DaPeCa5 - obesity at the time of diagnosis does not predict poor cancer-specific survival in patients with penile squamous cell carcinoma - a Danish National study

Background: Conflicting data on the prognostic significance of obesity in penile cancer have been presented in recent years.

Objective: The objective of this study was to investigate obesity as a prognostic factor in patients with penile squamous cell carcinoma (pSCC) in a large national Danish cohort. Furthermore we aimed to compare the BMI of pSCC patients to a large age-matched cohort of healthy men.

Methods: We evaluated 429 patients with invasive pSCC from a national retrospective penile cancer cohort and defined a body mass index (BMI) at 30 kg/m² as obese. Furthermore, we considered if a fitted model for BMI and mortality could define a critical BMI tipping point for increasing mortality by the means of BMI categories of 1 kg/m² width. We compared 29 pSCC patients with reported unintended weight loss at diagnosis to 400 with no reported weight loss. Cox regression with 95% confidence intervals was used for penile cancer-specific survival analysis. The comparison between 325 age-matched pSCC patients and 11,238 healthy men from an existing contemporary health database was done by nonparametric tests.

Results: There was no difference in cancer specific survival between patients with a BMI below and above 30 kg/m², cox hazard ratio (HR) 0.74 (0.47-1.18), p = .20, but 37 kg/m² was a tipping point for increasing mortality, HR = 2.10 (1.06-4.18), p = .035. Unintentional weight loss prior to diagnosis significantly predicted worse cancer specific outcome, cox hazard ratio 6.0 (3.5-10.0), p < 001 and cox hazard ratio adjusted for American Joint Committee of Cancer (AJCC)-stage at 1.8 (1.1-3.1), p = .03. Age-matched pSCC patients had a significantly higher BMI than healthy males, 28.4 ± 5.5 kg/m² vs. 26.2 ± 3.6 kg/m², p < .0001 and were more likely to smoke, p < .0001, and report alcohol intakes over 14 units/week, p < .0001.

Conclusion: In this Danish cohort, BMI above 30 kg/m² at diagnosis does not affect prognosis, but BMI at and above 37 kg/m² at diagnosis predicts poor prognosis. Unintentional weight loss is a predictor of high stage and poor prognosis. PSCC patients have a significantly higher BMI than age-matched healthy males.

Keywords: Penile cancer; cause specific survival; mortality; obesity; prognosis; squamous cell carcinoma; weight loss.