My take on rads

These posts were originally addressed to people who had unexpected and/or severe reactions to rads. Here is what I've learned form looking into radiation treatment beyond breastcancer.org.

I was troubled by the fact that rads are prescribed so casually, and looked at numerous posts about self-reported SEs of rads. The picture looks like a classic radiation poisoning even when the treatment is given only to the breast. ROs keep telling that's the treatment is external, and it is different from other cases when the internal organs are irradiated. The thing is, no one cancelled laws of physics, and the general mechanism of the interaction of the x-ray beam with any type of matter (lead of human tissue) produced scattered radiation that goes everywhere. There is no way to avoid it or shield from it. The amount of scattering may not be as much in human tissue as in lead simply because the density of human tissue is much lower, and the probability of interaction of x-ray photons with molecules is not that high (hence the usage of high-intensity beams).

Radiation poisoning is a result of radiation exposure, its also known as radiation syndrome or radiation sickness. Nausea and vomiting, dizziness, fatigue, metallic taste, diarrhea, leukopenia, burns to the skin - these are common when the whole body is radiated. It makes sense to me when ROs insist that rads induce mostly the local effects of skin burning, but it bothers me when they dismiss the effects of scattered radiation on the whole body. GI tract is very  sensitive to radiation,  thus some have diarrhea (bloody diarrhea in case of high doses) and metallic taste in the mouth . Bone marrow is also sensitive, hence leukopenia (neutropenia) and immune system impairment. If I remember correctly, radiation affects fast-dividing cells more than others, just like chemo. Hair loss is also taking place at high doses,  although it is seemingly not an issue when only a breast is irradiated. 

Now, about doses. A standard dose for the breast is 50 Gray given at in 2 Gray fractions. Gray is energy in joules per 1 kg of mass. Say, if the breast is 0.5 kg it will cumulatively receive the total 25 Joules of energy in 1 joule fractions (50 gray for 1 kg breast is equal to the total of 50 Joules ) . A dose of 2 to 10 Gray over the whole body delivered in a couple of hours is lethal. If  person's weight is 75 kg (165 pounds) the total is 150 - 750 Joules (which is a big number comparing to 25-50 Joules  received by a breads during rads). A person may  start feeling the effects of radiation at 1 Gray delivered to the whole body, i.e. 75 Joules for a 165-pound person. In this case, 25 Joules is only tree times less than that, but 50 Joules is quite comparable, and I bet its effect is not negligible. The flaw in these calculations is that the lethal dose is usually delivered within hours, whereas radiation treatment is given in fractions, over the lengthy period of time, giving human body a chance to repair the damage. This damage is two-fold: DNA damage and ionization, or production of ions in the cells. I believe, ionization triggers a cascade of different reactions, none of which I'm qualified to explain.

Below is an excerpt from a Wikipedia entry about radiotherapy. Wiki is a good source because it's unbiased. Please refer to the whole entry for references. The only point I would like to make is that even if the breast radiation is local, scattering affects the whole body, and thus all SEs listed below may manifest themselves. Each individual is unique in his/her response to radiation, hence a big range for the lethal dose, and the severity SEs in each case.

Radiation therapy

Side effects

Radiation therapy is in itself painless. Many low-dose palliative treatments (for example, radiation therapy to bony metastases) cause minimal or no side effects, although short-term pain flare-up can be experienced in the days following treatment due to oedema compressing nerves in the treated area. Higher doses can cause varying side effects during treatment (acute side effects), in the months or years following treatment (long-term side effects), or after re-treatment (cumulative side effects). The nature, severity, and longevity of side effects depends on the organs that receive the radiation, the treatment itself (type of radiation, dose, fractionation, concurrent chemotherapy), and the patient.

Most side effects are predictable and expected. Side effects from radiation are usually limited to the area of the patient's body that is under treatment.

The main side effects reported are fatigue and skin irritation, like a mild to moderate sun burn. The fatigue often sets in during the middle of a course of treatment and can last for weeks after treatment ends. The irritated skin will heal, but may not be as elastic as it was before.

