Answer to Question #8592 Submitted to "Ask the Experts"

Category: Medical and Dental Patient Issues — Therapy - Radiation Oncology

The following question was answered by an expert in the appropriate field:

Q
If a person has to undergo extensive radiation therapy to fight a cancer, what are the odds that she will develop some other type of cancer later in life due the radiation therapy? What area of the body would be most susceptible to having a cancer develop later in life if radiation therapy was needed?
A
There are many variables that will influence the answer to your question. First, there is the genetics of the individual. If someone has already developed a cancer, the probability that he/she will develop a second cancer is higher than that of a "normal" person. There are also cancers which are known to be markers for genetic susceptibility to other cancers. Retinoblastoma is such an example. The following paper details some of these considerations:
Kleinerman RA, Tucker MA, Tarone RE, Abramson DH, Seddon JM, Stovall M, Li FP, Fraumeni JF Jr. Risk of new cancers after radiotherapy in long-term survivors of retinoblastoma: An extended follow-up. Journal of Clinical Oncology 23(10):2272-2279; 2005.

Overall, the risk of developing a second cancer among long-term survivors of a first malignancy is 14 percent, only a fraction of which is possibly attributable to radiation therapy, from New Malignancies among Cancer Survivors: SEER Cancer Registries, 1973-2000. Thus, while this risk is not negligible, it is certainly low enough that a patient should not forego potentially lifesaving therapy of an existing cancer because of it.

In general, treating a person at a younger age will increase the probability of developing a second cancer. The following articles detail some concerns in the development of breast cancer after treatment of Hodgkin's disease:
Bhatia S, Robison LL, Oberlin O, Greenberg M, Bunin G, Fossati-Bellani F, Meadows AT. Breast cancer and other second neoplasms after childhood Hodgkin's disease. The New England Journal of Medicine 334(12):745-751; 21 March 1996.
Crump M, Hodgson D. Secondary breast cancer in Hodgkin's lymphoma survivors. Journal of Clinical Oncology 27(26):4229-4231; 2009.
The following websites have a discussion of secondary cancers:

University of Florida Shands Cancer Center
American Cancer Society

This question is further complicated by the fact that many chemotherapy agents are also carcinogens. The combination of radiation and chemotherapy can also enhance the development of secondary cancers. The positive side of this discussion is that most secondary cancers demonstrate a latent period, i.e., a period of time before the secondary cancer presents itself. This period can be of the order of years and within that latency period, medical research may develop better techniques to cure the secondary cancer. For any one person, this discussion needs to take place with a medical oncologist and a radiation oncologist familiar with the history of the individual.

Jean St. Germain, CHP, and Pat Zanzonico, PhD


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