Side effects of radiopharmaceutical therapy
What are the potential adverse effects of radiopharmaceutical therapy?
Side effects of radiopharmaceutical therapies are determined by the biodistribution and kinetics of the radiopharmaceutical agent as well as the different sensitivities of various organs to the effects of radiation. Toxicity can be subdivided into acute, subacute, and late phases.
The most common acute toxicity is nausea, which is a generic effect of radiation in any form and is dose dependent (the higher the dose, the more the nausea). Other acute toxicities specific to the treatment in question and its distribution are possible, such as salivary gland pain with radioiodine therapy.
In general, the bone marrow is the most sensitive organ to radiation, and with most therapeutics bone marrow suppression is the dose-limiting toxicity even when the bone marrow receives a relatively smaller dose than other normal organs. Whereas with cytotoxic chemotherapy bone marrow suppression is observed within about a week of treatment, bone marrow suppression from radiopharmaceuticals is usually seen several weeks after therapy with a nadir generally at about 4 to 6 weeks. This usually spontaneously recovers but can be prolonged or permanent.
Late toxicity from radiopharmaceutical therapy generally refers to the induction of malignancies. Leukemia is the most common malignancy induced by radiation exposure, but other cancers are also possible. There is a clear link between radiation dose and cancer induction with high acute doses of radiation (e.g., in atomic bomb survivors), but it is much more difficult to detect the effects of lower radiation doses used with radiopharmaceutical therapies, particularly given the relatively high incidence of nonradiation-induced cancers. Therefore, this risk is poorly understood but is generally observed to be fairly low.