Technical considerations for isolated limb perfusion: A consensus paper.

BACKGROUND: Isolated limb perfusion (ILP) is a well-established surgical procedure for the administration of high dose chemotherapy to a limb for the treatment of advanced extremity malignancy. Although the technique of ILP was first described over 60 years ago, ILP is utilised in relatively few specialist centres, co-located with tertiary or quaternary cancer centres. The combination of high dose cytotoxic chemotherapy and the cytokine tumour necrosis factor alpha (TNFα), mandates leakage monitoring to prevent potentially serious systemic toxicity. Since the procedure is performed at relatively few specialist centres, an ILP working group was formed with the aim of producing technical consensus guidelines for the procedure to streamline practice and to provide guidance for new centres commencing the technique. METHODS: Between October 2021 and October 2023 a series of face to face online and hybrid meetings were held in which a modified Delphi process was used to develop a unified consensus document. After each meeting the document was modified and recirculated and then rediscussed at subsequent meeting until a greater than 90% consensus was achieved in all recommendations. RESULTS: The completed consensus document comprised 23 topics in which greater than 90% consensus was achieved, with 83% of recommendations having 100% consensus across all members of the working group. The consensus recommendations covered all areas of the surgical procedure including pre-operative assessment, drug dosing and administration, perfusion parameters, hyperthermia, leakage monitoring and theatre logistics, practical surgical strategies and also post-operative care, response evaluation and staff training. CONCLUSION: We present the first joint expert-based consensus statement with respect to the technical aspects of ILP that can serve as a reference point for both existing and new centres in providing ILP.

Pleomorphic dermal sarcoma of the scalp - A single-centre experience.

BACKGROUND: Pleomorphic dermal sarcoma (PDS) of the scalp is a rare tumour which is usually slow growing, but occasionally displays rapid growth and has a low rate of local recurrence. Surgical resection is the mainstay of treatment, with or without radiotherapy. The aim of this study is to describe the surgical approach and the additional benefit of radiotherapy to the treatment of these patients. METHODS: Retrospective, single-centre analysis of patients with PDS of the scalp that underwent surgical resection between 2007 and 2021 (n = 24). Treatment variables including depth of resection (superficial or deep to the galea aponeurotica) and adjuvant radiotherapy were investigated. RESULTS: Twenty-four patients were included in this study. Median age was 80 (range, 52-95), with a median ASA score of 3 (2-3). Sixteen (66.6 %) patients underwent surgical resection including the galea, while the rest (n = 8) did not or was not known. Radiotherapy was given in 7 (29 %) patients in which only 3 (12.5 %) were in the galeal resection group. Reasons for radiotherapy administration were concomitant SCC found at the same area of resection and close margins. In a median follow-up of was 26.2 months (range, 13.6-102.5) there was only one recurrence event. CONCLUSIONS: PDS of the scalp can be safely managed with a surgical resection if clear surgical margins are achieved without radiotherapy with good oncological outcomes.

Low local recurrence rates following marginal surgical resection of non-coelomic Atypical Lipomatous Tumours/Well-differentiated Liposarcomas.

INTRODUCTION: High rates of local recurrence (LR) have been reported following resection of extremity Atypical lipomatous tumours/Well-differentiated liposarcomas (ALTs). This retrospective study of patients who underwent resection of primary deep extremity and trunk ALTs at a specialist sarcoma centre aims to assess morbidity and factors associated with low local recurrence rates (LRR). METHODS: To review a homogeneous cohort of patients with low-grade disease, tumours with known high-risk histological features were excluded. Prognostic variables potentially influencing local recurrence (LR) (age, size, site, margin status, and histological findings) were analysed. Endpoints were LR, distant recurrence (DR) and local disease-free survival (LDFS). RESULTS: 127 patients were identified, with median follow-up of 54 months (0-235). Median tumour size was 17.5 cm (5-36). 85 % occurred in the lower limb. 93.7 % underwent marginal resection. No patients received radiotherapy. Median hospital stay was 3 days (0-16). 7.9 % returned to theatre for evacuation of haematoma or infected seroma and 18.1 % had outpatient seroma aspiration. Surgical margins were R0/R1 in 93.7 % of patients and R2 in 6.3 % with a LR rate of 8.4 % and 75 % respectively at median time of 54 months. One- and 5-year LDFS was 100 % and 88.4 %, respectively. DR rate was 0.8 % (1/127) this patient had pleomorphic liposarcomatous transformation on recurrence and subsequently developed distant metastases. No patients died of disease. CONCLUSION: Function-preserving marginal resection of non-coelomic ALTs has low morbidity, low LR and extremely low rates of distant relapse. Patients with lower limb ALT were found to have significantly lower LR, which may impact follow-up protocols.

