Radiation and Melanoma: Where Are We Now?

PURPOSE OF REVIEW: This review summarizes the current role of radiotherapy for the treatment of cutaneous melanoma in the definitive, adjuvant, and palliative settings, and combinations with immunotherapy and targeted therapies. RECENT FINDINGS: Definitive radiotherapy may be considered for lentigo maligna if surgery would be disfiguring. High risk, resected melanoma may be treated with adjuvant radiotherapy, but the role is poorly defined since the advent of effective systemic therapies. For patients with metastatic disease, immunotherapy and targeted therapies can be delivered safely in tandem with radiotherapy to improve outcomes. Radiotherapy and modern systemic therapies act in concert to improve outcomes, especially in the metastatic setting. Further prospective data is needed to guide the use of definitive radiotherapy for lentigo maligna and adjuvant radiotherapy for high-risk melanoma in the immunotherapy era. Current evidence does not support an abscopal response or at least identify the conditions necessary to reliably produce one with combinations of radiation and immunotherapy.

Guided imagery for treatment (GIFT): protocol of a pilot trial of guided imagery versus treatment as usual to address radiotherapy-related distress in head and neck cancer.

BACKGROUND: Cancers of the head and neck region are associated with high symptom burden and elevated levels of psychological distress. Radiotherapy (RT) is a common treatment for patients with head and neck cancer (HNC) that is associated with psychological distress related to the immobilizing nature of the treatment, frequency of treatment delivery, and side effects. Guided imagery is a relaxation technique that is beneficial in reducing psychological distress in patients with other cancer diagnoses but has not been studied in this patient population. The purpose of this study is to evaluate the feasibility and acceptability of a brief guided imagery intervention (guided imagery for treatment, GIFT) to reduce RT-related anxiety and depression in patients with HNC relative to treatment as usual (TAU). METHODS: Patients with HNC planning to receive RT will be recruited to participate in a randomized controlled trial evaluating a brief, two-session guided imagery intervention (GIFT) relative to TAU alone. Primary aims include acceptability and feasibility evaluated through quantitative and qualitative methods. Measures of anxiety and depression, symptom burden, health-related quality of life, and anxiolytic medication use will be collected at baseline, during treatment, and at 1-month follow-up. DISCUSSION: There are no published interventions of guided imagery for anxiety and depression in patients with HNC despite its efficacy in other populations of patients with cancer. This proposed project evaluates the feasibility and acceptability of an intervention that has the potential to reduce psychological distress in a vulnerable population. Additionally, we will preliminarily examine the impact of behavioral intervention on psychological distress and the use of anxiolytic medication, a novel area of study. TRIAL REGISTRATION: Clinicaltrials.gov NCT03662698 ; registered on 9/6/2018.

Multiphoton Phosphorescence Quenching Microscopy Reveals Kinetics of Tumor Oxygenation during Antiangiogenesis and Angiotensin Signaling Inhibition.

PURPOSE: The abnormal function of tumor blood vessels causes tissue hypoxia, promoting disease progression and treatment resistance. Although tumor microenvironment normalization strategies can alleviate hypoxia globally, how local oxygen levels change is not known because of the inability to longitudinally assess vascular and interstitial oxygen in tumors with sufficient resolution. Understanding the spatial and temporal heterogeneity should help improve the outcome of various normalization strategies. EXPERIMENTAL DESIGN: We developed a multiphoton phosphorescence quenching microscopy system using a low-molecular-weight palladium porphyrin probe to measure perfused vessels, oxygen tension, and their spatial correlations in vivo in mouse skin, bone marrow, and four different tumor models. Further, we measured the temporal and spatial changes in oxygen and vessel perfusion in tumors in response to an anti-VEGFR2 antibody (DC101) and an angiotensin-receptor blocker (losartan). RESULTS: We found that vessel function was highly dependent on tumor type. Although some tumors had vessels with greater oxygen-carrying ability than those of normal skin, most tumors had inefficient vessels. Further, intervessel heterogeneity in tumors is associated with heterogeneous response to DC101 and losartan. Using both vascular and stromal normalizing agents, we show that spatial heterogeneity in oxygen levels persists, even with reductions in mean extravascular hypoxia. CONCLUSIONS: High-resolution spatial and temporal responses of tumor vessels to two agents known to improve vascular perfusion globally reveal spatially heterogeneous changes in vessel structure and function. These dynamic vascular changes should be considered in optimizing the dose and schedule of vascular and stromal normalizing strategies to improve the therapeutic outcome.

