James W. Welsh

Circulating MicroRNAs as Noninvasive Biomarkers in Breast Cancer

MicroRNAs (miRNAs) are master regulators of gene expression. By degrading or blocking translation of messenger RNA targets, these non-coding RNAs can modulate the expression of more than half the protein-coding genes in mammalian genomes. MiRNAs play important regulatory roles in a variety of cellular functions and in several diseases, including cancer. Aberrant miRNA expression has been well characterized in cancer, with implications for progression and prognosis. Recently, the discovery of miRNAs in body fluids, such as serum and plasma, opens up the possibility of using them as noninvasive biomarkers of disease and therapy response. In this chapter, we discuss the use of circulating miRNAs as biomarkers of disease and therapy response and as diagnostic and prognostic markers in breast cancer. We also discuss the main issues related to establishing circulating miRNAs as biomarkers in cancer.

CCAT2, a novel noncoding RNA mapping to 8q24, underlies metastatic progression and chromosomal instability in colon cancer

The functional roles of SNPs within the 8q24 gene desert in the cancer phenotype are not yet well understood. Here, we report that CCAT2, a novel long noncoding RNA transcript (lncRNA) encompassing the rs6983267 SNP, is highly overexpressed in microsatellite-stable colorectal cancer and promotes tumor growth, metastasis, and chromosomal instability. We demonstrate that MYC, miR-17-5p, and miR-20a are up-regulated by CCAT2 through TCF7L2-mediated transcriptional regulation. We further identify the physical interaction between CCAT2 and TCF7L2 resulting in an enhancement of WNT signaling activity. We show that CCAT2 is itself a WNT downstream target, which suggests the existence of a feedback loop. Finally, we demonstrate that the SNP status affects CCAT2 expression and the risk allele G produces more CCAT2 transcript. Our results support a new mechanism of MYC and WNT regulation by the novel lncRNA CCAT2 in colorectal cancer pathogenesis, and provide an alternative explanation of the SNP-conferred cancer risk.

Comparative Effectiveness of 5 Treatment Strategies for Early-Stage Non-Small Cell Lung Cancer in the Elderly

PURPOSE The incidence of early-stage non-small cell lung cancer (NSCLC) among older adults is expected to increase because of demographic trends and computed tomography-based screening; yet, optimal treatment in the elderly remains controversial. Using the Surveillance, Epidemiology, and End Results (SEER)-Medicare cohort spanning 2001-2007, we compared survival outcomes associated with 5 strategies used in contemporary practice: lobectomy, sublobar resection, conventional radiation therapy, stereotactic ablative radiation therapy (SABR), and observation. METHODS AND MATERIALS Treatment strategy and covariates were determined in 10,923 patients aged ≥ 66 years with stage IA-IB NSCLC. Cox regression, adjusted for patient and tumor factors, compared overall and disease-specific survival for the 5 strategies. In a second exploratory analysis, propensity-score matching was used for comparison of SABR with other options. RESULTS The median age was 75 years, and 29% had moderate to severe comorbidities. Treatment distribution was lobectomy (59%), sublobar resection (11.7%), conventional radiation (14.8%), observation (12.6%), and SABR (1.1%). In Cox regression analysis with a median follow-up time of 3.2 years, SABR was associated with the lowest risk of death within 6 months of diagnosis (hazard ratio [HR] 0.48; 95% confidence interval [CI] 0.38-0.63; referent is lobectomy). After 6 months, lobectomy was associated with the best overall and disease-specific survival. In the propensity-score matched analysis, survival after SABR was similar to that after lobectomy (HR 0.71; 95% CI 0.45-1.12; referent is SABR). Conventional radiation and observation were associated with poor outcomes in all analyses. CONCLUSIONS In this population-based experience, lobectomy was associated with the best long-term outcomes in fit elderly patients with early-stage NSCLC. Exploratory analysis of SABR early adopters suggests efficacy comparable with that of surgery in select populations. Evaluation of these therapies in randomized trials is urgently needed.

