Redefining the boundaries of advanced pelvic oncology surgery

After more than 25 years of performing pelvic exenteration for advanced primary and recurrent pelvic malignancy (Table 1) it is cathartic not only to explore how the concepts of pelvic oncology have evolved but, more importantly, also to look forward to evaluate where we can push the future boundaries and indulge in one of the most commonly asked questions: ‘Who should be performing pelvic exenteration?’1–3. What has become apparent, particularly with international collaborations such as PelvEx, is that the definitions of what constitutes an exenteration, tumour resectability, the pelvic compartments, and even an R0 margin vary from unit to unit, and in many cases direct comparison of outcomes is like comparing ‘apples and oranges’4. Pelvic exenteration operations between 1994 and 2020 Values in parentheses are percentages. *Includes anal squamous cell carcinoma (SCC), rectosigmoid, gynaecological cancers, and other. Pelvic exenteration operations between 1994 and 2020 Values in parentheses are percentages. *Includes anal squamous cell carcinoma (SCC), rectosigmoid, gynaecological cancers, and other. Complete soft tissue or ‘central’ pelvic exenteration for an advanced primary malignancy of rectal or genitourinary origin, while having obvious implications for the patient’s quality of life with two stomas, remains a relatively straightforward procedure for an experienced exenteration surgeon. The inherent difficulties in operating on recurrent cancer due to the absence of primary anatomical planes, and invariably previous radiotherapy fibrosis, have led to colorectal surgeons being the current surgical ‘leaders’ of complex pelvic oncology resections. The boundaries of resection have changed dramatically in the past 25 years. R0 rates have climbed from well below half of patients with recurrent rectal cancer (RRC) and less than one- third for those with recurrent tumours involving pelvic bone in the 1990s, to 60–75 per cent for all compartments now including bone and neurovascular involvement at specialized quaternary units. It seems logical that patients with more complex disease be referred to units with the volume, experience and outcome data to support these referrals. It is inherent that such centres be adequately funded, to provide not only the surgical service but also the medical and surgical specialties involved in decision-making both for and against surgery and, most importantly, the allied health and specialized nursing staff for the perioperative management of such complex patients. Like many past surgical innovations, the dictum of success in exenterative surgery, both objectively in terms of survival and subjectively in terms of quality of life and health economics, is based around ‘two-thirds decision-making and only one-third surgical technique’. Some of the most significant recent developments in advanced pelvic oncology, alongside surgical innovation, relate to improvements in MRI, navigational technology, the use of radiologically guided three-dimension al reconstructions to allow complete sacrectomy, and greater adoption of neoadjuvant treatments, including reirradiation, intraoperative radiotherapy and total neoadjuvant treatment5,6. As the radicality increases, the associated morbidity, impact on health-related quality of life, and the potential for functional deficits also increases. Long-term studies on subjective (patient-reported outcome measures) as well as objective (R0 margins, morbidity, recurrence and survival) outcomes become vital7,8. There is persistent and substantial unwarranted variation in treatment decision-making for people presenting with advanced/recurrent pelvic cancer worldwide. Most of the decision-making process, including the recommendation to support or not support advanced pelvic cancer surgery, is based on the experience of individuals and centres, and does not follow a comprehensive evidence-based approach that is well supported by cancer specialists, patients and carers. Treatment decision-making is commonly univariable, having survival as the solely desired postoperative outcome. There is no evidence on important composite measures, such as survival, morbidity and quality-of-life outcomes, to inform treatment decision-making. Moreover, definition of optimal outcomes and the views of cancer specialists, health economists, epidemiologists, health policy-makers, patients and carers on their accepted influence on decision-making is lacking. Therefore, the boundaries of pelvic surgical oncology of the future must try to address unwarranted treatment decision-making variation in patients with advanced or recurrent bowel cancer by developing simple evidence-based surgical information that includes patient choice, physical, nutritional and psychological information, surgical outcomes, patient-reported outcomes (quality of life), morbidity, treatment costs and survival. Funding for these quaternary units should also support prospective audit to ensure the highest standards are met and improved over time in what can be an ethical grey zone of offering as yet unproven techniques by controlled clinical trials. R0 margins for pelvic malignancy are an important audit tool as they relate not only to long-term survival but also to quality of life and operative morbidity. However, the actual definition of an ‘R0 margin’ can be manipulated from any ‘normal intervening tissue up to 1–2-mm margins. In now well over 250 RRCs (Table 1), an R0 margin is achieved in 78.6 per cent if defined by 0.5 mm of normal tissue, but in 68 per cent if 1 mm is used and in 54 per cent if 2 mm is used. There is no definition currently accepted for the margin of R0 versus R1, but in the author’s series there was no survival difference for margins greater than 0.5 mm. The current debate is whether ‘any normal tissue’ or 0.5 mm is an acceptable audit definition for an R0 margin in RRC9. What currently vexes surgical decision-making in achieving the holy grail of an R0 margin is determining not only the resectability of pelvic malignancy but also the radicality of the surgical approach required for the same tumour. Over several decades of progressive and repeated prospective audit in all pelvic compartments, the author and colleagues have adopted a ‘sarcoma’ policy for RRC: if the recurrence abuts or involves an organ, that organ should be resected en bloc and not ‘shaved’ free of tumour. This has led to dramatic improvements in R0 rates in the lateral compartment, from 21 to 68 per cent10, including when sciatic nerve resection occurs (R0 68 per cent)11, common and external iliac vessel resection (R0 74 per cent)12, and if sacrectomy posteriorly (R0 74 per cent) is required13. A recent international benchmark study14 from 10 French centres and two Australian centres is possibly the only direct comparison between ‘radicality concepts’; this study found that a more radical approach to potentially involved structures led to a 35 per cent difference in R0 rates for RRC in both concept and practice (86 versus 51 per cent). Refining techniques continue to facilitate ‘higher and wider’ resections at the periphery of the pelvis15. En bloc sciatic nerve and/or lumbosacral trunk excision for tumours that extend more laterally into the piriformis muscle have R0 rates similar to those of central pelvic tumors, and functional outcomes better than anticipated, with almost all patients (96 per cent) who require complete sciatic nerve resection able to mobilize after surgery with intensive physiotherapy and orthotics input11. Low sacrectomy (below S3) is now performed routinely by exenteration surgeons, with relatively low complication rates, whether performed prone or in the abdominolithotomy position16. A recent international multicentre collaboration17 demonstrated that high sacrectomy can be performed without compromising R0 rates, cancer-specific or overall survival, and is no longer considered a contraindication to surgery. Techniques for anterior cortical sacrectomy and abdominolithotomy sacrectomy have allowed 75 per cent of sacrectomies to be performed via an abdominoperineal approach by colorectal surgeons at the author’s centre, minimizing operating time and the added morbidity of a large additional prone incision16,18. The PelvEx and Beyond TME collaboratives, combined with local initiatives such as IMPACT (Association of Coloproctology of Great Britain and Ireland’s Improving Outcomes in Advanced Colorectal Tumours Initiative), have played an important role in facilitating national and international collaboration, understanding of different current practices and enhanced cooperation to help understand current and future clinical practice and research that continues to define the boundaries of pelvic oncology, changes the indications and contraindications of resectability, and hopefully helps to provide access and equity of quaternary pelvic oncological practice4,19,20. Disclosure. The author declares no conflict of interest.