INTRODUCTION

Reported cases of port-site tumour metastases following laparo-scopic cancer surgery have raised concerns about the role oflaparoscopy in the surgical treatment of cancer. Furthermore,experimental studies have shown that there is a greater likeli-hood of tumour seeding and port-site recurrences followinglaparoscopy with CO2 insufflation than following conventionalopen surgery.1,2 The mechanism by which port-site metastasesoccur is likely to be multifactorial, with the choice of insufflationgas used to create the pneumoperitoneum likely to play a sig-nificant role.3–6 A large number of experimental studies usinglaparoscopic cancer models have demonstrated that laparoscopywith CO2 insufflation is associated with a significant increase in theincidence of port-site metastases, as well as wider disseminationand implantation of intra-abdominal tumour, when comparedwith laparotomy or gasless laparoscopy.2,7,8 Further studies from theDepartment of Surgery and elsewhere, have also demonstratedthat helium, an inert gas, performs better than CO2 in regard to port-site recurrences and metastases.4,6,9

Various experimental studies suggest that metabolic changesinduced by CO2 pneumoperitoneum may be responsible for this problem.3,4 Carbon dioxide has been shown to cause localimmune suppression, and a release of inflammatory mediatorsin the peritoneum.10 Helium, when used for insufflation, is not asso-ciated with local or systemic acid-base changes and, unlike CO2,causes minimal alterations in the measures of immune func-tion.11,12 Therefore, it is possible that inert gases could be associatedwith a lower incidence of port-site metastases and less overalltumour cell spread following laparoscopic insufflation. For thisreason, we have sought to determine whether the advantages ofhelium insufflation that we have previously demonstrated in anexperimental model, are applicable to inert gases in general.

METHODS

This study utilized a previously described model for laparo-scopic cancer surgery that uses an immune-competent syngeneic ratmodel.13 Twenty-four Dark Agouti (DA) rats were randomized toundergo laparoscopic insufflation with one of the following fourgases (six rats in each group): CO2, helium, nitrogen and argon. A suspension of tumour cells derived from a native mammaryadenocarcinoma cell line, was injected into the peritoneal cavity ofthe rats at the time of surgery, and the pattern of subsequenttumour implantation and growth was evaluated.

All rats were anaesthetized for the surgical procedures, andthe respiratory status of the animals was monitored through-out surgery. Surgical procedures were performed under sterileoperating conditions. A pneumoperitoneum was established

ANZ J. Surg. 2002; 72: 254–257

ORIGINAL ARTICLE

TUMOUR IMPLANTATION FOLLOWING LAPAROSCOPY USINGDIFFERENT INSUFFLATION GASES

ANURAG GUPTA, DAVID I. WATSON, TANYA ELLIS AND GLYN G. JAMIESON

University of Adelaide Department of Surgery, Royal Adelaide Hospital, Adelaide, South Australia, Australia

Background: Because of the possibility of intraperitoneal seeding and port-site recurrences following laparoscopicsurgery, the role of laparoscopy in cancer surgery remains controversial. Previous experimental studies have suggested that chem-ical, metabolic and immunological changes following carbon dioxide (CO2) insufflation may be responsible for this phenomenon.Earlier experimental studies done by the University of Adelaide Department of Surgery have also shown that helium insufflationis associated with none of the adverse changes brought about by CO2 insufflation. Helium insufflation is also associated withlower rates of intra-abdominal tumour spread. The aim of this study was to determine whether these identified benefitsapply to inert gases in general.Methods: Twenty-four Dark Agouti rats were randomized to undergo laparoscopy with 40 min insufflation using one of thefollowing four gases (six rats in each group); CO2, helium, argon and nitrogen. A tumour cell suspension was injected into theabdominal cavity at the beginning of laparoscopy. The rats were killed 7 days after surgery, and the peritoneal cavity and portsites were examined for the presence of tumour.Results: Rats undergoing helium insufflation, had the least number of port-site recurrences and the least amount ofintraperitoneal tumour spread. Argon and nitrogen pneumoperitoneum were associated with a large number of port-siterecurrences and widespread tumour seeding. The effect of CO2 insufflation was intermediate.Conclusion: The choice of insufflation gas influences the incidence of port-site metastases and the degree of intraperitonealtumour spread following laparoscopic cancer surgery. The reduced port-site recurrences and intraperitoneal spread that followedhelium pneumoperitoneum is likely to be a unique property of this gas rather than a property of inert gases in general.

