Identification and treatment of aggressive thyroid cancers. Part 2: risk assessment and treatment

Most thyroid cancers are slow-growing, easily treatable tumors with an excellent prognosis after surgical resection and targeted medical therapy. Unfortunately, 10% to 15% of thyroid cancers exhibit aggressive behavior and do not follow an indolent course. Approximately one-third of patients with differentiated thyroid cancers will have tumor recurrences. Distant metastases are present in about 20% of patients with recurrent cancer. Approximately half of patients with distant metastases die within 5 years. The loss of the ability to concentrate radio-iodine and produce thyroglobulin is a sign of dedifferentiation, which occurs in about 30% of patients with persistent or recurrent thyroid cancer. Dedifferentiation is associated with poorer responses to conventional therapy and difficulty monitoring tumor burden. Clinicians must identify tumors with more aggressive biology and treat them accordingly with more aggressive regimens. Part 1 of this two-part article, which appeared in March, described in detail the distinct types of thyroid cancer, as well as risk factors, outcomes, treatment, and prognostic factors, with a focus on thyroid cancers of follicular cell origin. Part 2 covers risk assessment and staging, findings that suggest the presence of aggressive tumors, recurrent/metastatic disease, and treatment with chemotherapy and external-beam radiotherapy. Experimental treatments utilizing molecular targets, redifferentiation agents, and gene therapy are covered briefly as well.     

Non-Hodgkin's lymphoma in the elderly. Part 2: treatment of diffuse aggressive lymphomas

As noted in part 1 of this two-part article, non-Hodgkin's lymphoma is one of a few malignancies that have been increasing in incidence over the past several decades. Likewise, these disorders are more common in elderly patients, with a median age of occurrence of 65 years. Therapy in elderly patients may be affected by multiple factors, especially attendent comorbidities. The approaches to management of these patients, with either indolent or aggressive disease processes, have been based on prospective clinical trial results, many of which have included a younger patient population. Fortunately over the past decade, results of treatment trials that have targeted an older patient population have emerged. The disease incidence and treatment approaches for both follicular (part 1) and diffuse aggressive (part 2) histologies in elderly patients are reviewed, as well as the impact of aging on the care of these patients.     

Connexin26 expression is associated with aggressive phenotype in human papillary and follicular thyroid cancers

Connexin26 (Cx26), a component of GAP junctions and until recently believed to be a tumor suppressor gene, has been shown to play an important role in lymphatic invasion as well as lymph node and distant metastases in squamous lung cancer and breast cancer. In the study presented here, we investigated Cx26 expression in human papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC) and its relationship with various clinicopathological parameters. Of 69 PTCs, 33 were positive for Cx26 (47.8%), as were five of 11 FTCs (45.5%), all follicular thyroid adenomas (n=22) and normal thyroid tissues (n=20) were negative for Cx26. A statistically significant association was observed between Cx26 expression and large tumor size (p=0.028 for PTC) and lymph node metastases (p=0.053 (marginally significant) for PTC and p=0.035 for FTC). Presence of intra-glandular dissemination of tumor cells was significantly (p=0.048) more frequent in Cx26-positive (30.3%) than Cx26-negative PTCs (11.1%). Lymphatic vessel invasion was more frequent in Cx26-positive PTCs (6.1%) than in Cx26-negative PTCs (0%) though the difference was not statistically significant. These results suggest that Cx26 may be implicated in the pathogenesis of PTC and FTC and is associated with the biologically aggressive phenotypes of these tumors.     

Expansion of microsatellite in the thyroid hormone receptor-alpha1 gene linked to increased receptor expression and less aggressive thyroid cancer.

