Medicina nuclear y radioterapia

The objective of this study is to perform a thermo luminescent dosimetry (TLD) postal dose audit provided the International Atomic Energy Agency (IAEA) for a linear accelerator in Dong Nai General Hospital. The TLD were irradiated with an absorbed dose to water of 2 Gy for 6 MV and 15 MV photon beams generated by a linear accelerator (LINAC) (Siemens Medical Solutions, Concord, CA). The percentage deviation relative to IAEA measured dose was 0.4% and 3.4% for 6 MV and 16 MV, respectively. Agreement within ± 5% between the users stated dose and the IAEA measured dose is considered satisfactory. The results showed that all photon beams are within the IAEA’s acceptance limit of ± 5%. As a conclusion, the beam output of Siemens Primus is accuracy in delivery of absorbed dose within ± 5%.

Medullary thyroid cancer (MTC) is a neuroendocrine tumor that arises from the parafollicular Calcitonin-producing C-cells of the thyroid. Typically the MTC is an extremely slow-growing cancer; however, it has a tendency of spreading distant metastases fairly early. Systemic chemotherapy and external been radiotherapy have not shown to give a good MTC response. As of date radical thyroidectomy is the main method of choice for therapy. New compounds like tyrosine kinase inhibitors (TKIs) targeting signaling pathways may have a positive outcome and be of great clinical benefits in patients with advanced and metastatic MTC. Somatostatin receptor are over expressed in MTC and thus allows the use of radiolabeled somatostatin analogues for scintigraphic imaging before and after treatment for proper staging and follow-up of these patients. SPECT-CT is used to optimize somatostatin-receptor scintigraphic protocols for MTC imaging. We have presented a case report of a patient who underwent total thyroidectomy with bilateral lymphadenectomy in August 2006 due to the diagnosed MTC. This patient was treated by chemotherapy and surgery during the period between January/2007- December/2014 because of the recurrent disease. In December 2014 the calcitonin level reached 56 000 pg/ml; whole body scan with 740 MBq 99mTc-EDDA/HYNIC-TOC, followed by target SPECT-CT showed a total disease progression with advanced metastatic dissemination into the body. The assigned therapy was with Caprelsa®(Vandetanib) 300 mg/d orally which was initialized from March 2015 until present. In June 2016 a control SPECT-CT somatostatinreceptor scintigraphy with 740 MBq 99mTc-Tektrotyd was performed from which was reported a partial disease response with a reduction of about 60% in size and a decrease in the number of metastatic lesions shown to correlated with the decreased calcitonin level up to 1560 pg/ml. It can be concluded that SPECT-CT with 99mTc- Tektrotyd has important clinical role for re-staging and follow-up of patients with recurrent and metastatic MTC after target therapy.

Objective: We prospectively compared FDG-PET and FLT-PET in assessing patient responses to induction cetuximab and/or chemoradiotherapy (CRT) for advanced head and neck squamous cell carcinoma (HNSCC) and esophageal cancer (EC).

Methods: Sixteen patients were enrolled, 9 with HNSCC and 7 with EC. FDG-PET and FLT-PET scans were performed at baseline and two weeks into chemoradiotherapy (CRT) for patients with EC. Patients with HNSCC received two weeks of induction chemotherapy along with post-induction PET scans prior to starting CRT in addition to the baseline and intra-chemoradiotherapy PET scans. Changes in SUVmax and total lesion glycolysis/ proliferation (TLG/TLP) were compared with baseline.

Results: Median follow-up for living patients was 6.0 years. Median overall survival (OS) was 3.3 years and progression-free survival (PFS) was 2.5 years. Patients with HNSCC had higher baseline SUVmax, TLG and TLP than those with EC. Changes in SUVmax, TLG and TLP after induction chemotherapy or during CRT did not correlate with PFS or OS. Those with >40% decline in SUVmax on FDG-PET six weeks after completing CRT had better PFS (p<0.0001) and OS (p=0.0003) than those with less of a response. In addition, >70% decrease in posttreatment TLG correlated with better PFS (p=0.03) and OS (p=0.04).

Conclusions: Functional imaging performed early during chemoradiotherapy for advanced HNSCC and EC is feasible. Changes on post-induction and intra-CRT FLT and FDG PET did not correlate with PFS or OS. However, better PFS and OS were seen in patients with >40% decline in SUVmax and >70% decrease in TLG on FDG-PET performed six weeks after completing CRT. Further research is needed to determine the prognostic impact of PET performed during chemotherapy and radiotherapy.

