Comparison of acute skin reaction following morning versus late afternoon radiotherapy in patients with breast cancer who have undergone curative surgical resection

Impact of chrono-radiotherapy on the prognosis and treatment-related toxicity in patients with locally advanced nasopharyngeal carcinoma: A multicenter propensity-matched study

The timing of radiotherapy (RT) delivery has been reported to affect both cancer survival and treatment toxicity. However, the association among the timing of RT delivery, survival, and toxicity in locally advanced nasopharyngeal carcinoma (LA-NPC) has not been investigated. We retrospectively reviewed patients diagnosed with LA-NPC who received definitive RT at multiple institutions. The median RT delivery daytime was categorized as morning (DAY) and night (NIGHT). Seasonal variations were classified into the darker half of the year (WINTER) and brighter half (SUMMER) according to the sunshine duration. Cohorts were balanced according to baseline characteristics using propensity score matching (PSM). Survival and toxicity outcomes were evaluated using Cox regression models. A total of 355 patients were included, with 194/161 in DAY/NIGHT and 187/168 in WINTER/SUMMER groups. RT delivered during the daytime prolonged the 5-year overall survival (OS) (90.6% vs. 80.0%, p = 0.009). However, the significance of the trend was lost after PSM (p = 0.068). After PSM analysis, the DAY cohort derived a greater benefit in 5-year progression-free survival (PFS) (85.6% vs. 73.4%, p = 0.021) and distant metastasis-free survival (DMFS) (89.2% vs. 80.8%, p = 0.051) in comparison with the NIGHT subgroup. Moreover, multivariate analysis showed that daytime RT was an independent prognostic factor for OS, PFS, and DMFS. Furthermore, daytime RT delivery was associated with an increase in the incidence of leukopenia and radiation dermatitis. RT delivery in SUMMER influenced only the OS significantly (before PSM: p = 0.051; after PSM: p = 0.034). There was no association between toxicity and the timing of RT delivery by season. In LA-NPC, the daytime of radical RT served as an independent prognostic factor. Furthermore, RT administered in the morning resulted in more severe toxic side effects than that at night, which needs to be confirmed in a future study.

Chronotherapy in Glioblastoma: state of the art and future perspectives

Circadian rhythms regulate various processes in the human body, including drug metabolism. Chronotherapy optimizes treatment timing based on the circadian rhythm of the individual patient, such that the treatment efficacy is maximized, and adverse effects are minimized. It has been explored in different cancers with varying conclusions. Glioblastoma multiforme (GBM) is the most aggressive type of brain tumour with a very dismal prognosis. In recent years, there has been very little success in designing successful therapies to fight this disease. Chronotherapy offers the opportunity to leverage existing treatments to extend patient survival and to increase their quality of life. Here, we discuss recent advances in using chronotherapy regimens in the treatment of GMB, such as radiotherapy, temozolomide (TMZ) and bortezomib, as well as discuss novel treatments with drugs of short half-life or circadian phase specific activity, and examine the therapeutic potential of new approaches that target elements of the core circadian clock.

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.

Treatment time and circadian genotype interact to influence radiotherapy side-effects. A prospective European validation study using the REQUITE cohort

BACKGROUND

Circadian rhythm impacts broad biological processes, including response to cancer treatment. Evidence conflicts on whether treatment time affects risk of radiotherapy side-effects, likely because of differing time analyses and target tissues. We previously showed interactive effects of time and genotypes of circadian genes on late toxicity after breast radiotherapy and aimed to validate those results in a multi-centre cohort.

METHODS

Clinical and genotype data from 1690 REQUITE breast cancer patients were used with erythema (acute; n=340) and breast atrophy (two years post-radiotherapy; n=514) as primary endpoints. Local datetimes per fraction were converted into solar times as predictors. Genetic chronotype markers were included in logistic regressions to identify primary endpoint predictors.

