Skip metastases in colon cancer: assessment by lymph node mapping using molecular detection

Short term results of complete (D3) vs. standard (D2) mesenteric excision in colon cancer shows improved outcome of complete mesenteric excision in patients with TNM stages I-II

BACKGROUND

The aim of the present study was to investigate whether the new method of complete mesocolic excision (CME) with a high (apical) vascular tie (D3 resection) had an immediate effect compared with a conventional (standard) approach even in those patients without lymph node metastases.

METHODS

A cohort of 189 consecutive patients with tumour-nodal-metastasis (TNM) stages I-II and a mean age of 73 years were operated on in the period from January 2007 to December 2008 in three community teaching hospitals. The CME approach (n = 89), used in hospital A, was compared to the standard technique used (n = 105) in two other hospitals, B and C. Lymph node yields from the specimens were used as a surrogate measure of radical resections. Outcome was analysed after a median follow-up of 50.2 months.

RESULTS

In-hospital mortality rate was 2.8 % in the CME group and 8.6 % in the standard group. The 3-year overall survival (OS) in the CME group was 88.1 versus 79.0 % (p = 0.003) in the standard group, and the corresponding disease-free survival (DFS) was 82.1 versus 74.3 % (p = 0.026). Cancer-specific survival was 95.2 % in the CME group versus 90.5 % in the standard group (p = 0.067). Age, operative technique, and T category were significant in multiple Cox regressions of OS and DFS.

CONCLUSIONS

Compared with the standard (D2) approach, introduction of CME surgical management of colon cancer resulted in a significant immediate improvement of 3-year survival for patients with TNM stage I-II tumours as assessed by OS and DFS.

Improved lymph node harvest from resected colon cancer specimens did not cause upstaging from TNM stage II to III

BACKGROUND

The number of lymph nodes retrieved and examined from a resected colon cancer specimen may be crucial for correct staging. We examined if efforts to increase the lymph node harvest to more than 12 lymph nodes per specimen would upstage some patients from TNM stage II to III.

METHODS

Three hospitals compared results from 2000 with those of 2007 in 421 resected patients with stage II and III colon cancer. Hospital A endeavored to improve the surgical procedure while the pathologists enhanced the quality of lymph node sampling. Hospital B did not make any marked changes, while hospital C introduced the GEWF lymph node solvent (glacial acetic acid, ethanol, distilled water, and formaldehyde) in their pathology method.

RESULTS

In 2000, 12 or more lymph nodes were harvested in 39.6, 45.0, and 21.1% of the specimens from the three hospitals, while the figures for 2007 were 85.7, 42.0, and 90.3%, respectively. The significant increase in lymph node harvest in two of the hospitals in 2007 compared to 2000 (p < 0.001) did not affect the share of patients with stage III in 2007 (38.7%) compared to 2000 (44.1%) (p = 0.260). The number of positive lymph nodes and the lymph node ratio (LNR) decreased from 2000 to 2007. A lymph node yield of 12 or more was not associated with an increased probability of positive lymph nodes in a multivariable logistic regression analysis.

CONCLUSION

More radical surgery and dedicated pathologists and the use of the GEWF solvent significantly increased the lymph node yield but did not upstage patients from TNM stage II to III.

Positron emission tomography scan reveals an unusual source for cervical lymphadenopathy: right colon cancer

Cervical lymphadenopathy is usually related to the presence of an inflammatory disease or to a malignant localization. In the event of metastatic findings, the thyroid gland is the most likely primary site of a tumor. Metastatic lymphadenopathy represents a challenge when the primary tumor is unknown. A 64-year-old female with a supraclavicular palpable mass in the absence of underlying thyroid disease underwent ultrasonography of the neck, biopsy of the pathological lymph node, fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) and colonoscopy until right colon cancer was diagnosed. FDG-PET is a fast and reliable tool to discover the primary site of cervical masses of unknown origin.

Overall survival after resection for colon cancer in a national cohort study was adversely affected by TNM stage, lymph node ratio, gender, and old age

BACKGROUND

A national surveillance program of colon cancer treatment was introduced in 2007. We examined prognostic factors for colon cancer operated in 2000 with an aim of improving survival in the new program and a special focus on the merit of lymph node yield.

