RESPONSES TO DISCUSSION ON RECTAL CANCER

RESPONSES TO DISCUSSION ON RECTAL CANCER

by Shehu Salihu Umar -
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  1. Staging and Risk Stratification

What is the role of high-resolution pelvic MRI?

High-resolution pelvic MRI is the gold standard for local staging in rectal cancer. In practice, it provides vital structural information: exact anatomical tumor distance from the anal verge, depth of extramural invasion (T-category), regional lymph node involvement, relationship to the sphincter complex, and status of the circumferential resection margin (CRM/mesorectal fascia) and extramural vascular invasion (EMVI).

What is the significance of threatened CRM/MRF and positive EMVI?

Threatened CRM (≤ 1 mm): Places the patient at a high risk for local recurrence and positive surgical margins (R1/R2) if managed with upfront surgery, necessitating intensive neoadjuvant therapy to downstage the tumor prior to resection.

Positive EMVI: Denotes tumor invasion into veins outside the muscularis propria, serving as an independent negative prognostic indicator associated with a significantly elevated risk of synchronous and metachronous distant systemic metastases as well as reduced overall survival.

  1. Neoadjuvant Treatment

TNT versus Conventional Chemoradiotherapy followed by Surgery

I favor Total Neoadjuvant Therapy (TNT) — delivering both chemoradiotherapy and full-dose systemic consolidation or induction chemotherapy prior to surgery — over traditional preoperative chemoradiotherapy followed by postoperative adjuvant chemotherapy. TNT achieves superior compliance with systemic therapy, earlier elimination of micro-metastatic disease, higher rate of tumor regression, and improved compliance compared to postoperative administration.

Short-Course Radiotherapy (SCRT: 5 × 5 Gy) versus Long-Course Chemoradiotherapy (LCRT: 45–50.4 Gy with Fluoropyrimidine)

SCRT: Highly convenient (completed over 1 week) with low acute toxicities and lower economic burden. When followed by consolidation chemotherapy (as evaluated in the RAPIDO trial), it achieves robust tumor downstaging. However, long-term RAPIDO follow-up highlighted a slightly increased locoregional failure rate compared to standard chemoradiotherapy.

LCRT: Delivered over 5 to 6 weeks concurrently with capecitabine or 5-FU. It yields excellent local control and is traditionally preferred when maximum volumetric shrinkage is required to clear a threatened CRM.

Impact on pCR, Distant Disease Control, and Organ Preservation

Pathological Complete Response (pCR): TNT approximately doubles pCR rates (reaching ∼28% in trials like RAPIDO and PRODIGE 23) compared to standard chemoradiotherapy (∼14%).

Distant Disease Control: Systemic consolidation/induction chemotherapy given before surgery significantly decreases 3-year distant metastasis rates (from ∼26.8% down to ∼20.0%).

Organ Preservation: Increased tumor downstaging directly expands the pool of patients achieving a clinical complete response (cCR), rendering organ preservation strategies viable.

  1. Surgery and Organ Preservation

Feasibility of Sphincter Preservation at 4 cm from the Anal Verge

Sphincter preservation is technically feasible but challenging. At 4 cm, the tumor is located in the low rectum near the levator ani complex and internal anal sphincter. If neoadjuvant treatment produces substantial tumor regression and clears the distal margin by ≥ 1 cm (or ≥ 5 mm for microscopic clearance), an ultra-low anterior resection with intersphincteric resection and coloanal anastomosis can avoid permanent stoma creation, provided preoperative baseline sphincter function is adequate.

Low Anterior Resection (LAR) vs. Abdominoperineal Resection (APR)

LAR (Intersphincteric): Indicated if neoadjuvant therapy achieves sufficient shrinkage, leaving a tumor-free distal resection margin and preserving the external anal sphincter and levator ani muscles.

APR: Indicated if the tumor invades the external sphincter/levator muscle, if the threatened CRM/MRF cannot be cleared, or if baseline anal sphincter function is compromised.