NCCN Guidelines® Insights: Melanoma: Cutaneous, Version 2.2021.

Over the past few years, the NCCN Guidelines for Melanoma: Cutaneous have been expanded to include pathways for treatment of microscopic satellitosis (added in v2.2020), and the following Principles sections: Molecular Testing (added in v2.2019), Systemic Therapy Considerations (added in v2.2020), and Brain Metastases Management (added in v3.2020). The v1.2021 update included additional modifications of these sections and notable revisions to Principles of: Pathology, Surgical Margins for Wide Excision of Primary Melanoma, Sentinel Lymph Node Biopsy, Completion/Therapeutic Lymph Node Dissection, and Radiation Therapy. These NCCN Guidelines Insights discuss the important changes to pathology and surgery recommendations, as well as additions to systemic therapy options for patients with advanced disease.

Dexamethasone Increases Cisplatin-Loaded Nanocarrier Delivery and Efficacy in Metastatic Breast Cancer by Normalizing the Tumor Microenvironment.

Dexamethasone is a glucocorticoid steroid with anti-inflammatory properties used to treat many diseases, including cancer, in which it helps manage various side effects of chemo-, radio-, and immunotherapies. Here, we investigate the tumor microenvironment (TME)-normalizing effects of dexamethasone in metastatic murine breast cancer (BC). Dexamethasone normalizes vessels and the extracellular matrix, thereby reducing interstitial fluid pressure, tissue stiffness, and solid stress. In turn, the penetration of 13 and 32 nm dextrans, which represent nanocarriers (NCs), is increased. A mechanistic model of fluid and macromolecule transport in tumors predicts that dexamethasone increases NC penetration by increasing interstitial hydraulic conductivity without significantly reducing the effective pore diameter of the vessel wall. Also, dexamethasone increases the tumor accumulation and efficacy of ∼30 nm polymeric micelles containing cisplatin (CDDP/m) against murine models of primary BC and spontaneous BC lung metastasis, which also feature a TME with abnormal mechanical properties. These results suggest that pretreatment with dexamethasone before NC administration could increase efficacy against primary tumors and metastases.

Feasibility of rapid integrated radiation therapy planning with follow-up FDG PET/CT to improve overall treatment assessment in head and neck cancer.

Inflammatory changes and residual disease are difficult to distinguish after high dose, definitive radiotherapy of head and neck malignancies. FDG uptake located within a high dose field may more likely represent inflammatory changes, and FDG uptake outside of the radiation field could represent unsuspected and under treated disease. In situ knowledge of the precise radiotherapy fields, therefore, may be useful in distinguishing these etiologies. This study aimed to evaluate the clinical feasibility of rapid integration of radiation treatment field images during follow-up FDG PET/CT imaging. Twenty head and neck cancer patients who underwent radiation therapy were identified. A MIM based workflow was created which fused the radiation treatment CT, including the planning volumes and isodose curves, into the follow-up imaging. Two board certified physicians, blinded to treatment outcome, reviewed the follow-up exams, half with the treatment information and half without. Each exam was scored for recurrent or residual disease, confidence of the read and a qualitative assessment to the overall usefulness of the treatment plan. Interpretation accuracy improved from 80 to 90% with integration of the treatment plan. Similarly, the sensitivity improved from 71% to 86%, while the specificity increased from 85% to 92%. Confidence also increased by 0.7 on a 5 point scale for both readers. Data demonstrate the clinical feasibility of rapidly incorporating radiation treatment dosimetry into follow-up FDG PET/CT exams in patients with head and neck cancer. Preliminary results demonstrated a simple, efficient method which improved accuracy of interpretation and overall reader confidence.

Predictors of Treatment Response and Survival Outcomes in Meningioma Recurrence with Atypical or Anaplastic Histology.