FINDINGS

Significant predictors for erythema included BMI, radiation dose and PER3 genotype (OR 1.27(95%CI 1.03-1.56); P < 0.03). Effect of treatment time effect on acute toxicity was inconclusive, with no interaction between time and genotype. For late toxicity (breast atrophy), predictors included BMI, radiation dose, surgery type, treatment time and SNPs in CLOCK (OR 0.62 (95%CI 0.4-0.9); P < 0.01), PER3 (OR 0.65 (95%CI 0.44-0.97); P < 0.04) and RASD1 (OR 0.56 (95%CI 0.35-0.89); P < 0.02). There was a statistically significant interaction between time and genotypes of circadian rhythm genes (CLOCK OR 1.13 (95%CI 1.03-1.23), P < 0.01; PER3 OR 1.1 (95%CI 1.01-1.2), P < 0.04; RASD1 OR 1.15 (95%CI 1.04-1.28), P < 0.008), with peak time for toxicity determined by genotype.

INTERPRETATION

Late atrophy can be mitigated by selecting optimal treatment time according to circadian genotypes (e.g. treat PER3 rs2087947C/C genotypes in mornings; T/T in afternoons). We predict triple-homozygous patients (14%) reduce chance of atrophy from 70% to 33% by treating in mornings as opposed to mid-afternoon. Future clinical trials could stratify patients treated at optimal times compared to those scheduled normally.

FUNDING

EU-FP7.

Developments on tumour site-specific chrono-oncology towards personalised treatment

Research into chronotherapy has seen notable developments over the past decades, with a clear focus on the identification of circadian clock genes as potential treatment targets. Moreover, new factors are investigated, such as gender and the role of cancer stem cells in influencing the outcome of chronomodulated treatments. These factors could add to the arsenal of parameters that assist with patient stratification and treatment personalisation. Literature analysis showed that certain anatomical sites received more attention and the associated studies reported clinically significant results, even though some findings are contradictory. The aim of this work was to review the existing studies on chrono-oncology using a tumour site-specific approach and to highlight the status of research in various cancers. Inconsistencies in data reporting, the nature of the studies and the highly heterogeneous patient characteristics, highlight the need for well-designed randomised controlled trials to elucidate the real potential of chronotherapy in oncology.

Chronoradiobiology of Breast Cancer: The Time Is Now to Link Circadian Rhythm and Radiation Biology

Circadian disruption has been linked to cancer development, progression, and radiation response. Clinical evidence to date shows that circadian genetic variation and time of treatment affect radiation response and toxicity for women with breast cancer. At the molecular level, there is interplay between circadian clock regulators such as PER1, which mediates ATM and p53-mediated cell cycle gating and apoptosis. These molecular alterations may govern aggressive cancer phenotypes, outcomes, and radiation response. Exploiting the various circadian clock mechanisms may enhance the therapeutic index of radiation by decreasing toxicity, increasing disease control, and improving outcomes. We will review the body’s natural circadian rhythms and clock gene-regulation while exploring preclinical and clinical evidence that implicates chronobiological disruptions in the etiology of breast cancer. We will discuss radiobiological principles and the circadian regulation of DNA damage responses. Lastly, we will present potential rational therapeutic approaches that target circadian pathways to improve outcomes in breast cancer. Understanding the implications of optimal timing in cancer treatment and exploring ways to entrain circadian biology with light, diet, and chronobiological agents like melatonin may provide an avenue for enhancing the therapeutic index of radiotherapy.

New Insights Into Cancer Chronotherapies

Circadian clocks participate in the coordination of various metabolic and biological activities to maintain homeostasis. Disturbances in the circadian rhythm and cancers are closely related. Circadian clock genes are differentially expressed in many tumors, and accelerate the development and progression of tumors. In addition, tumor tissues exert varying biological activities compared to normal tissues due to resetting of altered rhythms. Thus, chronotherapeutics used for cancer treatment should exploit the timing of circadian rhythms to achieve higher efficacy and mild toxicity. Due to interpatient differences in circadian functions, our findings advocate an individualized precision approach to chronotherapy. Herein, we review the specific association between circadian clocks and cancers. In addition, we focus on chronotherapies in cancers and personalized biomarkers for the development of precision chronotherapy. The understanding of circadian clocks in cancer will provide a rationale for more effective clinical treatment of tumors.

