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Dive into the research topics where Mehmet Koc is active.

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Featured researches published by Mehmet Koc.


Medical Oncology | 2011

Gastrointestinal stromal tumor of the rectum with bone and liver metastasis: a case study.

Yilmaz Tezcan; Mehmet Koc

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor of the gastrointestinal tract and may arise from any part of the gastrointestinal system. However, it is most frequently observed in the stomach (60%) and small intestines (30%). GIST is observed at a rate of 4% in the rectum. Distant metastases of GIST are rare, and the liver is the most common site of metastasis. This case is presented because of the rare incidence of bone metastasis to the femur head.


Radiology and Oncology | 2011

Hepatocellular carcinoma with subcutaneous metastasis of the scalp.

Yilmaz Tezcan; Mehmet Koc

Hepatocellular carcinoma with subcutaneous metastasis of the scalp Background. The majority of subcutaneous metastases from hepatocellular carcinoma (HCC) originate from needle tracks or surgical wound contamination. Non-iatrogenic subcutaneous metastasis from hepatocellular carcinoma was rarely reported. Case report. A 70-year-old man presented with a mass in his left occipital region of the scalp. The surgical complete resection was performed. The histopathology report of the scalp mass showed a characteristic metastatic HCC. Computed tomography (CT) of the abdomen showed no primary or metastatic lesion in the abdomen; thats why the adjuvant treatment was not given after the surgery. Five months later, magnetic resonance imaging (MRI) of the brain revealed a 6 × 5.5 cm mass at the left posterior parietal region of the scalp. Second surgery was performed and histopathology of the specimen excised was again metastatic HCC. The external beam radiation therapy (XRT) was administered after the surgery. A follow-up MRI of the brain showed no recurrent disease after 9 months from XRT. Conclusions. HCCs should be considered in the differential diagnosis of carcinomas metastatic to the skin, even in the absence of liver symptoms.


Annals of Translational Medicine | 2015

Survival following reirradiation using intensity-modulated radiation therapy with temozolomide in selected patients with recurrent high grade gliomas

Meryem Aktan; Mehmet Koc; Gul Kanyilmaz

BACKGROUND High grade gliomas often recur after initial treatment. Despite so many treatment options, there is no standard treatment for recurrent gliomas. The aim of this study is to offer survival following reirradiation (re-RT) using intensity-modulated radiation therapy (IMRT) with temozolomide in selected patients with recurrent high grade gliomas. METHODS We examined the medical records of 21 adult patients with recurrent high grade gliomas who were reirradiated with IMRT at the time of tumor recurrence or progression. Tumor recurrence was shown by gadolinium-enhanced magnetic resonance imaging (MRI) and diagnosis was established by pathology review. Statistical analyses were performed with SPSS version 18.0.1 using Cox regression analyses, log-rank test and Kaplan-Meier method. RESULTS Eighteen patients presented by localized recurrence, three patients with diffuse recurrence. Median radiotherapy (RT) dose was 54 Gy. About 81% patients received temozolomide with re-RT. The time interval between two courses RT was median 39.3 months (range, 9.6-140.8 months). The response was checked by MRI. About 24% patients achieved complete response (CR) and 29% patient partial response (PR). Stable disease (SD) was observed in 47% patients. Median follow-up time from diagnosis was 41.4 months (range, 16.6-145.4 months) and 12.3 months (range, 2-27.6 months) from re-RT. Median time to recurrence was 39.3 months (range, 9.6-140.8 months). Median survival after re-RT was 18 months for anaplastic astrocytoma (AA), 14.1 months for glioblastoma multiforme (GBM) (range, 11-17.2 months) (P=0.1) and 7.1 months for patients with Karnofsky performance status (KPS) <70 before re-RT and 17.4 months for KPS >70 (P=0.02). CONCLUSIONS re-RT is one of the treatment options for recurrent high grade gliomas and IMRT can be an effective treatment modality for recurrent high grade brain tumors with only mild side effects. Survival is better in patients with good performance status and in recurrent anaplastic tumors after re-RT.