Key words: laparoscopy, tumour, spread, gases, insufflation.Abbreviations: CO2, carbon dioxide; DA, Dark Agouti.

A. Gupta MS; D. I. Watson MD, FRACS; T. Ellis BSc (Hons); G. G. Jamieson MS, FACS, FRACS, FRCS.

Correspondence: Associate Professor David I.Watson, University of AdelaideDepartment of Surgery, Royal Adelaide Hospital, North Terrace, Adelaide,SA 5000, Australia. Email: david.watson@adelaide.edu.au

Accepted for publication 5 December 2001.

using a Veress needle placed through a lower midline abdominalstab wound, and a disposable mini-laparoscopy cannula (UnitedStates Surgical Corporation, Norwalk, CT, USA) was used toprovide access for a 2-mm mini-laparoscope (Imagyn, LagunaNiguel, CA, USA) with an attached conventional laparoscopycamera. One additional ‘port’ was inserted under laparoscopicvision: an 18 gauge cannula in the right hypochondrium thatwas left open throughout the procedure to vent the insufflation gas. After commencing gas insufflation and placing the ‘ports’, a 200-µL volume of tumour cell suspension (containing 2 × 107 tumour cells) was introduced into the left upper quadrant of the peritoneal cavity under laparoscopic vision through aninsulin syringe. The tumour cell suspension was prepared using apreviously described method2,13,14 with previous studies used todetermine the appropriate tumour cell load introduced into theperitoneal cavity for the current study. Gas was insufflated atthe rate of 0.6 L/min and a pressure of 2 mmHg for 40 min afterintroducing the tumour cells into the peritoneal cavity, and aconstant gas flow was maintained throughout the venting (righthypochondrial) cannula. The ‘ports’ were then removed, and theskin at each wound site was closed using a single suture.

Seven days later, the rats were killed and their abdomenswere opened and examined for the presence of tumour. Theabdomen was divided into six sectors (Fig. 1). Each sector wasinspected for the presence of peritoneal tumour deposits, and thetumour density in each sector was scored using the peritonealcancer density index proposed by Eggermont et al.:14 0 = nointraperitoneal tumour; I = less than three minute tumour foci; II = moderate tumour; III = abundant or confluent tumour. Rep-resentative samples were examined histologically to confirm themacroscopic assessment. Analysis of tumour spread by sectors was

used to better quantify different degrees of tumour spread in dif-ferent groups. The port sites were also examined specifically forevidence of tumour implantation.

The protocol for this study was approved by the AnimalEthics Committee of the Institute of Medical and VeterinaryScience, Adelaide, South Australia.

RESULTS

Before surgery, and 7 days following surgery, the mean weights of the rats in each study group were similar. All rats in the CO2,helium and nitrogen gas groups remained well for the duration ofthe study. One rat from the Argon insufflation group died imme-diately following surgery, probably because of anaesthesia over-dose. This rat was excluded from the data analysis. Another rat inthe Argon group died 5 days after surgery. This rat had grossdissemination of tumour throughout the peritoneal cavity, andwas thought to have died because of widespread tumour dissemi-nation. While this rat died early, all sectors were heavily infiltratedby tumour, and no other factors were evident which were likely tohave contributed to death (e.g. sepsis). Hence, this rat remained inthe study group for data analysis.

