Article 1: Radiation Associated Brainstem Injury
The tolerance of the central nervous system (CNS) to radiation treatment is significant to patient under treatment for metastatic or primary diseases associated with neck, brain and head. In most cases, brainstem injury is graded by most widespread toxicity criterion of the Cancer Therapy Evaluation Program based on symptoms. The first grade is considered mild, the second grade is moderate and without the capacity to interfere with daily living activities. The third grade presents extreme interference with the activities of daily living while the fourth grade is life threatening. The manifestation of severe radiation therapy induced central nervous system injury occurs several months or years after therapy (Mayo, Ellen and Thomas 37). There are several challenges associated with the study of radiation therapy induced central nervous system injury; most patient survive only for short period, there is generally low injury incident and, it is often daunting to differentiate between disease progression and side effects for patients diagnosed with intracranial tumors.
There are recommended dose volume rations for radiation therapy recommended for effective radio therapy treatment in addition to reduced side effects. The recommendations in this article presented data in categories of cut points, reported complications, no complications, dose constrains. Cut points were considered as the value of doses that are statistically important for elevated risk (Mayo, Ellen and Thomas 37). Despite the fact that different authors do not quantify the anticipated incidence, the reported dose constrains utilized in therapy planning are assumed to be related with low risk. The article presents a number of recommendations that can aid in the comprehension of dose volume effects as well as provide clear data of the range of doses safely employed by medical experts. The article recommends that detailed data of brainstem dose-volume and outcome should be published (Noël et al 396).
Additionally, the patients should have a long term follow up even in cases where no toxicity has been witnessed. This is important given that the data are significant for emerging fractionated SRT regiments. Additionally, the article suggest that prospect research should be designed with machinery for reporting and obtaining customized outcome and dosimetric information in a appropriate form that can be employed for NTCP modeling. It also suggests clear description of method of rectifying dose distribution information for hypo-fractionaded treatments (Mayo, Ellen and Thomas 39). Similarly, the fundamental information pertaining to physical dose volume should be made available. In order to facilitate inter-comparison and data pooling, it is imperative for the definition of toxicities to employ the use of formal, common and clinically practical systems in future publications (Clark et al 670).
The article sees it imperative for studies pertaining to brainstem toxicity outcome to report both the standard deviation and mean for not less than four brainstem dosimetric variables at a less detailed level. The four variables should at least include; the Mean dose, Maximum dose (Dmax), Maximum dose per fraction (Dmax per fraction) and Dose per milliliter (D1mL). the specific values of these variables should be noted for patients exhibiting severe neuropathy or brainstem radiation necrosis.
Statistical data on brainstem doses that were more than 50 G were categorized under no-complication category. Statistical data that were not applicable to any of the categories presented were grouped under other reference. It was recommended that the entire brainstem maybe treated using a dose of 54 Gy through the use of convectional fractionation with limited risk of permanent or severe neurological impacts (Mayo, Ellen and Thomas 39). The brainstems in small volumes may be put under radiation using maximum doses of 59Gy for does fractions that are less than or equal to 2 Gy. The risk of radiation therapy appears to amplify markedly at doses that are greater than 64Gy. Information to determine whether there is additional volume effect is insufficient. In cases of single fraction SRS, utmost brainstem dose of 12.5 Gy is related to stumpy risk that are below 5 percent.
Article 2: Radiation Dose Volume effects in the Heart
Cardiac diseases that are associated with radiation are of importance to patients treated for breast cancer, lymphoma, seminoma, lung cancer, and peptic ulcer disease. This is because acute injury is usually chronic despite the fact that it is transient in most cases. Late injury is more clinically essential given that it manifests as coronary artery disease, conjestive heart failure and myocardial infarction more than a few months after radiation therapy. One of the leading sources of non-cancer transience among long term radiation therapy treated survivors of lymphoma is cardiovascular fatality (Gagliardi et al 77).
According to the article, clinical trials based on 3D dosimetric data in addition to cautiously long term monitor of patients who received potentially cardiotoxic chemotherapy are significant for enhanced toxicity prediction. The authors of this article present several recommendations that can aid in enhancing the outcome of future toxicity studies. Extra work is required in order to better assess whether the contemporary radiotherapy treatment advances for patients diagnosed with breast cancer is related with significant cardiac toxicity. There is need for more elucidation on the clinical importance of the perfusion abnormalities (Bentzen 704).
Also, supplementary study is required to relate doses to clinical outcomes to sub-volumes of the heart such as coronary arteries. It suggests that the use of computed tomography contrast could be essential for the definition of heart boarders (Darby 557). Supplementary studies are required in radiation-treated patients with other thoracic growth where elevated heart disease has been recorded but with limited data on dose volume (Das 19). Baseline cardiovascular risk factors should be incorporated in future studies so as to enable contemplation of potential interactive effects between traditional cardiac risk factors and radiation therapy. Example of risk factors that should be incorporated in future studies includes Reynolds and Framingham score.
Also, supplementary work is required to comprehend the effect of hypo-fractionated radiation treatments on the heart. In addition, a deeper comprehension of the global physiological effect of thoracic radiation therapy is required (Bentzen 704). Some of the effects of thoracic radiation therapy that require deeper understanding include the interaction between the lung and heart irradiation. The application of LENT-SOMA system should be considered in the description of cardiac effects. The authors of this article believe that LENT-SOMA system explicitly tackles radiological, functional and clinical assessments of cardiac dysfunction.
Works Cited
Bentzen, Søren M. "Preventing or reducing late side effects of radiation therapy: radiobiology meets molecular pathology." Nature Reviews Cancer6.9 (2006): 702-713.
Clark, Brenda G., et al. "The integral biologically effective dose to predict brain stem toxicity of hypofractionated stereotactic radiotherapy."International Journal of Radiation Oncology* Biology* Physics 40.3 (1998): 667-675.
Darby, Sarah C., et al. "Long-term mortality from heart disease and lung cancer after radiotherapy for early breast cancer: prospective cohort study of about 300 000 women in US SEER cancer registries." The lancet oncology6.8 (2005): 557-565.
Das, Shiva K., et al. "Predicting radiotherapy-induced cardiac perfusion defects." Medical physics 32.1 (2005): 19-27.
Gagliardi, Giovanna, et al. "Radiation dose–volume effects in the heart."International Journal of Radiation Oncology* Biology* Physics 76.3 (2010): S77-S85.
Mayo, Charles, Ellen Yorke, and Thomas E. Merchant. "Radiation associated brainstem injury." International Journal of Radiation Oncology* Biology* Physics 76.3 (2010): S36-S41.
Noël, Georges, et al. "Combination of photon and proton radiation therapy for chordomas and chondrosarcomas of the skull base: the Centre de Protontherapie D’Orsay experience." International Journal of Radiation Oncology* Biology* Physics 51.2 (2001): 392-398.
