Radioimmunoguided surgery and colorectal cancer

European Journal of Surgical Oncology 1996; 22:381-396

EDUCATIONAL SECTION

Radioimmunoguided surgery and colorectal cancer

E Aftab, H. S. Stoldt, A. Testori, A. lmperatori,

M. Chinol*, G. PaganeHi*

and

J. Geraghty

Departments of General Surgical Oncology and *Nuclear Medicine, European Institute of Oncology, Milan, Italy

Radioimmunoguided surgery is a technique that aims to delineate the extent of epithelial neoplasms (primary/recurrent) and their spread (local, regional, and distant) which are not adequately visualized by conventional imaging techniques. The target lesion binds radiolabelled, tumour-associated monoclonal antibodies which are administered in the days before surgery and which bind to the target lesion. The radiotracer is detected intraoperatively using a hand-held gamma detecting probe. This identifies the extent of the tumour, involvement of lymph nodes or other organs and may allow a more complete surgical clearance of the tumour. This article provides a basic understanding of the RIGS (radioimmunoguided surgery) technique, the monoclonal antibodies which are used and outlines the advantages and limitations of this technique.

Key words: radioimmunoguided surgery; monoclonal antibodies; avidin-biotin.

Introduction

Despite advances in anti-cancer therapy and the ability to detect colon cancer at an earlier stage by the use of screening rectal examination, stool occult blood and sigmoidoscopy, survival statistics remain largely unchanged) -3 Surgery is the mainstay of treatment and patients with apparently localized disease who undergo adequate resection may present with local or widespread recurrences. In an attempt to improve prognosis, Waagensteen et al. 4'5 advocated the use of 'second-look' surgery but a high rate of negative exploration (50%), a low resectability rate and poor survival benefit have limited the use of this policy. Several other methods including the measurement of circulating levels of carcinoembryonic antigen (CEA) have also been used:-" This, together with more sophisticated imaging techniques (ultrasound, computerized tomography (CT), etc.), have met with varying results) 2-~5's° The advent of immunoscintigraphy, which entails targeting specific tumourassociated antigens with radiolabelled antibodies and their subsequent detection by the gamma camera, has complemented existing techniques in the detection of malignant disease. The major limitation of this technique was that only large tumours (2cm or greater) could be detected, t6-~8 A hand-held gamma-detecting probe was Correspondence to: F. Aftab, FRCS (Ire), Department of General Surgical Oncology, European Institute of Oncology, Via Ripamonti 435, Milan 20141, Italy. 0748-7983/961040381+ 16 $12.00/0

designed to enhance the surgeon's ability to detect and resect microscopic tumour deposits intraoperatively. The concept of tumour targeting began at the turn of the 20th century when Paul Ehlrich ~9 postulated the idea of the 'Magic Bullet' to target abnormal cells selectively on the basis of antigenic differences between normal and abnormal cells. No clinical application of this concept took place until Pressman and Keighley:° in 1948 utilized labelled antibodies for cancer detection. Shortly thereafter, in 1953, the in vivo localization of a tumour-specific antibody in an animal model was reported. 2~ The main impetus towards the development of radioimmunodetection in colorectal cancer was provided by the discovery of carcinoembryonic antigen, 22a tumour-associated antigen against which antibodies could be targeted. This was followed in 1975 by the production of monoclonal antibodies by Kohler and Milstein. 23 This proved to be a major advance in the field of immunology with several authors demonstrating their successful clinical applications over the subsequent years. 24-29 In 1978, Goldenberg et al. 3° applied these concepts towards radioimmunodetection of diverse human carcinomas. Intraoperative tumour localization, using a hand-held gamma-detecting probe (GDP), constituted the first application of radioimmunoguided surgery (RIGS) and was first described in 1984) t'32 A patient with a primary adenocarcinoma of the rectum received an injection of I mlabelled anti-CEA serum pre-operatively, and the tumour was localized with an external gamma camera. At the time of surgery a hand-held GDP demonstrated tumour activity © 1996W.B.Saunders CompanyLimited

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Table 1. Monoclonal antibodies used in colorectal cancer and their characteristics *MoAb

Antigen

Immunoglobulin

Immunogen

Source

Tumour localization

Affinity constant

B 72.3~'~7'69-'-'78

TAG 72

IgG 1

Murine

69%

2.54 x 109]M

CC 4973.74 17-1-A63'~'67'7s

TAG 72 Lipoprotein antigen CEAI"

