Prognosis of Malignant Pheochromocytoma and Paraganglioma (MAPP-Prono Study): A European Network for the Study of Adrenal Tumors Retrospective Study

BACKGROUND

Malignant pheochromocytoma and paraganglioma (MPP) are characterized by prognostic heterogeneity. Our objective was to look for prognostic parameters of overall survival (OS) in MPP patients.

PATIENTS AND METHODS

Retrospective multicenter study of MPP characterized by a neck-thoraco-abdomino-pelvic CT or MRI at the time of malignancy diagnosis in European centers between 1998 and 2010.

RESULTS

One hundred sixty-nine patients from 18 European centers were included. Main characteristics of patients with MPP were: primary pheochromocytoma in 53% of patients; tumor- or hormone-related symptoms in 57% or 58% of cases; positive plasma or urine hormones in 81% of patients; identification of a mutation in SDHB in 42% of cases. Metastatic sites included bone (64%), lymph node (40%), lung (29%), and liver (26%); mean time between initial and malignancy diagnosis was 43 months (range, 0 to 614). Median follow-up was 68 months and median survival 6.7 years. Using univariate analysis, better survival was associated with head and neck paraganglioma, age <40 years, metanephrines less than fivefold the upper limits of the normal range, and low proliferative index. In multivariate analysis, hypersecretion [hazard ratio 3.02 (1.65 to 5.55); P = 0.0004] was identified as an independent significant prognostic factor of worst OS.

CONCLUSIONS

Our results do not confirm SDHB mutations as a major prognostic parameter in MPP and suggest additional key molecular events involved in MPP tumor progression. Aside from SDHB mutation, the biology of aggressive MPP remains to be understood.

VEGF, VEGFR3, and PDGFRB protein expression is influenced by RAS mutations in medullary thyroid carcinoma

BACKGROUND

Tyrosine kinase inhibitors (TKIs) have achieved remarkable clinical results in medullary thyroid carcinoma (MTC) patients. However, the considerable variability in patient response to treatment with TKIs remains largely unexplained. There is evidence that it could be due, at least in part, to alterations in genes associated with the disease via their effect on the expression of TKI targets. The objective of this study was to evaluate the influence of RAS mutations on the expression levels in MTC tumors of eight key TKI target proteins.

METHODS

We assessed by immunohistochemistry the expression of EGFR, KIT, MET, PDGFRB, VEGF, VEGFR1, VEGFR2, and VEGFR3 in a series of 84 primary MTC tumors that had previously been molecularly characterized, including 14 RAS-positive, 18 RET(M918T)-positive, and 24 RET(C634)-positive tumors, as well as 15 wild-type tumors with no mutations in the RET or RAS genes.

RESULTS

In contrast to RET-positive tumors, RAS-positive tumors expressed neither PDGFRB nor MET (p=0.0060 and 0.047, respectively). Similarly, fewer RAS-positive than RET-related tumors expressed VEGFR3 (p=0.00062). Finally, wild-type tumors expressed VEGF more often than both RAS- and RET-positive tumors (p=0.0082 and 0.011, respectively).

CONCLUSIONS

This is the first study identifying that the expression of TKI targets differs according to the presence of RAS mutations in MTC. This information could potentially be used to select the most beneficial TKI treatment for these patients.

DNA methylation profiling of well-differentiated thyroid cancer uncovers markers of recurrence free survival

Thyroid cancer is a heterogeneous disease with several subtypes characterized by cytological, histological and genetic alterations, but the involvement of epigenetics is not well understood. Here, we investigated the role of aberrant DNA methylation in the development of well-differentiated thyroid tumors. We performed genome-wide DNA methylation profiling in the largest well-differentiated thyroid tumor series reported to date, comprising 83 primary tumors as well as 8 samples of adjacent normal tissue. The epigenetic profiles were closely related to not only tumor histology but also the underlying driver mutation; we found that follicular tumors had higher levels of methylation, which seemed to accumulate in a progressive manner along the tumorigenic process from adenomas to carcinomas. Furthermore, tumors harboring a BRAF or RAS mutation had a larger number of hypo- or hypermethylation events, respectively. The aberrant methylation of several candidate genes potentially related to thyroid carcinogenesis was validated in an independent series of 52 samples. Furthermore, through the integration of methylation and transcriptional expression data, we identified genes whose expression is associated with the methylation status of their promoters. Finally, by integrating clinical follow-up information with methylation levels we propose etoposide-induced 2.4 and Wilms tumor 1 as novel prognostic markers related to recurrence-free survival. This comprehensive study provides insights into the role of DNA methylation in well-differentiated thyroid cancer development and identifies novel markers associated with recurrence-free survival.