The 2022 PSOGI International Consensus on HIPEC Regimens for Peritoneal Malignancies: Methodology

BACKGROUND

A group of experts from the Peritoneal Surface Oncology Group International (PSOGI) and the BIG-RENAPE group carried out a consensus among surgeons experienced in treating peritoneal malignancies from around the world to derive recommendations on indications of hyperthermic intraperitoneal chemotherapy (HIPEC), choice and details of HIPEC regimens, and areas for future research. This manuscript describes the methodology of achieving this consensus and the degree of participation of experts.

METHODS

The Delphi technique was used and the questionnaire comprised three categories: evidence-based recommendations using the GRADE (Grades of Recommendation, Assessment, Development, and Evaluation) system with the PICO (patient, intervention, comparison, and outcome) method, an opinion survey, and research recommendations. A consensus was achieved if any one option had >50% of votes, or positive or negative recommendations combined had > 70% of votes.

RESULTS

Of the 145 experts solicited, 71.1% in round I and 72.2% in round II took the survey. Participation was highest among surgeons treating both gastrointestinal and gynecological malignancies. Of 113 questions, after round I, a consensus was achieved for 72 (63.7%) questions, and after the second round, consensus was achieved for another 22 (19.4%) questions, making a total of 94 (83.1%) questions for which a consensus was achieved.

CONCLUSION

This consensus was carried out using a thorough review of literature and robust rating of evidence, and included key experts and opinion leaders from across the world. The results could guide clinicians on the use of HIPEC, both in their day-to-day clinical practice and in designing clinical trials.

Nab-PIPAC: a phase IB study protocol of intraperitoneal cisplatin and nab-paclitaxel administered by pressurised intraperitoneal aerosol chemotherapy (PIPAC) in the treatment of advanced malignancies confined to the peritoneal cavity

INTRODUCTION

Intraperitoneal dissemination is a major problem resulting in very poor prognosis and a rapid marked deterioration in the quality of life of patients. Pressurised intraperitoneal aerosol chemotherapy (PIPAC) is an emergent laparoscopic procedure aiming to maximise local efficacy and to reduce systemic side effects.

METHODS AND ANALYSIS

Nab-PIPAC, a bicentre open-label phase IB, aims to evaluate safety of nab-paclitaxel and cisplatin association using in patients with peritoneal carcinomatosis (PC) of gastric, pancreatic or ovarian origin as ≥1 prior line of systemic therapy. Using a 3+3 design, sequential intraperitoneal laparoscopic application of nab-paclitaxel (7.5, 15, 25, 37.5, 52.5 and 70 mg/m²) and cisplatin (10.5 mg/m²) through a nebuliser to a high-pressure injector at ambient temperature with a maximal upstream pressure of 300 psi. Treatment maintained for 30 min at a pressure of 12 mm Hg and repeated4-6 weeks intervals for three courses total.A total of 6-36 patients are expected, accrual is ongoing. Results are expected in 2024.The primary objective of Nab-PIPAC trial is to assess tolerability and safety of nab-paclitaxel and cisplatin combination administered intraperitoneally by PIPAC in patients with PC of gastric, pancreatic or ovarian origin. This study will determine maximum tolerated dose and provide pharmacokinetic data.

ETHIC AND DISSEMINATION

Ethical approval was obtained from the ethical committees of Geneva and Vaud (CCER-2018-01327). The study findings will be published in an open-access, peer-reviewed journal and presented at relevant conferences and research meetings.

TRIAL REGISTRATION NUMBER

NCT04000906.

Impact of etiology leading to abdominoperineal resection with anterolateral thigh flap reconstruction: A retrospective cohort study

BACKGROUND

Large and deep perineal defects following abdominal perineal resection (APR) are a challenge for reconstructive surgeons. Even if generally performed for oncological reasons, APR can be indicated as well in extended infection-related debridement for Hidradenitis suppurativa, Fournier's gangrene, or Crohn's disease. We aimed to compare the outcomes of two groups of patients with different indications for APR (infectious vs. oncological) after pedicled anterolateral thigh (ALT) flap coverage RESULTS: Forty-four consecutive pedicled ALT flap used for coverage after APR in 40 patients were analyzed. 26 patients (65%) underwent APR for oncological reasons and 14 patients (35%) for infectious reasons. The overall postoperative complications rate was significantly higher for infectious cases (76.5% vs. 40.7%, p = 0.0304). Major complications occurred in 52.9% of infectious cases versus 11.1% of oncological cases (p = 0.0045). Obesity and infectious etiology were independent risk factors for overall and major complications, respectively.