IgG 1 IgG, A

Breast, colon, non-small lung, ovarian, gastric, pancreatic carcinoma Colon, breast Colon

Murine Murine

91.5% 75%

16.18 x 109/M

IgG~

Various

Murine

89°/,,--98%

A-5-B-7a

* MoAb=monoclonal antibody. t CEA =carcinoembryonic antigen.

in the suspicious area, both before and after tumour resection) ~Subsequently, Oredipe et a l ) 3 were able to detect a tumour load of less than 1 mm 3 in diameter in a specimen of normal human colon, not detectable by inspection or palpation. Since that time, RIGS has been the subject of increasing clinical and experimental studies.

Monoclonal antibodies Since the discovery of carcinoembryonic antigen, a large number of tumour antigens such as CA19-9, CA-54, CA195 have been studied as potential targets for radiolabelled antibodies. Over 100 different monoclonal antibodies (MoAbs) have now been described in the literature, targeted against a variety of human carcinomas. 34 Most of the antibodies which have been used in the detection of colorectal carcinomas react with a high molecular weight, tumour-associated glycoprotein TAG72. 35 This is expressed by various tumours including breast, colorectal, non-small cell lung, gastric, ovarian and pancreatic adenocarcinomas. This glycoprotein is not secreted to an appreciable extent by normal tissues36 except by secretory phase endometrium 37 and transitional colonic mucosaY The surface glycoprotein is the target of radiolabelled monoclonal antibodies. Monoclonal antibodies used in the localization of colorectal carcinomas belong to the IgG class of immunoglobulins, are murine in origin and have varying affinity constants. Table 1 describes the properties of different MoAbs used in colorectal cancer. Using antibodies in tumour targeting can pose problems. Due to tumour heterogeneity,39 only a small amount of tagged MoAb localizes per gram of tumour (<0.01%) while the remainder continues to circulate and may have toxic effects on tissues such as bone marrow. 4° Further problems include non-uniform distribution of antibodies, which is particularly acute in tumours greater than 2 cm in diameterfl Binding affinity is another variable which often leads to binding that is confined to the perivascular marginY -~ Tumour catabolism s~ and MoAb specificity8~ are further difficulties that need to be considered. Finally, as most MoAbs used in clinical practice are murine in origin, there is the potential for anaphylactic reactions: 5 At present, a major limitation of the tagged antibodies used in the RIGS technique is the long interval required between the injection of radiolabelled MoAb and surgery,

i.e. the time required by the tagged antibody to clear from the circulation in order to reduce the background signal (a mean of 24 days is required for accurate G D P determination). To overcome this problem, antibody fragments, such as F(ab)-' or Fab' (faster clearance rates), 46.47 have been used. However, these fragments may have a decreased affinity for antigen. Another method to shorten the time interval between antibody injection and surgery is based upon the 'chase' strategy. This involves ligand binding to circulating antibodies, thereby forming complexes which are efficiently removed by the liver when the tumour-bound antibody has reached its optimal concentration. This consideration has led to the development o f ' t u m o u r pretargeting',4s ~ where MoAbs and radioisotopes are administered separately. One such strategy utilizes the 'Avidin-Biotin' system 5-''53'59 in which biotinylated or streptavidin-conjugated MoAbs are first injected, followed by labelled streptavidin or avidin in a two-step approach. ~'55 A modification of the two-step approach to reduce further the background interference is based on the injection of biotinylated antibody (step 1) followed by avidin (step 2) to precipitate circulating MoAbs and simultaneously to target tumour cells, allowing 'homing in' of subsequently labelled biotin (step 3). 5~59 Tumour pretargeting offers several advantages over direct administration of labelled MoAb, in that the isotope is cleared rapidly, removal of circulating antibodies is facilitated while MoAb immunoreactivity is preserved and signal amplification can be achievedY

Isotopes and probe Radio-tracers with short half-lives were initially used in immunodetection, but these did not allow sufficient time for tissue penetration, resulting in an inadequate radiolabelled antibody tissue concentration. Several authors 6~6-' have attempted imaging 3-5 days after ~3q-labelled antibody injection, using a subtraction technique to obviate this problem. The results were not encouraging and, as a result, radioisotopes with a longer half-life and a lower energy level have been used with promising results, so far. Further considerations are toxicity, availability and the cost of the radioisotope. Existing radionuclides and their properties are listed in Table 2. The intraoperative G D P is a portable unit, 18cm long