PURPOSE: The purpose of this study was to determine whether the length of the THRA1 microsatellite, which resides in a noncoding portion of the thyroid hormone receptor-alpha1 gene, affects receptor expression and is linked to clinicopathological parameters in thyroid cancer. EXPERIMENTAL DESIGN: In 30 cases of surgically resected sporadic thyroid cancer, the length of the THRA1 microsatellite was determined by DNA sequence analysis, and expression of thyroid hormone receptor-alpha1 was assessed immunohistochemically in thin sections cut from tumor blocks. The length of THRA1 and expression of thyroid hormone receptor-alpha1 were also assessed in seven cancer cell lines. Regression analysis was used to gauge the correlation between the size of THRA1 and receptor expression. Multivariate analysis was used to test for links to the clinical parameters of gender, age, histology, stage, nodal involvement, distant metastasis, extrathyroidal invasion and tumor-node-metastasis (TNM) classification. RESULTS: A statistically significant correlation between the length of THRA1 and thyroid hormone receptor-alpha1 expression was observed in both cell lines and primary thyroid cancers. Thyroid tumors that displayed higher than average thyroid hormone receptor-alpha1 expression had expanded THRA1 microsatellites and were less aggressive as judged by TNM ranking. A statistically significant correlation was also found between low thyroid hormone receptor-alpha1 expression and more aggressive thyroid cancer, as judged by extrathyroidal invasion and nodal involvement. CONCLUSIONS: Less aggressive thyroid cancer was found to be linked to increased thyroid hormone receptor-alpha1 expression and an expanded THRA1 microsatellite.     

Multiple primary cancers of the esophagus and thyroid gland.

The occurrence of multiple primary cancers in the aerodigestive tract is a well known phenomenon that has been explained by the concept of 'field carcinogenesis'. Metachronous or synchronous esophageal cancer has usually been identified in patients with head and neck cancer, gastric cancer or colon cancer. The incidence of multiple primary cancers of the esophagus and thyroid gland is very low. We treated four patients with synchronous cancers of the cervical esophagus and the thyroid gland. Histologically, all of the esophageal cancers were squamous cell carcinomas. Thyroid cancers were evaluated as papillary carcinoma or follicular carcinoma. Both the esophageal cancer and the thyroid cancer frequently metastasized to lymph nodes. All patients had multiple lymph nodes metastasis from the esophageal or the thyroid cancer. In one patient, both the esophageal and the thyroid cancers were detected in the same lymph node. Three of four patients died from recurrence of esophageal cancer. The prognosis of these patients was poor. In the treatment of esophageal carcinoma, cancers of other organs including the thyroid gland should be carefully investigated.     

Hypoxic cervical cancers with low apoptotic index are highly aggressive.

There is evidence from experimental work that hypoxia induces apoptosis in apoptosis-sensitive neoplastic cells and that this apoptotic sensitivity is lost during malignant progression. Oxygenation profiles and apoptotic indices in human squamous cell cancer of the uterine cervix have been determined, and a subgroup of tumors has been identified with low apoptotic index despite pronounced hypoxia representing carcinomas that consist of neoplastic cells with diminished apoptotic potential. These hypoxic low-apoptotic tumors show a high probability for lymphatic spread and for recurrence despite adjuvant treatment with radiation or chemotherapy in addition to radical surgery. The clinical results presented strongly support the hypothesis derived from experimental studies that the selection of apoptosis-insensitive neoplastic cell phenotypes in a hypoxic microenvironment is an important mechanism for malignant progression in solid tumors.     

Histological, molecular and functional subtypes of breast cancers

Increased understanding of the molecular heterogeneity that is intrinsic to the various subtypes of breast cancer will likely shape the future of breast cancer diagnosis, prognosis, and treatment. Advances in the field over the last several decades have been remarkable and have clearly translated into better patient care as evidenced by the earlier detection, better prognosis, and new targeted therapies. There have been two recent advances in the breast cancer research field that have lead to paradigm shifts: first, the identification of intrinsic breast tumor subtypes, which has changed the way we think about breast cancer and second, the recent characterization of cancer stem cells (CSCs), which are suspected to be responsible for tumor initiation, recurrence and resistance to therapy, have opened new exciting avenues to think about breast cancer therapeutic strategies. While these advances constitute major paradigm shifts within the research realm, the clinical arena has yet to adopt and apply our understanding of the molecular basis of the disease to early diagnosis, prognosis and therapy of breast cancers. Here, we will review the current clinical approach to classification of breast cancers, newer molecular-based classification schemes, and potential future of biomarkers representing a functional classification of breast cancer.     