CONCLUSION

Patients undergoing APR for acute or chronic infections had significantly more overall and major complications than patients having oncological APR. Modified care might be considered, especially in obese patients, in terms of surgical debridement, antibiotic treatment modalities, and postoperative management.

[Intraperitoneal therapy for carcinomatosis in ovarian cancer: proposed treatment algorithm]

Ovarian cancer is the first cause of death by gynecological cancer. Most of the patients are diagnosed with peritoneal carcinomatosis that represents a therapeutic challenge. Its management implies maximal cytoreductive surgery with survival benefit. Over the last three decades, several strategies of intra-peritoneal chemotherapy have been investigated. This includes intra-peritoneal adjuvant chemotherapy that is used mainly in North America, hyperthermic intraperitoneal chemotherapy (HIPEC) and more recently pressurized intraperitoneal aerosol chemotherapy (PIPAC). In the current article, we review the evidence in favor of each therapeutic approach, and we propose treatment algorithms depending on the clinical situation of ovarian cancer patients: upfront, platinum-sensitive and platinum-resistant relapse.

Current Opinion and Practice on Peritoneal Carcinomatosis Management: The North African Perspective

Background

The status of peritoneal surface malignancy (PSM) management in North Africa is undetermined. The aim of this study was to assess and compare current practice and knowledge regarding PSM and examine satisfaction with available treatment options and need for alternative therapies in North Africa.

Methods

This is a qualitative study involving specialists participating in PSM management in North Africa. The survey analyzed demographic characteristics and current knowledge and opinions regarding PSM management in different institutions. We also looked at goals and priorities, satisfaction with treatment modalities and heated intraperitoneal chemotherapy (HIPEC) usefulness according to specialty, country, years of experience, and activity sector.

Results

One-hundred and three participants responded to the survey (response rate of 57%), including oncologists and surgeons. 59.2% of respondents had more than 10 years experience and 45.6% treated 20–50 PSM cases annually. Participants satisfaction with PSM treatment modalities was mild for gastric cancer (3/10 [IQR 2–3]) and moderate for colorectal (5/10 [IQR 3–5]), ovarian (5/10 [IQR 3–5]), and pseudomyxoma peritonei (5/10 [IQR 3–5]) type of malignancies. Good quality of life and symptom relief were rated as main priorities for treatment and the need for new treatment modalities was rated 9/10 [IQR 8–9]. The perceived usefulness of systemic chemotherapy in first intention was described as high by 42.7 and 39.8% of respondents for PSM of colorectal and gastric origins, while HIPEC was described as highly useful for ovarian (49.5%) and PMP (73.8) malignancies.

Conclusions

The management of PSM in the North African region has distinct differences in knowledge, treatments availability and priorities. Disparities are also noted according to specialty, country, years of expertise, and activity sector. The creation of referral structures and PSM networks could be a step forward to standardized PSM management in the region.

Lurbinectedin in Refractory Diffuse Malignant Peritoneal Mesothelioma: Report of Two Cases

Mesothelioma is a malignancy of serosal membranes. Parietal pleura is the most common site, with peritoneum being the second most frequent location. Malignant peritoneal mesothelioma (MPM) is a rare and aggressive disease. The prognosis is often very poor with median overall survival ranging from 6 to 18 months in patients who are not candidates for cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) due to non-resectable disease or comorbid conditions. For patients with resectable disease, CRS and HIPEC have become the standard of care. However, for patients with unresectable malignant mesothelioma there is unfortunately no effective systemic treatment beyond the first line. Based on the results of a recent phase II trial, lurbinectedin has clinical activity and acceptable toxicity in the second- and third-line treatment of malignant pleural mesothelioma. However, until present, no data have been available for patients with MPM and for patients who become refractory after multiple treatment lines. We report on two patients with metastatic MPM who achieved durable disease control of 10+ and 8 months with lurbinectedin in the fourth and fifth treatment line, respectively.

