The side effects of cancer treatment vary. They depend mainly on the type and extent of the treatment. Also, each person reacts differently. Doctors try to plan the patient's therapy to keep side effects to a minimum, and they can help with any problems that occur.
      
Chemotherapy

With chemotherapy patients may have side effects, such as loss of appetite, nausea and vomiting, hair loss, or mouth sores. For some patients, the doctor may prescribe medicine to help with side effects, especially with nausea and vomiting.

Usually, these side effects gradually go away during the recovery period or after treatment stops.

Hair loss, another side effect of chemotherapy, is a major concern for many patients. Some chemotherapy drugs only cause the hair to thin out, while others may result in the loss of all body hair. Patients may feel better if they decide how to handle hair loss before starting treatment.

In some men and women, chemotherapy drugs cause changes that may result in a loss of fertility, which may be temporary or permanent. For men, sperm banking before treatment may be a choice. Women's menstrual periods may stop, and they may have hot flashes and vaginal dryness. Periods are more likely to return in young women.

Radiation

Since radiation is a local treatment, side effects are usually confined to the area being treated. The early effects of radiation may be seen a few days or weeks after treatments have started and may continue for several weeks after treatments have ended. Other effects may not show up until months, or even years, later. The major side effects may be:

Skin problems
During the first two weeks of treatment, you may notice a faint redness. Your skin may become tender or sensitive. Dryness and peeling of the skin may occur in three to four weeks. After that, the skin over the treatment area may become darker. This is because of the effect radiation has on the cells in the skin that produce pigment.

The skin may also become dry and itchy. Moisturizing the skin with aloe vera, lanolin, or vitamin E may help. Before using any skin products during treatment, ask the radiation doctor or nurse if it is safe.

Mouth and Throat
Mucositis (inflammation inside the mouth) is a short–term side effect that may happen when radiation is given to the head and neck area. It usually gets better within a few weeks after treatments are completed.

Dry mouth and a loss of taste can be caused by radiation damage to the salivary glands and taste buds. These side effects may go away after treatments are finished but in some cases may be permanent.

Good nutrition is important for people with cancer. If the pain and irritation make it hard to eat or swallow, you may need to have a feeding tube placed into your stomach for a while so you can take in enough nourishment. Your health care team will help you develop a plan to manage your symptoms.

 Radiation to the head and neck area can affect your teeth and increase your chances of getting cavities. Mouth care to prevent problems will be an important part of your treatment.

Brain
Radiation therapy to large areas of the brain can sometimes cause changes in brain function that can lead to memory loss, lower sexual desire, or create poor tolerance for cold weather. Nausea, unsteadiness, and changes in vision may also be noticed. Usually these symptoms are minor compared to those caused by a brain tumor, but they can be a bother.

Lung
When radiation treatments include the chest area, the lungs can be affected. One early change is a decrease in the levels of the substance called surfactant that helps keep the air passages open. Low surfactant levels keep the lungs from fully expanding. This may cause shortness of breath or cough. These symptoms are sometimes treated with steroids.

Depending on the location of the radiation, some people also have trouble swallowing.

Another possible effect of radiation on the lungs is fibrosis (stiffening or scarring). This reduces the ability of the lungs to inflate and take in air. If a large area of the lungs is irradiated (exposed to radiation), these changes can cause shortness of breath and less tolerance for physical exercise. This problem may show up months or years after treatment is completed.

Digestive tract
Radiation to the chest and abdomen may cause swelling and inflammation in the esophagus (swallowing tube), stomach, or intestine. This can cause pain, nausea, vomiting, or diarrhea.

Antacids, sometimes combined with a numbing medicine such as lidocaine, may be helpful in relieving pain from an inflamed esophagus. Diarrhea can be treated with medicines and by avoiding spicy, fried, or high–fiber foods.

Reproductive Organs
Radiation to the testicles can cause permanent loss of sperm production. Unless the cancer is in the testicles, they can usually be protected from radiation by using a shield that is known as a "clam shell."

It is harder to protect the ovaries in women getting radiation to the abdomen. If both ovaries are irradiated, permanent loss of fertility may occur along with early menopause. Sparing one ovary can prevent these side effects.

