Changes in skin microcirculation during radiation therapy for breast cancer

Laser speckle contrast imaging of perfusion in oncological clinical applications: a literature review

BACKGROUND

Laser speckle coherence imaging (LSCI) is an emerging imaging modality that enables noninvasive visualization and assessment of tissue perfusion and microcirculation. In this article, we evaluated LSCI in imaging perfusion in clinical oncology through a systematic review of the literature.

METHODS

The inclusion criterion for the literature search in PubMed, Web of Science and Scopus electronic databases was the use of LSCI in clinical oncology, meaning that all animal, phantom, ex vivo, experimental, research and development, and purely methodological studies were excluded.

RESULTS

Thirty-six articles met the inclusion criteria. The anatomic locations of the neoplasms in the selected articles were brain (5 articles), breasts (2 articles), endocrine glands (4 articles), skin (12 articles), and the gastrointestinal tract (13 articles).

CONCLUSIONS

While LSCI is emerging as an appealing imaging modality, it is crucial for more clinical sites to initiate clinical trials. A lack of standardized protocols and interpretation guidelines are posing the most significant challenge.

Comparing Performances of Predictive Models of Toxicity after Radiotherapy for Breast Cancer Using Different Machine Learning Approaches

PURPOSE

Different ML models were compared to predict toxicity in RT on a large cohort (n = 1314).

METHODS

The endpoint was RTOG G2/G3 acute toxicity, resulting in 204/1314 patients with the event. The dataset, including 25 clinical, anatomical, and dosimetric features, was split into 984 for training and 330 for internal tests. The dataset was standardized; features with a high p-value at univariate LR and with Spearman ρ>0.8 were excluded; synthesized data of the minority were generated to compensate for class imbalance. Twelve ML methods were considered. Model optimization and sequential backward selection were run to choose the best models with a parsimonious feature number. Finally, feature importance was derived for every model.

RESULTS

The model's performance was compared on a training-test dataset over different metrics: the best performance model was LightGBM. Logistic regression with three variables (LR3) selected via bootstrapping showed performances similar to the best-performing models. The AUC of test data is slightly above 0.65 for the best models (highest value: 0.662 with LightGBM).

CONCLUSIONS

No model performed the best for all metrics: more complex ML models had better performances; however, models with just three features showed performances comparable to the best models using many (n = 13-19) features.

Microcirculatory changes in the skin after postmastectomy radiotherapy in women with breast cancer

Postmastectomy radiotherapy (PMRT) increases the risk for complications after breast reconstruction. The pathophysiological mechanism underlying this increased risk is not completely understood. The aim of this study was to examine if there is a relationship between PMRT and microvascular perfusion in the skin directly after, and at 2 and 6 months after PMRT and to assess if there is impaired responsiveness to a topically applied vasodilator (Methyl nicotinate-MN) after PMRT. Skin microvascular responses after PMRT were measured on two sites in the irradiated chest wall of 22 women before, immediately after, and at 2 and 6 months after unilateral PMRT with the contralateral breast as a control. A significant increase in basal skin perfusion was observed in the irradiated chest wall immediately after RT (p < 0.0001). At 2 and 6 months after RT, there was no longer a difference in basal skin perfusion compared to the contralateral breast and compared to baseline. Similarly, the blood flow response in the skin after application of MN was stronger immediately after RT compared to before RT (p < 0.0001), but there was no difference at later time points. These results indicate that the increased risk for complications after surgical procedures are not directly related to changes in skin perfusion and microvascular responsiveness observed after postmastectomy RT.

Incidence of radiodermatitis and factors associated with its severity in women with breast cancer: a cohort study

BACKGROUND

One of the main adverse reactions of adjuvant radiotherapy for breast cancer is radiodermatitis.

OBJECTIVE

To assess the incidence of radiodermatitis in women with breast cancer, identify factors associated with its severity and determine the time at which this event occurs.

METHODS

Prospective cohort study in 113 women with breast cancer who were evaluated before radiotherapy and at every fifth session until the end of treatment. Logistic regression and Cox proportional regression model were used for the assessment of risk factors; P values < 0.05 were considered significant.