BACKGROUND: Recurrence rates for atypical and anaplastic meningiomas range between 9% and 50% after gross total resection and between 36% and 83% after subtotal resection. Optimal treatment of recurrent meningiomas exhibiting atypical/anaplastic histology is complicated because they are often refractory to both surgery and radiation. OBJECTIVE: To evaluate clinical determinants of recurrence and treatment-specific outcomes in patients with recurrent meningiomas exhibiting atypical/anaplastic histology at our institution. METHODS: A cohort study was conducted using clinical data of all patients treated for meningiomas with atypical/anaplastic histology at first recurrence between January 1985 and July 2014 at a tertiary cancer center. Predictors of second recurrence were analyzed using competing risks regression models. RESULTS: Nine hundred eighteen patients with meningioma were screened, of whom 60 (55% female) had recurrent disease with atypical/anaplastic histology at a median age of 58.1 yr at diagnosis. The median follow-up from the time of first recurrence was 36.7 mo, with 32 (53%) patients alive at last follow-up. There was no effect of extent of resection at first recurrence on time to a subsequent recurrence. Inclusion of radiation as primary or adjuvant therapy at first recurrence reduced the risk of progression or subsequent recurrence compared to surgery alone (P = .07). CONCLUSION: Treatment of recurrent meningiomas with atypical/anaplastic histology remains challenging. Our data, from one of the largest cohorts, suggest better tumor control with the addition of radiation and challenges the importance of extent of resection at first recurrence. A multicenter effort is needed to confirm these findings and propose treatment guidelines.

Patterns of fractionation for patients with T2N0M0 glottic larynx cancer undergoing definitive radiotherapy in the United States.

OBJECTIVES: Among patients with T2N0M0 glottic larynx cancer undergoing definitive radiotherapy, recent retrospective and prospective data have suggested improved outcomes with altered fractionation over conventional fractionation (CFxn). We sought to characterize national fractionation patterns and to compare outcomes among them. MATERIALS AND METHODS: We queried the National Cancer Database for T2N0M0 squamous cell carcinomas of the glottis diagnosed from 2004-2014 and managed with definitive radiotherapy. Dose-per-fraction and duration of radiotherapy were used to define cohorts undergoing CFxn, hypofractionation (HypoFxn), and hyperfractionation (HyperFxn). Logistic regression was performed to identify predictors of receiving altered fractionation. Cox regression and propensity-score matching (PSM) analyses were used to compare survival between schedules. RESULTS: We abstracted 2 006 CFxn patients, 1 166 HypoFxn patients, and 161 HyperFxn patients. Fractionation patterns changed significantly from 2004 to 2014, with use of HyperFxn decreasing from 6.3% to 1.8% and use of HypoFxn increasing from 23.9% to 54.1% (p<0.001). Receipt of altered fractionation was independently associated with later year of diagnosis and higher facility volume. On Cox regression, both HypoFxn (hazard ratio [HR] for mortality 0.84, 95% confidence interval [95%CI] 0.73-0.97) and HyperFxn (HR 0.74, 95%CI 0.56-0.99) were associated with improved survival over CFxn. The survival advantage of each altered fractionation schedule over CFxn was redemonstrated on comparison of PSM groups. CONCLUSION: Increasing utilization of HypoFxn for T2N0M0 glottic cancer is driving national practice patterns away from CFxn. Our findings support the use of altered fractionation, particularly HypoFxn, for patients undergoing definitive radiotherapy, although HyperFxn remains understudied in a prospective fashion.

Patterns of Care for Patients With Early-Stage Glottic Cancer Undergoing Definitive Radiation Therapy: A National Cancer Database Analysis.

PURPOSE: To characterize practice patterns, including temporal trends, in fractionation schedules among patients in the United States undergoing definitive radiation therapy for early-stage glottic cancer and to compare overall survival outcomes between fractionation schedules. METHODS AND MATERIALS: We queried the National Cancer Database for patients with TisN0M0, T1N0M0, or T2N0M0 squamous cell carcinoma of the glottic larynx diagnosed between 2004 and 2012 and undergoing definitive radiation therapy. Dose per fraction was calculated to define cohorts undergoing conventional fractionation (CFxn) and hypofractionation (HFxn). Logistic regression was performed to identify predictors of receiving HFxn, and Cox regression was used to determine predictors of death. One-to-one propensity score matching was then used to compare survival between fractionation schedules. RESULTS: The study included 10,539 patients, with 6576 undergoing CFxn and 3963 undergoing HFxn. Patients with T1 disease comprised a majority of each cohort. Use of HFxn increased significantly over the period studied (P<.001), but even in the final year, nearly one-half of patients continued to receive CFxn. Receipt of HFxn was also independently associated with higher income and facility types other than community cancer programs on logistic regression. On multivariate Cox regression, HFxn was associated with improved survival (hazard ratio [HR] for death, 0.90; 95% confidence interval [CI], 0.83-0.97; P=.008), a finding redemonstrated on univariate Cox regression among a well-matched cohort after propensity score matching (HR, 0.88; 95% CI, 0.80-0.96; P=.003). Subgroup Cox multivariate analysis demonstrated a significant survival advantage with HFxn among patients with T1 disease (HR, 0.90; 95% CI, 0.81-0.99; P=.042) but a nonsignificant benefit among those with Tis (HR, 0.86; 95% CI, 0.57-1.30; P=.472) or T2 (HR, 0.88; 95% CI, 0.76-1.02; P=.099) disease. CONCLUSIONS: Use of HFxn is increasing and is associated with improved survival over CFxn. Our findings support the broadened use of HFxn for patients with early-stage glottic cancer undergoing definitive radiation therapy.

