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Do patients enrolled in observational studies have better outcomes than non-participants? A retrospective analysis

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Abstract

Purpose

Patients are commonly enrolled into clinical trials. It has been reported that these patients may have better outcomes than those not enrolled into the study. The reasoning from these improvements could be attributable to closer follow-up, better patient adherence, more health aware patients have, or reaction to observation such as the Hawthorne effect.

Methods

Three hundred forty-six patients were approached for a prospective skin toxicity study in adjuvant breast cancer radiotherapy (RT) but declined participation between January 2018 and July 2019 (non-trial group). They were retrospectively reviewed and patient, treatment and RT-related characteristics, as well as the occurrence of skin reactions, and the usage of topical treatments were collected. This was compared with a comparison cohort of 349 patients who were enrolled into a previously conducted prospective study (trial group).

Results

More patients in the trial group had conventional RT (CFRT) versus hypofractionated RT (HFRT). Data was further stratified and there was no significant difference in moist desquamation, topical antibiotic usage, dressing application, home care use, topical corticoid steroid use, and oral analgesic use. There was a significantly lower pain score in the group compared with the non-trial group in both HFRT and CFRT (OR = 0.091 and OR = 0.348, p < 0.0001).

Conclusion

Our results demonstrated no differences other than pain between the trial group and non-trial group. Therefore, in this cohort, patients enrolled into an observational trial while undergoing adjuvant breast RT demonstrated similar experiences of skin reactions. There are challenges to assessing differences between these groups, as confounding is likely. Therefore, it is recommended for future studies to additionally assess the impact of study participation on outcomes such as quality of life, quality of care received, and/or anxiety levels.

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Funding

We thank the generous support of Bratty Family Fund, Michael and Karyn Goldstein Cancer Research Fund, Joey and Mary Furfari Cancer Research Fund, Pulenzas Cancer Research Fund, Joseph and Silvana Melara Cancer Research Fund, and Ofelia Cancer Research Fund.

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Authors and Affiliations

  1. Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada

    Gina Wong, Emily Lam, Edward Chow, Liying Zhang, Chun Nim Li, Gord Mawdsley, Irene Karam, Krista Ariello, Victoria McCarvell, Yasmeen Razvi & Mark Ruschin

Authors
  1. Gina Wong
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  2. Emily Lam
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  3. Edward Chow
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  4. Liying Zhang
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Corresponding author

Correspondence to Edward Chow.

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Our institution’s research ethic’s board approval was obtained for the review and collection of patient demographics from patients’ electronic health records.

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The authors declare that they have no conflict of interest.

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Wong, G., Lam, E., Chow, E. et al. Do patients enrolled in observational studies have better outcomes than non-participants? A retrospective analysis. Support Care Cancer 28, 5751–5761 (2020). https://doi.org/10.1007/s00520-020-05417-w

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  • DOI: https://doi.org/10.1007/s00520-020-05417-w

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