Variation in response rates to isolated limb perfusion in different soft-tissue tumour subtypes: an international multi-centre study.

OBJECTIVE: The aim of this study was to investigate the response rates of different extremity soft-tissue sarcoma subtypes (eSTS) after isolated limb perfusion (ILP), based on an international multi-centre study. MATERIALS AND METHODS: The retrospective cohort comprised eSTS patients from 17 specialised ILP centres that underwent melphalan-based ILP, with or without recombinant human tumour necrosis factor (rhTNFα) (TM-ILP and M-ILP, respectively). Response was measured on imaging (magnetic resonance imaging) and/or clinical response, for which M-ILPs were excluded. RESULTS: A total of 1109 eSTS patients were included. The three most common histological subtypes were undifferentiated pleomorphic sarcoma (17%, n = 184), synovial sarcoma (16%, n = 175) and myxofibrosarcoma (8%, n = 87). rhTNFα was used in 93% (TM-ILP) and resulted in a significantly better overall response rate (ORR, p = 0.031) and complete responses (CR, p < 0.001) in comparison to M-ILP, without significant differences among histological subgroups. The ORR of TM-ILP was 68%, including 17% CR. Also, 80% showed progressive disease. Significantly higher response rates were shown for Kaposi sarcoma (KS) with 42% CR and 96% ORR (both p < 0.001), and significantly higher CR rates for angiosarcoma (AS, 45%, p < 0.001) and clear cell sarcoma (CCS, 31%, p = 0.049). ILP was followed by resection ≤ 6 months in 80% of the patients. The overall limb salvage rate was 88%, without significant differences among histological subgroups, but was significantly higher for ILP responders compared to non-responders (93% versus 76%, p < 0.001). CONCLUSION: ILP resulted in high response and LRS among all eSTS subtypes, however, with significant differences between subtypes with most promising results for KS, AS and CCS.

Retrospective Analysis of Retroperitoneal-Abdominal-Pelvic Ganglioneuromas: An International Study by the Transatlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG).

OBJECTIVE: The Transatlantic Australasian Retroperitoneal Sarcoma Working Group conducted a retrospective study on the disease course and clinical management of ganglioneuromas. BACKGROUND: Ganglioneuromas are rare tumors derived from neural crest cells. Data on these tumors remain limited to case reports and single-institution case series. METHODS: Patients of all ages with pathologically confirmed primary retroperitoneal, intra-abdominal, and pelvic ganglioneuromas between January 1, 2000, and January 1, 2020, were included. We examined demographic, clinicopathologic, and radiologic characteristics, as well as clinical management. RESULTS: Overall, 328 patients from 29 institutions were included. The median age at diagnosis was 37 years with 59.1% of patients being female. Symptomatic presentation comprised 40.9% of cases, and tumors were often located in the extra-adrenal retroperitoneum (67.1%). At baseline, the median maximum tumor diameter was 7.2 cm. One hundred sixteen (35.4%) patients underwent active surveillance, whereas 212 (64.6%) patients underwent resection with 74.5% of operative cases achieving an R0/R1 resection. Serial tumor evaluations showed that malignant transformation to neuroblastoma was rare (0.9%, N=3). Tumors undergoing surveillance had a median follow-up of 1.9 years, with 92.2% of ganglioneuromas stable in size. With a median follow-up of 3.0 years for resected tumors, 84.4% of patients were disease free after resections, whereas recurrences were observed in 4 (1.9%) patients. CONCLUSIONS: Most ganglioneuromas have indolent disease courses and rarely transform to neuroblastoma. Thus, active surveillance may be appropriate for benign and asymptomatic tumors particularly when the risks of surgery outweigh the benefits. For symptomatic or growing tumors, resection may be curative.

Major vascular reconstruction in colorectal adenocarcinoma and retroperitoneal sarcoma: A retrospective study of safety and margins in a tertiary referral centre.