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Table 2. Radionuclides in use

Radionuclide

Energy

Emission in KeV

Half-life

Advantages

Disadvantages

~3~I

/3 ~, ),

606 364 159

8 days

Labelling chemistry Currently in use in RIT* Labelling chemistry Optimal energy for imaging

173 247 140

67 hrs

99Tc

y /3 y

6 hrs

Dehalogenation Volatile Availability Dehalogenation Half-life Expensive Exchange for transferrin Deposition in normal liver Half-life

12.~I

),

35

60 days

~.,31

.t In

13 hrs

Availability Energy for imaging Availability Optimal energy for imaging Availability Optimal energy for imaging Most used isotope in RIGSt

Dehalogenation

* RIT = radioimmunodetection. "I"RIGS =radioimmunoguided surgery.

and angled at the tip for better manoeuvrability. It has a 12mm diameter cadmium-telluride crystal at the tip, a preamplifier and a signal processing unit. The gamma ray emissions from the radioactive source are detected by the crystal and converted into digital readouts as well as audio signals by the signal processor. The audible signal has a pitch which is proportional to the radioactivity. Newer models are gas sterilizable, have a larger crystal, an improved amplifier, and the changes in crystal mounting have improved the counting rate by a factor of almost 2.5. Skin testing is performed before MoAbs are administered to check that the patient is not allergic to the antibodies. The patient is given potassium supplements 3 to 5 days before iodine-labelled MoAbs are administered to minimize the radio-uptake by the thyroid. The operative procedure involves a thorough exploration with lysis of adhesions, if necessary, and an assessment of the primary tumour and the potential sites of local or distant spread. With the hand-held GDP, the abdominal cavity is examined systematically for increased radiolabelled MoAb uptake. Particular attention is paid to the area around the resected specimen for evidence of residual disease. No intraoperative problems specific to RIGS have been described apart from an extension ofthe operative procedure by an extra 15-20 min. No biochemical alterations in the renal, hepatic or thyroid function have been reported.

Clinical applications

Since the initial report about the successful use of the G D P in an experimental mouse model, 3~and in the clinical setting by Martin et a/.,3-"RIGS has been used extensively in patients with colorectal cancer. Different MoAbs have been used with better tumour localization properties, thereby improving the ability to detect occult tumour deposits, and to help in decision-making. In 1986, O'Dwyer et al. 63 reported their experience in 18 patients with colorectal neoplasm (five primary and 13 recurrent tumours). The site of the tumour was correctly localized in 60% (3/5 cases) of primary tumours and 100% (13/13 cases) of recurrent tumours. In this study, only 50%

of liver metastasis were localized. Probe-associated findings resulted in changes in the operative strategy in 16%o of patients (Table 3). Sickle-Santanello e t al. 64 evaluated 38 patients with colorectal cancer using a different antibody (B72.3) and localization of primary and recurrent tumours was 89% (8/9 sites) and 82% (47/57 sites), respectively. Occult tumour deposits were identified in 26% of cases which resulted in a modification of the surgical procedure in all cases. Major abdominal and hepatic resections were avoided due to the presence of extrahepatic disseminated disease detected using RIGS (Table 3). There were two false-positive results relating to RIGS in this study (one an ischaemic colonic ulcer and the other a suspicious area on the anterior abdominal wall). Surgery was performed 16 days (range: 5-34 days) after antibody injection. The use of RIGS was reviewed in 66 patients with diverse solid tumours by Martin e t al. 65 Good tumour localization rates were achieved (83% and 79% in primary and recurrent colorectal cancer, respectively) but RIGS failed to identify tumour in 13/66 (20%) cases. The two most important sites of metastasis from recurrent colorectal cancer in this study were liver and pelvis. The probe correctly localized 17/22 (77%) liver metastases and 12/14 (86%) pelvic recurrences. RIGS also correctly identified 3/4 lymph nodes in primary and 10/11 lymph nodes in recurrent colorectal cancer. The lymph node sites localized were in the periaortic, periportal and mesenteric regions; there were false-negative results in 1/5 primary tumours and 6/39 recurrent cancers. In 1989, Sardi and co-workers~ analysed 32 patients with recurrent colorectal cancer. A slightly better tumour localization was observed with antibody B72.3 than with 17I-A (83% v s 7 5 % ) . 63'66'67'78The overall sensitivity of tumour localization was 41% with CT scan, compared with 81% with the gamma-detecting probe. In the same year, Neiroda e t al. 67 reported on a group of 10 patients with recurrent colorectal cancer. The gamma-detecting probe localized recurrent tumour in all patients including six patients with negative or equivocal CT scans. The usefulness of the G D P in detecting impalpable tumour was 80% (8/10 cases). The time lag between surgery and antibody injection in this study was 17 days (range: 3-13 days). In the UK, Dawson e t al. 6s reviewed 52 patients who

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Table 3. Radioimmunoguided surgery operative changes Study O'Dwyer Neiroda

et al. 63

eta/.

