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About 75% of medullary thyroid cancers (MTCs) are sporadic with 45-70% being driven by a RET mutation. Selpercatinib is an approved treatment for RET-mutated (mutRET) MTC, however, treatments are needed for wild-type RET MTC (wtRET). Genomic alterations and transcriptomic signatures of wtRET MTC may reveal new therapeutic insights.

We did a retrospective analysis of MTC samples submitted for DNA/RNA sequencing and PD-L1 expression using IHC at a CLIA/CAP-certified lab. Tumor microenvironment immune cell fractions were estimated using RNA deconvolution (quanTIseq). Transcriptomic signatures of inflammation and MAP kinase pathway activation scores (MPAS) were calculated. Mann-Whitney U, chi-square, and Fisher exact tests were applied (p-values adjusted for multiple comparisons).

The 160-patient cohort included 108 mutRET and 52 wtRET MTC samples. wtRET tumors frequently harbored MAPK pathway mutations, including HRAS (42.31%), KRAS (15.7%), NF1 (6.7%), and BRAF (2%) whereas only one MAPK pathway mutation (NF1) was identified among mutRET MTC. Recurrent mutations seen in wtRET MTC included MGA, VHL, APC, STK11, and NFE2L2. Increased transcriptional activation of the MAPK pathway was observed in wtRET patients harboring mutations in MAPK genes. While the frequency of PD-L1 expression was similar in wtRET and mutRET (10.2% vs 7.0%, p=0.531), wtRET tumors were more often TMB-high (7.7% vs 0.0%, p=0.011), and wtRET MTC exhibited higher expression of immune checkpoint genes.

We identified molecular alterations and immune-related features that distinguish wtRET from mutRET MTC. While RET mutation drives MTC in the absence of other alterations, we showed that wtRET MTC frequently harbors MAPK pathway mutations. These findings may indicate a potential basis for MAPK-targeted therapy, possibly in combination with oncology immune-oncology agents for selected patients with wtRET MTC.

Colorectal cancer (CRC) is the third most common cause of cancer mortality worldwide. Of these, approximately 25% will have liver metastasis. We performed 394 microwave ablations (MWA) and analyzed outcomes for survival and ablation failure.

Retrospective review of patients who underwent a surgical microwave ablation at a single center high-volume institution from October 2006 through September 2022 using a prospectively maintained database. Primary outcome was overall survival.

A total of 394 operations were performed on 328 patients with 842 tumors undergoing MWA. Median tumor size was 1.5 cm (range 0.4-7.0 cm), with the median number of tumors ablated per operation being 1 (range 1-11). A laparoscopic approach was used 77.9% of the time. Concomitant procedures were performed 63% of the time, most commonly hepatectomy (22.3%), cholecystectomy (17.5%), and colectomy (6.6%). Clavien-Dindo Grade III or IV complications occurred in 12 patients (3.6%), and all of these patients had undergone concomitant procedures. Mortality within 30 days occurred in 4 patients (1.2%). The rate of incomplete ablation (IA) was 1.5% per tumor. Local recurrence (LR) occurred at a rate of 6.3% per tumor. African Americans were found to have a higher incidence of IA and LR. One year survival probability was 91% [95% CI: 87.9 -94.3], with a mean overall survival of 57.6 months [95% CI: 49.9-65.4 months].

Surgical MWA offers a low-morbidity approach to treatment of colorectal liver metastasis (CRLM), with low rates of failure. This large series reviews the outcomes of MWA as definitive treatment for CRLM.