BACKGROUND: The role of en bloc vascular resection and reconstruction (EVRR) is controversial in colorectal adenocarcinoma (CRC), but well-established in retroperitoneal sarcoma (RPS). Sparse data exists regarding these complex procedures. METHODS: Patients undergoing curative intent EVRR for advanced CRC and RPS between 2014 and 2021 at a tertiary centre were included. Morbidity, margins, recurrence, and survival were evaluated. RESULTS: 24 patients underwent EVRR with 48 reconstructions (11 CRC and 13 RPS). For CRC, 100% of patients underwent Iliac system reconstructions. For RPS, inferior vena cava reconstructions were the most common (69.2%). There were 2 arterial and 1 venous graft thromboses. Primary graft patency was 89.4% arterial and 93.1% venous, while secondary patency was 100% arterial and 96.5% venous at last follow up. 1 venous and 1 arterial graft required reoperation for bleeding. There were no compromised limbs. Major complications occurred in 6 patients (25.0%) with no observed difference between CRC and RPS (OR 0.43 95%CI[0.60,3.19], P = 0.41). R1 margins occurred 1 CRC (90.9%) and 3 RPS (76.9%), with no R2 resections. All vascular resection margins were clear. There were 6 CRC (50%) and 4 RPS (33.3%) recurrences. Median recurrence time was 20.9 months for CRC and 'not yet reached' for RPS. Median follow-up was 19.4 months for CRC and 21.4 months for RPS. CONCLUSION: EVRR for locally advanced CRC or RPS is safe and achieves favorable R0 resection rates. CRC patients with major vascular invasion can still be considered for curative intent surgery. Larger cohorts with longer follow up are needed to assess oncologic outcomes.

Management of Locally Recurrent Retroperitoneal Sarcoma in the Adult: An Updated Consensus Approach from the Transatlantic Australasian Retroperitoneal Sarcoma Working Group.

BACKGROUND: Surgery is the mainstay of treatment for retroperitoneal sarcoma (RPS), but local recurrence is common. Biologic behavior and recurrence patterns differ significantly among histologic types of RPS, with implications for management. The Transatlantic Australasian RPS Working Group (TARPSWG) published a consensus approach to primary RPS, and to complement this, one for recurrent RPS in 2016. Since then, additional studies have been published, and collaborative discussion is ongoing to address the clinical challenges of local recurrence in RPS. METHODS: An extensive literature search was performed, and the previous consensus statements for recurrent RPS were updated after review by TARPSWG members. The search included the most common RPS histologic types: liposarcoma, leiomyosarcoma, solitary fibrous tumor, undifferentiated pleomorphic sarcoma, and malignant peripheral nerve sheath tumor. RESULTS: Recurrent RPS management was evaluated from diagnosis to follow-up evaluation. For appropriately selected patients, resection is safe. Nomograms currently are available to help predict outcome after resection. These and other new findings have been combined with expert recommendations to provide 36 statements, each of which is attributed a level of evidence and grade of recommendation. In this updated document, more emphasis is placed on histologic type and clarification of the intent for surgical treatment, either curative or palliative. Overall, the fundamental tenet of optimal care for patients with recurrent RPS remains individualized treatment after multidisciplinary discussion by an experienced team with expertise in RPS. CONCLUSIONS: Updated consensus recommendations are provided to help guide decision-making for treatment of locally recurrent RPS and better selection of patients who would potentially benefit from surgery.

Management of Primary Retroperitoneal Sarcoma (RPS) in the Adult: An Updated Consensus Approach from the Transatlantic Australasian RPS Working Group.

BACKGROUND: Retroperitoneal soft tissue sarcomas comprise a heterogeneous group of rare tumors of mesenchymal origin that include several well-defined histologic subtypes. In 2015, the Transatlantic Australasian RPS Working Group (TARPSWG) published consensus recommendations for the best management of primary retroperitoneal sarcoma (RPS). Since then, through international collaboration, new evidence and knowledge have been generated, creating the need for an updated consensus document. METHODS: The primary aim of this study was to critically evaluate the current evidence and develop an up-to-date consensus document on the approach to these difficult tumors. The resulting document applies to primary RPS that is non-visceral in origin, with exclusion criteria as previously described. The relevant literature was evaluated and an international group of experts consulted to formulate consensus statements regarding the best management of primary RPS. A level of evidence and grade of recommendation were attributed to each new/updated recommendation. RESULTS: Management of primary RPS was considered from diagnosis to follow-up. This rare and complex malignancy is best managed by an experienced multidisciplinary team in a specialized referral center. The best chance of cure is at the time of primary presentation, and an individualized management plan should be made based on the 29 consensus statements included in this article, which were agreed upon by all of the authors. Whenever possible, patients should be enrolled in prospective trials and studies. CONCLUSIONS: Ongoing international collaboration is critical to expand upon current knowledge and further improve outcomes of patients with RPS. In addition, prospective data collection and participation in multi-institution trials are strongly encouraged.