67

Sickle-Santanello et Arnold et

DiCarlo

et

al. 73

aLTM

al. ~

Year

Total number of changes

Changes in operative procedure

1986

3 (3/16 patients)

1989

25 (based on total of 15 procedures)

1987

8 (8/31 patients)

1992

33 (26/54 patients)

1994

7 (7/54 patients)

Re-resection of residual tumour (n= 1) Small bowel resection (n = 1) Probe directed biopsy (n = 1) Major surgical procedure avoided (n=5) Another procedure (n = 5) Probe directed biopsy (n = 9) Further therapy* (n=6) Hepatic resection avoided (n= 2) Major abdominal procedure avoided (n = 2) Extensive liver resection (n= 1) Extended nodal dissection (n= 17) Re-resection of intestinal anastomosis (n = 1) Small bowel resection (n = I ) Rectal resection (n = 1) Cystectomy (n = 1) Vaginectomy (n = 1) Brachytherapy (n=5) Abandoned hepatic resection (n = 3) Abandoned hepatic pump (n = 1) Colectomy (n = 2) Diaphragmatic resections (n = 1) Conversion into Myles procedure (n= I) Partial resection of vaginal wall (n= 1) Additional lymph node dissection (n = 1) Abandoned hepatic resection (n = 1)

* Chemotherapy n = 4; brachytherapy n = 2.

underwent RIGS treatment for colorectal cancer (43 primary and nine recurrent) using an anti-CEA antibody. Excellent localization of both primary and recurrent colorectal cancer was reported (98% and 89%, respectively). Additional information regarding the extent of primary t u m o u r was reported in 25.5% (l 1/43) patients and in 55% (5/9) patients with recurrent tumour. The incidence of false-positive (4/ 43) and false-negative (2/43) information was limited to patients with primary t u m o u r only. Significantly no falsepositive or negative reports occurred in this study in patients with recurrent tumour. Cohen's group, 69 in a multicentre trial of 105 patients with primary and recurrent colorectal cancer, reported an overall sensitivity of t u m o u r detection with RIGS of 77% and a positive predictive value of 78%. The probe was especially useful in recurrent colorectal cancer and, in this study, the operative decision-making was assisted by the findings at RIGS in 37 patients. In a multicentre trial of 54 patients with primary and recurrent colorectal cancer, DiCarlo e t al. 7° demonstrated that the ability of RIGS to detect t u m o u r was related to t u m o u r bulk and the a m o u n t of antigen expressed (18.8% stages I and II vs 72.2% stages III and IV). Recurrent t u m o u r sites expressed antigen in this study but there was a high false-negative incidence in primary compared with recurrent neoplasms (37.5% vs 16%). RIGS failed to detect liver metastasis in 9/45 (20%) patients expressing TAGantigen (4/20 primary and 5/25 recurrent disease). This failure was attributed to reduced antigen expression due to necrosis within the metastasis and also to inadequate signals as a result of their deep location. The positive predictive value was 95.5% for primary and 98% for recurrent tumours. Paganelli e t al. 7~ and Stella e t al. 72have recently advocated