Lobectomy, Sublobar Resection, and Stereotactic Ablative Radiotherapy for Early-Stage Non-Small Cell Lung Cancers in the Elderly

IMPORTANCE The incidence of early-stage non-small cell lung cancer (NSCLC) among the elderly is expected to rise dramatically owing to demographic trends and increased computed tomographic screening. However, to our knowledge, no modern trials have compared the most common treatments for NSCLC. OBJECTIVE To determine clinical characteristics and survival outcomes associated with the 3 most commonly used definitive therapies for early-stage NSCLC in the elderly. DESIGN, SETTING, AND PARTICIPANTS The Surveillance, Epidemiology, and End Results database linked to Medicare was used to determine the baseline characteristics and outcomes of 9093 patients with early-stage, node-negative NSCLC who underwent definitive treatment consisting of lobectomy, sublobar resection, or stereotactic ablative radiotherapy (SABR) from January 1, 2003, through December 31, 2009. MAIN OUTCOMES AND MEASURES Overall and lung cancer-specific survival were compared using Medicare claims through December 31, 2012. We used proportional hazards regression and propensity score matching to adjust outcomes for key patient, tumor, and practice environment factors. RESULTS The median age was 75 years, and treatment distribution was 79.3% for lobectomy, 16.5% for sublobar resection, and 4.2% for SABR. Unadjusted 90-day mortality was highest for lobectomy (4.0%) followed by sublobar resection (3.7%; P = .79) and SABR (1.3%; P = .008). At 3 years, unadjusted mortality was lowest for lobectomy (25.0%), followed by sublobar resection (35.3%; P < .001) and SABR (45.1%; P < .001). Proportional hazards regression demonstrated that sublobar resection was associated with worse overall survival (adjusted hazard ratio [AHR], 1.32 [95% CI, 1.20-1.44]; P < .001) and lung cancer-specific survival (AHR, 1.50 [95% CI, 1.29-1.75]; P < .001) compared with lobectomy. Propensity score-matching analysis reiterated these findings for overall survival (AHR, 1.36 [95% CI, 1.17-1.58]; P < .001) and lung cancer-specific survival (AHR, 1.46 [95% CI, 1.13-1.90]; P = .004). In proportional hazards regression, SABR was associated with better overall survival than lobectomy in the first 6 months after diagnosis (AHR, 0.45 [95% CI, 0.27-0.75]; P < .001) but worse survival thereafter (AHR, 1.66 [95% CI, 1.39-1.99]; P < .001). Propensity score-matching analysis of well-matched SABR and lobectomy cohorts demonstrated similar overall survival in both groups (AHR, 1.01 [95% CI, 0.74-1.38]; P = .94). CONCLUSIONS AND RELEVANCE Lobectomy was associated with better outcomes than sublobar resection in elderly patients with early-stage NSCLC. Propensity score matching suggests that SABR may be a good option among patients with very advanced age and multiple comorbidities.

Clinical outcome and predictors of survival and pneumonitis after stereotactic ablative radiotherapy for stage I non-small cell lung cancer

BackgroundStereotactic ablative radiotherapy (SABR) can achieve excellent local control rates in early-stage non-small cell lung cancer (NSCLC) and has emerged as a standard treatment option for patients who cannot undergo surgery or those with isolated recurrences. However, factors that may predict toxicity or survival are largely unknown. We sought here to identify predictors of survival and pneumonitis after SABR for NSCLC in a relatively large single-institution series.MethodsSubjects were 130 patients with stage I NSCLC treated with four-dimensional computed tomography (4D CT) –planned, on-board volumetric image–guided SABR to 50 Gy in 4 fractions. Disease was staged by positron emission tomography/computed tomography (PET/CT) and scans were obtained again at the second follow-up after SABR.ResultsAt a median follow-up time of 26 months, the 2-year local control rate was 98.5%. The median overall survival (OS) time was 60 months, and OS rates were 93.0% at 1 year, 78.2% at 2 years, and 65.3% at 3 years. No patient experienced grade 4–5 toxicity; 15 had radiation pneumonitis (12 [9.3%] grade 2 and 3 [2.3%] grade 3). Performance status, standardized uptake value (SUV)max on staging PET/CT, tumor histology, and disease operability were associated with OS on univariate analysis, but only staging SUVmax was independently predictive on multivariate analysis (P = 0.034). Dosimetric factors were associated with radiation pneumonitis on univariate analysis, but only mean ipsilateral lung dose ≥9.14 Gy was significant on multivariate analysis (P = 0.005).ConclusionsOS and radiation pneumonitis after SABR for stage I NSCLC can be predicted by staging PET SUVmax and ipsilateral mean lung dose, respectively.

