Second Primary Malignancy among Cancer Survivors - Epidemiology, Prognosis and Clinical Relevance

Background: Rising population age and advances in treatment with improved survival from cancer have led to more frequent survivors of cancer treatment and subsequently to more patients with a second primary tumour. The consequences are presented in this overview. Method: For the literature review, the Medline database (PubMed) was searched under the key words "multiple primary malignant tumors" and "(Neoplasms, second primary) AND "Neoplasms, Second Primary"[Mesh]". Primarily, publications in the last 7 years (2005 - 2011) were sought. Results: The prevalence of patients with second primary cancer is reported in various cancer registries with 6.6% to 9%. Here, the risk of developing new primary cancer in cancer survivors, depending on age, compared to the general population is increased at least by 20%. Among childhood cancer survivors, the risk was even 3 - to 6-times higher than would have been expected in the general population. The incidence of second malignant neoplasms is crucially dependent on the prognosis of the first tumour. Fifteen years after initial diagnosis, in patients with prognostically unfavourable tumours such as pancreatic or gastric carcinoma, second primary malignancies are detected in less than 5%. However, the cumulative incidence of all second cancers combined is approximately 15% at 25 years in patients with colorectal or thyroid cancer. Conclusion: Implications from these data arise for primary diagnostics which must look at cancers with frequent synchronous second malignancies for respective tumours before treatment. Examples are synchronous colorectal lesions in patients with colorectal carcinoma or synchronous cancers of the oral cavity and pharynx in patients with oesophageal carcinoma. Another consequence is a targeted follow-up of corresponding risk populations. This includes the screening for metachronous colorectal cancer, the exclusion of gastrointestinal second malignancies in patients with GIST, or the breast cancer screening in young female thyroid cancer survivors. Since radiotherapy increases the rate of second primary neoplasms, adjuvant radiotherapy should be well justified. Nevertheless, this is true only for young patients, mainly in childhood. The risk of a second cancer after irradiation in adults is small.