Characterising the immune microenvironment in liposarcoma, its impact on prognosis and the impact of radiotherapy.

BACKGROUND AND OBJECTIVES: Limited literature exists examining the immune microenvironment in liposarcoma, particularly with regard to the impact of radiotherapy. A major problem is the lack of scoring system for the tumour-infiltrating lymphocytes (TILs) in sarcoma. This study aims to describe the immune environment pre- and postradiotherapy and identify the optimal immune infiltrate scoring system for sarcoma. METHODS: Thirty-nine paired tissue samples (pre- and postradiotherapy) from patients with liposarcoma were scored by two pathologists for TILs using pre-existing systems (for breast cancer and melanoma) and compared for interobserver reliability. Immunohistochemical staining was performed for various immune markers. RESULTS: The TIL scoring system for breast cancer yielded perfect agreement (κ = 1.000). 21% of patients had increased TILs after radiotherapy, 87.5% of whom had dedifferentiated liposarcoma. Immune suppressor expression was increased frequently after radiotherapy (CD68 increased in 59.4%, PD-L1 increased in 25%). Immune effector expression (CD8) was unchanged in 84.4%. CONCLUSIONS: Breast cancer TIL scoring is reproducible in liposarcoma and has high interobserver reliability. Radiotherapy was observed to have a limited impact on immune effectors but seemed to have more impact in upregulating immune suppressors, suggesting radiotherapy may contribute to disease control through immunomodulatory effects. Dedifferentiated liposarcoma represents a uniquely responsive subtype.

Prostate-specific membrane antigen expression in melanoma metastases.

BACKGROUND: Prostate-specific membrane antigen (PSMA) is a prostatic epithelial protein that is used as a radiotracer (68Ga-PSMA-11) for prostate cancer staging. PSMA-PET/CT (positron emission tomography/computed tomography) performed for prostate cancer has been observed to detect melanoma metastases. The aim of this study was to investigate the performance of PSMA immunohistochemistry on resected melanoma metastases to explore its use as a diagnostic imaging biomarker for melanoma. METHODS: A total of 41 specimens with stage III/IV melanoma were stained with PSMA immunohistochemistry. All specimens required both disease and control regions. Two pathologists scored the specimens and a receiver operating characteristic (ROC) curve was plotted. Western blot and multiplex immunofluorescence were also performed. RESULTS: The area under the ROC curve was 0.82, suggesting that PSMA has excellent discriminatory power in melanoma metastases. Sensitivity is 82.9% and specificity 73.2%. Immunohistochemistry and Western blot reveal that PSMA staining in melanoma consistently and most intensely occurs in tumor neovasculature. Multiplex immunofluorescence shows that melanocytes may also weakly express PSMA. CONCLUSION: The performance of PSMA immunohistochemistry in melanoma metastases contrasts with that reported in prostate cancer studies. This study indicates that PSMA shows promise for use as a novel biomarker in melanoma and justifies further research in the clinical setting with potential as a PET/CT radiotracer and intraoperative fluorescence marker for melanoma.

Correlation between percutaneous biopsy and final histopathology for retroperitoneal sarcoma: a single-centre study.