RESULTS

The incidence rate of radiodermatitis was 98.2% and it was demonstrated that for each additional point of the Body Mass Index (BMI), the chance of occurrence of grades II to IV radiodermatitis increases by 14% (OR=1.14 [95% CI 1.04-1.26]; p=0.004) and statin use increases the risk of more severe skin lesions by four-fold (OR=4.27 [95% CI 1.11-16.42]; p=0.035). The exclusive use of hydrogel for skin hydration was an independent factor in delaying the onset of radiodermatitis (HR=0.55 [95% CI 0.36-0.82]; p=0.004).

STUDY LIMITATIONS

The main limitation of this study was its external validity. The identified factors should be considered for services and populations similar to those in this study.

CONCLUSIONS

There was a high incidence of radiodermatitis and its severity was related to higher BMI, statin use; there was a protective effect of hydrogel use.

MEASUREMENT OF SKIN DOSE AND RADIATION-INDUCED CHANGES IN SKIN MICROCIRCULATION IN CHRONIC TOTAL OCCLUSION PERCUTANEOUS CARDIAC INTERVENTIONS (CTO-PCI)

Skin injuries may occur when radiation doses to the skin exceed 2 Gy. This study aimed to measure changes in skin microcirculation in patients undergoing chronic total occlusion percutaneous coronary interventions (CTO-PCI). In 14 patients, peak skin dose (PSD) was estimated with radiographic films and skin microcirculation was assessed with laser speckle contrast imaging (LSCI), before, 1 day after the intervention, and 4-6 weeks later. The mean PSD was 1.8 ± 0.9 Gy. Peak skin microcirculation increased by 12% from 45 ± 6 PU before to 50 ± 9 PU 1 day after the intervention (p = 0.01), and returned to 46 ± 8 PU after 4-6 weeks (p = 0.15). There was no significant correlation between PSD and the change in perfusion, neither 1 day (r = -0.13, p = 0.69) nor 4-6 weeks after the intervention (r = 0.33, p = 0.35). These results suggest that there are no radiation-induced microvascular changes in the skin after CTO-PCI at skin doses below 2 Gy.

Enhanced perfusion of elliptical wound closures using a novel adhesive suture retention device

BACKGROUND AND AIMS

The purpose of this investigation was to test the hypothesis that a novel adhesive retention suture device (ARSD) can increase perfusion at elliptical wound closures by distributing stress away from the suture site.

METHODS

Stress in the skin around a suture both with and without support from an ARSD was evaluated using a finite element model. A single-center, randomized split-scar comparison trial using laser speckle contrast analysis was used to quantify the perfusion at elliptical wound closures in human patients both with and without an ARSD.

RESULTS

The finite element model revealed that the ARSD promoted load transfer to the skin over a larger area, thus reducing the local stress and deformation in the skin around the suture site. Results from the split-scar study showed a mean improvement of 25% perfusion units with the ARSD, and the improvement was statistically significant (p = 0.002).

CONCLUSION

The reduction in local stress and enhanced perfusion around the suture site reveals the potential benefit of using an ARSD to enable more efficient healing by avoiding complications associated with both low perfusion and skin tearing, such as dehiscence, infection, and cheese wiring.

Lower endothelium-dependent microvascular function in adult breast cancer patients receiving radiation therapy

Purpose

Cancer patients with a history of radiotherapy are at an increased risk of ischemic heart disease. Preclinical animal studies demonstrate markedly impaired acetylcholine (ACh)-mediated endothelium-dependent vasorelaxation within days to weeks post-irradiation, however, whether microvascular function is affected in the intact human circulation during cancer radiation therapy has yet to be determined.

Materials and methods

Using laser-Doppler flowmetry, microvascular endothelium-dependent and independent responses were evaluated through iontophoresis of acetylcholine (ACh) (part 1, n = 7) and sodium nitroprusside (SNP) (part 2, n = 8), respectively, in women currently receiving unilateral chest adjuvant radiation therapy for breast cancer. Measurements were performed at the site of radiation treatment and at a contralateral control, non-radiated site. Cutaneous vascular conductance (CVC) was calculated by normalizing for mean arterial pressure.

Results and Conculsions

In part 1, patients received an average radiation dose of 2104 ± 236 cGy. A significantly lower peak ACh-mediated endothelium-dependent vasodilation was observed within the radiated microvasculature when compared to non-radiated (radiated: 532 ± 167%, non-radiated 1029 ± 263%; P = 0.02). In part 2, the average radiation dose received was 2251 ± 196 cGy. Iontophoresis of SNP elicited a similar peak endothelium-independent vasodilator response in radiated and non-radiated tissue (radiated: 179 ± 58%, non-radiated: 310 ± 158; P = 0.2). The time to 50% of the peak response for ACh and SNP was similar between radiated and non-radiated microvasculature (P < 0.05). These data provide evidence of early endothelium-dependent microvascular dysfunction in cancer patients currently receiving chest radiation and provide the scientific premise for future work evaluating coronary endothelial function and vasomotor reactivity using more detailed and invasive procedures.