HIPEC Methodology and Regimens: The Need for an Expert Consensus

BACKGROUND

Hyperthermic intraperitoneal chemotherapy (HIPEC) is performed with a wide variation in methodology, drugs, and other elements vital to the procedure. Adoption of a limited number of regimens could increase the collective experience of peritoneal oncologists, make comparison between studies more meaningful, and lead to a greater acceptance of results from randomized trials. This study aimed to determine the possibility of standardizing HIPEC methodology and regimens and to identify the best method of performing such a standardization.

METHODS

A critical review of preclinical and clinical studies evaluating the pharmacokinetic aspects of different HIPEC drugs and drug regimens, the impact of hyperthermia, and the efficacy of various HIPEC regimens as well as studies comparing different regimens was performed.

RESULTS

The preclinical and clinical data were limited, and studies comparing different regimens were scarce. Many of the regimens were neither supported by preclinical rationale or data nor validated by a dose-escalating formal phase 1 trial. All the regimens were based on pharmacokinetic data and did not take chemosensitivity of peritoneal metastases into account. Personalized medicine approaches such as patient-derived tumor organoids could offer a solution to this problem, although clinical validation is likely to be challenging.

CONCLUSIONS

Apart from randomized trials, more translational research and phases 1 and 2 studies are needed. While waiting for better preclinical and clinical evidence, the best way to minimize heterogeneity is by an expert consensus that aims to identify and define a limited number of regimens for each indication and primary site. The choice of regimen then can be tailored to the patient profile and its expected toxicity and the methodology according regional factors.

Guidelines for Perioperative Care in Elective Colorectal Surgery: Enhanced Recovery After Surgery (ERAS®) Society Recommendations: 2018

BACKGROUND

This is the fourth updated Enhanced Recovery After Surgery (ERAS®) Society guideline presenting a consensus for optimal perioperative care in colorectal surgery and providing graded recommendations for each ERAS item within the ERAS® protocol.

METHODS

A wide database search on English literature publications was performed. Studies on each item within the protocol were selected with particular attention paid to meta-analyses, randomised controlled trials and large prospective cohorts and examined, reviewed and graded according to Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system.

RESULTS

All recommendations on ERAS® protocol items are based on best available evidence; good-quality trials; meta-analyses of good-quality trials; or large cohort studies. The level of evidence for the use of each item is presented accordingly.

CONCLUSIONS

The evidence base and recommendation for items within the multimodal perioperative care pathway are presented by the ERAS® Society in this comprehensive consensus review.

Intraperitoneal aerosolization of albumin-stabilized paclitaxel nanoparticles (Abraxane™) for peritoneal carcinomatosis - a phase I first-in-human study

BACKGROUND

Nanoparticles hold considerable promise for aerosol-based intraperitoneal delivery in patients with carcinomatosis. Recently, results from preclinical and early clinical trials suggested that albumin-bound paclitaxel (ABP, Abraxane™) may result in superior efficacy in the treatment of peritoneal metastases (PM) compared to the standard solvent-based paclitaxel formulation (Taxol™). Here, we propose a phase I study of pressurized intraperitoneal aerosol chemotherapy (PIPAC) using ABP in patients with upper Gastrointestinal, breast, or ovarian cancer.

METHODS

Eligible patients with advanced, biopsy-proven PM from ovarian, breast, gastric, hepatobiliary, or pancreatic origin will undergo three PIPAC treatments using ABP with a 4-week interval. The dose of ABP will be escalated from 35 to 140 mg/m² using a Bayesian approach until the maximally tolerated dose is determined. The primary end point is dose-limiting toxicity. Secondary analyses include surgical morbidity, non-access rate, pharmacokinetic and pharmacodynamic analyses, quality of life, and exploratory circulating biomarker analyses.

DISCUSSION

ABP holds considerable promise for intraperitoneal aerosol delivery. The aim of this study is to determine the dose level for future randomized phase II trials using ABP in PIPAC therapy.

TRIAL REGISTRATION

This trial is registered as EudraCT: 2017-001688-20 and Clinicaltrials.gov: NCT03304210.

Enhanced recovery after surgery-ERAS-principles, practice and feasibility in the elderly

This is a short overview of the principles of a novel development in surgery called enhanced recovery after surgery (ERAS) programs. This is an evidence-based approach to perioperative care that has shown to reduce complications and recovery time by 30–50%. The main mechanism is reduction of the stress reactions to the operation. These principles have been shown to be particularly well suited for the compromised patient and hence very good for the elderly people who often have co-morbidities and run a higher risk of complications.

