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EDITORIALS |
From Beth Israel Medical Center, New York, New York.
Correspondence: Address correspondence to: Warren E. Enker, MD, Beth Israel Medical Center, 350 East 17th Street, Baird Hall, Room 1622, New York, NY 10003; Fax: 212-420-2846; E-mail: wenker{at}bethisraelny.org
In the February issue of the Annals of Surgical Oncology, Stipa et al.1 provided a retrospective, well-focused study that attempts to correlate preoperative stage of rectal cancer as determined by endorectal ultrasound (ERUS), with postoperative pathologic stage after neoadjuvant therapy, in patients who were selected for neoadjuvant treatment because they were deemed to have locally advance lesions. The data derives from a specialty service that is well known for its clinical outcomes and for its expertise in ERUS.2 The authors estimate that 54% of patients had regional (i.e., mesorectal disease before combined modality treatment [CMT]) and, pathologically, that 27% had regional disease even after the completion of neoadjuvant treatment. The study concludes that, despite recent enthusiasm, neoadjuvant therapy does not eradicate all regional disease to a degree that would eliminate the need for formal rectal and mesorectal resection. Although the authors focus on the incidence of residual lymph node disease after treatment, other factors are equally compelling in determining the need for resection.
Previous studies have indicated that from 10% to 30% of patients demonstrate objective regression of disease (i.e., a complete pathologic response) after neoadjuvant therapy.3–5 The obverse, or corollary, is that 70% to 90% of patients harbor residual mesorectal tumor, despite their preoperative treatment, requiring formal curative rectal and mesorectal resection.6
No proven correlation exists between the regression of a primary tumor and the regression of regional, mesorectal nodal disease. Why primary tumors shrink in response to radiation and chemotherapy (RTCRx), whereas disease in the mesorectum can remain relatively unaffected in a substantial number of cases, remains a clinical mystery. Whereas shrinkage of a bulky, primary tumor situated within a narrow pelvis can offer the surgeon an easier opportunity to perform an adequate resection, shrinkage alone is not a sign of clinical down-staging in a disease that is overwhelmingly regional in its presentation (
T3, or N1-N2 in 65% to 80% of patients).7,8 Designing patient care around the aftereffects of RTCRx, as opposed to determining treatment on the basis of the original stage at presentation, has many pitfalls and hazards. Currently, shrinkage of the primary tumor is not a sufficient foundation upon which to alter treatment in mid-course from a resection of regional disease (i.e., total mesorectal excision [TME]) to local excision.
Lymph nodes are by no means the exclusive markers of regional disease. Despite their absence as a staging criterion, other adverse pathologic risk factors continue to play a significant role in the risk of local recurrence. Our data suggest that the incidence of microscopic adverse pathologic features (e.g., lymphatic, vascular or perineural invasion, mucinous carcinoma, poor degree of differentiation, extracapsular nodal penetration) rises in direct proportion to the increase in T stage and N stage. The incidence or these clinically and radiologically undetectable features ranges from 10% to 30% in patients with stage T1-T4N0 disease, to as much as 38% to 62% in stages T1-T4N2.7,9 Despite that none of these microscopic features are detectable by any form of preoperative staging, their presence must be anticipated by all members of the disease management team, particularly in patients with locally advanced disease, or for any with T3 stage. Currently, no rationale exists for changing one’s original intention to perform a regional resection in such patients, despite tumor regression after radiation and chemotherapy.
Multidisciplinary treatment efforts continue to select patients who would benefit most from perioperative treatment while minimizing needless toxicity. Patients with cancers of the distal rectum, locally advanced disease by either clinical or imaging criteria, poorly differentiated cancers, circumferential tumors, or tumor that are obstructing or perforated represent the broadly accepted criteria for the selection of neoadjuvant therapy. It is just this very group that is most likely to be harboring regional mesorectal disease, whether it is detectable by current imaging standards.
Although the authors’ expertise in ERUS is acknowledged, their ability to detect small lymph nodes (i.e., <5 mm) is not a level of resolution that is universally shared by others. Most radiologists, in fact, rely on the criteria of enlarged nodes as signs of mesorectal lymph node metastases. Nevertheless, Herrera and Villareal10 have reported that 50% of the patients with involved lymph nodes harbor lymph nodes that are <5 mm in diameter.6 This size is too small for detection by most imaging techniques, whether ERUS, computed tomography (CAT) scan, CAT-positron emission tomography scan, or standard magnetic resonance imaging (MRI). It is hoped that current advances, including high-definition MRI, as reported by Brown et al.,11 suggest that regional disease may be more accurately evaluated in the not too distant future. Whereas the authors’ expertise in ERUS suggests apparent down-staging, they do not resolve the question of whether one can reliably count on any imaging techniques to provide us with accurate preoperative staging.
A fundamental issue for all prospective as well as retrospective studies is the current standard of pathologic evaluation. Quirke et al.12 and Birbeck et al.13 have outlined the criteria for serial sectioning of rectal cancer specimens that have been resected in accordance with the principles of TME. Standardized pathology is an essential backup for comparative studies and whether treatment programs for rectal cancer are to be comprehensive. Careful identification of nodal involvement and the determination of R0, R1, or R2 resection require the universal adoption of standardized methodology as we witness the adoption of TME as the standard for rectal care.7
For accurate staging, a diligent assessment of each resected specimen is required by a dedicated pathologist. Joseph et al.14 have recently reported on the minimal number of lymph nodes needed for accurate staging. Although radiation therapy is known to reduce the number of lymph nodes in a targeted specimen and the node counts in the mesorectum are often lower than can be detected in the colonic mesentery, any discussion of down-staging requires a foundation of accurate pathologic evaluation if we are to make use of such data in designing and advocating future treatment programs.
Received for publication December 17, 2003. Accepted for publication January 13, 2004.
REFERENCES
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