Current-Induced Vasodilation Specifically Detects, and Correlates With the Time Since, Last Aspirin Intake: An Interventional Study of 830 Patients

BACKGROUND

Galvanic current-induced vasodilation (CIV) is impaired in patients under low-dose aspirin (ASA; ≤ 500 mg/day), but potential covariates and the impact of the time since the last ASA intake are unknown.

OBJECTIVES

We used tissue viability imaging (TiVi) in patients at risk of cardiovascular disease and examined its association with self-reported treatments.

PATIENTS/METHODS

We recorded the age, gender, height, weight, smoking status, and use of 14 different drug categories in 822 patients either with known peripheral artery disease or at risk thereof. The difference between TiVi arbitrary units (TAUs) where stimulation was applied and an adjacent skin area was recorded, as well as the time since the last ASA intake. Step-by-step regression analysis was used to determine the factors that affect CIV amplitude.

RESULTS AND CONCLUSIONS

CIV was 28.2 ± 22.9 vs. 14.6 ± 18.0 TAUs (P < 0.001) in patients treated with ASA (n = 287) and not treated with ASA (n = 535), respectively. The main determinants of CIV amplitude, by order of importance, were: aspirin intake, diabetes mellitus, age, and male sex. In ASA-treated patients, the main determinants were diabetes mellitus, time since the last ASA intake, male gender, and age. Non-invasive determination of the physiological effects of low-dose ASA is feasible in routine clinical practice. It could be a clinical approach to provide objective evidence of ASA intake, and potentially could be used to test adherence to treatment in ASA-treated patients.

Objective assessment of skin microcirculation using a smartphone camera

BACKGROUND

Existing techniques for assessment of microcirculation are limited by their large size and high costs and are often not so easy to use. Advances in mobile technology have enabled great improvements in smartphone sensor technology. In this study, we used SkinSight, an app for iPhone and iPad, to measure changes in skin microcirculation during physiological provocations. The system estimates changes in the concentration of hemoglobin in the skin by analyzing the reflected light emitted from the built-in light-emitting diode and detected by the camera of the smartphone.

METHODS

A relative hemoglobin (Hb) index was measured during a 5-min arterial occlusion, post-occlusive reactive hyperemia, and a 5-min venous occlusion in 10 healthy subjects, on two separate days. The index was calculated in an area of the skin from the color information in the images acquired by the phone camera. Polarized light spectroscopy imaging was used to measure changes in red blood cell concentration for comparison.

RESULTS

During arterial occlusion, relative Hb index was unchanged compared to baseline (P = .40). After release of the cuff, a sudden 60%-75% increase in Hb index was observed (P < .001) followed by a gradual return to baseline. During venous occlusion, Hb index increased by 80% (P < .001) followed by a gradual decrease to baseline after reperfusion. Day-to-day reproducibility of the relative Hb index was excellent (ICC: 0.92, r = 0.94), although relative Hb index was consistently higher during the second day, possibly as a result of changed lighting conditions or calibration issues.

CONCLUSION

Microvascular responses to physiological provocations in the skin can be accurately and reproducibly measured using a smartphone application. Although the system offers a handheld, easy to use and flexible technique for skin microvascular assessment, the effects of lighting on the measured values and need for calibration need to be further investigated.

Tracking tumor radiotherapy response in vivo with Cherenkov-excited luminescence ink imaging