Multicenter comprehensive methodological and technical analysis of 832 pressurized intraperitoneal aerosol chemotherapy (PIPAC) interventions performed in 349 patients for peritoneal carcinomatosis treatment: An international survey study

BACKGROUND

Pressurized intraperitoneal aerosol chemotherapy (PIPAC) is a new drug delivery method offered in selected patients suffering from non-resectable peritoneal carcinomatosis (PC). As reported experience is still limited, we conducted a survey among active PIPAC centers aiming to report their technical approach and clinical findings.

METHODS

An online survey was sent to active PIPAC centers worldwide. The questionnaire consisted of 34 closed questions and was conducted over a period of 3 months beginning in March 2017.

RESULTS

Nine out of 15 contacted centers completed the questionnaire totaling 832 PIPAC procedures in 349 patients. Most common indications for PIPAC were PC from gastric, ovarian and colorectal origin. The mean time between each PIPAC procedure was 6-8 weeks. Seven of nine (77.8%) centers evaluate the PCI at every PIPAC procedure. At least four tissue samples for histopathology analysis were retrieved in 5 (55.6%). All centers (100%) use the same chemotherapy protocol: oxaliplatin at a dosage of 92mg/m² for PC of colorectal origin and a combination of cisplatin and doxorubicin at a dosage of 7.5mg/m² and 1.5mg/m², respectively, for other types of PC. Eight centers (88.9%) perform routine radiological evaluation before first PIPAC and after third PIPAC.

CONCLUSION

These data confirm that PIPAC procedures are homogeneously performed in established centers. Standardization of the procedure will facilitate future international multicenter prospective clinical trials.

[Novelties in surgery in 2016]

The year 2016 allowed further implementation of previous years innovations with the PIPAC treatment for peritoneal carcinomatosis, the development of new surgical technologies and procedures and challenging general principles in general and digestive surgery, including cholecystectomy and appendectomy. Prevention, improved general and perioperative care (ERAS program) become an integral part of our standard surgical activity.

Comorbidity and nutritional indices as predictors of morbidity after transurethral procedures: A prospective cohort study

INTRODUCTION

Preoperative scores are widely used predictors of complications after major surgery. These scores, however, are not widely used in transurethral procedures. The aim of this study was to assess the value of the Charlson Comorbidity Index (CCI), the age-adjusted CCI, the American Society of Anesthesiologist score (ASA) and the Nutritional Risk Score (NRS) in predicting early morbidity after transurethral urological procedures.

METHODS

Consecutive patients undergoing transurethral resection of the bladder or the prostate were prospectively enrolled. The scores were calculated preoperatively; 30-day complications were prospectively recorded according to the Dindo-Clavien classification. Univariate logistic regression was performed to investigate the value of each score and of other factors (i.e., age, sex, body mass index, anemia, smoking habit, type of operation and anaesthesia) as predictors of complications. A multivariate model was then calculated using these predictors.

RESULTS

Overall, 197 patients were included. The mean age was 72 (standard deviation ± 10). In total, 26.9% patients had at least 1 complication. Using univariate analysis, we found that each score significantly predicted complications. In multivariate analysis, only the ASA (odds ration [OR] 2.11; 95% confidence interval [CI] 1.01-4.43) and the NRS (OR 2.42; 95% CI 1.56-3.74) remained independent predictors. The best model incorporated ASA, NRS and gender, and predicted morbidity with an area under the curve of 76%. Our study's main limitations are population heterogeneity and limited sample size.

CONCLUSION

The ASA and the NRS are important and independent determinants of early morbidity after transurethral procedures. The use of these indices may assist clinicians in the decision-making process to balance the possible benefits of transurethral procedures with the potential risks.

Surgery for incarcerated hernia: short-term outcome with or without mesh

BACKGROUND

Incarcerated hernias represent about 5-15 % of all operated hernias. Tension-free mesh is the preferred technique for elective surgery due to low recurrence rates. There is however currently no consensus on the use of mesh for the treatment of incarcerated hernias, especially in case of bowel resection.