When is a Watch-and-Wait (W&W) Strategy Appropriate?

A Watch-and-Wait protocol is appropriate only when the patient demonstrates a sustained Clinical Complete Response (cCR) evaluated at least 8 to 12 weeks post-completion of neoadjuvant therapy. I define cCR by:

  1. Digital Rectal Exam: Normal mucosal feel with no palpable induration or mass.

  1. Endoscopy: Flat scar, telangiectasia, white mucosal patch, and absence of ulceration or nodularity (confirmed by negative bioptic restaging if clinically suspicious).

  1. High-Resolution MRI: Dark signal on T2-weighted sequences (fibrosis) with complete absence of restricted diffusion on diffusion-weighted imaging (DWI) and complete regression of pathological lymph nodes.

4. Resource-Constrained Setting

How Short-Course RT or TNT Reduces Time, Cost, and Logistical Barriers

  1. Resource Efficiency: SCRT (5 × 5 Gy over 5 days) drastically reduces radiation machine burden and patient travel expenses relative to 25–28 fractions of LCRT over 5–6 weeks.

  1. Logistical Utility: Outpatient consolidation chemotherapy can be administered locally, decreasing non-medical costs (lodging, transport, lost work days) for patients in rural or underserved areas.



Practical Adaptations in an Out-of-Pocket Healthcare System

  1. Adopt SCRT-Based TNT: Utilizing 5 × 5 Gy followed by 4 cycles of CAPOX or 6 cycles of FOLFOX minimizes total hospital stay and radiation unit charges.

  1. Tolerable Chemotherapy Regimens:* Favoring oral Capecitabine plus Oxaliplatin (CAPOX) reduces infusion chair charges and central line access costs compared to FOLFOX/FOLFIRINOX where feasible.

  1. Selective Staging/Surveillance: Streamlining follow-up protocol intervals without compromising oncological safety, focusing on clinical examination, CEA monitoring, and dedicated low-cost imaging modalities when high-resolution MRI is cost-prohibitive during post-treatment surveillance.

​References

​Conroy, T., Bosset, J. F., Etienne, P. L., Rio, E., François, É., Mesroghli, N., ... & Unicancer-GI Group. (2021). Neoadjuvant chemotherapy with FOLFIRINOX and preoperative chemoradiotherapy for patients with locally advanced rectal cancer (UNICANCER-PRODIGE 23): a multicentre, randomised, open-label, phase 3 trial. The Lancet Oncology, 22(5), 702-715. https://doi.org/10.1016/S1470-2045(21)00079-6

​Bahadoer, R. R., Dijkstra, E. A., van Etten, B., Marijnen, C. A., Putter, H., Kranenbarg, E. M. K., ... & RAPIDO collaborative group. (2021). Short-course radiotherapy followed by chemotherapy before total mesorectal excision (TME) versus preoperative chemoradiotherapy, TME, and optional adjuvant chemotherapy in locally advanced rectal cancer (RAPIDO): a randomised, open-label, phase 3 trial. The Lancet Oncology, 22(1), 29-42. https://doi.org/10.1016/S1470-2045(20)30555-6

​Dijkstra, E. A., Nilsson, P. J., Hospers, G. A., Bahadoer, R. R., Meershoek-Klein Kranenbarg, E., Roodvoets, A. G., ... & RAPIDO collaborative group. (2023). Locoregional failure during and after total neoadjuvant treatment: long-term results of the RAPIDO trial. Annals of Oncology, 34(1), 82-93. https://doi.org/10.1016/j.annonc.2022.10.008

​Garcia-Aguilar, J., Patil, S., Gollub, M. J., Kim, J. K., Yuval, J. B., Thompson, H. M., ... & OPRA Investigators. (2022). Organ preservation in patients with rectal adenocarcinoma treated with total neoadjuvant therapy. Journal of Clinical Oncology, 40(23), 2546-2556. https://doi.org/10.1200/JCO.22.00032