This study demonstrates remote imaging for in vivo detection of radiation-induced tumor microstructural changes by tracking the diffusive spread of injected intratumor UV excited tattoo ink using Cherenkov-excited luminescence imaging (CELI). Micro-liter quantities of luminescent tattoo ink with UV absorption and visible emission were injected at a depth of 2 mm into mouse tumors prior to receiving a high dose treatment of radiation. X-rays from a clinical linear accelerator were used to excite phosphorescent compounds within the tattoo ink through Cherenkov emission. The in vivo phosphorescence was detected using a time-gated intensified CMOS camera immediately after injection, and then again at varying time points after the ink had broken down with the apoptotic tumor cells. Ex vivo tumors were imaged post-mortem using hyperspectral cryo-fluorescence imaging to quantify necrosis and compared to Cherenkov-excited light imaging of diffusive ink spread measured in vivo. Imaging of untreated control mice showed that ink distributions remained constant after four days with less than 3% diffusive spread measured using full width at 20% max. For all mice, in vivo CELI measurements matched within 12% of the values estimated by the high-resolution ex vivo sliced luminescence imaging of the tumors. The tattoo ink spread in treated mice was found to correlate well with the nonperfusion necrotic core volume (R2 = 0.92) but not well with total tumor volume changes (R2 = 0.34). In vivo and ex vivo findings indicate that the diffusive spread of the injected tattoo ink can be related to radiation-induced necrosis, independent of total tumor volume change. Tracking the diffusive spread of the ink allows for distinguishing between an increase in tumor size due to new cellular growth and an increase in tumor size due to edema. Furthermore, the imaging resolution of CELI allows for in vivo tracking of subtle microenvironmental changes which occur earlier than tumor shrinkage and this offers the potential for novel, minimally invasive radiotherapy response assay without interrupting a singular clinical workflow.

Acute radiation-induced skin toxicity in hypofractionated vs. conventional whole-breast irradiation: An objective, randomized multicenter assessment using spectrophotometry

PURPOSE

Radiation dermatitis represents one of the most frequent side effects in breast cancer patients undergoing adjuvant whole-breast irradiation (WBI). Whether hypofractionated WBI induces comparable or less acute radiation-induced skin reactions than conventional WBI is still not fully clarified, as randomized evidence and objective assessments are limited. The aim of this study was to objectively determine frequency and severity of acute radiation-induced skin reactions during hypofractionated vs. conventionally fractionated adjuvant WBI.

METHODS

In this randomized multicenter study, a total of 140 breast cancer patients underwent either hypofractionated or conventional WBI following breast-preserving surgery. Maximum radiation dermatitis severity was assessed at completion and during follow-up by physician-assessed CTCAE v4.03 and the patient-reported RISRAS scale. Additionally, photospectrometric skin readings were performed to objectify skin color differences between both treatment arms.

RESULTS

Radiation dermatitis severity was significantly lower in patients receiving hypofractionation compared with conventional fractionation (mean 1.05 vs. 1.43, p = .024). Grade 0 radiation dermatitis occurred in 21.43% vs. 4.28%, grade ≥2 in 27.14% vs. 42.91% and grade ≥3 in 0% vs. 4.34% of patients following hypofractionated and conventional WBI, respectively. Objective photospectrometric measurements (n = 4200) showed both decreased erythema severity (p = .008) and hyperpigmentation (p = .002) in the hypofractionation arm. Patients allocated to hypofractionated WBI also reported less pain (p = .006), less hyperpigmentation (p = <0.001) and less limitations of day-to-day activities (p = <0.001).

CONCLUSION

Physician and patient-assessed toxicity scorings as well as objective photospectrometric skin measurements revealed that hypofractionated WBI yielded lower rates and severity of acute radiation-induced skin toxicity.

Quantitative Thermal Imaging Biomarkers to Detect Acute Skin Toxicity From Breast Radiation Therapy Using Supervised Machine Learning

PURPOSE

Radiation-induced dermatitis is a common side effect of breast radiation therapy (RT). Current methods to evaluate breast skin toxicity include clinical examination, visual inspection, and patient-reported symptoms. Physiological changes associated with radiation-induced dermatitis, such as inflammation, may also increase body-surface temperature, which can be detected by thermal imaging. Quantitative thermal imaging markers were identified and used in supervised machine learning to develop a predictive model for radiation dermatitis.

METHODS AND MATERIALS

Ninety patients treated for adjuvant whole-breast RT (4250 cGy/f_x = 16) were recruited for the study. Thermal images of the treated breast were taken at 4 intervals: before RT, then weekly at f_x = 5, f_x = 10, and f_x = 15. Parametric thermograms were analyzed and yielded 26 thermal-based features that included surface temperature (°C) and texture parameters obtained from (1) gray-level co-occurrence matrix, (2) gray-level run-length matrix, and (3) neighborhood gray-tone difference matrix. Skin toxicity was evaluated at the end of RT using the Common Terminology Criteria for Adverse Events (CTCAE) guidelines (Ver.5). Binary group classes were labeled according to a CTCAE cut-off score of ≥2, and thermal features obtained at f_x = 5 were used for supervised machine learning to predict skin toxicity. The data set was partitioned for model training, independent testing, and validation. Fifteen patients (∼17% of the whole data set) were randomly selected as an unseen test data set, and 75 patients (∼83% of the whole data set) were used for training and validation of the model. A random forest classifier with leave-1-patient-out cross-validation was employed for modeling single and hybrid parameters. The model performance was reported using receiver operating characteristic analysis on patients from an independent test set.

