Does Time of Daily Treatment Matter in Radiation Therapy for Head and Neck Cancer?

Clock in radiation oncology clinics: cost-free modality to alleviate treatment-related toxicity

A large number of studies have reported that tumor cells are often out of sync with the surrounding healthy tissue. Exploiting this misalignment may be a way to obtain a substantial gain in the therapeutic window. Specifically, based on reports to date, we will assess whether radiotherapy outcomes differ depending on the administration time. Collectively, 24 studies met the inclusion criteria, out of which 12 at least reported that radiation therapy is less toxic when administered at a particular time, probably because there is less collateral damage to healthy cells. However, discrepancies exist across studies and urge further investigation. Mechanistic studies elucidating the relationship between radiotherapy, circadian rhythms, and cell cycle, combined with either our “digital” or “biological” chronodata, would help oncologists successfully chronotype individual patients and strategize treatment plans accordingly.

The prognostic impact of daytime and seasonality of radiotherapy on head and neck cancer

BACKGROUND

The potential impact of daytime and season of radiotherapy application on prognosis is unclear. This was analyzed in a retrospective cohort of patients who were diagnosed with non-metastatic head and neck squamous cell carcinoma (HNSCC) and treated with definitive radiotherapy with or without chemotherapy.

MATERIALS AND METHODS

Patient and tumor characteristics, treatment parameters and outcome until last follow-up or death were obtained. Median radiotherapy delivery daytime of each patient was categorized as morning (AM) and afternoon (PM). Treatment season was defined by median date of treatment course. Each year was divided into DARK and LIGHT according to equinoxes. Time-to-event endpoints were defined by first biopsy confirming the HNSCC.

RESULTS

Six hundred fifty-five cases were identified who were treated with (chemo)radiotherapy between 2002 and 2015. Median follow-up was 47 months. No significant heterogeneity in patient, tumor and treatment characteristics were observed between DARK and LIGHT or regarding median daily fraction time (X2 p > 0.05). Five-year loco-regional control (73% vs. 61%; p = 0.0108) and progression-free survival (51% vs. 43%; p = 0.0374) were superior when radiotherapy was administered in DARK. Neither the daytime nor any other treatment time-related parameter affected prognosis.

CONCLUSION

This is the first study investigating and presenting the prognostic impact of seasonality regarding the treatment course on loco-regional control and progression-free survival (DARK > LIGHT). The biological mechanism of action is unclear. These results should be interpreted with caution and our findings have to be validated externally.

The impact of delivery daytime and seasonality of radiotherapy for head and neck cancer on toxicity burden

AIM

The potential impact of the daytime and season of radiotherapy application on acute and late toxicity burden was analyzed on a cohort of curatively treated head and neck squamous cell carcinoma patients.

METHODS

Through a retrospective chart review, patient and tumor characteristics, treatment parameters and outcome were obtained. Patients treated with definitive or adjuvant radiotherapy with and without chemotherapy receiving ≥60 Gy between 2002 and 2015 were included (n = 617). Daily fraction times and dates were extracted. Median radiotherapy delivery time of each patient was categorized as morning (AM) and afternoon (PM). Treatment season was defined by the median day of the treatment course. Each year was divided into DARK and LIGHT by the March and September equinoxes. Acute (T) and late (A) toxicity were defined by TAME methodology.

RESULTS

Median follow-up was 51 months. Mean T and A scores during and after radiotherapy in DARK vs. LIGHT were 1.98 vs. 1.61 (p = 0.0127) and 0.41 vs. 0.30 (p = 0.1699), respectively. Mean T and A scores during and after AM vs. PM radiotherapy were 1.71 vs. 1.88 (p = 0.0387) and 0.31 vs. 0.41 (p = 0.2638), respectively. Multivariate analyses indicated DARK vs. LIGHT as the only independent treatment time-related factor among other factors such as tumor subsite, UICC stage, radiotherapy technique, and chemotherapy for T.

CONCLUSION

This is the first study investigating the impact of seasonality on toxicity burden, showing higher acute toxicity with radiotherapy in DARK. The daytime did not predict the toxicity. The hypothesis-generating findings of this retrospective study should be further investigated.