Does timing matter in radiotherapy of hepatocellular carcinoma? An experimental study in mice

This study investigates whether a chronotherapeutic treatment of hepatocellular carcinoma (HCC) may improve treatment efficacy and mitigate side effects on non-tumoral liver (NTL). HCC was induced in Per2::luc mice which were irradiated at four time points of the day. Proliferation and DNA-double strand breaks were analyzed in irradiated and nonirradiated animals by detection of Ki67 and γ-H2AX. Prior to whole animal experiments, organotypic slice cultures were investigated to determine the dosage to be used in whole animal experiments. Irradiation was most effective at the proliferation peaks in HCC at ZT02 (early inactivity phase) and ZT20 (late activity phase). Irradiation effects on NTL were minimal at ZT20. As compared with NTL, nonirradiated HCC revealed disruption in daily variation and downregulation of all investigated clock genes except Per1. Irradiation affected rhythmic clock gene expression in NTL and HCC at all ZTs except at ZT20 (late activity phase). Irradiation at ZT20 had no effect on total leukocyte numbers. Our results indicate ZT20 as the optimal time point for irradiation of HCC in mice at which the ratio between efficacy of tumor treatment and toxic side effects was maximal. Translational studies are now needed to evaluate whether the late activity phase is the optimal time point for irradiation of HCC in man.

A protective effect of morning radiotherapy on acute skin toxicity in patients with breast cancer: A prospective cohort study

The focus of this prospective cohort study was to evaluate the risk factors of severe acute skin toxicity (grade ≥2) in 100 patients with breast cancer (BC) during radiotherapy (RT).The patients were evaluated weekly during RT and 3 months after treatment. The endpoint included the occurrence of skin toxicity grade ≥2, according to Radiation Therapy Oncology Group (RTOG). Survival analysis was conducted by univariate and multivariate Cox regression analysis.In the multivariate analysis, RT in the afternoon (0-3 pm) (hazard ratios [HR] = 1.566, P = .042) was significantly associated with the early occurrence of skin toxicity, indicating a potential effect of chronotherapy related to this adverse event. In the univariate and multivariate analysis, skin phototype moderate brown (HR = 1.586, P = .042; HR = 1.706, P = .022, respectively) and dark brown or black (HR = 4.517, P < .001; HR = 5.336, P < 0.001, respectively) was significantly associated with the skin toxicity. Tangential field separation >21 cm (HR = 2.550, P = .009, HR = 2.923, P = .003), in women that were submitted to conservative surgery indicates indirectly that large breast size was also significantly associated with skin toxicity.Women with large breasts and dark brown or black skin should be followed more carefully during RT, which should be undergone in the morning, especially when submitted to conventional RT techniques, common in developing countries.

Temporal determinants of tumour response to neoadjuvant rectal radiotherapy

Introduction

In locally advanced rectal cancer, longer delay to surgery after neoadjuvant radiotherapy increases the likelihood of histopathological tumour response. Chronomodulated radiotherapy in rectal cancer has recently been reported as a factor increasing tumour response to neoadjuvant treatment in patients having earlier surgery, with patients receiving a larger proportion of afternoon treatments showing improved response. This paper aims to replicate this work by exploring the impact of these two temporal factors, independently and in combination, on histopathological tumour response in rectal cancer patients.

Methods

A retrospective review of all patients with rectal adenocarcinoma who received long course (≥24 fractions) neoadjuvant radiotherapy with or without chemotherapy at a tertiary referral centre was conducted. Delay to surgery and radiotherapy treatment time were correlated to clinicopathologic characteristics with a particular focus on tumour regression grade. A review of the literature and meta-analysis were also conducted to ascertain the impact of time to surgery from preoperative radiotherapy on tumour regression.

Results

From a cohort of 367 patients, 197 patients met the inclusion criteria. Complete pathologic response (AJCC regression grade 0) was seen in 46 (23%) patients with a further 44 patients (22%) having at most small groups of residual cells (AJCC regression grade 1). Median time to surgery was 63 days, and no statistically significant difference was seen in tumour regression between patients having early or late surgery. There was a non-significant trend towards a larger proportion of morning treatments in patients with grade 0 or 1 regression (p = 0.077). There was no difference in tumour regression when composite groups of the two temporal variables were analysed. Visualisation of data from 39 reviewed papers (describing 27379 patients) demonstrated a plateau of response to neoadjuvant radiotherapy after approximately 60 days, and a meta-analysis found improved complete pathologic response in patients having later surgery.