Radiology and Oncology | 2011

3-D conformal radiotherapy with concomitant and adjuvant temozolomide for patients with glioblastoma multiforme and evaluation of prognostic factors

Yilmaz Tezcan; Mehmet Koc

3-D conformal radiotherapy with concomitant and adjuvant temozolomide for patients with glioblastoma multiforme and evaluation of prognostic factors Background. The aim of the retrospective study was to evaluate the outcome and prognostic factors of newly diagnosed glioblastoma patients who received 3-D conformal radiotherapy (RT) combined with concomitant and/or adjuvant temozalamide (TMZ) postoperatively. Patients and methods. Fifty patients with glioblastoma multiforme were treated with 3-D conformal RT combined with concomitant and/or adjuvant TMZ postoperatively. Median age was 57 years (range, 12-79) and median Karnofsky performance status (KPS) was 70 (range, 40-100). A multivariate Cox regression model was used to test the effect of age, sex, KPS, extent of surgery, tumour dimension (<5cm vs. ≥5cm), full dose RT (≥60 Gy vs. <60 Gy), concurrent TMZ and adjuvant TMZ treatment (adjuvant therapy plus 6 cycles of TMZ group versus <6 cycles of TMZ group) on the overall survival. Results. The median follow up time was 10 months (range 3-42). One- and 2-year overall survival rates were 46% and 20%, respectively. The prognostic factors important for the overall survival were a full dose RT (≥60 Gy) (p=0.005) and the application of adjuvant TMZ for 6 cycles (p=0.009). Conclusions. The results of our study confirm the efficiency of RT plus concomitant and adjuvant TMZ, with an acceptable toxicity in patients. We suggest that at least 6 cycles of adjuvant TMZ should be administered to obtain a benefit from the adjuvant treatment.


Annals of Translational Medicine | 2015

Two cases of gastrointestinal stromal tumor of the small intestine with liver and bone metastasis

Meryem Aktan; Mehmet Koc; Berrin Benli Yavuz; Gul Kanyilmaz

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. These tumors most commonly occur in the stomach (60%), jejunum and ileum (30%). Metastasis is characteristically the malignant behavior of the GISTs. GISTs most frequently metastasize to the liver and peritoneum, whereas bone and lung metastases are uncommon sites. Here, we described two cases of bone and liver metastases in patients with advanced GISTs. Both of them showed liver metastasis at disease presentation and bone metastasis in early time after the diagnosis. Bone metastases involved the lumber spine and right femur in first patient and L2 vertebral body in the second case. All of the lesions presented a lytic pattern. These cases are presented because of the rare incidence of bone metastasis to femur and vertebral bodies. More attention should be paid to the diagnosis of bone metastases from GISTs in clinical practice despite the shortage of available data on the sensitivity and specificity of bone scintigraphy and PET-CT.


Annals of Translational Medicine | 2015

Outcomes of reirradiation in the treatment of patients with multiple brain metastases of solid tumors: a retrospective analysis

Meryem Aktan; Mehmet Koc; Gul Kanyilmaz; Yilmaz Tezcan

BACKGROUND Patients with multiple brain metastases are often treated with whole brain radiation therapy (WBRT). Second course of WBRT is an important treatment option for patients with clinical or radiological intracranial disease progression. This study examines the outcomes in patients with multiple brain metastases who underwent reirradiation. METHODS We examined the medical records of 34 patients with multiple brain metastases who were treated WBRT. The median dose for the first course of WBRT was 30 Gy (range, 25-30 Gy) and for the second course 25 Gy (range, 20-30 Gy). Statistical analyses were performed with using Cox regression analyses, log-rank test and Kaplan-Meier method. RESULTS The median Karnofsky performance status (KPS) was 80 (range, 50-100) before reirradiation. Patients with KPS of >70 had a median survival of 11.4 months, compared to 2.2 months with KPS of ≤70 (P=0.012) and patients who have severe symptoms at the time of reirradiation with median survival 2.2 months while those with mild symptoms had a median of 4.8 months survival (P=0.08). The median overall survival for all patients after diagnosis of metastases was 24.7 months, after the re-irradiation WBRT (re-WBRT) it was 5.3 months (95% CI, 4.08-6.62) and from the diagnosis of primary tumor was 27.1 months (95% CI, 17.75-37.04). CONCLUSIONS In select patients who have good performance status and who do not have severe symptoms might benefit from re-WBRT and re-WBRT seems to be associated with minimal toxicity in patients treated with lower palliation doses.