Table 1 summarizes the overall pattern of tumour growthfound in each study group. The majority of the rats had tumourgrowth somewhere within the peritoneal cavity, although four of thesix rats which underwent helium insufflation did not developtumour growth anywhere in the peritoneal cavity, and only seven outof 36 sectors in the helium group had tumour implantation. The ratsin the argon and the nitrogen groups had more extensive tumourinvolvement than the rats undergoing CO2 insufflation: 29 out of 30 sectors in the argon group (P < 0.0001, helium vs argon) and 30 out of 36 sectors in the nitrogen group (P < 0.0001, helium vsnitrogen) had tumour involvement (Table 2), and all rats hadextensive intra-abdominal tumour implantation. If analysed using thecriteria of ‘tumour present anywhere vs absent from the peri-toneal cavity’, the difference between the helium group and the other

TUMOUR IMPLANTATION FOLLOWING LAPAROSCOPY 255

Fig. 1. Division of the abdominal cavity into 6 sectors, and locationof trocar entry sites. L = Laparoscope cannula,V = Venting cannula,I = site of injection of tumour cells.

Table 1. Peritoneal tumour index (number of sectors involvedwith each tumour density grade)

Tumour Grade CO2 Helium Nitrogen Argon

0 15 29 6 1I 7 1 11 4II 8 4 9 8III 6 2 10 17

Table 2. Analysis of tumour involvement in each abdominalsector (numbers in columns 2–4 in table represent number ofsectors containing macroscopic tumour, regardless of densitygrade, for each study group)

Sector number CO2 Helium Nitrogen Argon(n = 6) (n = 6) (n = 6) (n = 5)

1 0 0 3 52 4 0 4 53 4 1 5 54 6 2 6 55 3 2 6 56 4 2 6 4

groups approached but did not reach statistical significance (2/6 vs6/6; P = 0.06, Fisher’s exact test).

Port-site involvement was also at its lowest following helium gas insufflation (Table 3). Three out of 12 port sites had tumourinvolvement in the helium group, while 6 out of 12 and 9 out of 12port sites were involved following CO2 and nitrogen insufflationrespectively. All 10 port sites were infiltrated by tumour followingargon insufflation.

DISCUSSION

Despite the wide acceptance of laparoscopic techniques in manyareas of abdominal surgery, the role of laparoscopy in cancersurgery remains controversial.15–17 This is partly because of con-cerns about intraperitoneal seeding of tumour during laparo-scopic surgery, as well as the potential for tumour recurrence inlaparoscopic port sites. These concerns have been supported byevidence from experimental studies using small animals which havedemonstrated that intra-abdominal tumour growth and meta-stasis are more likely following laparoscopic procedures withCO2 insufflation than following open surgery.1,2 Nevertheless,laparoscopic surgery may also confer advantages to patientsundergoing surgery for cancer, for example: less postoperative pain,earlier return to normal physical activity, and better preservation of systemic immune function.18 Hence, strategies which reduce the likelihood of tumour growth and metastasis following laparoscopic cancer surgery are important, because they mayincrease the safety of laparoscopy for patients undergoingsurgery for cancer.

Previous studies from the department of surgery that used asmall animal model5,13 have shown that gasless laparoscopy mayhave advantages over CO2 insufflation, namely, a lower inci-dence of port-site metastases and less intraperitoneal tumourspread. These studies suggest that some factor inherent in theuse of gas insufflation during laparoscopy could be contributing to tumour metastasis following laparoscopic cancer surgery.However, the non-uniform elevation of the abdominal wallwhich is usually encountered with gasless laparoscopy is aproblem during clinical surgery. In particular the reduced exposureof the abdominal flanks renders this a poor option for laparo-scopic colectomy. In a randomized trial of conventional versusgasless laparoscopic surgery, the disadvantages of gaslesslaparoscopy (impaired exposure, the requirement to convert toconventional pneumoperitoneum and technical difficulty), out-weighed the potential advantages.19

Several recent experimental studies, including studies fromthe department of surgery, have shown that substituting CO2

with helium as the insufflation gas reduces the incidence ofport-site tumour recurrences and intraperitoneal metastases.3,4,6

The use of an alternative insufflation gas is a potentially attractivesolution to the potential problem of CO2-induced tumour spread.Other studies have shown that CO2 insufflation is associatedwith local tissue acidosis, respiratory changes, alterations in the

host immune system, and the release of inflammatory mediatorsinto the peritoneal cavity.10,20 Further studies in both animalsand humans suggest that replacing CO2 with helium insufflationreverses the adverse metabolic effects of CO2 pneumoperi-toneum.11,12,21 Being an inert gas, helium does not generate local orsystemic acid–base shifts, and it is associated with minimalhaemodynamic and immunological alterations.22