A comprehensive comparative analysis of treatment modalities for sinonasal malignancies.

BACKGROUND: Sinonasal malignancies are a rare and heterogeneous group of tumors for which there is a paucity of robust data with which to guide management decisions. The authors used the National Cancer Data Base to better understand the presenting characteristics of these tumors and to compare outcomes by treatment modality. METHODS: The National Cancer Data Base was queried for sinonasal malignancies diagnosed between 2004 and 2012. Overall survival was assessed using multivariate analyses and propensity score matching. RESULTS: A total of 11,160 patients were identified for the initial analysis. The majority were male, aged 40 to 69 years, with tumors of the nasal cavity or maxillary sinus. Squamous cell histology was most common. The majority of patients presented with advanced tumor stage but without locoregional lymph node or distant metastases. Treatment modalities were compared for squamous cell carcinomas. In multivariate analysis, compared with surgery alone, patients who received adjuvant radiotherapy (hazard ratio [HR], 0.658 [P<.001]), adjuvant chemoradiotherapy (HR, 0.696 [P = .002]), or neoadjuvant therapy (HR, 0.656 [P = .007]) had improved overall survival. Patients who received radiotherapy alone (HR, 1.294 [P = .001]) or chemotherapy alone (HR, 1.834 [P<.001]) had worse outcomes. These findings were validated in propensity score matching. It is important to note that neoadjuvant chemoradiotherapy was associated with achieving a negative surgical margin (odds ratio, 2.641 [P = .045]). CONCLUSIONS: Surgery is the mainstay of therapy for patients with sinonasal malignancies, but multimodality therapy is associated with improved overall survival. Cancer 2017;123:3040-49. © 2017 American Cancer Society.

Metastatic nasopharyngeal carcinoma: Patterns of care and survival for patients receiving chemotherapy with and without local radiotherapy.

BACKGROUND AND PURPOSE: Radiotherapy (RT) to the primary nasopharyngeal tumor is frequently offered to patients with metastatic nasopharyngeal carcinoma (mNPC). However, only limited data exist to support RT in this setting. We used the National Cancer Database (NCDB) to evaluate outcomes for mNPC patients receiving chemotherapy with and without local RT. METHODS: The NCDB was queried for patients with mNPC with synchronous metastatic disease at diagnosis who received chemotherapy. Overall survival (OS) was analyzed using the Kaplan-Meier method, Cox proportional hazards models, and propensity score-matched analyses. RESULTS: From 2004 to 2013, 718 cases were identified (39% chemotherapy-alone, 61% chemotherapy+RT). At a median follow-up of 4.4years, RT was associated with improved survival on univariate analysis (median OS 21.4 vs 15.5months; 5-year OS 28% vs 10%; p<0.001) and multivariate analyses (HR, 0.61; CI, 0.51-0.74; p<0.001). Propensity score analysis with matched baseline characteristics demonstrated a similar OS advantage with RT (HR, 0.68; CI, 0.55-0.84; p<0.001). The benefits of RT remained consistent in models controlling for single vs multi-organ metastases and anatomic sites of metastatic involvement. RT dose was an independent prognostic factor as both a continuous and categorical variable, with OS benefits observed among patients receiving ≥50Gy. Long-term survival of >10years was only observed in the RT cohort. CONCLUSIONS: This analysis supports strategies incorporating local RT with chemotherapy for mNPC. Prospective trials evaluating RT integration for mNPC are warranted.

High-dose-rate brachytherapy of rhabdomyosarcoma limited to the external auditory canal.