Acute side effects

Nausea and vomitingThis is not a general side effect of radiation therapy, and mechanistically is associated only with treatment of the stomach or abdomen (which commonly react a few hours after treatment), or with radiation therapy to certain nausea-producing structures in the head during treatment of certain head and neck tumors, most commonly the vestibules of the inner ears.^[As with any distressing treatment, some patients vomit immediately during radiotherapy, or even in anticipation of it, but this is considered a psychological response. Nausea for any reason can be treated with antiemetics.
Damage to the epithelial surfacesEpithelial surfaces may sustain damage from radiation therapy. Depending on the area being treated, this may include the skin, oral mucosa, pharyngeal, bowel mucosa and ureter. The rates of onset of damage and recovery from it depend upon the turnover rate of epithelial cells. Typically the skin starts to become pink and sore several weeks into treatment. The reaction may become more severe during the treatment and for up to about one week following the end of radiation therapy, and the skin may break down. Although this moist desquamation is uncomfortable, recovery is usually quick. Skin reactions tend to be worse in areas where there are natural folds in the skin, such as underneath the female breast, behind the ear, and in the groin.
Mouth, throat and stomach soresIf the head and neck area is treated, temporary soreness and ulceration commonly occur in the mouth and throat. If severe, this can affect swallowing, and the patient may need painkillers and nutritional support/food supplements. The esophagus can also become sore if it is treated directly, or if, as commonly occurs, it receives a dose of collateral radiation during treatment of lung cancer. When treating liver malignancies and metastases, it is possible for collateral radiation to cause gastric, stomach or duodenal ulcers This collateral radiation is commonly caused by non-targeted delivery (reflux) of the radioactive agents being infused. Methods, techniques and devices are available to lower the occurrence of this type of adverse side effect.
Intestinal discomfortThe lower bowel may be treated directly with radiation (treatment of rectal or anal cancer) or be exposed by radiation therapy to other pelvic structures (prostate, bladder, female genital tract). Typical symptoms are soreness, diarrhoea, and nausea.
SwellingAs part of the general inflammation that occurs, swelling of soft tissues may cause problems during radiation therapy. This is a concern during treatment of brain tumors and brain metastases, especially where there is pre-existing raised intracranial pressure or where the tumor is causing near-total obstruction of a lumen (e.g., trachea or main bronchus). Surgical intervention may be considered prior to treatment with radiation. If surgery is deemed unnecessary or inappropriate, the patient may receive steroids during radiation therapy to reduce swelling.
InfertilityThe gonads (ovaries and testicles) are very sensitive to radiation. They may be unable to produce gametes following direct exposure to most normal treatment doses of radiation. Treatment planning for all body sites is designed to minimize, if not completely exclude dose to the gonads if they are not the primary area of treatment. Infertility can be efficiently avoided by sparing at least one gonad from radiation.

Late side effects

Late side effects occur months to years after treatment and are generally limited to the area that has been treated. They are often due to damage of blood vessels and connective tissue cells. Many late effects are reduced by fractionating treatment into smaller parts.

FibrosisTissues which have been irradiated tend to become less elastic over time due to a diffuse scarring process.
EpilationEpilation (hair loss) may occur on any hair bearing skin with doses above 1 Gy. It only occurs within the radiation field/s. Hair loss may be permanent with a single dose of 10 Gy, but if the dose is fractionated permanent hair loss may not occur until dose exceeds 45 Gy.
DrynessThe salivary glands and tear glands have a radiation tolerance of about 30 Gy in 2 Gy fractions, a dose which is exceeded by most radical head and neck cancer treatments. Dry mouth (xerostomia) and dry eyes (xerophthalmia) can become irritating long-term problems and severely reduce the patient's quality of life. Similarly, sweat glands in treated skin (such as the armpit) tend to stop working, and the naturally moist vaginal mucosa is often dry following pelvic irradiation.
LymphedemaLymphedema, a condition of localized fluid retention and tissue swelling, can result from damage to the lymphatic system sustained during radiation therapy. It is the most commonly reported complication in breast radiation therapy patients who receive adjuvant axillary radiotherapy following surgery to clear the axillary lymph nodes .
CancerRadiation is a potential cause of cancer, and secondary malignancies are seen in a very small minority of patients – usually less than 1/1000. It usually occurs 20 – 30 years following treatment, although some haematological malignancies may develop within 5 – 10 years. In the vast majority of cases, this risk is greatly outweighed by the reduction in risk conferred by treating the primary cancer. The cancer occurs within the treated area of the patient.
Heart diseaseRadiation has potentially excess risk of death from heart disease seen after some past breast cancer RT regimens.
Cognitive declineIn cases of radiation applied to the head radiation therapy may cause cognitive decline. Cognitive decline was especially apparent in young children, between the ages of 5 to 11. Studies found, for example, that the IQ of 5 year old children declined each year after treatment by several IQ points.
Radiation enteropathyThe gastrointestinal tract can be damaged following abdominal and pelvic radiotherapy. Atrophy, fibrosis and vascular changes produce malabsorption, diarrhea, steatorrhea and bleeding with bile acid diarrhea and vitamin B12 malabsorption commonly found due to ileal involvement. Pelvic radiation disease includes radiation proctitis, producing bleeding, diarrhoea and urgency, and can also cause radiation cystitis when the bladder is affected.

Cumulative side effects

Cumulative effects from this process should not be confused with long-term effects—when short-term effects have disappeared and long-term effects are subclinical, reirradiation can still be problematic.