Objectives: The most active organs of the reticuloendothelial system (RES) are the liver, spleen and bone marrow, having immune mechanisms against malignancy including neutrophils and platelets. RES may be imaged by different modalities, like PET scan. Neutrophil lymphocyte ratio (NLR) and platelet lymphocyte ratio (PLR) have gained importance as proinflammatory markers in cancer, e.g. lung cancer. The aim of this study was to investigate the relationship between PET parameters of pulmonary mass or RES, and hematological parameters, and to evaluate the role of these factors in differentiating the pathological character of the mass. Methods: A retrospective analysis of the data of 131 patients, retrieved from the department archives, with pulmonary mass limited to mediastinum was made. Patients were grouped according to pathological results: benign mass (n=46), squamous cell carcinoma (n=38), and non-squamous cancer of lung (n=47). All patients underwent PET/CT scanning and images were analyzed retrospectively. Maximum and mean SUV were calculated from primary lesions and RES. NLR and PLR were calculated from CBC. Results: SUVmax and SUVmean of RES organs were similar for both groups with benign and malignant pulmonary masses, and among the subgroups. SUVmax ratios of pulmonary mass were significantly different between the groups (the highest value in the squamous cell carcinoma and the lowest in the benign groups). No significant difference was determined between the subgroups for NLR and PLR. NLR was significantly correlated with SUVmax ratios of spleen and the mass, and SUVmean ratios of spleen and bone marrow. PLR was significantly correlated with SUVmax ratios of spleen, bone marrow, the mass and SUVmean ratios of spleen, bone marrow. Conclusion: SUV of RES and primary mass were correlated with NLR and PLR, indicators of systemic inflammation. The associations between NLR and PLR, and SUV should be clearly defined by further investigations.

Background and Objectives: Both TomoTherapy and RapidArc have been examined in hippocampus sparing whole brain irradiation in adults. We aim to compare both techniques in pediatrics with relatively smaller brain volume. Patients and Methods: The hippocampus, the whole brain and the eyes were manually contoured in 3 pediatric patients. TomoTherapy plan was created aiming at adequate brain coverage and as low as possible hippocampus dose, RapidArc was challenged to achieve similar or better plan results. The prescription dose was 36 Gy in 20 treatment fractions to the whole brain. Results: TomoTherapy was able to achieve a mean hippocampus dose of 13.6 Gy with brain homogeneity index [HI] of 0.14 Using RapidArc [single arc], the same hippocampus dose was not achievable without compromising the brain HI significantly. By using 2 arcs, similar results to the TomoTherapy plan were achieved. The treatment time for TomoTherapy was 3.5 minutes while it was 1.2 minutes for single arc and 2.4 minutes for two arcs. Conclusions: TomoTherapy can achieve better target coverage with lower doses to the hippocampus compared to single arc RapidArc technique, while using 2 arcs RapidArc can achieve similar results with shorter treatment time.

Purpose: To quantify the incidental radiation dose delivered to axilla and internal mammary nodal (IMN) area by Conventional Tangential Radiation Therapy (CRT), 3 Dimensional Conformal Radiation Therapy (3DCRT) and Intensity Modulated Radiation Therapy (IMRT).

Methods and Materials: We prospectively evaluated incidental radiation to axilla in twenty cases of breast cancer treated with adjuvant radiation therapy. Three plans were generated for each case, comprising CRT, 3DCRT and IMRT tangents. Radiation doses to axillary levels I, II, III, and IMN areas were evaluated for mean dose, V95, V80 and V50. Comparisons were made using ANOVA.

Results: The mean volume and range of the axillary level I, II, III, and IMN were 61.1 cc and 142-57 cc; 42.6 cc and 61-21cc; 19.5 cc and 34-15 cc; 13.2 cc and 21-9 cc respectively. The mean dose to axilla by 3 techniques (by IMRT, 3DCRT and CRT) to Level I, II, III, and IMN were 75%, 53%, 38%, and 61% vs. 81%, 64%, 44% and 77% vs. 92%, 86%, 53% and 92% respectively (p<0.05). The V95 values (volume receiving 95% of dose) for the three techniques were 43%, 39%, 17% and 49% by IMRT: 40%, 45%, 21% and 59% by 3DCRT; 72%, 61%, 24% and 65% by CRT (IMRT vs. 3DCRT for level II axilla, IMRT vs. CRT and 3DCRT vs. CRT-p<0.05) The V80 were 49%, 53%, 29%, and 57% by IMRT; 55%, 47%, 34% and 68% by 3DCRT; 85%, 77%, 44% and 69% by CT (IMRT vs. 3DCRT for level III axilla and IMN, IMRT vs. CRT and 3DCRT vs. CRT -p<0.05). The V50 values were 75%, 65%, 41% and 66% by IMRT; 82%, 53%, 57% and 84% by 3DCRT; 94%, 89%, 42% and 90% by CRT (IMRT vs. 3DCRT, IMRT vs. CRT, and 3DCRT vs. CRP–p<0.05).

Conclusion: Axillary and internal mammary nodal areas receive substantial amount of incidental radiation doses with all the three techniques; however, conformal techniques (IMRT, 3DCRT) deliver significantly lesser incidental radiation to lower axilla than CRT technique.