Conclusions

There was no observed benefit of chronomodulated radiotherapy in our cohort of rectal cancer patients. Review of the literature and meta-analysis confirms the benefit of delayed surgery, with a plateau in complete response rates at approximately 60-days between completion of radiotherapy and surgery. In our cohort, time to surgery for the majority of our patients lay along this plateau and this may be a more dominant factor in determining response to neoadjuvant therapy, obscuring any effects of chronomodulation on tumour response. We would recommend surgery be performed between 8 and 11 weeks after completion of neoadjuvant radiotherapy in patients with locally advanced rectal cancer.

Circadian Variation in Efficacy of Medications

Although much has been learned about circadian clocks and rhythms over the past few decades, translation of this foundational science underlying the temporal regulation of physiology and behavior to clinical applications has been slow. Indeed, acceptance of the modern study of circadian rhythms has been blunted because the phenomenology of cyclic changes had to counteract the 20th century dogma of homeostasis in the biological sciences and medicine. We are providing this review of clinical data to highlight the emerging awareness of circadian variation in efficacy of medications for physicians, clinicians, and pharmacists. We are suggesting that gold-standard double-blind clinical studies should be conducted to determine the best time of day for optimal effectiveness of medications; also, we suggest that time of day should be tracked and reported as an important biological variable in ongoing clinical studies hereafter. Furthermore, we emphasize that time of day is, and should be considered, a key biological variable in research design similar to sex. In common with biomedical research data that have been historically strongly skewed toward the male sex, most pharmaceutical data have been skewed toward morning dosing without strong evidence that this is the optimal time of efficacy.

The Time for Chronotherapy in Radiation Oncology

Five decades ago, Franz Halberg conceived the idea of ​​a circadian-based therapy for cancer, given the differential tolerance to treatment derived from the intrinsic host rhythms. Nowadays, different experimental models have demonstrated that both the toxicity and efficacy of several anticancer drugs vary by more than 50% as a function of dosing time. Accordingly, it has been shown that chemotherapeutic regimens optimally timed with the circadian cycle have jointly improved patient outcomes both at the preclinical and clinical levels. Along with chemotherapy, radiation therapy is widely used for cancer treatment, but its effectiveness relies mainly on its ability to damage DNA. Notably, the DNA damage response including DNA repair, DNA damage checkpoints, and apoptosis is gated by the circadian clock. Thus, the therapeutic potential of circadian-based radiotherapy against cancer is mainly dependent upon the control that the molecular clock exerts on DNA repair enzymes across the cell cycle. Unfortunately, the time of treatment administration is not usually considered in clinical practice as it varies along the daytime working hours. Currently, only a few studies have evaluated whether the timing of radiotherapy affects the treatment outcome. Several of these studies show that it is possible to reduce the toxicity of the treatment if it is applied at a specific time range, although with some inconsistencies. In this Perspective, we review the main advances in the field of chronoradiotherapy, the possible causes of the inconsistencies observed in the studies so far and provide some recommendations for future trials.

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.

