Types of cancer in adolescents and young adults
Nine major cancer groups are found in AYA patients with cancer: leukaemia, lymphomas, tumours of the central nervous system, bone cancers, soft tissue sarcomas, germ cell cancers, melanomas, carcinomas and other unspecified cancers.
The four most commonly diagnosed cancers among AYA patients in Australia are melanoma (accounting for one-quarter of all cancers in this age group), followed by gonadal germ cell cancers, Hodgkin lymphoma and thyroid carcinoma.6 Together, these four cancers represent just over half of all cancers in AYAs. In addition to these more common tumours in the AYA population, AYAs of any age can also have the epithelial malignancies commonly seen in adults (breast, colorectal and lung cancers) and embryonal cancers (neuroblastoma, Wilms tumours and teratomas). They can also have the leukaemias and brain tumours that are more commonly seen in paediatric patients. The variety in tumour types occurring in this age range requires specialist clinicians to have both paediatric and adult expertise to be able to provide age-appropriate and tumour-specific management.
The frequency of different tumours changes as patients get older (Figure 1). Among AYAs, lymphomas, leukaemias, sarcomas and brain tumours have the highest incidence in the 15- to 19-year age group. Melanomas, testicular cancer and carcinomas have the highest incidence in the 20- to 24-year age group (Figure 2).
Differences in the incidence of tumours between males and females are also seen in AYA patients. Gonadal tumours, osteosarcoma and rhabdomyosarcoma are more commonly diagnosed in males, and thyroid cancer is more common in females.6
What are the causes of the differences in cancer survival for adolescents and young adults?
The reasons for differences in survival in AYAs are likely to be multifactorial, with variations in tumour biology, response to treatment and treatment protocols all having an impact. Some of these factors are discussed below.
Reduced awareness and delays in diagnosis and treatment
Cancers in the AYA age group are very rare and can be difficult to diagnose.9 Cancer- related symptoms account for a very low percentage of GP consultations with AYAs. In one review of AYA patients, only 4% of consultations were related to cancer symptoms. Despite the low incidence of cancer- related symptoms in AYAs, symptoms such as a lump, mass or swelling have been associated with a higher absolute risk of cancer.10
AYAs with cancer have longer symptom intervals,11-13 and it has been hypothesised that the longer delays in cancer diagnosis for this age group contribute to a decrease in survival, because AYAs tend to be at later cancer stages and have fewer treatment options available at presentation. However, this link has not been clearly shown, as the symptom interval changes between cancer types and the reasons for longer symptom intervals are multifactorial. In a review of AYA consultations with GPs, 86% of AYAs had visited their GP in the three months before a diagnosis, and 42% had visited their GP four times or more before being referred to a cancer centre.10
It has been shown that a delay in cancer diagnosis has an impact on the relationship between AYA patients and clinicians.14 This impact may continue into treatment and have an effect on trust, adherence to treatment and survival. Delays often also occur because AYAs diagnosed with cancer are often seen by several specialists, including emergency, surgical, general, paediatric and adult specialists, when they are referred to hospital before they start treatment. AYAs may delay seeking medical advice due to the lack of importance these symptoms present for them, the need to plan a review at a time when parent can go with them, or the conflict of AYA life events and school taking a greater importance in their lives.
The Early Detection of Cancer in AYAs Cancer Guideline has been developed by the Clinical Oncological Society of Australia (COSA) for GPs and other primary health professionals involved in the management of AYAs with cancer.15 It provides evidence- based recommendations and practice points to assist GPs to recognise signs and symptoms that could be caused by cancer in AYA patients, make decisions about appropriate investigations and make timely and appropriate referrals for AYAs with suspected cancer.