Prospective Multicenter Comprehensive Survey on Male Sexual Dysfunction following Laparoscopic, Robotic, and Transanal Approaches for Rectal Cancer (the LANDMARC Study)

Robotic rectal surgery cut ejaculatory dysfunction from 41% to 25% vs. laparoscopic at 12 months — no edge on erections

Journal: Annals of Surgery | Published: 2024-10-22 | Type: Prospective multicenter open-label phase 2 trial | PMID: 39435538 Authors: Numata Masakatsu et al. (Yokohama City University Medical Center; 49 institutions of the Japanese Society of Laparoscopic Colorectal Surgery) Funding/COI: Not listed; authors report no conflicts of interest

Summary

One in three men who undergo minimally invasive rectal cancer surgery will have measurable erectile dysfunction a year later, and nearly one in three will have ejaculatory problems — numbers that prior IIEF-based studies inflated by conflating reduced sexual activity with actual dysfunction. The LANDMARC study is the first large prospective multicenter trial to assess post-surgical sexual function using the Erection Hardness Score and a custom ejaculatory questionnaire, sidestep the IIEF's intercourse-assumption problem, and directly compare laparoscopic, robotic, and transanal approaches in a propensity-matched cohort. The headline result: robotic surgery is meaningfully better for ejaculatory preservation, not for erections.

Claims

• At 12 months, overall ErD incidence was 34.7% and EjD incidence was 29.8% (n = 399 full analysis set)
• EjD rate at 12 months: robotic 25.0% vs. laparoscopic 40.9% — statistically significant after propensity score matching (n = 152 per arm)
• No statistically significant difference in ErD rate between robotic and laparoscopic groups
• Potency impairment at 6 months: laparoscopic 32.7% vs. robotic 22.3%; at 12 months: 29.0% vs. 17.8% — robotic significantly lower at both timepoints
• Transanal group (n = 25) showed elevated ErD and EjD at 3 months with partial recovery by 12 months; too small for matched comparison
• Prior IIEF-based studies reported ErD rates of 40–70%, likely inflated by reduced postoperative sexual activity rather than actual erectile impairment

Study Quality

This is a well-constructed prospective multicenter phase 2 trial conducted across 49 institutions with 399 enrolled patients and a structured follow-up schedule at 3, 6, and 12 months. Propensity score matching on eight clinically relevant covariates (age, BMI, tumor location, cT/cN stage, preoperative treatment, lateral lymph node dissection, diverting stoma) produced balanced cohorts of 152 pairs for the laparoscopic-robotic comparison. The choice to use the Erection Hardness Score over IIEF-5 is methodologically defensible and directly addresses a known confound in this population.

The study has real limitations that constrain interpretation. The transanal arm shrank to 25 patients — too few for matched analysis — because robotic adoption in Japan accelerated during enrollment following 2018 insurance coverage expansion, distorting the original 2:2:1 ratio. This is an open-label design with no sham control, so surgeon technique, experience level, and institutional volume differences are partially but not fully controlled. The study captures incidence at fixed timepoints but does not report recovery trajectories with granularity sufficient to assess whether EjD rates continue converging after 12 months.

Red Flags

• No blinding — open-label design; surgeons and institutions self-selected approach
• Transanal arm underpowered — n = 25 is descriptive only, not analytically useful; original design assumptions failed
• No funding source disclosed — unusual for a 49-institution trial; no clarity on whether any device manufacturer had any role
• Japan-specific practice patterns — upfront surgery without neoadjuvant treatment is standard in Japan vs. preoperative chemoradiotherapy in Western practice; limits generalizability to international cohorts where nerve injury patterns may differ
• 12-month endpoint may be premature — nerve recovery after pelvic surgery can continue beyond a year; longer follow-up is needed
• Custom ejaculatory questionnaire is not validated — EHS has validation data; the ejaculatory instrument does not, making cross-study comparison difficult

Strengths

• Largest prospective multicenter study specifically designed to assess both ErD and EjD after minimally invasive rectal cancer surgery
• Methodological improvement over IIEF: EHS doesn't penalize men who aren't sexually active postoperatively
• Prospective design with pre-operative baseline capture and structured multi-timepoint follow-up
• Propensity score matching reduces (though doesn't eliminate) selection bias between surgical arms
• Surgeon-level certification data collected, allowing partial control for operative experience

Verdict

LANDMARC is the most credible prospective evidence to date that robotic rectal surgery offers a meaningful ejaculatory function advantage — roughly halving the 12-month EjD rate compared to laparoscopic. That's a real signal worth noting, particularly given the mechanistic plausibility (ejaculation runs on hypogastric nerves; robotic dissection may be gentler on them). The null finding on erections is equally notable: no robotic edge there. The underpowered transanal arm is a write-off for this analysis. The missing funding disclosure is an odd gap in an otherwise thorough paper. Worth reading for anyone tracking surgical quality-of-life outcomes; not sufficient alone to declare robotic surgery superior.