METHODS

A cohort of 269 patients, 152 women (56.5%), with a mean age of 71 years, was operated for colon cancer in 2000 at three teaching hospitals and followed up for 7 years.

RESULTS

Overall 5-year survival was 58.0%, and overall hospital mortality was 5.2%, with 4.5% in elective cases and 12.5% after urgent surgery. In only 41.1% of the specimens were 12 or more lymph nodes retrieved, but this did not affect survival in the combined cohort, although one of the hospitals achieved a significantly better result with a harvest of 12 or more lymph nodes. In a multivariate analysis, old age, gender, a high lymph node ratio (LNR) at stage III, and tumor-node-metastasis stage were adverse factors for survival.

CONCLUSIONS

The operative mortality was high and should be reassessed. The lymph node count did not have a significant impact on outcome overall, whereas the LNR proved significant for stage III. A prospective protocol using overall lymph node yield as a surrogate measure for more radical surgery, nevertheless, seems warranted to improve the lymph node harvest according to international recommendations.

Lymph node harvest in colon cancer specimens depends on tumour factors, patients and doctors, but foremost on specimen handling

There are good indications that the number of lymph nodes found in the specimen after resections for colon cancer somehow has a bearing on prognosis. Many factors have been reported in the literature to influence lymph node retrieval. We wanted to assess these closer with special focus on the pathology handling process in our own practice. A range of international literature was reviewed to study what has been found to influence lymph node harvest. A questionnaire was sent to 13 renowned national and international institutions to explore their handling of the colon cancer specimens to obtain a histological diagnosis. A retrospective, hospital audit was undertaken to examine if the number of lymph nodes and staging after examinations of the specimens varied between individual pathologists. In the literature, tumour and patient characteristics, as well as the surgeon and the pathologist, are found to be influential, but it is difficult to ascertain which ones are truly essential. Fat solvents were found by several to increase the lymph node yield, although some also opposed this finding. Our questionnaire showed some variations in the routines of each Department. A junior pathologist was more likely to inspect the specimen first hand and not more than half employed specific lymph node detection strategies while three of 13 did not seek a minimum number of lymph nodes. Still every department had implemented a standard procedure for such examinations. The internal audit showed without doubt that the devotion of the pathologist secured significantly more lymph nodes from the specimen and this may also have detected more stage III cancers. Several tumour and individual patient characteristics, surgical approach and specimen handling may influence lymph node yield and theoretically, TNM staging. Our investigation specifically suggests that tissue handling by pathologists may be a prominent factor in lymph node harvest from colon cancer specimens.

Oncological outcome of unresectable lung metastases without extrapulmonary metastases in colorectal cancer

AIM: To explore the oncological outcomes of unresectable lung metastases without extrapulmonary metastases in colorectal cancer.

METHODS: Patients with unresectable isolated lung metastases from colorectal cancer were prospectively collected in a single institution during a 5-year period. All patients received either the fluorouracil/leucovorin plus oxaliplatin, fluorouracil/leucovorin plus irinotecan or capecitabine plus oxaliplatin regimen as first-line treatment. The resectability after preoperative chemotherapy was evaluated. Patients’ outcome and predictive factors for overall survival were also investigated by univariate and multivariate analysis.

RESULTS: A total of 70 patients were included in the study. After standardized first-line chemotherapy, only 4 patients (5.7%) were converted to resectable disease. The median overall survival time in all patients was 19 mo (95% CI: 12.6-25.4), with a 2-year overall survival rate of 38.8%. No survival difference was found among different first-line chemotherapeutic regimens. Prognostic analysis demonstrated that only the first response assessment for first-line treatment was the independent factor for predicting overall survival. The median survival time in partial response, stable disease and progressive disease patients were 27 mo, 16 mo and 8 mo (P = 0.00001).

CONCLUSION: Pulmonary metastasectomy can only be performed in a small part of unresectable lung metastases patients after chemotherapy. Patients’ first response assessment is an important prognostic factor.

How uncommon are isolated lung metastases in colorectal cancer? A review from database of 754 patients over 4 years

BACKGROUND

It is commonly thought that colon cancer metastases to the lungs without involvement of the liver are rare.