Clinical effects of morning and afternoon radiotherapy on high-grade gliomas

Initial clinical reports comparing the delivery of radiotherapy (RT) at distinct times of the day suggest that this strategy might affect toxicity and oncologic outcomes of radiation for multiple human tissues, but the clinical effects on high-grade gliomas (HGG) are unknown. The present study addresses the hypothesis that radiotherapy treatment time of the day (RT-TTD) influences outcome and/or toxic events in HGG. Patients treated between 2009-2018 were reviewed (n = 109). Outcomes were local control (LC), distant CNS control (DCNSC), progression-free survival (PFS), and overall survival (OS). RT-TTD was classified as morning if ≥50% of fractions were delivered before 12:00 h (n = 70) or as afternoon (n = 39) if after 12:00 h. The average age was 62.6 years (range: 14.5-86.9) and 80% were glioblastoma. The median follow-up was 10.9 months (range: 0.4-57.2). The 1y/3y LC, DCNSC, and PFS were: 61.3%/28.1%, 86.8%/65.2%, and 39.7%/10.2%, respectively. Equivalent PFS was found between morning and afternoon groups (HR 1.27; p = .3). The median OS was 16.5 months. Patients treated in the afternoon had worse survival in the univariate analysis (HR 1.72; p = .05), not confirmed after multivariate analysis (HR 0.92, p = .76). Patients with worse baseline performance status and treatment interruptions showed worse PFS and OS. The proportion of patients that developed grade 3 acute toxicity, pseudo progression, and definitive treatment interruptions were 10.1%, 9.2%, and 7.3%, respectively, and were not affected by RT-TTD. In conclusion, for patients with HGG, there was no difference in PFS and OS between patients treated in the morning or afternoon. Of note, definitive treatment interruptions adversely affected outcomes and should be avoided, especially in patients with low performance status. Based on these clinical findings, high-grade glioma cells may not be the best initial model to be irradiated in order to study the effects of chronotherapy.

An Optimal Time for Treatment-Predicting Circadian Time by Machine Learning and Mathematical Modelling

Tailoring medical interventions to a particular patient and pathology has been termed personalized medicine. The outcome of cancer treatments is improved when the intervention is timed in accordance with the patient's internal time. Yet, one challenge of personalized medicine is how to consider the biological time of the patient. Prerequisite for this so-called chronotherapy is an accurate characterization of the internal circadian time of the patient. As an alternative to time-consuming measurements in a sleep-laboratory, recent studies in chronobiology predict circadian time by applying machine learning approaches and mathematical modelling to easier accessible observables such as gene expression. Embedding these results into the mathematical dynamics between clock and cancer in mammals, we review the precision of predictions and the potential usage with respect to cancer treatment and discuss whether the patient's internal time and circadian observables, may provide an additional indication for individualized treatment timing. Besides the health improvement, timing treatment may imply financial advantages, by ameliorating side effects of treatments, thus reducing costs. Summarizing the advances of recent years, this review brings together the current clinical standard for measuring biological time, the general assessment of circadian rhythmicity, the usage of rhythmic variables to predict biological time and models of circadian rhythmicity.

Hypoxia, metabolism, and the circadian clock: new links to overcome radiation resistance in high-grade gliomas

Radiotherapy is the cornerstone of treatment of high-grade gliomas (HGGs). It eradicates tumor cells by inducing oxidative stress and subsequent DNA damage. Unfortunately, almost all HGGs recur locally within several months secondary to radioresistance with intricate molecular mechanisms. Therefore, unravelling specific underlying mechanisms of radioresistance is critical to elucidating novel strategies to improve the radiosensitivity of tumor cells, and enhance the efficacy of radiotherapy. This review addresses our current understanding of how hypoxia and the hypoxia-inducible factor 1 (HIF-1) signaling pathway have a profound impact on the response of HGGs to radiotherapy. In addition, intriguing links between hypoxic signaling, circadian rhythms and cell metabolism have been recently discovered, which may provide insights into our fundamental understanding of radioresistance. Cellular pathways involved in the hypoxic response, DNA repair and metabolism can fluctuate over 24-h periods due to circadian regulation. These oscillatory patterns may have consequences for tumor radioresistance. Timing radiotherapy for specific times of the day (chronoradiotherapy) could be beneficial in patients with HGGs and will be discussed.

Radiation chronotherapy-clinical impact of treatment time-of-day: a systematic review

PURPOSE

Many brain tumor patients suffer from radiation-induced toxicities. Chronotherapy is a treatment modality that utilizes circadian rhythms to optimize the effect on tumor while minimizing negative outcomes on healthy tissue. This review aims to systematically examine the literature on the application of a radiation chronotherapeutic for all cancers and determine the possible advantages of incorporating a circadian-based fixed time-of-day for radiotherapy into CNS cancers.

METHODS

A systematic review of the literature was conducted in two electronic databases from inception to February 1, 2019. Primary research manuscripts were screened for those related to adult human subjects exposed to ionizing radiation using the chronotherapy technique.

