Therapeutic radiation and the potential risk of second malignancies

Abstract

Radiation has long been associated with carcinogenesis. Nevertheless, it is an important part of multimodality therapy for many malignancies. It is critical to assess the risk of secondary malignant neoplasms (SMNs) after radiation treatment. The authors reviewed the literature with a focus on radiation and associated SMNs for primary hematologic, breast, gynecologic, and pediatric tumors. Radiation appeared to increase the risk of SMN in all of these; however, this risk was found to be associated with age, hormonal influences, chemotherapy use, environmental influences, genetic predisposition, infection, and immunosuppression. The risk also appears to be altered with modern radiotherapy techniques. Practitioners of all specialties who treat cancer survivors in follow‐up should be aware of this potential risk. Cancer 2016;122:1809–21. © 2016 American Cancer Society.

Radiation risk of incident colorectal cancer by anatomical site among atomic bomb survivors: 1958–2009

“…Sex‐averaged ERRs/Gy for colon cancer in our study and in the latest study were 0.54 (95% CI: 0.30; 0.81) and 0.63 (90% CI: 0.34; 0.98), respectively, while ERR/Gy for rectum cancer were 0.22 (95% CI: −0.081; 0.13) and 0.19 (90% CI: −0.04; 0.47), respectively . Our findings of significant radiation risk of colon cancer are also consistent with the radiation risk reported in studies of medically irradiated populations . The positive association between BMI and overall colon cancer risk observed in our study is compatible with the results of a systematic review and meta‐analysis of prospective studies .…”

“…Strong evidence has been found for a relationship between ionizing radiation exposure and colon cancer risk, although evidence for rectal cancer has been inconsistent . Among atomic bomb survivors, the colon cancer rates increased with radiation dose in studies of incidence and mortality, while there was no evidence of radiation effects on rectal cancer rates .…”

Impact of latency time on survival for adolescents and young adults with a second primary malignancy

“…Moreover, younger populations, particularly AYAs, tend to be more mobile, and this may lower the number of SPMs identified because subsequent cancers are not recorded for patients who migrate from their original geographic areas. Also, many SPMs, especially radiation‐induced solid tumors, are not diagnosed until more than 15 to 20 years after the PM and, therefore, would not be captured in our analyses . This leads to under‐ascertainment of SPMs because during longer follow‐up many more survivors would develop an SPM and, therefore, conservative overestimates of cancer survival.…”

Radiation and Second Primary Thyroid Cancer Following Index Head and Neck Cancer

“…About one‐third of all head and neck cancer (HNC) survivors in the United States die from competing causes of mortality, and 12% of these deaths from competing mortality are due to SPMs . Of all cancer sites, no other cancer site is known to develop SPMs more frequently than HNC, which is a late effect of cancer treatment and associated with lower survival rates among patients . Although most of the SPMs developed by HNC survivors are tobacco‐associated, such as lung and esophageal second primaries, about 7% are second primary thyroid cancers (SPTCs) …”