Effect of radiotherapy on long-term quality of life in recurrence-free rectal cancer survivors (LaTE study): nationwide inverse probability of treatment-weighted registry-based cohort study and survey.

Background: Radiotherapy reduces local recurrence in locally advanced rectal cancer, but may cause harm in patients who do not experience recurrence. The aim was to investigate the impact of radiotherapy on long-term quality of life after curative treatment for rectal cancer, i.e. in patients without a recurrence during the follow-up.

Methods: All patients operated on for rectal cancer in Norway under 75 years of age between 30 September 2007 and 1 October 2020 were identified using the Cancer Registry of Norway. Exclusion criteria were distant metastasis, recurrence and dementia. The primary outcome measure was the Gastrointestinal Quality of Life Index. Secondary outcome measures included the 36-item Short Form Survey. Inverse probability weights based on a multiple logistic regression model were used to balance prechosen covariates between the radiotherapy and no radiotherapy groups when assessing differences in outcomes.

Results: Of 5014 invited patients, 2142 (43%) eligible patients answered the questionnaires. Of these 762 (36%) were treated with neoadjuvant radiotherapy plus surgery and 1380 (64%) with surgery alone. The mean follow-up time was 6.4 and 7.4 years respectively. After propensity score matching, the Gastrointestinal Quality of Life Index differed significantly between irradiated and non-irradiated patients ((mean(s.d.), mean score 103.8(19.4) versus 110.8(19.6) respectively, mean difference: -6.96 (95% c.i. -8.72 to -5.19); P < 0.001). Among patients without a stoma the mean difference was -8.1 points, whereas it was -5.7 for patients with a stoma. The radiotherapy group also scored significantly lower in 7 of 8 36-item Short Form Survey domains compared with the surgery alone group.

Conclusion: Long-term quality of life was significantly lower in patients without a recurrence during the follow-up who received radiotherapy compared with patients who did not. These findings warrant a critical re-evaluation of the use of radiotherapy both in traditional neoadjuvant treatment and in modern organ-preserving treatment regimens.