Obesity Increases the Risk of Chest Wall Pain From Thoracic Stereotactic Body Radiation Therapy

PURPOSE Stereotactic body radiation therapy (SBRT) is increasingly being used to treat thoracic tumors. We attempted here to identify dose-volume parameters that predict chest wall toxicity (pain and skin reactions) in patients receiving thoracic SBRT. PATIENTS AND METHODS We screened a database of patients treated with SBRT between August 2004 and August 2008 to find patients with pulmonary tumors within 2.5 cm of the chest wall. All patients received a total dose of 50 Gy in four daily 12.5-Gy fractions. Toxicity was scored according to the NCI-CTCAE V3.0. RESULTS Of 360 patients in the database, 265 (268 tumors) had tumors within <2.5 cm of the chest wall; 104 (39%) developed skin toxicity (any grade); 14 (5%) developed acute pain (any grade), and 45 (17%) developed chronic pain (Grade 1 in 22 cases [49%] and Grade 2 or 3 in 23 cases [51%]). Both skin toxicity and chest wall pain were associated with the V30, or volume of the chest wall receiving 30 Gy. Body mass index (BMI) was also strongly associated with the development of chest pain: patients with BMI≥29 had almost twice the risk of chronic pain (p=0.03). Among patients with BMI>29, diabetes mellitus was a significant contributing factor to the development of chest pain. CONCLUSION Safe use of SBRT with 50 Gy in four fractions for lesions close to the chest wall requires consideration of the chest wall volume receiving 30 Gy and the patients BMI and diabetic state.

The c-Met receptor tyrosine kinase inhibitor MP470 radiosensitizes glioblastoma cells

PurposeGlioblastoma multiforme (GBM) is resistant to current cytotoxic therapies, in part because of enhanced DNA repair. Activation of the receptor tyrosine kinase c-Met has been shown to protect cancer cells from DNA damage. We hypothesized that inhibiting c-Met would decrease this protection and thus sensitize resistant tumor cells to the effects of radiation therapy.Materials and methodsEight human GBM cell lines were screened for radiosensitivity to the small-molecule c-Met inhibitor MP470 with colony-count assays. Double-strand (ds) DNA breaks was quantified by using antibodies to gamma H2AX. Western blotting demonstrate expression of RAD51, glycogen synthase kinase (GSK)-3β, and other proteins. A murine xenograft tumor flank model was used for in vivo radiosensitization studies.ResultsMP470 reduced c-Met phosphorylation and enhanced radiation-induced cell kill by 0.4 logs in SF767 cells. Cells pretreated with MP470 had more ds DNA damage than cells treated with radiation alone. Mechanistically, MP470 was shown to inhibit dsDNA break repair and increase apoptosis. MP470 influences various survival and DNA repair related proteins such as pAKT, RAD51 and GSK3β. In vivo, the addition of MP470 to radiation resulted in a tumor-growth-delay enhancement ratio of 2.9 over radiation alone and extended survival time.ConclusionsGBM is a disease site where radiation is often used to address both macroscopic and microscopic disease. Despite attempts at dose escalation outcomes remain poor. MP470, a potent small-molecule tyrosine kinase inhibitor of c-Met, radiosensitized several GBM cell lines both in vitro and in vivo, and may help to improve outcomes for patients with GBM.

Therapeutic Delivery of miR-200c Enhances Radiosensitivity in Lung Cancer

The microRNA (miR)-200s and their negative regulator ZEB1 have been extensively studied in the context of the epithelial-mesenchymal transition. Loss of miR-200s has been shown to enhance cancer aggressiveness and metastasis, whereas replacement of miR-200 miRNAs has been shown to inhibit cell growth in several types of tumors, including lung cancer. Here, we reveal a novel function of miR-200c, a member of the miR-200 family, in regulating intracellular reactive oxygen species signaling and explore a potential application for its use in combination with therapies known to increase oxidative stress such as radiation. We found that miR-200c overexpression increased cellular radiosensitivity by direct regulation of the oxidative stress response genes PRDX2, GAPB/Nrf2, and SESN1 in ways that inhibits DNA double-strand breaks repair, increase levels of reactive oxygen species, and upregulate p21. We used a lung cancer xenograft model to further demonstrate the therapeutic potential of systemic delivery of miR-200c to enhance radiosensitivity in lung cancer. Our findings suggest that the antitumor effects of miR-200c result partially from its regulation of the oxidative stress response; they further suggest that miR-200c, in combination with radiation, could represent a therapeutic strategy in the future.

