Figure provided by Dr. Eric Chow.
Early detection, improved cancer treatment and the combined efforts of patients, philanthropists, physicians and researchers have been critical in increasing cancer survivor numbers. People are also living longer after cancer remission. However, cancer survivors are at risk and closely monitored not only for cancer recurrence but also other health complications whose occurrences are not well studied. For instance, the different treatment options’ influence on health outcomes following cancer remission is not known.
Among cancer survivors, some patients underwent hematopoietic cells transplantation (HCT) but few data are available on the health complications affecting transplanted individuals relative to the non-transplanted (non-HCT) patients. This is especially relevant knowing that the number of HCT-receiving cancer patients has increased, and that more than 70% of two-year survivors will become long-term survivors. What serious health events occur in HCT versus non-HCT cancer survivors relative to the general population? Where should the medical attention focus in this population? These are questions that Drs. Eric Chow and Scott Baker, both member of the Clinical Research Division and Cancer Survivorship program at the Fred Hutch, along with other colleagues from University of Washington and Mayo Clinic, asked when they initiated a study among two-year cancer survivor patients just published in Journal of Clinical Oncology.
For this purpose, a cohort of 1,792 two-year cancer survivors who underwent HCT were analyzed. In parallel, 5,455 non-HCT two-year cancer survivors were identified from the Washington State Cancer Registry. These two cohorts were matched based on sex ratio, age at diagnosis or HCT, year of diagnosis or HCT, and type of cancers (hematologic malignancy or nonhematologic solid tumor). Finally, as a reference for healthy population, 16,430 individuals were pulled from the Washington State Department of Licensing (DOL) files. This cohort also matched the other two based on age and gender distribution. In these three cohorts, morbidities and mortalities were studied based on the rate and causes of hospitalizations, as well as deaths. These data were accessible thanks to the Washington State Comprehensive Hospital Abstract Reporting System and the State Death Registry.
Morbidities and mortalities were significantly higher in the HCT cohort, relative to the non-HCT group and general population. According to Dr. Chow, “among 2+ year survivors, HCT patients had about a 10% increased risk (hazard) of late deaths versus non-HCT patients. Among 5+ year survivors, HCT patients had about a 20% increased risk (hazard) of late deaths versus non-HCT patients.” The rate of hospitalizations was significantly higher in the HCT population: 28% versus 17.3% for the HCT and non-HCT individuals respectively (p<0.001). Hospitalizations following infections and respiratory complications were higher in the HCT individuals. Cancer recurrences were not different, however more HCT individuals developed cancer within one year, and were more prone to oral and skin cancers than the non-HCT group. The intensity of total body irradiation prior to transplantation also influenced the outcomes. Psychological complications were not different between HCT and non-HCT patients, but occurred more frequently than in the general population. Finally, pregnancies-related hospitalizations were lower in the HCT group.
These results show that there is not one but many risks for HCT cancer survivors. “It’s hard to pin it down on any single factor,” explained Dr. Chow, “since we didn’t have information on how non-HCT patients were treated, or for HCT patients, what treatments they received prior to their HCT. But among HCT survivors, not surprisingly, those who had chronic GVHD (graft-versus-host-disease) that required systemic immunosuppression had a greater burden of hospitalizations and deaths”.
It is recommended that cancer survivors be monitored several times a year. Guidelines have been established for clinicians to focus on the risks associated with their patient history and based on physical examination. Such studies are critical to better understand the risks and to help improving these guidelines. Dr. Chow wrote “I think these results just show the importance of long-term HCT survivors being engaged in close follow-up, not just for recurrence of their original disease, but also to monitor them for other organ toxicity, especially lung issues. We also probably need to better determine immune function in long-term survivors, as our results would suggest that serious late infections, even years after HCT, are not uncommon. We hope to take a closer look at the specific lung and infectious complications we found, and see if we can better identify clinical and patient characteristics that may predict those who will be at greater risk in the future.”
Funding for this study was provided by the National Institutes of Health.
Chow EJ,Cushing-Haugen KL,Cheng GS,Boeckh M,Khera N,Lee SJ,Leisenring WM,Martin PJ,Mueller BA,Schwartz SM,Baker KS. 2016. Morbidity and Mortality Differences Between Hematopoietic Cell Transplantation Survivors and Other Cancer Survivors. Journal of Clinical Oncology.