METHODS

We performed a retrospective review of all patients with colorectal cancer diagnosed between December 2003 and August 2007 in Singapore. Isolated lung metastases were determined as (1) Definite if there was confirmed histology or cytology of the lung lesion(s) in the absence of liver lesions on CT scan, and (2) Probable if there were only radiological evidence suggestive of lung metastases rather than lung primary also in the absence of liver lesions on CT scan.

RESULTS

There were 196 patients with rectal and 558 patients with colon cancer (369 left-sided and 189 right-sided). There were 13 definite isolated lung metastases, and the remaining 43 were probable. Twenty-three (12%) patients with rectal cancer and 33 (6%) patients with colon cancer had isolated lung metastases (OR 2.11, 95% CI 1.21-3.70). Patients with >or=pT3 lesions (OR 1.92, 95% CI 0.75-4.93) and >or=pN1 (OR 1.56, 95% CI 0.86- 2.83) were more likely to have isolated lung metastases.

CONCLUSION

The true incidence of isolated lung without liver metastases in colorectal cancer is likely to lie between 1.7% and 7.2%. While the incidence of isolated lung metastases is twice as common in patients with rectal cancer, it is still significant in patients with colon cancer. The absence of liver involvement should not preclude a search for lung metastases.

Lymphoscintigraphic localization of sentinel node in early colorectal cancer: results of a monocentric study

BACKGROUND AND OBJECTIVES

Evaluation of the feasibility of the sentinel node technique in early colorectal neoplasms and its overall accuracy in predicting nodal metastases.

METHODS

Thirty-five patients with colon or rectal lesions or degenerate polyps not radically excised by endoscopy were included. Lymphatic mapping was performed with 99mTc labeled albumin colloid injected submucosally by an endoscopic route the afternoon before the surgical procedure. The day of the intervention, 2.5% patent blue V dye (S.A.L.F: Italy) was injected circumferentially around the tumor. A hand held gamma detecting probe (Scintiprobe m100, Pol-Hi-Tech, Italy) was employed to detect "hot" nodes, in vivo and ex vivo. All sentinel nodes were embedded separately for haematoxylin and eosin staining. No IHC or PCR techniques were employed.

RESULTS

Sentinel lymph nodes (SLN) were successfully identified in 35 out of 35 patients. Concordance between SLN and nodal status was observed in 32 out of 35 cases (91.4%); four patients (11.4%) were upstaged. Three skip nodal metastases were observed (false-negative rate: 8.5%).

CONCLUSIONS

The sentinel node technique with blue dye and radiotracer seems valuable in early colorectal cancers detected by screening programs: a good organization and a learning curve are needed, as further multicentric studies.

Clinical significance of skip metastasis in patients with gastric cancer

BACKGROUND

Metastasis appearing to bypass or skip tiers of lymph nodes (LNs) has been referred to as skip metastasis. The clinical impact of skip metastasis in gastric cancer remains unclear.

METHODS

In patients with gastric cancer, the clinicopathological features and postoperative prognoses of 21 patients with skip metastasis were evaluated and compared with findings in patients with group 1 (N1) or group 2 (N2) LN metastasis.

RESULTS

Of the 21 patients with skip metastasis, 9 patients had metastasis in the LN along the common hepatic artery (No. 8a), 8 patients had metastasis in the LN along the left gastric artery (No. 7), 2 patients had metastasis in LNs No. 7 and No. 8a, 1 patient had metastasis in the LN at the splenic hilum (No. 10), and 1 patient had metastasis in LN No. 10 and the LN along the splenic artery (No. 11). The mean diameter of the tumors in the patients with skip metastasis was 5.7 +/- 2.4 cm, which was significantly smaller than those in the N1 patients (7.9 +/- 4.1 cm) and N2 patients (9.3 +/- 4.6 cm). The incidence of serosal invasion, lymphatic vessel invasion, and peritoneal metastasis was lower in patients with skip metastasis compared with N2 patients. The 5-year survival rates were 70.2%, 62.0%, and 31.2% in patients with skip metastasis, patients with metastasis in group 1 LNs, and those with metastasis in group 2 LNs, respectively. The prognosis of patients with metastasis in group 2 LNs was significantly worse than that of patients with either skip metastasis (P = 0.0029) or metastasis in group 1 LNs (P < 0.0001).