For these reasons, we hypothesized that the physiological andmetabolic changes caused by CO2 insufflation are responsiblefor the high incidence of these metastases or port-site recur-rences in experimental models, and the reduced incidence ofthese problems following helium insufflation is because of the inertnature of the gas. If this hypothesis were correct, then it would bereasonable to expect that similar benefits would be associatedwith the use of other inert gases, including argon and nitrogen.However, in the present study argon and nitrogen insufflationwere followed by increased tumour growth, and consequentlyour original hypothesis is not substantiated. The benefits seenfollowing helium insufflation demonstrated in previous studiescannot be extrapolated to other inert gases. These findings arepartly supported by the results from a previous study reportedby Eisenhauer et al.23 which demonstrated that argon insuffla-tion can be associated with significant haemodynamic effects,and for this reason argon may not be physiologically inert,despite argon being chemically inert.

When considering the outcome of our current study and othersimilar studies that have used experimental models, we shouldremain cognizant of the potential pitfalls associated withdirectly translating these outcomes to clinical surgical practice.18 Itis possible that species differences between humans and ratsmay account for at least some of the reported outcomes, and for thisreason the results from our study and studies reported by otherworkers should be used to construct hypotheses for further evalu-ation and confirmation in clinical studies, rather than to bedirectly applied in clinical practice. Nevertheless, the use ofexperimental models does enable efficient testing of a range ofhypotheses before clinical trials are undertaken.

As a consequence of our current study, we believe that thepotential advantages of minimal metabolic effect and acid-basealteration associated with insufflation with inert gases ingeneral, is unlikely to be relevant to the problem of port-sitetumour recurrence or intraperitoneal tumour spread followinglaparoscopic cancer surgery. Nevertheless, helium insufflationhas been consistently shown to be associated with a lower rate ofdevelopment of port-site metastases in several different experi-mental models.3,4,6,9 It is possible, therefore, that helium gascould be toxic to tumour cells, or some other factor inherent inhelium insufflation could be the reason for reduced tumourmetastasis in experimental models. This warrants further evaluation,in experimental models as well as in clinical trials.

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ment of the risk of tumour recurrence after laparoscopicsurgery. Surgery 1998; 123: 427–31.

2. Mathew G, Watson DI, Rofe AM, Baigrie CF, Ellis T,Jamieson GG. Wound metastases following laparoscopic andopen surgery for abdominal cancer in a rat model. Br. J. Surg.1996; 83: 1087–90.

3. Jacobi CA, Sabat R, Bohm B, Zieren HU, Volk HD, Muller JM.Pneumoperitoneum with carbon dioxide stimulates growth ofmalignant colonic cells. Surgery 1997; 121: 72–8.

256 WATSON ET AL.

Table 3. No. port sites with tumour present

CO2 Helium Nitrogen Argon

Port sites involved 6 3 9 10Total no. of port sites 12 12 12 10

P < 0.0001 (chi-squared test).

TUMOUR IMPLANTATION FOLLOWING LAPAROSCOPY 257

4. Neuhaus SJ, Ellis T, Rofe AM, Pike GK, Jamieson GG, WatsonDI. Tumor implantation following laparoscopy using differentinsufflation gases. Surg. Endosc. 1998; 12: 1300–2.

5. Watson DI, Mathew G, Ellis T, Baigrie CF, Rofe AM,Jamieson GG. Gasless laparoscopy may reduce the risk of port-sitemetastases following laparoscopic tumour surgery. Arch. Surg.1997; 132: 166–8.

6. Neuhaus SJ, Watson DI, Ellis T et al. Wound metastases following different insufflation gases. Surgery 1998; 123:579–83.

7. Bouvy ND, Marquet RL, Jeekel H, Bonjer HJ. Impact of gas(less) laparoscopy and laparotomy on peritoneal tumor growth andabdominal wall metastases. Ann. Surg. 1996; 224: 694–700.

