Polymerase chain reaction in the staging of solid tumors

Quantitative RT-PCR detection of colorectal tumor cells in peripheral blood--a systematic review

BACKGROUND

Twenty percent to 40% of patients with node-negative colorectal cancer die of metastatic disease. Detection of cancer cell dissemination has been proposed as a tool to select patients at highest risk for recurrence. In this review, we summarize the evidence for detection with quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assays of circulating tumor cells (CTCs) in peripheral blood of colorectal cancer patients.

MATERIALS AND METHODS

Pubmed and Embase were systematically searched for all English publications relevant to circulating cancer cells, peripheral blood, quantitative RT-PCR (q-RT-PCR), and colorectal cancer. Cross-references and the "related articles" function were used to broaden the search. Manuscripts reporting on the results of nonquantitative RT-PCR assays were excluded. The study methodology, CTCs detection rates in peripheral blood, and prognostic value were reviewed.

RESULTS

Twelve manuscripts on qRT-PCR were retrieved. Stage dependence was found for detection of CTCs in four of 10 studies. From univariate analysis performed for disease-free survival and overall survival in 4 of 12 studies, there was evidence (P < 0.05) for an effect of the detection of CTCs with qRT-PCR. None of the included trials identified detection of CTCs in peripheral blood as an independent predictor of survival.

CONCLUSION

Quantification of CTCs in peripheral blood holds promise in predicting stage and outcome in colorectal cancer patients. At present, evidence from the literature is too scarce to integrate quantitative RT-PCR assays to detect CTCs into the management of colorectal cancer.

Enzyme-Linked Electrochemical Detection of PCR-Amplified Nucleotide Sequences Using Disposable Screen-Printed Sensors. Applications in Gene Expression Monitoring

Electrochemical enzyme-linked techniques for sequence-specific DNA sensing are presented. These techniques are based on attachment of streptavidin-alkaline phosphatase conjugate to biotin tags tethered to DNA immobilized at the surface of disposable screen-printed carbon electrodes (SPCE), followed by production and electrochemical determination of an electroactive indicator, 1-naphthol. Via hybridization of SPCE surface-confined target DNAs with end-biotinylated probes, highly specific discrimination between complementary and non-complementary nucleotide sequences was achieved. The enzyme-linked DNA hybridization assay has been successfully applied in analysis of PCR-amplified real genomic DNA sequences, as well as in monitoring of plant tissue-specific gene expression. In addition, we present an alternative approach involving sequence-specific incorporation of biotin-labeled nucleotides into DNA by primer extension. Introduction of multiple biotin tags per probe primer resulted in considerable enhancement of the signal intensity and improvement of the specificity of detection.

Childhood melanoma: update and treatment

Childhood melanoma is a rare but potentially fatal disease that is important to include in the differential diagnosis of any pigmented lesion in a child. The best prognosis is achieved with early diagnosis and definitive surgical excision. Adjuvant chemotherapy and immunotherapy are options for those with more advanced tumors. Melanoma in children must be treated as aggressively as in adults because childhood melanoma may be equally devastating.

Selective sentinel lymphadenectomy for malignant melanoma, Merkel cell carcinoma, and squamous cell carcinoma

To date, selective sentinel lymphadenectomy (SSL) should be considered a standard approach for staging patients with primary invasive melanoma greater than or equal to 1 mm. It is imperative that the multidisciplinary team master the techniques of preoperative lymphoscintigraphy, intraoperative lymphatic mapping, and postoperative pathologic evaluation of the sentinel lymph nodes (SLNs). An SLN is defined as a blue, "hot" and any subsequent lymph node greater than 10% of the ex vivo count of the hottest lymph node. Any enlarged or indurated lymph node in the nodal basin should be excised. Frozen sections are not recommended. For extremity melanoma, delayed SSL may be performed. Preoperative lymphoscintigraphy for extremity melanoma may be done the night before so that the surgery can be scheduled as the first case of the following day. Every surgeon who uses blue dye should be aware of the potential adverse reaction to isosulfan blue and treatment for such a potential fatal reaction. A complete lymph node dissection is done if the SLN is found to be positive. Elective lymph node dissection (ELND) should not be done if an SSL can be performed as a staging procedure. SSL has further been applied to stage the nodal basin for Merkel cell carcinoma and high-risk squamous cell carcinoma. It is important for investigators involved with the SSL to follow the clinical outcome of these patients, so that the role of SSL can be further defined.