CONCLUSION

Our data indicate that both the clinicopathological characteristics and the prognoses of patients with skip metastasis were similar to those of patients with N1 LN metastasis, but these features were not similar to those in patients with N2 LN metastasis. The sites of skip metastasis presented in the current study may be the key for applying the concept of the sentinel node in gastric cancer.

Validity of modified gastrectomy combined with sentinel node navigation surgery for early gastric cancer

BACKGROUND

The present study examined the clinical validity of modified gastrectomy for early gastric cancer, in terms of the results of sentinel node navigation surgery (SNNS), using infrared ray electronic endoscopy (IREE) plus indocyanine green (ICG) staining.

METHODS

One-hundred and sixty-one patients with fT1N0 gastric cancer were enrolled in the study. ICG (0.5 ml, 5 mg/ml) was injected endoscopically into four quadrants of the submucosa surrounding the cancer. Twenty minutes after the injection, sentinel lymph nodes (SNs) stained with ICG were observed intraperitoneally around the serosa and surrounding fat tissue. IREE was used to illuminate regional lymph nodes from the serosal side.

RESULTS

Group 2 lymph nodes were judged as SNs in 52 patients (32%). The most common locations of the SNs were stations No. 7 in each of the upper-, middle-, and lower-thirds of the stomach. In two patients, lymph node metastasis was positive. One of these patients, with cancer in the middle one-third of the stomach, had SNs in stations No. 3, 4sb, 4d, 7, and No. 11p, and had metastatic lymph nodes in No. 3 and No. 7 (all SNs). The other patient, with cancer in the lower one-third of the stomach, had SNs in No. 1, 3, 4d, and 6, and had a metastatic lymph node in No. 4d (SN). Skip metastasis was not observed in this study, and metastatic lymph nodes were judged to have been dissected by the D1+a procedure.

CONCLUSION

For T1N0 gastric cancer, modified gastrectomy (D1+a dissection) combined with SNNS is suitable; however, for those whose Group 2 lymph nodes are judged to be SNs, additional dissection of lymphatic basins detected by SNNS should be performed to confirm the absence of lymph node metastasis.

Oncologic results of laparoscopic D3 lymphadenectomy for male sigmoid and upper rectal cancer with clinically positive lymph nodes

BACKGROUND

Many Japanese surgeons routinely perform extended D3 lymph node dissection for the treatment of advanced rectosigmoid cancer with a view to achieving better tumor control. However, the application of a laparoscopic approach to perform D3 lymphadenectomy has been challenging. This phase 2 prospective study aimed to explore the oncologic results of this surgical approach.

METHODS

The study was conducted during a 6-year period, in consideration of median follow-up time being >3 years. The study subjects were tumor, node, metastasis system stage III rectosigmoid cancer staged by clinical images. The extent of D3 dissection and the postoperative lymph node mapping were according to the guidelines of the Japanese Society for Cancer of the Colon and Rectum. Patients were stratified according to the histopathologically proved highest level of involved lymph nodes and placed into N0, N1, N2, and N3 groups. The primary end points of the study were the estimated time to recurrence and 5-year recurrence rate of cancer after laparoscopic D3 dissection.

RESULTS

The estimated 5-year recurrence rate (20% in the N0 group [n = 10]; 25% in N1 [n = 44]; 33.3% in N2 [n = 30]; and 42.8% in N3 [n = 14]), time to recurrence (mean [95% confidence interval] 59.8 [42.6-76.9] months in the N0 group; 56.8 [48.3-65.2] months in N1; 46.8 [37.5-56.1] months in N2; and 43.9 [28.3-59.4] months in N3), and recurrence patterns were without significant difference (all P values >.05) among N0, N1, N2, and N3 groups. Therefore, by laparoscopic wide anatomic dissection, patients with lymph node involvement could be treated as well as those without lymph node metastasis. Laparoscopic D3 dissection facilitated the collection of more lymph nodes (mean +/- standard deviation, 27.4 +/- 4.2) for histopathologic examination. Mapping of dissected lymph nodes showed that 18.2% (16 of 88) patients had skip lymph node metastasis. D3 dissection facilitated upstaging of cancer (from N0 to N3) in five patients (5.1%). However, this procedure resulted in transient voiding dysfunction in 77.5% patients and loss of ejaculatory function in 91.7%. By laparoscopic approach, the D3 lymph node dissection was safely performed through small wounds, resulting in quick functional recovery and only moderate blood loss (324.8 +/- 44.5 mL), but at the expense of a long operation time (294.4 +/- 34.8 minutes).