Effects on reproduction

During the first two weeks after fertilization, radiation therapy is lethal but not teratogenic. High doses of radiation during pregnancy induce anomalies, impaired growth and intellectual disability, and there may be an increased risk of childhood leukemia and other tumours in the offspring.

In males previously having undergone radiotherapy, there appears to be no increase in genetic defects or congenital malformations in their children conceived after therapy.However, the use of assisted reproductive technologies and micromanipulation techniques might increase this risk.

Effects on pituitary system

Hypopituitarism commonly develops after radiation therapy for sellar and parasellar neoplasms, extrasellar brain tumours, head and neck tumours, and following whole body irradiation for systemic malignancies.Radiation-induced hypopituitarism mainly affects growth hormone and gonadal hormones.In contrast, adrenocorticotrophic hormone (ACTH) and thyroid stimulating hormone (TSH) deficiencies are the least common among people with radiation-induced hypopituitarism.Changes in prolactin-secretion is usually mild, and vasopressin deficiency appears to be very rare as a consequence of radiation.

Shielding during radiation treatment.

Shielding is used to lessen the intensity or to block the radiation beam. Sources used for radiation treatment of cancer vary, but breast cancer is treated with high-energy x-rays. X-rays are highly penetrable, this means that they are not readily absorbed by human tissues and can go through without much interaction with it. How effective the material in absorbing x-rays is characterized by a half-value layer (HVL) : this is the thickness of any given material where 1/2 of the incident energy has been attenuated. Attenuation is exponential, but the steepness of the curve depends on the material and the energy of photons used for radiation. An x-ray beam is a stream of photons. The energy of x-ray photons depends the x-ray machine. Usually x-ray machines emit photons with a variety of energies ( a spectrum of energies), unless special filters are used . The usual shielding material for all types of radiation is lead. It is needed 1.2 cm (about 0.5 inch) of lead to decrease the intensity of the x-ray beam in half (HVL=1.2 cm for lead) . HVL for breast tissue is about 50 cm (about 1.5 feet) thus the x-ray beam shoots through the breast without a significant attenuation. (When doing these calculations I referred to the maximum energy applied to the x-ray tubes listed by manufacturers and assumed that all photons have the energy of 1MeV (info for specialists).Technically, such energetic x-rays should be classified as gamma-rays, but there is no clear distinction between them.)) I do not know the intensity of the beams used for radiation treatment but suspect they are pretty high, because the breast tissue is not very effective in attenuating x-rays. (High intensity is needed to increase the probability of photons hitting  atoms or molecules). In this case, you probably need meters of lead or concrete to block the beam completely, thus putting on lead aprons or laying on lead tables will not shield you anyways. What protects your other parts is that the beam is not fanning out over a big angle, and thus does not hit other parts of the body. The fanning angle can be decreased via a technique called collimation. I do not know how effective is collimation and my RO did not tell me anything about the angle. The intensity is not uniform within this angle. ROs are using at least two beams in an attempt to uniformly irradiate the breast and the adjacent areas up to the clavicle bone, ribs and auxiliary lymph nodes under the armpit. It's a big area. Scattered photons will go inside your body , but the beams themselves will not hit any other parts , hence shielding of other parts is impractical.

How much dose can you get from scattered radiation? It's a good question. From reading medical papers I found that the heart receives 5 Grays when 50 Grays are given to the left breast, and 2 Grays - when it's given to the right, which makes about 5-10% of the total dose.

Why radiation treatment?

It's an experimental fact that radiation decreases the local recurrence rates for several years after the treatment. There are several studies that show 50% decrease in the recurrence rates for DCIS; I haven't looked at IDC or ILC cases. I haven't seen too many papers describing why 50%, it's just an experimental fact. The mechanism may be killing off a significant number of cancer cells (all cells cannot be killed because of the low probability of interaction, but a certain number can be damaged. The damaged cancer cells have  a diminished capacity for repair. The immune system may then take care of the ones that were not hit by radiation) and/or the immune response to trauma to the tissues. This 50% rate was found experimentally, by comparing the number of recurrences in cases treated with and without rads. If the recurrence rate is low, say 2%, it decreases it (mathematically) to 1%, which is not statistically significant. If the recurrence rate is estimated to be about 60% (6 out of 10 chance) , then the decrease to 30% (3 out of 10 chance) may be meaningful ( although it is always nice to know the uncertainty range). All these percentages are statistical, and mean very little when it comes to each specific case. We are unique individuals, although doctors treat us as part of statistics.

According to Wikipedia, "the effect of radiotherapy on control of cancer has been shown to be limited to the first five years after surgery, particularly for breast cancer. The difference between breast cancer recurrence in patients who receive radiotherapy vs. those who don't is seen mostly in the first 2–3 years and no difference is seen after 5 years.^[6] This is explained in detail here".