More than 1.5 million cancer survivors in the United States are parents living with children younger than age 18, according to a study published online today in the journal Cancer.

The researchers hope this figure — calculated for the first time — will help make health care providers more aware of these families and provide them with additional support.

"I think people have vastly underestimated the number of children who are affected by a parent's cancer," Dr. Paula Rauch, who was not involved in the study, told Reuters Health.

"It has been easier to measure the number of people who die from cancer, and often people still imagine that most cancer deaths and cancer survivors are elderly and don't have dependent children," added Rauch, who is founder and director of the Parenting At a Challenging Time, or PACT, program at Massachusetts General Hospital, Boston.

Dr. Kathryn Weaver of Wake Forest University Baptist Medical Center in Winston-Salem, North Carolina and colleagues analyzed data from 13,385 cancer survivors who participated in U.S. national health surveys conducted between 2000 and 2007.

The analysis revealed that an estimated 18 percent of newly diagnosed cancer survivors and 14 percent of all U.S. cancer survivors live with one or more of their minor children.

Scaling these numbers up to reflect the entire U.S. population, the authors calculated that about 1.58 million cancer survivors in the U.S. are living with about 2.85 million children. An estimated 562,000 kids are living with a parent in the early phases of cancer treatment and recovery.

The figures are likely an underestimate of the true number of cancer survivors living with minors, the researchers say, because the study did not include survivors who live with grandchildren, nieces and nephews, or other young family members.

Weaver and her colleagues say that parents who are cancer survivors and their families may need extra support, but that talking to patients about family and home life is often not part of the treatment process.

For example, parents with cancer might have extra stress from worrying about the possibility of not being able to see their children grow up. Spouses of survivors often have to take on the roles of both parents during treatment, and the cost of treatment can put strain on the family. In addition, the authors say, children of survivors might need counseling or extra attention at school.

For health care providers, "the most important thing is to screen all members of the family and find out — what are their issues?" Weaver said. "Some families certainly may be doing very well. Others may have multiple family members that are struggling."