CONCLUSIONS

The good short-term oncologic results and quick convalescence mean that the laparoscopic D3 dissection may be recommended for patients with stage III rectosigmoid cancer who could accept the genitourinary dysfunction.

Detection of micrometastases and skip metastases with ex vivo sentinel node mapping in carcinoma of the colon and rectum

BACKGROUND

The debate over sentinel lymph node mapping (SLNM) and focused pathologic examination to detect micrometastases in patients with colorectal cancer (CRC) continues. We present in this paper our experience with SLNM for CRCs to improve staging. In addition, we have detailed the mapping procedure on an anatomical basis to define skip metastasis.

MATERIALS AND METHODS

Forty-seven patients underwent ex vivo SLNM. Immediately after resection, 1 ml of patent blue VF was injected submucosally around the tumor. Lymph nodes harvested from the first 15 patients were mapped in a standard fashion as the blue-stained nodes (SLNs), and the others (non-SLNs) were dissected away. In the remaining 32 patients, the lymph nodes were also mapped separately in relation to their anatomic location and described as epicolic-paracolic, intermediate, and principal. The blue-stained nodes (SLNs) and non-SLNs, negative by hematoxylin and eosin stain, were further stained with cytokeratin immunohistochemical analysis and carcinoembryonic antigen.

RESULTS

A total of 873 histologically confirmed LNs were examined with a mean of 18.6+/-8.1 nodes per patient. In 46 of 47 patients (97.8%), SLNs were identified. Immunohistochemical staining revealed micrometastases in the lymph nodes of four patients, which were negative by conventional methods. Anatomical skip metastases were noted in 4 of 32 patients studied (12.5%).

CONCLUSION

Ex vivo SLNM in CRCs is a feasible technique with a high SLN identification rate. Results of anatomical mapping of lymph nodes correlates with the limited literature, suggesting that occult skip metastases can occur in the apical lymph node group and may occur outside the resected area.

Impact of skip metastasis in gastric cancer

BACKGROUND

Several studies have shown the features of skip metastasis in other cancers besides gastric cancer. Since minimally invasive surgery has been applied to gastric cancer, the concerns and awareness of skip metastasis have grown in the medical community. We conducted the present retrospective study to reveal the clinicopathological characteristics of patients with skip metastasis. We also wished to clarify the clinical impact of skip metastasis for gastric cancer.

METHODS

Five hundred and eighty-nine patients having lymphatic metastases were enrolled in the present study. Among them, 266 patients had positive nodes extending into the N2 group. We divided these patients into the skip positive (+) and the skip negative (-) group, and we comparatively analysed clinicopathological factors and calculated the survival probabilities for the two groups.

RESULTS

The skip (+) and skip (-) groups involved 14 (5.3%) and 252 (94.7%) patients, respectively. Of all the investigated factors, a significant difference between two groups was observed only in the total number of retrieved nodes. Stations of skip nodes were along left gastric (7), anterior common hepatic (8a), celiac (9), splenic (11) artery and right paracardial nodes (1). The survival curves calculated in the present study did not show any statistical differences between the groups.

CONCLUSIONS

Due to problems of skip metastasis in gastric cancer, D2 lymph node dissection should be performed until sentinel node detection is feasible and reliable. The potential risk from skip metastasis is not great and skip metastasis itself should not be a major consideration in therapeutic decisions.

Ex Vivo Lymphatic Mapping: A Technique to Improve Pathologic Staging in Colorectal Cancer