Intensity-Modulated Proton Therapy Further Reduces Normal Tissue Exposure During Definitive Therapy for Locally Advanced Distal Esophageal Tumors: A Dosimetric Study

PURPOSE We have previously found that ≤ 75% of treatment failures after chemoradiotherapy for unresectable esophageal cancer appear within the gross tumor volume and that intensity-modulated (photon) radiotherapy (IMRT) might allow dose escalation to the tumor without increasing normal tissue toxicity. Proton therapy might allow additional dose escalation, with even lower normal tissue toxicity. In the present study, we compared the dosimetric parameters for photon IMRT with that for intensity-modulated proton therapy (IMPT) for unresectable, locally advanced, distal esophageal cancer. PATIENTS AND METHODS Four plans were created for each of 10 patients. IMPT was delivered using anteroposterior (AP)/posteroanterior beams, left posterior oblique/right posterior oblique (LPO/RPO) beams, or AP/LPO/RPO beams. IMRT was delivered with a concomitant boost to the gross tumor volume. The dose was 65.8 Gy to the gross tumor volume and 50.4 Gy to the planning target volume in 28 fractions. RESULTS Relative to IMRT, the IMPT (AP/posteroanterior) plan led to considerable reductions in the mean lung dose (3.18 vs. 8.27 Gy, p<.0001) and the percentage of lung volume receiving 5, 10, and 20 Gy (p≤.0006) but did not reduce the cardiac dose. The IMPT LPO/RPO plan also reduced the mean lung dose (4.9 Gy vs. 8.2 Gy, p<.001), the heart dose (mean cardiac dose and percentage of the cardiac volume receiving 10, 20, and 30 Gy, p≤.02), and the liver dose (mean hepatic dose 5 Gy vs. 14.9 Gy, p<.0001). The IMPT AP/LPO/RPO plan led to considerable reductions in the dose to the lung (p≤.005), heart (p≤.003), and liver (p≤.04). CONCLUSIONS Compared with IMRT, IMPT for distal esophageal cancer lowered the dose to the heart, lung, and liver. The AP/LPO/RPO beam arrangement was optimal for sparing all three organs. The dosimetric benefits of protons will need to be tailored to each patient according to their specific cardiac and pulmonary risks. IMPT for esophageal cancer will soon be investigated further in a prospective trial at our institution.

Esophageal cancer dose escalation using a simultaneous integrated boost technique

PURPOSE We previously showed that 75% of radiation therapy (RT) failures in patients with unresectable esophageal cancer are in the gross tumor volume (GTV). We performed a planning study to evaluate if a simultaneous integrated boost (SIB) technique could selectively deliver a boost dose of radiation to the GTV in patients with esophageal cancer. METHODS AND MATERIALS Treatment plans were generated using four different approaches (two-dimensional conformal radiotherapy [2D-CRT] to 50.4 Gy, 2D-CRT to 64.8 Gy, intensity-modulated RT [IMRT] to 50.4 Gy, and SIB-IMRT to 64.8 Gy) and optimized for 10 patients with distal esophageal cancer. All plans were constructed to deliver the target dose in 28 fractions using heterogeneity corrections. Isodose distributions were evaluated for target coverage and normal tissue exposure. RESULTS The 50.4 Gy IMRT plan was associated with significant reductions in mean cardiac, pulmonary, and hepatic doses relative to the 50.4 Gy 2D-CRT plan. The 64.8 Gy SIB-IMRT plan produced a 28% increase in GTV dose and comparable normal tissue doses as the 50.4 Gy IMRT plan; compared with the 50.4 Gy 2D-CRT plan, the 64.8 Gy SIB-IMRT produced significant dose reductions to all critical structures (heart, lung, liver, and spinal cord). CONCLUSIONS The use of SIB-IMRT allowed us to selectively increase the dose to the GTV, the area at highest risk of failure, while simultaneously reducing the dose to the normal heart, lung, and liver. Clinical implications warrant systematic evaluation.