- What are the most important side effects that ovarian cancer patients should be watching for when undergoing radiation therapy?
- How is radiation therapy used in palliative care for ovarian cancer?
- In what situations is radiation therapy used for adjuvant therapy in ovarian cancer? How often is it used?
Because the three above questions are very related to each other, I am going to answer all of them in one response. You can share the same answer for each or break it down according to the question.
Throughout the past two decades, the role of radiation therapy in treatment of ovarian cancer has been consistently diminishing. This is due to two major factors. The first factor is the increasing knowledge that most of ovarian cancers, especially the ones which are not localized and require more than surgical intervention i.e. adjuvant treatment, are considered either systemic disease or at least putting the entire abdominal cavity at risk of recurrence. The second factor is the advances made in chemotherapy, not only by having better supportive care so that the patients can tolerate chemotherapy better but also in the number new chemotherapy agents.
The main difference between chemotherapy and radiation therapy is the fact that chemotherapy is a systemic treatment and radiation is a local treatment. In this sense radiation is similar to surgery and would only address the area which is receiving radiation. With chemotherapy, once it is injected into your blood stream, it goes everywhere in your system. That is like a double-edge sword though because often it affects organs which do not necessarily need to receive chemotherapy such as your hair, your nails, your bone marrow, or kidney etc. But the fact that it addresses your entire system has the advantage of killing any cancer cell that potentially has cut loose through your system. More and more research is done on creating mechanisms towards targeted therapy that is to direct chemotherapy towards the cancer cells only and avoid side effects of chemotherapy by sparing the normal tissues.
When radiation therapy was routinely used for ovarian cancer, it was given in the form of whole abdominal radiation. That is the radiation was covering all and every tissue below diaphragm down to the pelvis. These large radiation fields were very difficult to tolerate. Large does could not be delivered to these large fields and patients had to endure many side effects particularly nausea, vomiting, and diarrhea. Later on injection of Phosphorus-32, a radioactive isotope of phosphorus into the abdominal cavity replaced the external radiation to the whole abdomen. Nowadays even that has been mostly replaced by injection of chemotherapy agents into the abdominal cavity.
Currently surgery and chemotherapy are the mainstays of treatment of ovarian cancer and as opposed to many other cancers, repeating surgery either in the form of debulking the disease or for second look, takes place before considering radiation therapy. That has limited the role of radiation therapy in treatment of ovarian cancer to treating the metastatic areas. That is if the cancer spreads to the bone, brain or other organs, radiation may be used to address those areas in a palliative manner. Also if disease becomes resistant to second and third line chemotherapy agents, and surgery is not an option either, radiation can be used to locally treat the residual or progressive disease at the primary site.
Side effect of radiation therapy entirely depends on the area we are irradiating. For example the side effects of radiation the the brain because of a brain metastasis are entirely different from the side effects due to the radiation of a bone metastasis in a bone. Generally speaking though some fatigue and minor skin reaction would be involved with radiation no matter where it is given. Due to significant improvements in the radiation technology in the past couple of decades, we are increasingly capable of sparing most of normal tissue and critical organs from unnecessary radiation and focus radiation on the area we intend to irradiate. That is even in radiation therapy field we are moving into the direction of targeted therapy and are able to deliver higher doses of radiation to the cancer only without causing major side effects which is usually as a result of unnecessary radiation to the normal tissues.
I often tell my patients that there is no good time for developing cancer but if there is such a thing, this is the best time for treating it and it is only getting better!