Sentinel lymph node (SLN) biopsy is widely used for solid tumors and has been proposed for use in staging colorectal cancer (CRC). Few studies have examined the ex vivo lymphatic mapping (EVLM) technique for staging CRC. We hypothesized that EVLM is technically feasible, sensitive, accurate, and improves the staging of CRC. After standard resection for colorectal cancer, 1 mL of isosulfan blue dye was injected circumferentially around the tumor. Blue-stained nodes were dissected separately and examined by hematoxylin and eosin (H&E) and immunohistochemical (IHC) stains. Routine pathologic evaluation was performed on all other harvested lymph nodes. Forty patients underwent 43 cancer resections with EVLM from July 2000 to December 2003. SLN were identified in 39 of 43 (91%) specimens. The mean number of SLN obtained was 1.9 (range, 0–5). Pathologic evaluation demonstrated nodal metastasis in 16 of 39 (39%) specimens. The SLN was tumor-positive in 9 of these 16 (56%) patients. The overall accuracy of EVLM was 82%. Two patients (9%) with H&E node negative disease were upstaged when found to have micrometastases by IHC staining. In conclusion, EVLM is technically possible in 90 per cent of patients with CRC. Although overall accuracy was high, the SLN status correlated poorly with the true nodal status of the CRC. However, EVLM improves pathologic staging in 9 per cent of patients and therefore may be of value in CRC.

Sentinel lymph node mapping in colon cancer

BACKGROUND

By systematically reviewing the literature on sentinel lymph node mapping of colon cancers, this study aimed to evaluate this technique as it applies to colon cancers.

METHODS

Human studies on lymphatic mapping for colon cancers were reviewed. Multiple publications of the same studies, abstracts, and case reports were excluded. Current Contents, MEDLINE, EMBASE, and Cochrane Library databases were investigated.

RESULTS

Lymphatic mapping appears to be readily applicable to colon cancers, identifying lymph nodes most likely to harbor metastases. Identification of sentinel lymph nodes varied from 58% to 100% and carried a false-negative rate of approximately 10% in larger studies, but potentially rose 4% to 25% among patients representing a range from node-negative to node-positive (micrometastases) conditions. The prognostic implication of these micrometastases requires further evaluation. Lymphatic mapping in 6% to 29% of cases identified aberrant lymphatic drainage that altered the extent of the lymphadenectomy.

CONCLUSIONS

Further follow-up evaluation to assess the prognostic significance of micrometastases for colon cancers is required before the staging benefits of sentinel node mapping can have therapeutic implications. Lymphatic mapping offers the possibility of improving staging by identifying patients with early disseminated disease who should be considered for adjuvant treatment or included in trials of adjuvant treatment to speed up the breakthrough of more effective adjuvant regimens. Large studies are needed to determine whether the sentinel node concept is as valid for colon cancers as studies so far have shown it is for malignant melanoma and breast cancer.

Detection of occult tumour cells in lymph nodes of colorectal cancer patients using real-time quantitative RT-PCR for CEA and CK20 mRNAS

The purpose of our study was to develop specific, sensitive, objective assays for early detection of disseminated tumour cells in patients with colorectal cancer (CRC). Carcinoembryonic antigen (CEA) and cytokeratin 20 (CK20) were chosen as markers because they are selectively expressed in epithelial cells with maintained expression in CRC. Real-time quantitative RT-PCR assays with RNA copy standards were constructed. Regional lymph nodes were collected from patients with CRC (n = 51) and benign intestinal disease (n = 10). Results were compared to routine histopathology and anti-CEA immunohistochemistry. Lymph node levels of CEA and CK20 mRNA correlated strongly (p < 0.0001, r = 0.8). Lymph nodes from non-CRC patients had <0.01 CEA and <0.001 CK20 mRNA copies/18S rRNA unit. Lymph nodes from 3/6 Dukes' A, 17/26 Dukes' B, 10/10 Dukes' C and 7/9 Dukes' D patients had CEA mRNA levels above cut-off. Corresponding figures for CK20 mRNA were 3/6, 10/26, 9/10 and 5/9, respectively. CEA mRNA levels varied from 0.001 to 100 copies/18S rRNA unit in Dukes' A and B, and 50% of the Dukes' B patients had CEA mRNA levels within the range of Dukes' C patients. Three Dukes' B patients have died from CRC or developed distant metastases. All 3 had high CEA and CK20 mRNA levels. Determination of mRNA was superior to immunohistochemistry in showing CEA expression in lymph nodes. The present qRT-PCR assay for CEA mRNA seems to be a superior tool to identify individuals with disseminated tumour cells. Future extended studies will establish the clinically most relevant cut-off level.

Sentinel lymph node mapping in colorectal cancer

BACKGROUND

Ultrastaging, by serial sectioning combined with immunohistochemical techniques, improves detection of lymph node micrometastases. Sentinel lymph node mapping and retrieval provides a representative node(s) to facilitate ultrastaging. The impact on staging of carcinoma of the colon and rectum in all series emphasizes the importance of this technique in cancer management. Now the challenge is to determine the biological relevance and prognostic implications.

