Second primary cancers: Incidence and outcomes from a population of patients accrued in six prospective controlled trials at a tertiary cancer institute.

Background: The aim of this study was to document the incidence, spectrum and outcomes of Second Primary Malignancy (SPM) in a prospectively followed-up population of Head and Neck Squamous carcinoma (HNSCC) patients accrued in six prospective trials and treated with definitive radiotherapy.

Materials and methods: Patients were prospectively followed up over time and data on SPM collected after IRB approval after establishing the diagnosis of SPM based on clinical criteria. Descriptive statistics to determine clinic demographic characteristics and spectrum of SPM encountered, time to event outcomes (SPM-DFS - Disease-free survival after diagnosis of second primary, SPM-OS - Overall survival after diagnosis of second primary) and univariate analysis of factors of likely prognostic significance were performed.

Results: A total of 656 individual patient records were examined. A total of 43 SPM s were detected at a median follow-up of 62 months (IQR -39-97 months), accounting for a cumulative incidence of 6.5%. The median time to development of an SPM was 48 months. The head and neck (41.84%) and the esophagus (34.8)% were the most common sites of SPM. At a median follow-up of 7 months post-diagnosis of SPM, the 1 year estimates of SPM-DFS and SPM-OS were 37.6% and 40% respectively. Radical intent treatment emerged as a significant predictor of improved SPM-OS and SPM-DFS.

Conclusion: SPMs are a major cause of morbidity and mortality in HNSCC survivors. Timely detection allows for more cases to be treated with radical intent to offer chances for long term control and survival.