BACKGROUND: Retroperitoneal sarcomas are rare soft tissue tumours accounting for 10-15% of soft tissue sarcomas. Patient prognosis and treatment recommendations (including extent of surgery and neoadjuvant strategies) are determined by the pre-operative histopathological subtype and grade obtained from biopsy and thus it is important to understand the accuracy of biopsy in retroperitoneal masses. METHODS: This study presents a case series of primary retroperitoneal sarcomas managed at Peter MacCallum Cancer Centre (PMCC) between 2008 and 2019. Statistical analyses were performed to determine correlation between histopathology from percutaneous biopsy and surgical excision. RESULTS: A total of 117 patients who underwent percutaneous core biopsy and surgical excision of retroperitoneal sarcoma were included. Diagnostic accuracy varied with histopathological diagnosis, but overall precise concordance between biopsy and final histopathology was seen in 61% (κ = 0.57). Biopsy was most sensitive for identifying well-differentiated liposarcoma (WDLPS) (sensitivity 85%, 95% CI 0.06-0.96) and leiomyosarcoma (sensitivity 81%, 95% CI 0.54-0.96) and was least sensitive for identifying de-differentiated liposarcoma (DDLPS) (sensitivity 40%, 95% CI 0.25-0.56). Overall agreement between biopsy and final histopathology increased with use of PET/CT scan pre-biopsy and with use of fluorescence in situ hybridisation testing on biopsy, however, neither test improved recognition of de-differentiated components within WD/DDLPS on core biopsy. CONCLUSIONS: Pre-operative biopsy is important for clinical decision making in the treatment of retroperitoneal sarcoma. A significant portion of patients with a WDLPS will have a de-differentiated component identified at the time of resection that was not identified on initial biopsy.

Primary iliocaval leiomyosarcomas: The path beyond surgery.

INTRODUCTION: Iliocaval leiomyosarcoma (ICLM) is a rare and aggressive form of sarcoma within the retroperitoneum. Surgery is the mainstay of treatment, with no consensus on the benefit of chemoradiotherapy in the neo/adjuvant setting. This study aims to describe the natural history of a chemotherapy-naïve ICLM treated in a tertiary cancer centre and to explore potential directions to improve oncological outcome. MATERIALS AND METHODS: A prospective database was used to identify patient demographics, clinicopathological variables and oncological outcomes in 30 patients who underwent surgical resection in our institution for primary non-metastatic ICLM between 2003 and 2018. RESULTS: There was no 90-day mortality. With a median follow-up time of 70.0 months (95% CI 52.6-87.4), 5/30 patients (16.7%) developed local recurrence while 11/30 (36.7%) developed distant metastatic disease. 1 patient (3.3%) developed both local and distant recurrence. Median overall survival of our cohort was 41.0 months (95% CI 33.6-48.4) and 5-year overall survival rate was 32.1%. Multivariate survival analysis using the Cox proportional hazard model identified tumour grade and blood loss of more than 600 mL as key prognostic factors in our model. CONCLUSION: Management of ICLM should be centralised in high-volume sarcoma centres with expertise in the management of retroperitoneal sarcomas. Integration of tumour biology with a concerted effort to conduct conclusive multi-centre phase III in histological and molecularly defined sarcoma subgroups is necessary to improve patient outcome. We eagerly await the results of STRASS 2 study to gain more insights to the efficacy of neoadjuvant chemotherapy on patient prognosis.

Conservative Re-excision is a Safe and Simple Alternative to Radical Resection in Revision Surgery for Dermatofibrosarcoma Protuberans.

BACKGROUND: Dermatofibrosarcoma protuberans (DFSP) is a dermal sarcoma often diagnosed by excision biopsy, and is often incompletely excised, with high recurrence rates. Traditional wide excision involves resection margins of 2-4 cm, often resulting in morbid procedures requiring surgical reconstruction. An alternative is conservative re-excision (CRE), which results in narrower margins and less-frequent reconstruction. The aim of this study is to assess the effectiveness of CRE in providing local control. PATIENTS AND METHODS: A retrospective review of patients treated for DFSP at a tertiary sarcoma centre over a 10-year period. RESULTS: Ninety-eight patients were analysed. Median follow-up was 53 months. Fifty-four patients had microscopically incompletely excised DFSP, and of these, 41 underwent CRE of DFSP scar. Seven (17.1%) patients required more than one CRE to achieve negative margins. The mean width of CRE was 15.4 mm. Fifty-four patients had resection of intact tumours, with 19 (35.2%) requiring surgical reconstruction. One patient (1%) developed local recurrence, and one patient (1%) distant recurrence-both of these patients had high-grade fibrosarcomatous DFSP. No patient with classical DFSP who had clear margins sustained recurrence, regardless of whether their surgery was CRE of scar or wide excision of tumour. CONCLUSIONS: CRE is a safe and acceptable alternative to traditional wide excision, with no patients developing local recurrence (LR). CRE results in low rates of surgical reconstruction, and hence lower morbidity; this is partially offset by the higher rates of inadequate excision requiring further surgery. However, the lesser rate of inadequate excision compared with rates of reconstruction makes CRE an attractive option.