Asian Pacific Journal of Cancer Prevention | 2016

Thoracic Re-irradiation for Locally Recurrent Lung Cancer

Meryem Aktan; Gul Kanyilmaz; Mehmet Koc; Serhat Aras

Background: Patients with recurrent or progressive lung cancer experience a significant symptom burden, negatively affecting quality of life and reducing life expectancy. Thoracic re-irradiation can be used for palliative treatment to relieve symptoms or as a curative treatment. Methods: Using patient charts, we identified and reviewed 28 cases that had received palliative thoracic re-irradiation for recurrent lung cancer. Results: Before re-irradiation, 32% of patients had stage III non-small cell lung cancer and six had small cell lung cancer. The median interval between treatments was 18.7 months. Median follow-up was 31.2 months from the initial radiotherapy and 5 months after re-irradiation. A better performance status before re-irradiation (<80 vs >80, p=0.09) and a lower overlap 90% isodose (<70 vs >70, p=0.09) showed trends toward improved survival. Grade 1-2 toxicity from re-irradiation was recorded in 12/28 patients, and no grade 3 or 4 acute toxicity was encountered. Conclusion: The role of palliative treatment in survival is not clear but it can provide symptomatic relief in patients, with no high grade toxicity. Further studies with greater patient numbers and longer follow-up times should facilitate determination of the role of this treatment in toxicity and effects on survival.


Turkish Journal of Medical Sciences | 2018

Prognostic value of interferon-gamma, interleukin-6, and tumor necrosis factor-alpha in the radiation response of patients diagnosed with locally advanced non-small-cell lung cancer and glioblastoma multiforme

Çiğdem Damla Deniz; Mehmet Gürbilek; Mehmet Koc

Background/aim: This study aimed to investigate the effect of chemoradiotherapy (CRT) on interferon-gamma (IFN-γ), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α), which are critical markers of the clinical radiation response of patients with locally advanced non-small-cell lung cancer (NSCLC) and glioblastoma multiforme (GBM). Materials and methods: Thirty patients who were treated with CRT and 20 healthy controls were prospectively evaluated. Circulating levels of cytokines were measured by enzyme-linked immunosorbent assay procedure. Post-CRT and pre-CRT levels were compared. Results: Post-CRT, TNF-α and IFN-γ levels were significantly lower than pre-CRT levels in the NSCLC and GBM groups, respectively. The statistical analysis did not show any significant difference between the post- and pre-CRT IL-6 levels. However, the pre-CRT IL-6 levels in the GBM group and post-CRT IL-6 levels in the NSCLC group were significantly higher than those of the control group. Conclusion: CRT affected TNF-α levels in NSCLC and IFN-γ levels in GBM, with the levels of both decreasing significantly. The IL-6 levels of the post-CRT NSCLC group were higher than those of the post-CRT GBM group. Irradiation-induced IL-6 may be responsible for tumor regrowth. Therefore, treatment with IL-6 inhibitors could be a potential therapeutic strategy for sensitizing NSCLC to irradiation in the clinic.


Medical Dosimetry | 2017

Radiation-induced hypothyroidism in patients with breast cancer: a retrospective analysis of 243 cases

Gul Kanyilmaz; Meryem Aktan; Mehmet Koc; Hikmettin Demir; Lütfi Saltuk Demir

This study aims to estimate the incidence of hypothyroidism (HT) and to evaluate the predictors affecting the development of HT after radiotherapy (RT) for breast cancer, with a focus on radiation dose-volumetric parameters. Between 2009 and 2015, 243 patients undergoing RT for breast cancer were retrospectively analyzed. Free triiodothyronine (FT3), free thyroxin (FT4), and thyrotropin (TSH) were monitored before and after RT. The relation between the doses to thyroid gland (Dmean, Dmax, Dmin), percentage of thyroid volume receiving > 10 Gy, 20 Gy, 30 Gy, 40 Gy, and 50 Gy (V10 to V50), absolute thyroid volume, and HT were analyzed. The risk of HT according to radiation fields and the other clinic factors were also evaluated. The median follow-up was 41 (range; 6 to 130) months. Sixty-seven percent of the patients received RT to the breast/chest wall and ipsilateral supraclavicular fossa. Of 243 patients, 51 (21%) were diagnosed with HT. The median time to the onset of HT was 27 (range; 5 to 64) months. There were no significant relationships observed between Dmin or V10 to V50 and HT. The surgery type, clinical stage, nodal status, RT field, Dmean, and Dmax were statistically significant predictors for HT in univariate analysis. The Dmean was the only prognostic factor predicting HT in multivariate analysis, and Dmean > 21 Gy was a threshold value for the evolvement of HT. In this study, we present evidence that postoperative irradiation of patients with breast cancer may frequently lead to HT. Patients who have received RT for breast cancer, especially irradiation on the supraclavicular region, may require thyroid function screening after RT.


Breast Cancer | 2015

Efficacy of manual lymphatic drainage and intermittent pneumatic compression pump use in the treatment of lymphedema after mastectomy: a randomized controlled trial

Hulya Uzkeser; Saliha Karatay; Burak Erdemci; Mehmet Koc; Kazim Senel

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