AIM

The aims of this study were (i) to report our current practice for the treatment of incarcerated hernias, (ii) to identify risk factors for postoperative complications, and (iii) to assess the safety of mesh placement in potentially infected surgical fields.

METHODS

This retrospective study included 166 consecutive patients who underwent emergency surgery for incarcerated hernia between January 2007 and January 2012 in two university hospitals. Demographics, surgical details, and short-term outcome were collected. Univariate analysis was employed to identify risk factors for overall, infectious, and major complications.

RESULTS

Eighty-four patients (50.6 %) presented inguinal hernias, 43 femoral (25.9 %), 37 umbilical hernias (22.3 %), and 2 mixed hernias (1.2 %), respectively. Mesh was placed in 64 patients (38.5 %), including 5 patients with concomitant bowel resection. Overall morbidity occurred in 56 patients (32.7 %), and 8 patients (4.8 %) developed surgical site infections (SSI). Univariate risk factors for overall complications were ASA grade 3/4 (P = 0.03), diabetes (P = 0.05), cardiopathy (P = 0.001), aspirin use (P = 0.023), and bowel resection (P = 0.001) which was also the only identified risk factor for SSI (P = 0.03). In multivariate analysis, only bowel incarceration was associated with a higher rate of major morbidity (OR = 14.04; P = 0.01).

CONCLUSION

Morbidity after surgery for incarcerated hernia remains high and depends on comorbidities and surgical presentation. The use of mesh could become current practice even in case of bowel resection.

[Enhanced recovery after surgery applied to cystectomy patients]

Enhanced Recovery After Surgery (ERAS) is a multimodal concept combining pre, intra and postoperative evidence-based care elements to reduce surgical stress. ERAS pathways have been shown to significantly reduce morbidity, length of hospital stay and total costs when applied to colorectal surgery. It is therefore considered standard of care in this specialty. There can be no doubt that ERAS principles can be applied also in other major surgeries. However, uncritical application of the guidelines issued from colonic procedures seems inappropriate as the surgical procedures in pelvic cancer surgery differ considerably. This article reports on the first steps of an ERAS project and his introduction in urology.

Guidelines for perioperative care after radical cystectomy for bladder cancer: Enhanced Recovery After Surgery (ERAS(®)) society recommendations

PURPOSE

Enhanced recovery after surgery (ERAS) pathways have significantly reduced complications and length of hospital stay after colorectal procedures. This multimodal concept could probably be partially applied to major urological surgery.

OBJECTIVES

The primary objective was to systematically assess the evidence of ERAS single items and protocols applied to cystectomy patients. The secondary objective was to address a grade of recommendation to each item, based on the evidence and, if lacking, on consensus opinion from our ERAS Society working group.

EVIDENCE ACQUISITION

A systematic literature review was performed on ERAS for cystectomy by searching EMBASE and Medline. Relevant articles were selected and quality-assessed by two independent reviewers using the GRADE approach. If no study specific to cystectomy was available for any of the 22 given items, the authors evaluated whether colorectal guidelines could be extrapolated.

EVIDENCE SYNTHESIS

Overall, 804 articles were retrieved from electronic databases. Fifteen articles were included in the present systematic review and 7 of 22 ERAS items were studied. Bowel preparation did not improve outcomes. Early nasogastric tube removal reduced morbidity, bowel recovery time and length of hospital stay. Doppler-guided fluid administration allowed for reduced morbidity. A quicker bowel recovery was observed with a multimodal prevention of ileus, including gum chewing, prevention of PONV and minimally invasive surgery.

CONCLUSIONS

ERAS has not yet been widely implemented in urology and evidence for individual interventions is limited or unavailable. The experience in other surgical disciplines encourages the development of an ERAS protocol for cystectomy.

[Preoperative nutrition in abdominal surgery: recommendations and reality]

Malnutrition concerns up to 50% at in-hospital admission. Its diagnosis and treatment are fundamental parts of the surgical approach because nutritional status directly influences the clinical outcome. The Nutritional Risk Score (NRS-2002) represents the recommended screening tool by the European Society of Parenteral and Enteral Nutrition (ESPEN). Patients with a score > or = 3 and aged > 70 years old, should receive a nutritional support during 7-14 day before surgery. Depending on patient's clinical conditions, the enteral route of administration should be preferred. Despite strong evidence in favor of nutritional supplementation, much effort must be done to implement these supportive strategies in the everyday clinical practice.