Treatment of patients with primary retroperitoneal sarcoma: predictors of outcome from an Australian specialist sarcoma centre.

BACKGROUND: Several unanswered questions surround the management of retroperitoneal sarcoma (RPS). Guidelines recommend treatment by a multidisciplinary team at a specialized referral centre. The objective of this study was to describe the management of RPS at an Australian specialist sarcoma centre, comparing outcomes to international standards and analysing for predictors of local failure. METHODS: A retrospective review of a prospectively maintained database was performed on patients with RPS treated between 2008 and 2016. A 5-year outcome analyses focussed on patients undergoing curative-intent surgery for primary, non-metastatic RPS. RESULTS: Eighty-eight patients underwent surgery for primary RPS. Five-year overall survival was 66%, 5-year freedom from local recurrence was 65% and 5-year freedom from distant metastasis was 71%. Overall survival was associated with tumour grade (hazard ratio (HR) 6.1, P < 0.001) and histologic organ invasion (HR 5.7, P < 0.001). Variables associated with improved freedom from local recurrence were macroscopically complete resection (HR 0.14, P < 0.001) and neoadjuvant radiotherapy (HR 0.33, P = 0.014). Treatment at a specialist sarcoma centre was associated with a higher rate of preoperative biopsy and neoadjuvant radiotherapy (both with P < 0.001). There was a trend towards improved local control for patients undergoing surgery at a specialist centre (P = 0.055). CONCLUSION: This is the largest Australian series of RPS and outcomes are comparable to major international sarcoma centres. Patients treated at a specialist centre had higher rates of preoperative diagnosis and tailored therapy which was associated with improved outcomes. Patients with suspected RPS should be referred to a specialist centre for optimal preoperative evaluation and multidisciplinary management.

Incidental Metastatic Melanoma Identified on 68Ga-Prostate-Specific Membrane Antigen PET/CT for Metastatic Prostate Cancer.

A 78-year-old man with a history of surgically treated prostate cancer and melanoma underwent Ga-prostate-specific membrane antigen (PSMA) PET/CT for biochemical recurrence of his prostate cancer. This revealed locoregionally recurrent prostate cancer and a separate PSMA-avid nodule in his left arm. Subsequent F-FDG PET/CT and excision confirmed this to be an in-transit melanoma metastasis. Prostate-specific membrane antigen PET/CT has become a widely used and valuable tool in the assessment of prostate cancer, particularly biochemically recurrent. Uptake of PSMA has been described in a multitude of different benign and malignant conditions, but it has only rarely been documented in melanoma.

Irrigation versus suction alone during laparoscopic appendectomy; A randomized controlled equivalence trial.

INTRODUCTION: The objective of this study was to compare operative peritoneal irrigation versus suction alone during laparoscopic appendectomy in adult patients; our hypothesis was that the two methods are equivalent in terms of rate of post-operative intra-abdominal abscess. There has been only one prospective, randomized, superiority trial in children, that showed non-significant difference in the rate of intra-abdominal abscess comparing irrigation to suction alone during laparoscopic appendectomy for perforated appendicitis. Non-significant difference in a superiority trial does not imply equivalence. METHODS: This was a single-institution, prospective, randomized controlled equivalence study based on a null-hypothesis of non-equivalence between irrigation and suction alone. Adult patients with intra-operative findings of an acutely inflamed appendix, with suppuration or perforation localized to the right iliac fossa, paracolic gutter or pelvis were randomized to irrigation or suction alone. The primary endpoint was the rate of intra-abdominal abscess. An unconditional exact test of equivalence was used to test the null-hypothesis. RESULTS: Eighty-one patients were included for analysis. Two (5%) of 40 patients in the irrigation group and two (4.9%) of 41 in the suction-only group developed postoperative intra-abdominal abscess. The 95% confidence interval for the difference between the two groups was -0.1200 to 0.1244, captured within the pre-defined δ limits (-0.15, 0.15). With reference to the rate of intra-abdominal abscess, equivalence was demonstrated between irrigation and suction-only techniques. CONCLUSIONS: In patients with suppurative or perforated appendicitis, the rate of intra-abdominal abscess is equivalent between groups treated with peritoneal irrigation and suction alone.