Sentinel lymph node mapping and selective lymphadenectomy: the standard of care for melanoma

Selective sentinel lymphadenectomy (SSL) should be considered a standard of care approach for staging patients with primary invasive melanoma 1 mm or greater. It is essential that multidisciplinary teams should master the techniques of preoperative lymphoscintigraphy, intraoperative lymphatic mapping, and pathologic evaluation of the sentinel lymph nodes (SLNs). An SLN may be blue, hot, or any lymph node (LN) greater than 10% of the in-vivo count of the hottest LN. An enlarged or indurated LN should be removed because it may contain metastatic cancer cells that block blue dye or radiotracer entry. Frozen sections are not recommended. Surgeons who use isosulfan blue dye should be cognizant of treatment for a potentially fatal reaction. Prophylactic LN dissection should not be performed if a SSL can be performed as a staging procedure. A complete LN dissection is performed if the SLN is positive. It is important to follow the clinical outcome of patients undergoing SSL, thus its role can be further defined.

Paradigm of metastasis for melanoma and breast cancer based on the sentinel lymph node experience

Lymph node status is the most reliable prognostic indicator for patients with melanoma and breast cancer. Because it is the first node draining the primary cancer, the sentinel lymph node (SLN) is most likely to harbor metastatic cancer cells. The Breslow thickness of the primary melanoma and the size of primary breast cancer are highly correlated with SLN metastasis. If the SLN is negative, its negative predictive value for the remaining nodal basin exceeds 95%; thus, survival rates for melanoma and breast cancer increase when the SLN is negative. The rate of SLN identification is more than 95%, and the false-negative rate is about 5%. SLN data from melanoma and breast cancer are so convincing that they have been incorporated into the new American Joint Committee on Cancer classification of these cancers. The therapeutic value of additional lymph node dissection after a positive SLN for melanoma or breast cancer is still controversial. In melanoma, a 3-year follow-up may confirm better survival when the SLN is negative. However, about 25% of histologically negative SLNs may be upstaged by molecular techniques, and patients whose SLNs are positive by polymerase chain reaction (PCR) assay may develop recurrence. In most cases, melanoma and breast cancer follow an orderly progression of metastasis to the SLN; however, a small subgroup may develop systemic dissemination without SLN involvement. Current SLN experience has confirmed that the earlier the cancer, the less its potential for metastasis. Since treatments for metastatic cancer are still limited, early detection and resection are imperative. Better understanding of the molecular and genetic mechanisms of metastasis will be critical to select high-risk patients for adjuvant therapy.

The assessment and surgical management of early-stage vulvar cancer

The treatment of early vulvar cancer has undergone a major paradigm shift from a radical surgical approach to tissue-sparing surgery and preservation of sexual function. Stage I and II tumours represent two-thirds of the cases, and 5-year survival rates reach 80-90%. These tumours, with clinically negative nodes, do not require metastatic work-up, and the patients are submitted to surgery. Stage IA tumours, with a depth of stromal invasion of less than 1 mm, have a very low risk of lymph node (LN) involvement (<1%) and are treated by radical (wide) local excision without the need for lymphadenectomy. The remaining patients with stage I or II disease undergo radical (wide) local excision of the vulvar lesion, accompanied by some sort of inguinal lymphadenectomy. Evaluation of the lymph nodes using sentinel node mapping appears promising and is extensively reviewed. It should probably include serial sectioning and immunohistochemistry to detect micrometastases, although their true clinical importance remains to be determined. Molecular detection methods that reveal cancer cells in sites not detectable by routine histology have been introduced to evaluate sentinel lymph nodes and may eventually become part of the routine metastatic work-up.

Selective sentinel lymphadenectomy for malignant melanoma

To date, selective sentinel lymphadenectomy (SSL) should be considered a standard approach for staging patients with primary invasive melanoma greater than or equal to 1 mm. It is imperative that the multidisciplinary team master the techniques of preoperative lymphoscintigraphy, intraoperative lymphatic mapping, and postoperative pathologic evaluation of the sentinel lymph nodes (SLNs). A SLN is defined as a blue, "hot", or any subsequent lymph node greater than 10% of the in vivo count of the hottest lymph node and as an enlarged or indurated lymph node. Frozen sections are not recommended. For extremity melanoma, delayed SSL may be performed. Preoperative lymphoscintigraphy for extremity melanoma may be done the night before so that surgery can be scheduled as the first case of the following day. Every surgeon who uses blue dye should be cognizant of the potential adverse reaction to isosulfan blue and treatment for such a potential fatal reaction. A complete lymph node dissection is done if the SLN is found to be positive. Elective lymph node dissection should not be done if SSL can be done as a staging procedure. It is important for investigators involved with SSL to follow the clinical outcome of their patients so that the role of SSL can be further defined.