A fast-track program reduces complications and length of hospital stay after open colonic surgery

BACKGROUND & AIMS

A fast-track program is a multimodal approach for patients undergoing colonic surgery that combines stringent regimens of perioperative care (fluid restriction, optimized analgesia, forced mobilization, and early oral feeding) to reduce perioperative morbidity, hospital stay, and cost. We investigated the impact of a fast-track protocol on postoperative morbidity in patients after open colonic surgery.

METHODS

A randomized trial of patients in 4 teaching hospitals in Switzerland included 156 patients undergoing elective open colonic surgery who were assigned to either a fast-track program or standard care. The primary end point was the 30-day complication rate. Secondary end points were severity of complications, hospital stay, and compliance with the fast-track protocol.

RESULTS

The fast-track protocol significantly decreased the number of complications (16 of 76 in the fast-track group vs 37 of 75 in the standard care group; P = .0014), resulting in shorter hospital stays (median, 5 days; range, 2-30 vs 9 days, respectively; range, 6-30; P < .0001). There was a trend toward less severe complications in the fast-track group. A multiple logistic regression analysis revealed fluid administration greater than the restriction limits (odds ratio, 4.198; 95% confidence interval, 1.7-10.366; P = .002) and a nonfunctioning epidural analgesia (odds ratio, 3.365; 95% confidence interval, 1.367-8.283; P = .008) as independent predictors of postoperative complications.

CONCLUSIONS

The fast-track program reduces the rate of postoperative complications and length of hospital stay and should be considered as standard care. Fluid restriction and an effective epidural analgesia are the key factors that determine outcome of the fast-track program.

Prospective randomized study of monopolar scissors, bipolar vessel sealer and ultrasonic shears in laparoscopic colorectal surgery

Background

Many instruments are used for laparoscopic dissection, including monopolar electrosurgery scissors (MES), electrothermal bipolar vessel sealers (BVS) and ultrasonically coagulating shears (UCS). These three devices were compared with regard to dissection time, blood loss, safety and costs.

Methods

Sixty-one consecutive patients undergoing laparoscopic left-sided colectomy were randomized to MES, BVS or UCS. The primary endpoint was dissection time.

Results

Patient and operation characteristics did not differ between the groups. Median dissection time was significantly shorter with BVS (105 min) and UCS (90 min) than with MES (137 min) (P &lt; 0·001). With BVS and UCS, significantly fewer additional clips were required (MES 9 versus BVS 0 versus UCS 3; P &lt; 0·001) and there was a trend towards lower blood loss (125 versus 50 versus 50 ml respectively; P = 0·223) and a reduced volume of suction fluid (425 versus 80 versus 110 ml; P = 0·058). Overall satisfaction was similar for the three instruments. Dissection with BVS and UCS was significantly cheaper than with MES, assuming a centre volume of 200 cases per year (P = 0·009).

Conclusion

BVS and UCS shorten dissection time in laparoscopic left-sided colectomy and are cost-effective compared with MES. Registration number: NCT00517608 (http://www.clinicaltrials.com).

Phase II trial of gemcitabine in advanced non-small-cell lung cancer

Gemcitabine has shown activity in different solid tumors. In the present study we have evaluated its efficacy in 32 patients with advanced non-small-cell lung cancer in a phase II trial. Gemcitabine (1250 mg/m2) was given intravenously as a 30-minute infusion on days 1, 8 and 15. Cycles were repeated every 4 weeks. Twenty-nine patients were evaluable for response and all patients for toxicity. Partial remissions and stable disease were seen in 4 (14%) and 13 (45%) patients, respectively. Improvement of symptoms occurred in 54% of the patients. Side effects were mild and included predominantly leukopenia and thrombocytopenia. In conclusion, gemcitabine is active and well tolerated in patients with advanced non-small-cell lung cancer.

On the efficient two-dimensional energy coding characteristics of spatial vision

Recent evidence indicates that the vertebrate visual system possesses units whose receptive fields may be represented as narrow-band orientation and frequency specific filters. It has been indirectly demonstrated that equivalent psychophysical units act in such a way as to not discriminate the individual frequency components within each frequency band. Here we directly demonstrate this to be the case with digital images and so show an efficient energy code for spatial vision.