracer , a toxicity study  acute and chronic  has been undertaken in dogs ( beagles ) , with the nonradioactive analogue re - sss / lipiodol , prepared in the same conditions as for clinical preparation ( sterile gmp kits , same amounts of reactants , remote - controlled procedure ) . the re - sss / lipiodol was injected for less than 24  h after preparation . for the first phase ( 7 days ) , animals ( 3 males + 3 females ) received a single injection at d1 , and for the second one , animals ( 2 males + 2 females ) received one dose at d1 and one at d30 . no change related to the parenchyma of organs or at the site of injection has been detected , either at d7 or at d59 . this study thus demonstrated lack of toxicity of re - sss / lipiodol , opening the way for the injection in human . files were submitted to the relevant authorities , that is , french agency for the safety of health products ( afssaps ) , french nuclear safety authority ( asn ) , and ethical committee ( comit de protection des personnes , cpp ) , and approval was eventually granted . a phase 1 escalation dose study was thus initiated ( lip - re-1 , eudract no . this study will comprise 4 dose stages , ranging from 1.85 to 7.4  gbq . each stage will comprise 3 to 6 patients , depending on the toxicity ( or lack thereof ) of the compound . to date , 5 patients have been injected ( 3 with 1.85  gbq and 2 with 3.7  gbq ) . for illustration , spect / ct scans of the third patient 1  h after injection of 1.85  gbq of re - sss / lipiodol are shown in figure 14 , displaying the good targeting of the radiopharmaceutical candidate ( tumour - to - nontumour max ratio = 15 ) . this patient ( 71-year - old male , with multifocal hcc , in progression after sorafenib treatment ) responded well to the treatment , and his disease was stabilised for a couple of months . in conclusion , we have developed a potential hcc treatment by radioembolisation , with a phase 1 clinical trial currently in progress . its clinical relevance has now to be demonstrated , and its efficiency and tolerance have to be compared to other existing therapeutic options .
hepatocellular carcinoma ( hcc ) is the 5th most common tumour worldwide and has a dark prognosis . for nonoperable cases , 
 metabolic radiotherapy with lipiodol labelled with -emitters is a promising therapeutic option . 
 the comprehensive cancer centre eugne marquis and the national graduate school of chemistry of rennes ( enscr ) have jointly developed a stable and efficient labelling of lipiodol with rhenium-188 ( emax = 2.1  mev ) for the treatment of hcc . 
 the major  milestones  of this development , from the first syntheses to the recent first injection in man , are described .