PURPOSE: To report on the single-catheter high-dose-rate brachytherapy treatment of a 21-month-old girl child with an embryonal, botryoid-type, rhabdomyosarcoma limited to the external auditory canal (EAC). METHODS AND MATERIALS: A 2.4-mm diameter catheter was inserted into the right EAC and placed against the tympanic membrane. A computed tomography simulation scan was acquired. A brachytherapy treatment plan, in which 21 Gy in seven fractions was prescribed to a 1-mm depth along the distal 2 cm of the catheter, was generated. Treatments were delivered under anesthesia without complication. A dosimetric comparison between this plan and an intensity-modulated radiation therapy (IMRT) plan was then conducted. A clinical target volume (CTV), which encompassed a 1-mm margin along the distal 2 cm of the catheter, was delineated for both plans. Given positioning uncertainty under image guidance, a planning target volume (PTV = CTV + 3-mm margin) was defined for the IMRT plan. The IMRT plan was optimized for maximal CTV coverage but subsequently normalized to the same CTV volume receiving 100% of the prescription dose (V100) of the brachytherapy plan. RESULTS: The IMRT plan was normalized to the brachytherapy CTV V100 of 82.0%. The PTV V100 of this plan was 34.1%. The PTV exhibited dosimetric undercoverage within the middle ear and toward the external ear. Mean cochlea doses for the IMRT and brachytherapy plans were 26.7% and 10.5% of prescription, respectively. CONCLUSIONS: For rhabdomyosarcomas limited to the EAC, a standard brachytherapy catheter can deliver a highly conformal radiation plan that can spare the nearby cochlea from excess radiation.

Strategy of Using Intratreatment Hypoxia Imaging to Selectively and Safely Guide Radiation Dose De-escalation Concurrent With Chemotherapy for Locoregionally Advanced Human Papillomavirus-Related Oropharyngeal Carcinoma.

PURPOSE: To report a small substudy of an ongoing large, multi-arm study using functional imaging to assess pre-/intratreatment hypoxia for all head and neck cancer, in which we hypothesized that pre- and early-treatment hypoxia assessment using functional positron emission tomography (PET) imaging may help select which human papillomavirus (HPV)-positive (HPV(+)) oropharyngeal cancer (OPC) patients can safely receive radiation de-escalation without jeopardizing treatment outcomes. METHODS AND MATERIALS: Patients with HPV(+) oropharyngeal carcinoma were enrolled on an institutional review board-approved prospective study of which de-escalation based on imaging response was done for node(s) only. Pretreatment (18)F-fluorodeoxyglucose and dynamic (18)F-FMISO (fluoromisonidazole) positron emission tomography (PET) scans were performed. For patients with pretreatment hypoxia on(18)F-FMISO PET (defined as a >1.2 tumor to muscle standard uptake value ratio), a repeat scan was done 1 week after chemoradiation. Patients without pretreatment hypoxia or with resolution of hypoxia on repeat scan received a 10-Gy dose reduction to metastatic lymph node(s). The 2-year local, regional, distant metastasis-free, and overall survival rates were estimated using the Kaplan-Meier product-limit method. A subset of patients had biopsy of a hypoxic node done under image guidance. RESULTS: Thirty-three HPV(+) OPC patients were enrolled in this pilot study. One hundred percent showed pretreatment hypoxia (at primary site and/or node[s]), and among these, 48% resolved (at primary site and/or node[s]); 30% met criteria and received 10-Gy reduction to the lymph node(s). At the median follow-up of 32 months (range, 21-61 months), the 2-year locoregional control rate was 100%. One patient failed distantly with persistence of hypoxia on (18)F-FMISO PET. The 2-year distant metastasis-free rate was 97%. The 2-year OS rate was 100%. Hypoxia on imaging was confirmed pathologically. CONCLUSIONS: Hypoxia is present in HPV(+) tumors but resolves within 1 week of treatment in 48% of cases either at the primary site and/or lymph node(s). Our 100% locoregional control rate suggests that intratreatment functional imaging used to selectively de-escalate node(s) to 60 Gy was confirmed safe using our stringent imaging criteria. Intratreatment functional imaging warrants further study to determine its ultimate role in de-escalation treatment strategies.

Palliative head and neck radiotherapy with the RTOG 8502 regimen for incurable primary or metastatic cancers.