the avidin-biotin system as a more effective way of targeting of tumours. T u m o u r localization rates were comparable with earlier trials and the mean time interval between the injection of M o A b and surgery was shorter (mean 7 days). This study also demonstrated a reduced sensitivity of RIGS in stage II disease, compared with stages III and IV (37.5% vs 100%) in patients with primary cancer. 7~ One of the disadvantages of this technique is that antigen-antibody complexes are metabolized in the liver and, as a result, the gamma probe is unable to detect small liver lesions. Arnold e t aL, 73 using a second generation antibody (CC49), analysed 60 patients with primary and recurrent colorectal cancer. Eighty-six per cent (18/21) of patients with primary t u m o u r and 97% (29/30) of those with recurrent t u m o u r were localized. These detection rates were better than those achieved with the antibody B72.3, where the corresponding rates were 75% and 63%, respectively. Despite this high rate of localization, 11% of specimens removed from recurrent colorectal cancer were R I G S false-negative. RIGS altered the planned surgical procedure in 50% (12/ 24) of patients with primary tumours and 47% (14/30) of patients with recurrent disease (Table 3). In a follow-up study, the same authors TM reported on 36 patients with primary colorectal cancer, in whom the antibody CC 49 correctly localized the t u m o u r in thirty (83%) patients. Additional information as a result of RIGS, ranging from diffuse nodal involvement (retroperitoneal, coeliac, gastrohepatic) to widespread metastatic disease, was found intraoperatively in 80% (11/36) of patients. Furthermore, t u m o u r upstaging was possible in 11/36 patients. Nine patients with stage I and II disease were upgraded to stage III, due to the detection of metastatic nodes, and two with stage I and II were upgraded to stage

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Table 4. Clinical studies (chronological order) in colorectal carcinoma evaluating different parameters of radioimmunoguided surgery Study and year

No. of patients

MoAb* used

Primary CRC'I" localized

Recurrent CRC'[" localized

Surgery modified

Subclinical tumour deposits

Surgery in days after MoAb* injected

O'Dwyer et al. 198663

18

60%

100%0

18%

NA~

NA

Sickle-Santanello et al. 1987~ Martin et al. 198865 Sardi et al. 1989~

38

Mab 17- I-A F(ab) B 72.3

89%

82%

26%

26%

NA

45 32

82.3% NA

79% 81%

NA 26%

66% 18%

19 (5-42) 16 (3-34)

Neiroda et al. 198967

10

NA

100%

50%

20%

17 (3-30)

Cohen et al. 199169 Neiroda et al. 19917~

105 191

75% NA

63% 73%

NA 25%

27% 19%

NA 8.9-23

Dawson et al. 199168 Arnold et al. 199273 Arnold et al. 1992TM Di Carlo et al. 1992TM Paganelli et al. 19947~

52 54 36 54 20

98% 86% 83% 60% 73%

89% 97% 80% 82% 65%

5%-33% 50%--47% 25% 3%--27% 40%

25%-55% NA NA 38% 15%

NA NA 21 NA 7 (3-13)

Stella et al. 19947"

20

B 72.3 B 72.3 Mabl7-1-A B 72.3 Mabl7-l-A Mab 72.3 17-1-A Mab 72.3 A 5B7 CC 49 CC 49 B 72.3 B 72.3 FO23C5 B 72.3 FO23C5

67%

80%

15%

NA

7 (3-13)

* MoAb = monoclonal antibody. [" CRC = colorectal cancer. NA = not available.

Table 5. Patient survival data Group

Number of patients

Survival (mo)

Alive (no. of patients)

Total

RIGS resectable* Traditionalt unresectable RIGS unresectable:~ Addressed§

49 53 18 I1

82.3 (6-108) 13.7 (3-44) 15.5 (4--43) 20.5 (6-70)

27 0 0 2

27 (55%) 0 0 2 (18.7%)

Total

131

29

29 (22.1%)

* All macroscopic disease and RIGS-positive tissue removed. -i-Extent of gross disease precluded a curative resection. :~Extent of RIGS-positive tissue precluded a curative resection or the bed of resection was RIGSpositive at the end of procedure. § (a) Macroscopic or RIGS-positive tissue, confined and amenable to other protocol modalities; brachytherapy, intraoperative radiation therapy, hepatic chemoinfusion lines, or hepatic artery ligation; (b) Extensive peritoneal disease treated with cytoreduction, and mitomycin C intraperitoneal hyperthermic perfusion. IV in patients with occult distant metastatic disease. In this study, the antibody failed to localize the primary tumour in 16% (6/36) of patients. Table 4 briefly outlines all the studies in chronological order. In conclusion, at the present time, the sensitivity of R I G S in detecting recurrent disease is better than that in the detection of primary colorectal cancer. The advent of second generation M o A b s has improved its efficacy in localizing disease in primary colorectal cancer, though with better understanding of tumour biology and antigen expression further improvements are likely.