RESULTS

Nine manuscripts were included in the review from 79 eligible articles. Three were prospective randomized trails and 6 were retrospective reviews. This survey revealed that overall survival and tumor control do not have consistent effects with only 60% and 55.5% of paper which included the variables having some significance, respectively. Treatment symptoms were the primary endpoint for both the prospective trials and were examined in 3 of the retrospective reviews; effects were observed in sensitive tissue for all 5 studies including mucosal linings and skin basal layer.

CONCLUSIONS

Existing literature suggests that the application of radiation chronotherapy may reduce negative symptom outcome within highly proliferative tissues. Further examination of radiation chronotherapy in well-designed prospective trials and studies in brain tumor patients are merited.

It's About Time: Advances in Understanding the Circadian Regulation of DNA Damage and Repair in Carcinogenesis and Cancer Treatment Outcomes

The circadian rhythm is established by a coordinated network of peripheral clocks interlocked and regulated by a central pacemaker. This network is maintained by the rhythmic expression of core clock genes, which in turn generate oscillatory expression patterns of different sets of target proteins in a tissue-specific manner. Precise regulation of biological processes driven by the body's circadian network in response to periodic changes in the environment determines healthy life. The delicate balance in the cycling of enzymes, metabolites, cofactors, and immune regulators is essential to achieve cellular homeostasis. Disruption of this circadian homeostasis has been linked with the development and progression of various diseases including cancer. Over the years, circadian regulation of drug metabolism and processing has been employed in the treatment of diabetes, hypertension, peptic ulcers, and allergic rhinitis. Although time dictated drug administration was demonstrated many decades ago, its application in cancer treatment is limited due to insufficient mechanistic data supporting experimental results and inconsistency between clinical trials. However, timed administration of anti-cancer drugs is rapidly gaining attention as studies with animal and human models unveil molecular intricacies involved in the circadian control of biological pathways. In this regard, striking a balance between maximizing tumor responsiveness and minimizing side effects is crucial to achieve positive patient outcomes. This review focuses on regulation of the circadian clock in carcinogenesis outcomes through DNA damage and repair mechanisms and its application in therapy with specific emphasis on skin and breast cancers.

Genetic Variants Predict Optimal Timing of Radiotherapy to Reduce Side-effects in Breast Cancer Patients

AIMS

Radiotherapy is an important treatment for many types of cancer, but a minority of patients suffer long-term side-effects of treatment. Multiple lines of evidence suggest a role for circadian rhythm in the development of radiotherapy late side-effects.

MATERIALS AND METHODS

We carried out a study to examine the effect of radiotherapy timing in two breast cancer patient cohorts. The retrospective LeND cohort comprised 535 patients scored for late effects using the Late Effects of Normal Tissue-Subjective Objective Management Analytical (LENT-SOMA) scale. Acute effects were assessed prospectively in 343 patients from the REQUITE study using the CTCAE v4 scales. Genotyping was carried out for candidate circadian rhythm variants.

RESULTS

In the LeND cohort, patients who had radiotherapy in the morning had a significantly increased incidence of late toxicity in univariate (P = 0.03) and multivariate analysis (P = 0.01). Acute effects in the REQUITE group were also significantly increased in univariate analysis after morning treatment (P = 0.03) but not on multivariate analysis. Increased late effects in the LeND group receiving morning radiotherapy were associated with carriage of the PER3 variable number tandem repeat 4/4 genotype (P = 6 × 10-3) and the NOCT rs131116075 AA genotype (P = 5 × 10-3).

CONCLUSION

Our results suggest that it may be possible to reduce toxicity associated with breast cancer radiotherapy by identifying gene variants that affect circadian rhythm and scheduling for appropriate morning or afternoon radiotherapy.