Metastatic cancers of the thyroid gland. Diagnostic difficulties

Metastatic carcinoma of the thyroid is uncommon in surgical pathology and may masquerade as primary thyroid cancer. We studied 6 cases of biopsied and/or surgically resected metastatic carcinoma of the thyroid and their corresponding primary carcinoma, with emphasis on the differential diagnosis. There were 4 men and 2 women patients aged 44 to 77. The primary carcinoma was a breast infiltrating duct carcinoma (3 cases), a colorectal adenocarcinoma (2 cases) and a bronchial oat-cell carcinoma (1 case). The interval between primary carcinoma and secondary thyroid carcinoma was 2 to 9 years in 4 cases; 2 other cases showed simultaneous occurrence. Five patients died with widespread metastases 1 to 14 months following the diagnosis of secondary carcinoma of the thyroid; 1 patient was alive after 24 months. The histological differentiation of secondary from primary thyroid cancer may be difficult in the following situations: clear-cell, Hürthle-cell and signet ring cell changes; positivity of mucins stains; production of melanin; epidermoid differentiation; very rare miscellaneous tumours ("columnar cell carcinoma" and primary thymoma of the thyroid). Immunoperoxidase methods and mucin histochemistry may help.     

Current management of unusual genitourinary cancers. Part 2: Urethral cancer

Often overshadowed by more common genitourinary cancers, such as prostate, testicular, and kidney cancers, penile and urethral cancers nonetheless represent difficult treatment challenges for the clinician. The management of these cancers is slowly evolving. In the past, surgery, often extensive, was the treatment of choice. Recently, however, radiation and chemotherapy have begun to play larger roles as initial therapies, with surgery being reserved for salvage. With these modalities in their treatment armamentarium, oncologists may now be able to spare patients some of the physical and psychological sequelae that often follow surgical intervention without compromising local control and survival. Part 1 of this two-part article, published in last month's issue, dealt with cancer of the penis. This second part focuses on cancer of the urethra in both females and males.     

Cytologic and molecular diagnosis of thyroid cancers

The Bethesda system for standardized reporting of thyroid fine needle aspiration (FNA) cytology has positively affected the clarity of communication of results and management of patients evaluated for thyroid nodules. Problematic areas still exist in the triage of some of these samples, particularly those in the categories of "follicular lesion with atypia of uncertain significance" and "follicular lesion." The literature on molecular and genetic abnormalities in thyroid lesions is reviewed. Potentially useful markers for distinguishing currently problematic categories of FNA cytologic samples, especially nondiagnostic samples, atypia of uncertain significance, and follicular lesions, are discussed. The predictive value of the respective molecular analyses in these settings is examined. Evaluation of FNA samples with negative or suboptimal follicular cytology for Ras mutations may be useful in detecting potentially significant follicular lesions (carcinomas) but is quite low in overall yield. Cytologic samples with atypia of uncertain significance, which may include the possibility of papillary carcinomas, may be fruitfully evaluated using a panel of molecular tests for BRAF, RET/PTC, PAX8/PPARG1, and Ras. Other markers also have potential utility in the workup of thyroid lesions. An era of combined modality testing in thyroid cytology is emerging in which classical cytologic findings can be coupled with molecular data to increase the predictive power of diagnostic interpretations; however, there remains a group of atypical cytologic samples negative for known molecular markers in which the risk of malignancy is too high to simply follow expectantly.     

BRAF is a therapeutic target in aggressive thyroid carcinoma.

