Cancer in 15- to 29-year-olds by primary site.

INCIDENCE: Cancer occurring between the ages of 15 and 30 years is 2.7 times more common than cancer occurring during the first 15 years of life, yet is much less common than cancer in older age groups, and accounts for just 2% of all invasive cancer. Cancer in adolescents and young adults is unique in the distribution of the types that occur. Hodgkin lymphoma, melanoma, testis cancer, female genital tract malignancies, thyroid cancer, soft-tissue sarcomas, non-Hodgkin lymphoma, leukemia, brain and spinal cord tumors, breast cancer, bone sarcomas, and nongonadal germ cell tumors account for 95% of the cancers in this age group. The frequency distribution of cancer types changes dramatically from age 15-30, such that the pattern at the youngest age does not resemble the one at the oldest. The incidence of cancer in this age group increased steadily during the past quarter century. This increase is declining and at the older end of the age range appears to be returning to the incidence of the 1970s. Males in the 15- to 29-year age group have been at higher risk of developing cancer, with the risk directly proportional to age. Non-Hispanic whites have had the highest risk of developing cancer during this phase of life, and Asians, American Indians and Native Alaskans the lowest. Males had a worse prognosis than females. African-Americans, American Indian/Alaska Natives had a worse prognosis than white non-Hispanics and Asians. MORTALITY & SURVIVAL: At the beginning of the last quarter century, the diagnosis of cancer in 15- to 29-year-olds carried a more favorable prognosis, on the average, relative to cancer at other ages. Since then, there has been a lack of progress in survival improvement among older adolescents and young adults relative to all other ages. Survival improvement trends portend a worse prognosis for young adults diagnosed with cancer today than 25 years ago. The survival deficit is increasing with longer follow-up of the survivors, and is worse in males. Among 15- to 29-year-olds, non-Hispanic whites had the best survival and African Americans/blacks had the worst survival, with a 20% difference apparent by 5 years. Asians/Pacific Islanders had the second best survival, with Hispanics and American Indians/Alaska Natives next in sequence. RISK FACTORS: In general, there are relatively scant data to support either an environmental causation or an inherited predisposition to cancer in this age group. The majority of cases of cancer occurring before age 30 appear to be spontaneous and unrelated to either carcinogens in the environment or family cancer syndromes. Overall, family cancer syndromes appear to account for less than 5% of the cases of cancer in the age group. Melanoma, cervical carcinoma and Kaposi sarcoma, non-Hodgkin lymphoma, Hodgkin and Burkitt lymphomas accounting for the majority of environmentally induced malignancies (ultraviolet light, human papillomavirus, human immunodeficiency virus, and Epstein-Barr virus, respectively). Ultimately, a larger proportion of cases may be attributable to specific factors or genetic predisposition, but at present, most cancer in this age group appears to be sporadic and random.