Sexual impact in women
Radiation to the pelvic area can cause the vagina to be tender and inflamed during and for a few weeks after treatment. Scarring of the area may occur as it heals and can interfere with the ability of the vagina to stretch. The lining of the vagina also gets thinner, which may cause light bleeding after sex. A few women get ulcers, or sore spots, in their vaginas. It may take many months after the end of radiation therapy for these areas to heal.

Sexual impact in men
Radiation therapy to the pelvis can damage the arteries and nerves that supply the penis and cause problems with erections. The higher the dose of radiation and the wider the area of the pelvis that is treated, the greater the chance that an erection problem will develop. About one man out of three who gets radiation notices a change in his ability to have erections.

This change most often develops slowly over the first year or so after radiation treatment. Some men continue to have full erections but lose them before reaching climax. Others no longer get firm erections at all. 

Testosterone is a male hormone that plays an important role in erections. Some men have less testosterone after pelvic radiation. The testicles, which produce testosterone, may have been affected either by a mild dose of scattered radiation or by the general stress of cancer treatment. The testosterone level will usually recover within six months of radiation therapy.

Second Cancer
The link between radiation and cancer was confirmed many years ago through studies of the survivors of the atomic bombs in Japan, the exposures of workers in certain jobs, and patients treated with radiation therapy for cancer and other diseases

Some cases of leukemia are related to previous radiation exposure. Most develop within a few years of exposure, with the risk peaking at five to nine years and then slowly declining.

Other types of cancer that develop after radiation exposure have been shown to take much longer to show up. These are solid tumor cancers, like cancer of the breast or lung. Most are not seen for at least 10 years after radiation exposure, and some are diagnosed even more than 15 years later.

Surgery

Side effects vary depending on the  specific surgery. In general, most cancer operations carry a risk of:

Pain
Pain is a common side effect of most operations. Some cause more pain than others do. Your health care team will tell you how to keep your pain to a minimum and will provide medications to reduce or eliminate the pain.

Infection
The site of your surgery can become infected. Your health care team will show you how to care for your wound after surgery. Follow this routine closely to avoid infection, which can lengthen your recovery time after surgery. Doctors treat infections most often with antibiotics.

Loss of organ function
In order to remove your cancer, the surgeon may need to remove an entire organ. For example, your kidney may need to be removed if you have kidney cancer. For some such operations, the remaining organ can function sufficiently to compensate for the loss, but in other situations you may be left with impairments. For instance, removal of a lung (pneumonectomy) may cause difficulty breathing.

Bleeding
All operations carry a risk of bleeding. Your surgeon will try to minimize this risk.

Blood clots
While you're recovering from surgery, you're at an increased risk of developing a blood clot. Though the risk is small, this complication can be serious.

Blood clots most commonly occur in the legs and may cause some swelling and pain. A blood clot that breaks off and travels to the lung could cause a pulmonary embolism, a dangerous and sometimes deadly condition. Your surgeon will take precautions to prevent blood clots from developing, such as getting you up and out of bed as soon as possible after your operation.

Immediately after your surgery you may experience difficulty having a bowel movement or emptying your bladder. This typically resolves in a few days, depending on your specific operation.

Hormonal Therapy

Hormone therapy can cause a number of side effects. Patients may have nausea and vomiting, swelling or weight gain, and, in some cases, hot flashes.

In women, hormone therapy also may cause interrupted menstrual periods, vaginal dryness, and, sometimes, loss of fertility. Hormone therapy in men may cause impotence, loss of sexual desire, or loss of fertility. These changes may be temporary, long–lasting, or permanent.

Biological or Immunotherapy

The side effects of biological therapy depend on the type of treatment. Often, these treatments cause flu–like symptoms such as chills, fever, muscle aches, weakness, and loss of appetite, nausea, vomiting, and diarrhea. Some patients get a rash, and some bleed or bruise easily. In addition, interleukin therapy can cause swelling.

Depending on how severe these problems are, patients may need to stay in the hospital during treatment. These side effects are usually short-term; they gradually go away after treatment stops. 
Source: http://seniorhealth.about.com/cs/cancer/a/cancer_treat_se.htm

Whatever cancer treatment your doctor recommends, you're likely to feel some anxiety about your condition and the treatment process. Knowing what to expect can help. Use this information to help you talk with your doctor and ask informed questions. 
Source: http://www.mayoclinic.com/health/cancer-surgery/CA00033