Many of the cancers that occur in children are not seen in adults. For example, Wilms tumor, neuroblastoma, retinoblastoma, hepatoblastoma, and atypical teratoid rhabdoid tumor are almost entirely restricted to the very young, generally less than 5 years old. Rhabdomyosarcoma and medulloblastoma are also diseases of childhood.
On the other hand, carcinomas of breast, gastrointestinal tract, head and neck, lung, pancreas and prostate are diseases of older adults, with 0.1% or less diagnosed among those 0-20 years of age.
In addition, the vast majority of patients with malignant melanoma are adults, with only 0.6% diagnosed in individuals under age 21 years.
Why are some cancers restricted to the pediatric age and others to adults? For cancers of the young, one reason could be that the cells undergoing malignant transformation are embryonic in origin, meaning they play a role in normal development, and then disappear early in life.
Also, certain genetic predispositions may play a role. In contrast, cancers typically found in adults may be related to long-term low-level exposure to toxins, taking many years to develop.
Inherent genetic factors also can be identified in some adult patients. Regardless, whenever a cancer occurs in an uncharacteristic age group, genetic factors and carcinogenic exposure should be considered.
Recently, our pediatric oncology group has been caring for two teenagers with non-small cell lung cancer – this is virtually unheard of in pediatrics.
We are also seeing two teens with gastric adenocarcinoma, another with squamous cell carcinoma of the tongue, and two younger children with malignant melanoma.
These children and their families present important challenges that demand unique solutions. Unraveling the mystery of why they developed these cancers may help us to help them, and may also teach us important lessons about the biology of these cancers.
How can a pediatric oncologist create a state-of-the-art treatment plan for a disease he or she may have never treated?
It takes a great deal of effort and collaboration to do it well.
First of all, at University of Chicago Medicine, we have access to a wealth of experience in treating adult malignancies, and so we turn to our colleagues — many of whom are international experts on specific diseases.
A mainstay of diagnosis and treatment at most academic medical centers is a series of regularly held multidisciplinary patient-centered conferences, or tumor boards, usually organized around disease types.
I normally do not participate in tumor boards for adults since I am a pediatric oncologist, but for cases like these, I do.
I share with my adult counterparts the story of my patients and I have the opportunity to obtain expert feedback from a multidisciplinary team that regularly diagnoses and treats these cancers.
In addition to the recommendations of the adult tumor board, some considerations when assessing treatment options for adult cancers in children include:
1) Any potential special problems with the use of the adult treatment plan on a growing and developing child.
2) Availability of specific drug therapies in forms that can be given to children, e.g., appropriate pill sizes and strengths that children are able to swallow, and compounding techniques to convert a capsule or tablet into a liquid form, when necessary.
3) Availability of information about drug metabolism and dosing in children, FDA approval status for use of the drug in children, and insurance approval for use of the drug for the indication in children.
4) Modification of dosing according to age, weight or body surface area, rather than using a general adult dose.
5) Review of the pediatric literature for similar cases.
Because the occurence of these cancers outside of the usual age range may suggest a genetic predisposition, I also refer all of these patients to our Pediatric Familial Cancer Clinic.
For the pediatric oncologist, treating these types of cancers is an enlightening experience. We are often employing drug regimens, and sometimes surgery and radiation techniques, that are rarely used in children.
Although extra time is taken to develop and apply this truly collaborative approach between adult and pediatric practitioners, my experience is that such time is well spent and gives the patient the best chance of success.