METHODS

The electronic literature (1966 to present) on sentinel node mapping in carcinoma of the colon and rectum was reviewed. Further references were obtained by cross-referencing from key articles.

RESULTS

Lymphatic mapping appears to be readily applicable to colorectal cancer and identifies those lymph nodes most likely to harbour metastases. Sentinel node mapping carries a false-negative rate of approximately 10 per cent in larger studies, but will also potentially upstage a proportion of patients from node negative to node positive following the detection of micrometastases. The prognostic implication of these micrometastases requires further evaluation.

CONCLUSION

Further follow-up to assess the prognostic significance of micrometastases in colorectal cancer is required before the staging benefits of sentinel node mapping can have therapeutic implications.

Does tumor burden limit the accuracy of lymphatic mapping and sentinel lymph node biopsy in colorectal cancer?

PURPOSE

Sentinel lymph node (SLN) biopsy is a widely accepted method for staging breast cancer and melanoma, and it has recently been proposed as a means of improving staging in colorectal cancer. However, lymphatic mapping in colorectal cancer has been plagued by studies demonstrating high false-negative rates. The purpose of this study was to evaluate possible mechanisms for high false-negative rates after SLN biopsy in colorectal cancer. We hypothesized that poor accuracy may be due to bulky tumor or complete replacement of lymph nodes by tumor.

PATIENTS AND METHODS

Patients with colorectal adenocarcinoma underwent standard colorectal resection with lymphatic mapping. At operation, 1 mL of isosulfan blue dye was injected at the tumor site, using either an in vivo or an ex vivo technique. Routine pathological evaluation was performed. The sentinel node was examined by hematoxylin and eosin stains, and if these results were negative, by cytokeratin immunohistochemistry. The patient's age, operation type, tumor stage, tumor diameter, method of SLN detection, presence of palpable nodes, and pathological description of nodes completely replaced by tumor were recorded.

RESULTS

Fifty patients (mean age, 62.8, 50% men) undergoing colorectal cancer resection underwent 51 lymphatic mapping procedures. Right- and left-sided colorectal resections were almost equally distributed (48% vs 42%). SLNs were successfully identified in 47 of 51 specimens (92%). The mean number of SLNs obtained from each specimen was 1.5 (range, 1-5). Routine pathological evaluation demonstrated lymph node metastasis in 20 of the 47 patients (43%) who had an SLN identified. The SLN was positive for metastasis in 10 of these 20 patients (50%). Ten of 20 patients with metastatic disease had a negative SLN, resulting in a false-negative rate of 50%. The false-negative rate was significantly higher in patients undergoing left-sided procedures versus right-sided procedures. Differences among gender, tumor stage, tumor diameter, method of SLN detection, presence of palpable nodes, and pathological description of nodes completely replaced by tumor were not associated with a higher false-negative rate.

DISCUSSION

Identification of the SLN in colorectal cancer is technically possible in more than 90% of patients. However, SLN status correlates poorly with the true nodal status of the colorectal cancer, and the false-negative rate is 50%. This high false-negative rate is not clearly explained by extensive tumor burden, and it was also independent of gender, tumor stage, and type of lymphatic mapping technique. However, staging accuracy was lower in patients who underwent left-sided colorectal resection. Further studies are needed to clarify the limitations of lymphatic mapping in colorectal cancer.

Polymerase chain reaction in the staging of solid tumors

Polymerasechain reaction (PCR) is a molecular biology technique that holds great promise as a way to perform molecular staging of cancer by detecting very early metastatic disease. Significant data suggest that PCR analysis may play an important role in the management of colorectal cancer in the future. However, for PCR staging of breast cancer, progress awaits identification of gene markers that have sufficient sensitivity and specificity. Within the next few years, the results of the Sunbelt Melanoma Trial and other ongoing studies will determine whether PCR evaluation of sentinel lymph nodes and peripheral blood cells has prognostic relevance in melanoma. The future of cancer management will likely revolve around the molecular staging of tumors, and PCR is but one method that may better define subgroups of patients that are appropriate candidates forvarious anticancer therapies.