RESULTS

Thirty-seven patients presented with adverse skin effects, denoted by a CTCAE score ≥2, and had significantly higher local increases in skin temperature, reaching 36.06°C at f_x = 10 (P = .029). However, machine-learning models demonstrated early thermal signals associated with skin toxicity after the fifth RT fraction. The cross-validated model showed high prediction accuracy on the independent test data (test accuracy = 0.87) at f_x = 5 for predicting skin toxicity at the end of RT.

CONCLUSIONS

Early thermal markers after 5 fractions of RT are predictive of radiation-induced skin toxicity in breast RT.

Prophylactically applied Hydrofilm polyurethane film dressings reduce radiation dermatitis in adjuvant radiation therapy of breast cancer patients

PURPOSE

Radiation-induced skin injury represents one of the most common side effects in breast cancer patients receiving adjuvant whole-breast radiotherapy. Numerous systemic and topical treatments have been studied in the prevention and management of radiation-induced skin injury without providing sustainable treatment strategies. While superficial barrier-forming skin products such as dressings are the standard of care in wound care management, their utilization as preventive treatment approach in radiotherapy has barely attracted attention.

METHODS

In this prospective, intra-patient randomized study, Hydrofilm polyurethane film dressings were applied prophylactically to either the medial or lateral breast half of 62 patients with breast cancer undergoing adjuvant radiation therapy following breast conserving surgery. The breast half contralateral to the film dressing was concurrently treated with 5% urea lotion as control skin care. Maximum severity of radiation dermatitis was assessed using RTOG/EORTC toxicity scores, photospectrometric erythema measurements and patient-assessed modified RISRAS scale.

RESULTS

In the Hydrofilm compartments, mean maximum RTOG/EORTC radiation dermatitis severity grades were significantly reduced from 1.33 to 0.35 and photospectrometric measurements showed significantly reduced erythema severity, as compared to the control compartments, with an overall response rate of 89.3%. Hydrofilm completely prevented moist desquamation and significantly reduced patients' subjective experience of itching and pain.

CONCLUSION

The obtained results along with a favorable cost-benefit ratio and an easy and quick application suggest a prophylactic application of Hydrofilm in adjuvant radiotherapy of breast cancer patients to reduce or even prevent radiation dermatitis.

Correcting for motion artifact in handheld laser speckle images

Laser speckle imaging (LSI) is a wide-field optical technique that enables superficial blood flow quantification. LSI is normally performed in a mounted configuration to decrease the likelihood of motion artifact. However, mounted LSI systems are cumbersome and difficult to transport quickly in a clinical setting for which portability is essential in providing bedside patient care. To address this issue, we created a handheld LSI device using scientific grade components. To account for motion artifact of the LSI device used in a handheld setup, we incorporated a fiducial marker (FM) into our imaging protocol and determined the difference between highest and lowest speckle contrast values for the FM within each data set (Kbest and Kworst). The difference between Kbest and Kworst in mounted and handheld setups was 8% and 52%, respectively, thereby reinforcing the need for motion artifact quantification. When using a threshold FM speckle contrast value (KFM) to identify a subset of images with an acceptable level of motion artifact, mounted and handheld LSI measurements of speckle contrast of a flow region (KFLOW) in in vitro flow phantom experiments differed by 8%. Without the use of the FM, mounted and handheld KFLOW values differed by 20%. To further validate our handheld LSI device, we compared mounted and handheld data from an in vivo porcine burn model of superficial and full thickness burns. The speckle contrast within the burn region (KBURN) of the mounted and handheld LSI data differed by <4  %   when accounting for motion artifact using the FM, which is less than the speckle contrast difference between superficial and full thickness burns. Collectively, our results suggest the potential of handheld LSI with an FM as a suitable alternative to mounted LSI, especially in challenging clinical settings with space limitations such as the intensive care unit.