MIS for cervical cancer: Is it not for anyone or not for everyone?

Shock waves moved through the gynecologic oncology world on Oct. 31, 2018, when the New England Journal of Medicine published two papers on survival outcomes for women undergoing surgery for early stage cervical cancer.

Dr. Emma C. Rossi

The first was a randomized controlled trial of laparotomy and minimally invasive surgery (MIS) for radical hysterectomy called the LACC trial.¹ In the multicenter, international trial of 631 women, the primary objective was disease-specific survival (cervical cancer–related deaths) and was powered to detect noninferiority of the MIS approach when compared with laparotomy. The trial was closed early when investigators noted a lower than expected rate of 3-year, disease-free survival (91% vs. 97%) from cervical cancer in the MIS group, which was made up of 84% laparoscopic and 16% robotic approaches, versus laparotomy. There were 19 deaths in the MIS group observed versus three in the laparotomy group. The conclusions of the trial were that MIS surgery is associated with inferior cervical cancer survival.

In the second study, authors analyzed data from large U.S. databases – the National Cancer Database (NCDB) and the Surveillance, Epidemiology, and End Results (SEER) Program – to collect all-cause mortality for patients with early-stage cervical cancer who had undergone radical hysterectomy during 2010-2013.² Among 2,461 observed results, 1,225 had undergone MIS surgery with the majority (79.8%) via robotic-assistance. Women undergoing MIS approaches had smaller, lower grade tumors; were more likely to be white, privately insured, and of a higher income; and had surgery later in the cohort and by nonacademic centers. The researchers adjusted for risk factors with an analytic process called propensity-score weighting, which matched the groups more closely in an attempt to minimize confounders. They identified higher all-cause mortality among women who were treated with an MIS approach, compared with those treated with laparotomy (hazard ratio, 1.65). They also observed a significant decline in the survival from cervical cancer annually that corresponded to the uptake of MIS radical hysterectomies.

In the wake of these publications, many concluded that gynecologic oncologists should no longer offer a minimally invasive approach for radical hysterectomy. Certainly level I evidence published in a highly influential journal is compelling, and the consistency in findings over two studies adds further weight to the results. However, was this the correct conclusion to draw from these results? Surgeons who had been performing MIS radical hysterectomies for many years with favorable outcomes are challenging this and are raising questions about external generalizability and whether these findings were driven by the surgery itself or by the surgeon.

The studies’ authors proposed hypotheses for their results that implicate the surgical route rather than the surgeon; however, these seem ad hoc and not well supported by data, including the authors’ own data. The first was the hypothesis that cervical tumors were being disrupted and disseminated through the use of uterine manipulators in MIS approaches. However, cervical cancers are fairly routinely “disrupted” by preoperative cone biopsies, loop electrosurgical excision procedures (LEEP), and sharp biopsies, which are arguably more invasive than placement of a manipulator. Uterine manipulators routinely are used in endometrial cancer surgeries, in which the manipulator is embedded within the tumor, without an associated negative survival effect in randomized trials.³ Additionally, not all surgeons utilize manipulators for radical hysterectomies, and these studies did not measure or report on their use; therefore, it is impossible to know whether, and by what magnitude, manipulators played a role. Finally, if uterine manipulators are the explanation for inferior survival, surely the recommendation should be to discourage their use, rather than abandon the MIS approach all together.

The other explanation offered was exposure of the tumor to CO₂ gas. This seems an even less plausible explanation because CO₂ gas is routinely used in MIS cancer surgeries for endometrial, prostate, gastric, and colorectal surgeries and is used as insufflation for malignant interventional endoscopies without a significant deleterious effect. Additionally, the cervix is not exposed to CO₂ until colpotomy at the procedure’s end – and only briefly. The in vitro studies implicating a negative effect of simulated CO₂ pneumoperitoneum are neither compelling nor consistent.^4,5

I would like to propose another hypothesis for the results: surgical proficiency. Surgery, unlike medical interventions, is not a simple variable that is dichotomous – performed or not. Surgeons do not randomly select operative approaches for patients. We select surgical approaches based on patients’ circumstances and surgeon factors, including our own mastery of the various techniques. Randomized surgical trials rely on the notion that a surgeon is equally skilled in both or all approaches offered, but this is clearly not the case, and any surgeon recognizes this if he or she has observed more than one surgeon or has attempted a procedure via different routes. While some procedures, such as extrafascial hysterectomy for endometrial cancer, are relatively straightforward and surgeon capabilities are more equitable across different approaches, cervical cancer surgery is quite different.

Early-stage cervical cancer primarily exerts radial growth into the cervical stroma and parametria. Curative surgical excision requires broadly negative margins through this tissue, a so called “radical hysterectomy.” The radicality of hysterectomy has been categorized in stages, acknowledging that different sized lesions require different volumes of parametrial resection to achieve adequate clearance from the tumor.⁶ In doing so, the surgeon must skeletonize and mobilize the distal ureters, cardinal ligament webs, and uterosacral ligaments. These structures are in close proximity to major vascular and neural structures. Hence, the radical hysterectomy is, without dispute, a technically challenging procedure.