PURPOSE: Oncogenic conversion of BRAF occurs in approximately 44% of papillary thyroid carcinomas and 24% of anaplastic thyroid carcinomas. In papillary thyroid carcinomas, this mutation is associated with an unfavorable clinicopathologic outcome. Our aim was to exploit BRAF as a potential therapeutic target for thyroid carcinoma. EXPERIMENTAL DESIGN: We used RNA interference to evaluate the effect of BRAF knockdown in the human anaplastic thyroid carcinoma cell lines FRO and ARO carrying the BRAF V600E (V600EBRAF) mutation. We also exploited the effect of BAY 43-9006 [N-(3-trifluoromethyl-4-chlorophenyl)-N'-(4-(2-methylcarbamoyl pyridin-4-yl)oxyphenyl)urea], a multikinase inhibitor able to inhibit RAF family kinases in a panel of six (V600E)BRAF-positive thyroid carcinoma cell lines and in nude mice bearing ARO cell xenografts. Statistical tests were two sided. RESULTS: Knockdown of BRAF by small inhibitory duplex RNA, but not control small inhibitory duplex RNA, inhibited the mitogen-activated protein kinase signaling cascade and the growth of ARO and FRO cells (P < 0.0001). These effects were mimicked by thyroid carcinoma cell treatment with BAY 43-9006 (IC50 = 0.5-1 micromol/L; P < 0.0001), whereas the compound had negligible effects in normal thyrocytes. ARO cell tumor xenografts were significantly (P < 0.0001) smaller in nude mice treated with BAY 43-9006 than in control mice. This inhibition was associated with suppression of phospho-mitogen-activated protein kinase levels. CONCLUSIONS: BRAF provides signals crucial for proliferation of thyroid carcinoma cells spontaneously harboring the (V600E)BRAF mutation and, therefore, BRAF suppression might have therapeutic potential in (V600E)BRAF-positive thyroid cancer.     

Distinct mitotic segregation errors mediate chromosomal instability in aggressive urothelial cancers.

PURPOSE: Chromosomal instability (CIN) is believed to have an important role in the pathogenesis of urothelial cancer (UC). The aim of this study was to evaluate whether disturbances of mitotic segregation contribute to CIN in UC, if these processes have any effect on the course of disease, and how deregulation of these mechanisms affects tumor cell growth. EXPERIMENTAL DESIGN: We developed molecular cytogenetic methods to classify mitotic segregation abnormalities in a panel of UC cell lines. Mitotic instabilities were then scored in biopsies from 52 UC patients and compared with the outcome of tumor disease. Finally, UC cells were exposed in vitro to a telomerase inhibitor to assess how this affects mitotic stability and cell proliferation. RESULTS: Three distinct chromosome segregation abnormalities were identified: (a) telomere dysfunction, which triggers structural rearrangements and loss of chromosomes through anaphase bridging; (b) sister chromatid nondisjunction, which generates discrete chromosomal copy number variations; and (c) supernumerary centrosomes, which cause dramatic shifts in chromosome copy number through multipolar cell division. Chromosome segregation errors were already present in preinvasive tumors and a high rate mitotic instability was an independent predictor of poor survival. However, induction of even higher levels of the same segregation abnormalities in UC cells by telomerase inhibition in vitro led to reduced tumor cell proliferation and clonogenic survival. CONCLUSION: Several distinct chromosome segregation errors contribute to CIN in UC, and the rate of such mitotic errors has a significant effect on the clinical course. Efficient tumor cell proliferation may depend on the tight endogenous control of these processes.     

Genomic alterations and molecular subtypes of gastric cancers in Asians

Gastric cancer (GC) is a highly heterogenic disease, and it is the second leading cause of cancer death in the world. Common chemotherapies are not very effective for GC, which often presents as an advanced or metastatic disease at diagnosis. Treatment options are limited, and the prognosis for advanced GCs is poor. The landscape of genomic alterations in GCs has recently been characterized by several international cancer genome programs, including stud-ies that focused exclusively on GCs in Asians. These studies identiifed major recurrent driver mutations and provided new insights into the mutational heterogeneity and genetic proifles of GCs. An analysis of gene expression data by the Asian Cancer Research Group (ACRG) further uncovered four distinct molecular subtypes with well-deifned clini-cal features and their intersections with actionable genetic alterations to which targeted therapeutic agents are either already available or under clinical development. In this article, we review the ACRG GC project. We also discuss the implications of the genetic and molecular ifndings from various GC genomic studies with respect to developing more precise diagnoses and treatment approaches for GCs.