RIGS and prognosis in colorectal cancer Martin and Carey 75 reviewed survival rates of 86 patients with colorectal cancer for 2, 3, 4 and 5 years following

'second-look' surgery. The patients were divided into three groups: resectable using R I G S (all gross and probe-positive tissue completely resectable using RIGS), resectable by traditional method (all gross tumours appeared resectable on inspection and palpation but unresectable using R I G S ) and R I G S unresectable (gross tumours unresectable using RIGS). The predicted survival rate for the R I G S resectable group at 5 years was 60%, compared with no survivors for both traditional and R I G S unresectable groups. This rate is better than that of patients undergoing CEA-directed 'second-look' l a p a r o t o m y Y 5 Recently, Bertch e t al. 76 reviewed a larger series of 131 patients over an 8 year period and divided them into four groups (Table 5), depending on operative findings, R I G S status (i.e. resectable or unresectable by R I G S ) at the completion of the procedure and the type o f the procedure performed. The reported survival rate was 55% ranging

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over a 2- to 8-year period for recurrent disease. Ninetythree per cent of the survivors belonged to the RIGS resectable group, i.e. all gross and RIGS-positive tissue resectable (Table 5). The survival among patients undergoing RIGS for primary disease has been reviewed by Arnold et al. 77 They reported on 31 patients with primary colorectal cancer with a follow-up period of 30 to 54 months. All patients (n = 14) cleared of RIGS-positive tissue (i.e. complete R I G S clearance) were alive 24 to 48 months after surgery, compared with two patients (n=15/17) with tissue left behind on completion of the RIGS procedure, who died of their disease. However, it should be pointed out that 50% of patients in the RIGS-negative group had stage III disease whereas 78% of patients were grouped together in stages III and IV in the RIGS-positive group. It is clear, therefore, that RIGS allows the opportunity to restage patients intraoperatively. The information regarding nodal status is normally available only after pathological examination. In its ability to detect occult nodal disease at the time of surgery, RIGS has the ability to stage patients more accurately, and possibly to alter prognosis in colorectal cancer. Prospective, randomized trials, however, are needed to address this particular question.

RIGS and its future

Although still in its infancy, RIGS may change the management and modify the eventual outcome in primary and recurrent colorectal cancer treatment. Potential ways of improving the technique include the development of more selective MoAbs, antibody 'cocktails',79 bio-engineered antibodies with less antigenic reactions along with improvements in isotopes. The potential of incorporating RIGS with laparoscopy and endoscopy may have important implications in its future use. Pre-operative t u m o u r staging with the help of laparoscopy can already help to establish t u m o u r extent and its spread. The development of a radioimmunoguided probe which can be utilized laparoscopically may have an important impact on laparoscopic surgery in oncology. The adequacy of resection from an oncological viewpoint is one of the major objections to the use of laparoscopy in oncological procedures at the moment. The ability to detect occult disease using laparoscopic RIGS probes may help to obviate this problem with laparoscopic surgery, and alleviate existing concerns with this new technology in oncology.

References

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28.

29.

30.

31. 32. 33. 34. 35. 36. 37. 38.

39.

40.

41.

42.

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Self-assessment exercise Based on the Educational Section in the June 1996 issue of the Journal (Answers given on p. 396) 1. The aims of therapy in patients with cachexia is to abort the process and increase muscle bulk and weight. 2. In assessing the cachectic state, modified subject global assessment questionnaires and the hepatic acute phase protein response is indispensable. 3. Cachectic patients with malignant disease will benefit from prolonged parenteral nutritional support and show enhanced response to anti-cancer therapy (chemotherapy, radiotherapy). 4. The following agents have been shown to increase appetite and weight in cachectic patients: (a) insulin; (b) dexamethasone; and (c) megestrol acetate. 5. The Veterans Affairs Total (VAT) Parenteral Nutrition Cooperative Study demonstrated benefit to patients undergoing surgery for malignant disease and receiving parenteral nutritional support. 6. Dietary supplementation with L-glutamine has been shown to be clinically beneficial for patients undergoing surgery. 7. The amino acid L-arginine, if given in pharmacological doses is immunosuppressive. In particular, it inhibits natural cytotoxicity. 8. Polyribonucleotides have been shown to enhance host defences in the peri-operative period and minimize the immune suppression induced by surgery. 9. External nutrition, supplemented with selected nutrients (L-arginine, RNA and n-3 essential fatty acids), has been shown in patients' upper gastro-intestinal tract tumours to reduce post-operative complications and reduce post-operative hospital stay.