Committee looks at secondary fall-out from radiotherapy

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According to findings published online in the Journal of the National Cancer Institute (JNCI), there is little to no clinical guidance nor any good studies that have looked at the consequences of radiation therapy, specifically radiotherapy-induced diseases like secondary cancers and cardiovascular disease (CVD).

Radiotherapy has played a very important role in the treatment of several subtypes of lymphoma for decades, making the report relevant to those with the disease and those previously treated for the disease.

While epidemiological studies have been carried out on the hazards associated with radiotherapy, they have not tended to look at patient outcomes from these secondary diseases.

Thus a committee was appointed by the National Council on Radiation Protection and Measurements (NCRP) in order to determine the state of knowledge about radiotherapy-induced cancers and CVD. After five years, that committee has issued its summary report in the JNCI, and it includes seven major conclusions:

-- A growing number of cancer survivors are affected by radiation-induced second malignancies and CVD.
-- Quantitative estimates of radiation-induced second malignancies are based on older regimens but are still applicable to risk assessment in terms of organ-specific radiation doses and dose-response relationships.
-- Newer radiation therapy modalities and techniques have different organ dose distributions.
-- Models developed for secondary malignancy risk assessment remain useful for older regimens, and similar models are needed for assessment of cardiovascular risk.
-- Low-dose radiation exposure in cardiac tissue has not been convincingly linked to CVD; whole-body dose assessments based on atomic bomb survivors may have relevance to low cardiac doses related to scatter and collimator leakage.
-- Few studies have examined survival among patients with radiation-induced second malignancies or CVD.
-- Risk assessment should not be based on effective dose but on organ-specific absorbed dose, biological effectiveness for the endpoint of interest, and radiation type.

While the summary is appearing in the JNCI now, the entire 425 page report won't be available online until later this spring at www.ncrponline.org.

Source: MedPage Today

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