Radiotherapy, side effects

Since the late 1990s, therapy radiographers have been trained to administer medicines for the management of radiotherapy side effects, such as pain rectal symptoms, constipation, diarrhoea skin reactions, wound care oral care nausea and vomiting. They are also beginning to use PGDs for X-ray contrast agents. 

Modem cancer therapy has been primarily dependent upon surgery, radiotherapy, chemotherapy, and hormonal therapy (72) (see Chemotherapeutics,anticancer Hormones Radiopharmaceuticals). Chemotherapeutic agents maybe able to retard the rate of growth, but are unable to eradicate the entire population of neoplastic cells without significant destmction of normal host tissue. This serious side effect limits general use. More recentiy, the immunotherapeutic approach to cancer has involved modification and exploitation of the cellular and molecular mechanisms in host defense, regulation of tissue proliferation, tissue differentiation, and tissue survival. The results have been more than encouraging. 

In this chapter we have summarised the mechanisms through which ionizing radiation kills cancer and normal cells and the strategies useful to increase the curative potential of photon energy. If we consider clinical efficacy and the incidence of side effects visible at the inception of radiotherapy, we are aware of the improvements acquired through the... 

Radiotherapy is a local treatment aiming to achieve local control or cure of locally confined tumours. It cannot treat metastases. Radiotherapy may be administered as external beam radiotherapy with X-rays or gamma rays, in sealed radioactive sources (e.g. prostate brachytherapy), or unsealed sources (e.g. orally administered radioiodine for thyroid cancer, intravenous strontium-89 for bone metastases). In external beam radiotherapy, the X-ray or gamma ray beams are targeted at the tumour to damage and kill the tumour cells. Inevitably, surrounding normal tissues are also affected resulting in the early and late side effects of radiotherapy. 

A frequently used procedure is targeted irradiation with y-rays, which block cell reproduction due their mutagenic effect (see p. 256). Another approach is to inhibit cell growth by chemotherapy. The growth-inhibiting substances used are known as cytostatic drugs. Unfortunately, neither radiotherapy nor chemotherapy act selectively—i. e., they damage normal cells as well, and are therefore often associated with severe side effects. 

For treating psoriasis, UVB phototherapy and PUVA are effective treatments that permit rapid control of the disease, but their side effects are similar to those of radiotherapy and chemotherapy. While these treatments can suppress the pathogenic change and rapidly improve the skin lesions, the heat penetrates into the blood, consumes the blood and Yin, and generates heat-toxin. Once the therapy is finished, the heat quickly arises and the skin lesions appear again, even worse than before the treatment, and the skin becomes more sensitive in general. In herbal treatment, one needs to reduce the heat-toxin, cool the blood, promote blood circulation and nourish the Yin. 

At the turn of the century. Dr. William B. Coley, a young surgeon in New York City, made the remarkable discovery that injection of live or inactivated pathogenic bacteria into patients with otherwise incurable cancers would oftentimes induce dramatic necrosis (a specific type of cell death) and regression of the tumors. Owing to a nmnber of factors including lack of standardization of the potency of the bacterial injections, toxic side effects, variability and sometimes total lack of effect, and the simultaneous advent of radiotherapy, these intriguing results were not followed up until much later. 

In a study of 56 patients treated with ricin A chain immunotoxin, 12 required interruption or termination of treatment due to the severity of side-effects, and two patients died as a result of vascular leak syndrome (Baluna et al, 1996). Vascular leak syndrome was more common in patients who had received radiotherapy prior to immunotherapy (Schindler et al, 2001). 

The 5-HT3 antagonists ondansetron (Zofran) and granisetfon (Kyttil) are effective in relieving the nausea and vomiting that are side-effects of radiotherapy and treatment with cytotoxic drugs. They probably function by a combination of central and peripheral actions. 

Radiographers have been trained since 1998 to administer select drugs for treatment and management of side effects of radiotherapy under PGDs. 

A patient has been receiving abdominal radiotherapy for a period of time for the treatment of colon cancer. She has suffered quite serious nausea as a result of the treatment. You have supplied metoclopramide (in 28 packs of 10 mg tablets) to the patient on a regular basis under PGDs. The patient is now complaining that this drug does not seem to work any more. She has also been experiencing facial muscle spasms and wonders if this could be a side effect of her radiotherapy or the drug. In addition, the patient has developed a painful skin rash over the treatment area. 

Published work in this area (Westbrook and Hodgetts, 1997) revealed that the role of the doctor (oncologist) was often unnecessary in the patient review process and, out of 79 recorded activities to obtain medication for the relief of side effects from radiotherapy, there was only one case where the patient needed to be seen by a doctor. 

In an early series at our own institution patients with glioblastomas had been treated with one single dose of 4 Gy of electrons within 30 min after PDT [21]. The results remained unchanged to that without immediate X-radiation treatment, therefore this treatment protocol has not been continued. Radiotherapy was commenced, in addition, in all patients with primary untreated glioblastomas within 10 days of surgery and PDT. We did not see any increased side effects from this radiotherapy. In another series conventional radiation treatment of 60 Gy was started up to four weeks after PDT with no side effects observed [19]. 

With the advent of modem radiotherapy, survival rates of people with certain types of cancers have increased significantly. Unfortunately, the side effects of radiation impose devastating effects on the quality of life of cancer patients. Moreover, radiation therapy often leads to secondary malignancies such as melanoma, medullablastoma, soft-tissue... 

Denise D. Correa, Ph.D., aboard certified neuropsychologist at Memorial Sloan-Kettering Cancer Center in NewYork City who specializes in the cognitive side effects of radiotherapy and chemotherapy, likes to use a specific analogy to describe these attentional and executive function difficulties. It s as if you have a file cabinet and most files are there, but they re not in order or they re not labeled clearly, she says. So you can t find them efficiently. ... 

Effects on humans are separated into deterministic effects caused by severe exposures to high doses and stochastic effects (mostly cancer) caused by much lower exposures. Data on deterministic effects come from side effects of radiotherapy, exposure of the early radiobiologists, atomic bomb effects in Japan, and a few severe accidents. Data on stochastic effects are mostly based on epidemiological studies on the survivors of the atomic bomb detonations in Japan, on patients exposed to medical treatments, and on industrial exposures to workers. Animal studies are also used to evaluate human effects. 

Radiotherapy destroys a fairly large volume of tissue and its effects can be likened to those of a deep burn. The cells and other exposed tissue structures disintegrate and die, forming toxic breakdown products that have to be carried off by the bloodstream and excreted in the urine. It is believed that the unpleasant systemic side effects of radiotherapy (nausea, lassitude) are caused by this sudden metabolic overload of toxic by-products. Ascorbic acid is essential for the proper functioning of a group of liver enzymes concerned with the detoxification and disposal of noxious substances, and it is therefore quite possible that a high intake of ascorbate reduces the unpleasant side effects of irradiation. 

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