Striving to excel – effects from vacation periods on cancer incidence and outcome

Sweden has a strong tradition for long summer vacations, which typically last 4–5weeks between late June and midAugust. In the healthcare system, planning for the summer period starts early in the year to adjust services and secure sufficient staffing. During holidays and vacation periods diagnostic capacities are reduced with temporary halts in cancer screening programs and reduced access to primary care. In specialized care, surgical capacities are reduced and chemotherapy holidays are recommended for patients where this is deemed safe. At the same time, there is increasing evidence to suggest that patients with cancer may be especially vulnerable to the effects of altered care patterns during holidays and vacation periods based on studies that suggest negative effects on cancer diagnosis and outcome of treatment during vacation periods. In this issue of Acta Oncologica, Wik en et al. report on decreased incidences of several cancer types during vacation periods and excess mortality for individuals diagnosed during these periods based on data from Swedish cancer care [1]. In a population-based study of 882,980 patients diagnosed between 1990 and 2019 cancer incidence and excess mortality for nine cancer types were assessed based on data from the National Cancer Registry. The diagnoses included prostate cancer, breast cancer, lung cancer, urothelial cancer, colorectal cancer, pancreatic cancer, melanoma of the skin, non-Hodgkin lymphoma, and acute leukemia. Seasonal variation in cancer incidence was most pronounced for prostate cancer, breast cancer, and colorectal cancer with similar but less pronounced patterns in lung cancer, urothelial cancer, and non-Hodgkin lymphoma. The agestandardized incidence rate (IRR) indeed decreased to 0.58 for breast cancer and 0.60 for prostate cancer during vacation periods. A significant, but less pronounced effect, was observed also for pancreatic cancer with an IRR of 0.92 during the vacation periods. In melanoma of the skin, an increased incidence during the late spring and early summer was observed followed by a decrease in incidence during the summer months. Similar seasonal variations in melanoma incidence have been reported in several countries with a peak in the spring and early summer, which has been linked to summer clothing and more visible skin, though a potential effect on melanoma prognosis is uncertain [2,3]. Seasonal trends in cancer diagnoses linked to hospital delays during vacation periods have indeed been observed in Sweden already in data from 1980’s [4]. Wilk en et al. further demonstrate excess cancer mortality for patients diagnosed within the vacation season with significant differences at two years for patients with colorectal cancer, urothelial cancer, pancreatic cancer, breast cancer, prostate cancer, and malignant melanoma [1]. Adverse effects remained also at five years after diagnosis for some of these diagnoses. The study does, however, not provide information related to drivers of excess mortality such as tumor stage, treatment, and lead times, which are needed to unravel key determinants of adverse effects from vacationperiod diagnostics. In 2009, a Swedish study based on Cancer Registry data from 1964–2004 suggested a higher risk (HR 1.14–1.20) for death in men and women diagnosed with prostate cancer and breast cancer, respectively, during the summer months [5]. The authors also demonstrated a higher proportion of advanced-stage disease during the summer months and noted that the trend was stronger in the later years of the study period. In 2017, a study based on more than 228,000 patients with 16 types of cancer in Swedish cancer care confirmed adverse effects on disease-specific mortality for breast cancer and for subgroups of cancers of, e.g., the colon, the rectum, head and neck, thyroid, and urological cancers, in patients that had undergone surgery during vacation periods [6]. This observation sparked more detailed analyses on the potential effects of diagnosis and treatment during vacation periods for various cancer diagnoses and treatment types. A Swedish study on patients undergoing oesophagectomy during vacation periods did not demonstrate any increased short-term or long-term mortality, suggesting that adequate surgical experience is maintained during the holiday periods [7]. In urinary bladder cancer, a study on Swedish registry-based data did not suggest differences in outcome and survival for patients who underwent radical cystectomies during holiday