Perspectives on the relevance of the circadian time structure to workplace threshold limit values and employee biological monitoring

The circadian time structure (CTS) and its disruption by rotating and nightshift schedules relative to work performance, accident risk, and health/wellbeing have long been areas of occupational medicine research. Yet, there has been little exploration of the relevance of the CTS to setting short-term, time-weighted, and ceiling threshold limit values (TLVs); conducting employee biological monitoring (BM); and establishing normative reference biological exposure indices (BEIs). Numerous publications during the past six decades document the CTS substantially affects the disposition - absorption, distribution, metabolism, and elimination - and effects of medications. Additionally, laboratory animal and human studies verify the tolerance to chemical, biological (contagious), and physical agents can differ extensively according to the circadian time of exposure. Because of slow and usually incomplete CTS adjustment by rotating and permanent nightshift workers, occupational chemical and other contaminant encounters occur during a different circadian stage than for dayshift workers. Thus, the intended protection of some TLVs when working the nightshift compared to dayshift might be insufficient, especially in high-risk settings. The CTS is germane to employee BM in that large-amplitude predictable-in-time 24h variation can occur in the concentration of urine, blood, and saliva of monitored chemical contaminants and their metabolites plus biomarkers indicative of adverse xenobiotic exposure. The concept of biological time-qualified (for rhythms) reference values, currently of interest to clinical laboratory pathology practice, is seemingly applicable to industrial medicine as circadian time and workshift-specific BEIs to improve surveillance of night workers, in particular. Furthermore, BM as serial assessments performed frequently both during and off work, exemplified by employee self-measurement of lung function using a small portable peak expiratory flow meter, can easily identify intolerance before induction of pathology.

Does chronomodulated radiotherapy improve pathological response in locally advanced rectal cancer?

The predominant mode of radiation-induced cell death for solid tumours is mitotic catastrophe, which is in part dependent on sublethal damage repair being complete at around 6 h. Circadian variation appears to play a role in normal cellular division, and this could influence tumour response of radiation treatment depending on the time of treatment delivery. We tested the hypothesis that radiation treatment later in the day may improve tumour response and nodal downstaging in rectal cancer patients treated neoadjuvantly with radiation therapy. Recruitment was by retrospective review of 267 rectal cancer patients treated neoadjuvantly in the Department of Radiation Oncology at the Canberra Hospital between January 2010 and November 2015. One hundred and fifty-five patients met the inclusion criteria for which demographic, pathological and imaging data were collected, as well as the time of day patients received treatment with each fraction of radiotherapy. Data analysis was performed using the Statistical Package R with nonparametric methods of significance for all tests set at p < 0.05. Of the 45 female and 110 male patients, the median age was 64. Seventy-three percent had cT3 disease and there was a mean tumour distance from the anal verge of 7 cm. Time to surgical resection following radiotherapy ranged from 4 to 162 days with a median of 50 days, with a complete pathological response seen in 21% of patients. Patients exhibiting a favourable pathological response had smaller median pre- and postradiotherapy tumour size and had a greater change in tumour size following treatment (p < 0.01). Patients who received the majority of their radiotherapy fractions after 12:00 pm were more likely to show a complete or moderate pathological response (p = 0.035) and improved nodal downstaging. There were also more favourable responses amongst patients with longer time to surgical resection postradiotherapy (p < 0.004), although no relationship was seen between response and tumour distance from the anal verge. Females were less likely to exhibit several of the above responses. Neoadjuvant radiotherapy for locally advanced rectal cancer performed later in the day coupled with a longer time period to surgical resection may improve pathological tumour response rates and nodal downstaging. A prospective study in chronomodulated radiotherapy in this disease is warranted.

Patient-reported symptoms of radiation dermatitis during breast cancer radiotherapy: a pilot study

PURPOSE

To find out which symptoms most frequently and severely affect breast cancer patients during radiotherapy and how patients manage the symptoms and unmet needs.

METHODS

A cross-sectional survey was conducted with 111 patients who receive radiotherapy for breast cancer from January to April 2015 at Samsung Medical Center in Seoul, South Korea. Participants were asked about symptoms and discomfort due to radiotherapy, management methods for radiation dermatitis, unmet needs for radiation dermatitis care, and clinical and socio-demographic information.

RESULTS

Of total, 108 out of 111 patients (97.3%) reported symptoms related to radiation dermatitis. Hyperpigmentation was the most commonly reported uncomfortable symptom followed by erythema. On average, patients reported 8.6 radiotherapy-induced skin problems (range, 0-11). Of total, 59 (53.2%) patients stated that they wanted care for radiation dermatitis, and 80.0, 59.4, and 51% of patients searched for information, used products, and visited the hospital to manage radiotherapy-related skin problems. Patients who experienced dryness, burning feelings, irritation, roughness, and hyperpigmentation were 11.73, 7.02, 5.10, 4.27, and 2.80 times more likely to have management needs than patients without those symptoms, respectively, adjusting age, current cycle of radiation therapy, chemotherapy, and type of surgery.