8. Jones DB, Guo LW, Reinhard MK et al. Impact of pneumo-peritoneum on trocar site implantation of colon cancer inhamster model. Dis. Colon Rectum 1995; 38: 1182–8.

9. Jacobi CA, Wegner F, Sabat R, Volk T, Ordemann J, MullerJM. The impact of laparoscopy with carbon dioxide versushelium on immunologic function and tumor growth in a ratmodel. Dig. Surg. 1998; 15: 110–16.

10. Watson RW, Redmond HP, McCarthey J, Burke PE, BouchierHayes D. Exposure of the peritoneal cavity to air regulatesearly inflammatory responses to surgery in a murine model. Br. J.Surg. 1995; 82: 1060–5.

11. Neuberger TJ, Andrus CH, Wittgen CM, Wade TP, KaminskiDL. Prospective comparison of helium versus carbon dioxidepneumoperitoneum. Gastrointest. Endosc. 1996; 43: 38–41.

12. Rademaker BM, Bonnenberg JJ, Kalkman CJ, Meyer DW.Effects of pneumoperitoneum with helium on hemodynamicsand oxygen transport: a comparison with carbon dioxide. J. Laparoendosc. Surg. 1995; 5: 15–20.

13. Mathew G, Watson DI, Rofe AM, Ellis T, Jamieson GG.Adverse impact of pneumoperitoneum on intraperitonealimplantation and growth of tumor cell suspension in an experi-mental model. ANZ J. Surg. 1997; 67: 289–92.

14. Eggermont AM, Steller EP, Marquet RL, Jeekel J, Sugerbaker PH.Local regional promotion of tumor growth after abdominalsurgery is dominant over immunotherapy with interleukin-2 andlymphokine activated killer cells. Cancer Detect. Prev. 1988;12: 421–9.

15. Kruitwagen RF, Swinkels BM, Keyser KG, Doesburg WH,Schijf CP. Incidence and effect on survival of abdominal wallmetastases at trocar or puncture sites following laparoscopy orparacentesis in women with ovarian cancer. Gynecol. Oncol.1996; 60: 233–7.

16. Wexner SD, Cohen SM, Ulrich A, Reissman P. Laparoscopiccolorectal surgery – are we being honest with our patients? Dis. Colon Rectum 1995; 38: 723–7.

17. Nduka CC, Monson JR, Menzies Gow N, Darzi A. Abdominalwall metastases following laparoscopy. Br. J. Surg. 1994; 81:648–52.

18. Allardyce RA. Is the port site really at risk? Biology, mecha-nisms and prevention: A critical view. ANZ J. Surg. 1999; 69:479–85.

19. Johnson PL, Sibert KS. Laparoscopy. Gasless vs. CO2 pneumo-peritoneum. J. Reprod. Med. 1997; 42: 255–9.

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Port-Site and Wound Recurrences in Cancer Surgery.Edited by M. A. Reymond, H. J Bonjer and F. Hockling. Heidelberg:Springer-Verlag, 2000, 136 pages. ISBN number 3-540-66929-9.Euro 99.95.

This short text is the definitive reference text on port-sitewound recurrences associated with laparoscopic surgery. Theincidence, pathogenesis and prevention of port-site woundrecurrences are discussed in great detail, and this discussion isinterspersed with an occasional case report. The individualchapters are excellent reviews of the literature and have beenwritten by leaders in laparoscopic research with a particularbent towards laboratory research and the potential mechanisms ofimplantation. The book is a mandatory read for anyone plan-

ning a masters thesis or publishing clinical or laboratory studiespertaining to port-site recurrences. However, it is probably tooheavy to be a light read for a surgeon with an interest in laparo-scopic cancer surgery.

Overall the book is well laid out: a researcher would find it easyto define the chapters of particular interest. Despite multiplecontributing authors, a standard writing style and layout isachieved in all chapters. This is an excellent reference text but aheavy book to read for interest only.

Director of Research MICHAEL J. SOLOMON, FRACSUniversity of Sydney and Central SydneyDepartments of Colorectal SurgerySydney, NSW, Australia

BOOK REVIEW