CONCLUSIONS

Most of the breast cancer patients experience multiple symptoms associated with radiation dermatitis. Hyperpigmentation was the most common and uncomfortable symptom followed by erythema. Majority of patients wanted management for radiation dermatitis and patients who experienced dryness, burning feelings, irritation, roughness, and hyperpigmentation had higher needs for radiation dermatitis management.

DHA-mediated regulation of lung cancer cell migration is not directly associated with Gelsolin or Vimentin expression

AIMS

Deaths associated with cancer metastasis have steadily increased making the need for newer, anti-metastatic therapeutics imparative. Gelsolin and vimentin, actin binding proteins expressed in metastatic tumors, participate in actin remodelling and regulate cell migration. Docosahexaenoic acid (DHA) limits cancer cell proliferation and adhesion but the mechanisms involved in reducing metastatic phenotypes are unknown. We aimed to investigate the effects of DHA on gelsolin and vimentin expression, and ultimately cell migration and proliferation, in this context.

MAIN METHODS

Non-invasive lung epithelial cells (MLE12) and invasive lung cancer cells (A549) were treated with DHA (30μmol/ml) or/and 8 bromo-cyclic adenosine monophosphate (8 Br-cAMP) (300μmol/ml) for 6 or 24h either before (pre-treatment) or after (post-treatment) plating in transwells. Migration was assessed by the number of cells that progressed through the transwell. Gelsolin and vimentin expression were measured by Western blot and confocal microscopy in cells, and by immunohistochemistry in human lung cancer biopsy samples.

KEY FINDINGS

A significant decrease in cell migration was detected for A549 cells treated with DHA verses control but this same decrease was not seen in MLE12 cells. DHA and 8 Br-cAMP altered gelsolin and vimentin expression but no clear pattern of change was observed. Immunofluorescence staining indicated slightly higher vimentin expression in human lung tissue that was malignant compared to control.

SIGNIFICANCE

Collectively, our data indicate that DHA inhibits cancer cell migration and further suggests that vimentin and gelsolin may play secondary roles in cancer cell migration and proliferation, but are not the primary regulators.

The circadian timing system in clinical oncology

The circadian timing system (CTS) controls several critical molecular pathways for cancer processes and treatment effects over the 24 hours, including drug metabolism, cell cycle, apoptosis, and DNA damage repair mechanisms. This results in the circadian time dependency of whole-body and cellular pharmacokinetics and pharmacodynamics of anticancer agents. However, CTS robustness and phase varies among cancer patients, based on circadian monitoring of rest- activity, body temperature, sleep, and/or hormonal secretion rhythms. Circadian disruption has been further found in up to 50% of patients with metastatic cancer. Such disruption was associated with poor outcomes, including fatigue, anorexia, sleep disorders, and short progression-free and overall survival. Novel, minimally invasive devices have enabled continuous CTS assessment in non-hospitalized cancer patients. They revealed up to 12-hour differences in individual circadian phase. Taken together, the data support the personalization of chronotherapy. This treatment method aims at the adjustment of cancer treatment delivery according to circadian rhythms, using programmable-in-time pumps or novel release formulations, in order to increase both efficacy and tolerability. A fixed oxaliplatin, 5-fluorouracil and leucovorin chronotherapy protocol prolonged median overall survival in men with metastatic colorectal cancer by 3.3 months as compared to conventional delivery, according to a meta-analysis (P=0.009). Further analyses revealed the need for the prevention of circadian disruption or the restoration of robust circadian function in patients on chronotherapy, in order to further optimize treatment effects. The strengthening of external synchronizers could meet such a goal, through programmed exercise, meal timing, light exposure, improved social support, sleep scheduling, and the properly timed administration of drugs that target circadian clocks. Chrono-rehabilitation warrants clinical testing for improving quality of life and survival in cancer patients.