OBJECTIVES: To report on our institutional experience of palliative radiotherapy (RT) of cancers in the head and neck by the RTOG 8502 'QUAD SHOT' regimen. METHODS: Seventy-five patients completed at least 1 cycle of palliative RT to the head and neck for primary or metastatic disease based on the RTOG 8502 regimen (3.7 Gy twice daily over 2 consecutive days at 4 week intervals per cycle) between 2/2005 and 7/2014. RESULTS: Median patient age was 76 years (range 23-97). The most common histologies were squamous cell carcinoma (55%), non-anaplastic thyroid carcinoma (10%) and salivary gland carcinoma (9%). Thirty patients (40%) received prior RT at the palliative site. Twenty-eight patients (37%) completed at least three RTOG 8502 cycles. Sixty-five percent of all patients had a palliative response. Median overall survival was 5.67 months (range, 0.20-34.5). Grade 3 toxicity in 4 patients (5%) consisted of acute dermatitis and functional mucositis. Palliative response was significantly correlated with increasing number of RTOG 8502 cycles (p = 0.012), but not KPS, prior RT, palliative chemotherapy, prior surgery, histology or stage. On survival analysis, palliative response (p < 0.001), KPS ⩾ 70 (p = 0.001), and greater number of RTOG 8502 cycles (p = 0.022) remained independent predictors of improved survival. CONCLUSIONS: For patients with incurable malignant disease in the head and neck, the palliative RTOG 8502 'QUAD SHOT' regimen provides excellent rates of palliative response with minimal associated toxicity. Patients who are able to complete greater number of RT cycles have higher rates of palliative response and overall survival.

The Effect of Adjuvant Trastuzumab on Locoregional Recurrence of Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer Treated with Mastectomy.

BACKGROUND: Human epidermal growth factor receptor 2 (HER2) overexpression was associated with locoregional recurrence (LRR) in the preadjuvant trastuzumab era. This study aimed to examine the effect of trastuzumab on LRR in mastectomy patients and whether it varied with postmastectomy radiation (PMRT). METHODS: From the authors' institutional database, 501 women with stages I-III HER2-positive breast cancer who underwent mastectomy from 1998 to 2007 were identified. A landmark analysis was performed to compare two cohorts: 170 women who received trastuzumab and 281 who did not. Kaplan-Meier methods were used to estimate locoregional recurrence-free survival (LRRFS). A propensity score analysis was used to balance the treatment groups with respect to multiple covariates. Analogous methods were used to study the effect of PMRT. RESULTS: The women in the trastuzumab group were more likely to be node positive and to receive systemic therapy or PMRT (p < 0.01). The 5-year LRRFS was 98 % in the trastuzumab troup versus 94 % in the no trastuzumab group [hazard ratio (HR) 0.31; 95 % confidence interval (CI) 0.09-1.09; p = 0.07]. After adjustment for multiple covariates, including receipt of chemotherapy and PMRT, trastuzumab decreased LRR rates (HR 0.21; 95 % CI 0.04-0.94; p = 0.04). Among the women who received PMRT, trastuzumab reduced the 5-year LRR rate (0 vs 5 %; p = 0.06). Among those who did not receive PMRT, trastuzumab did not significantly decrease LRR (3 vs 6 %; p = 0.26). CONCLUSION: High rates of locoregional control (5-year rate, 98 %) were observed among patients who received trastuzumab and mastectomy ± PMRT. Trastuzumab decreased LRR in HER2-positive women who received mastectomy and PMRT, suggesting that the largest benefit is seen in a higher-risk subset of patients.

Metabolic tumor profiling with pH, oxygen, and glucose chemosensors on a quantum dot scaffold.

Acidity, hypoxia, and glucose levels characterize the tumor microenvironment rendering pH, pO2, and pGlucose, respectively, important indicators of tumor health. To this end, understanding how these parameters change can be a powerful tool for the development of novel and effective therapeutics. We have designed optical chemosensors that feature a quantum dot and an analyte-responsive dye. These noninvasive chemosensors permit pH, oxygen, and glucose to be monitored dynamically within the tumor microenvironment by using multiphoton imaging.

A Nanocrystal-based Ratiometric pH Sensor for Natural pH Ranges.

A ratiometric fluorescent pH sensor based on CdSe/CdZnS nanocrystal quantum dots (NCs) has been designed for biological pH ranges. The construct is formed from the conjugation of a pH dye (SNARF) to NCs coated with a poly(amido amine) (PAMAM) dendrimer. The sensor exhibits a well-resolved ratio response at pH values between 6 and 8 under linear or two-photon excitation, and in the presence of a 4% bovine serum albumin (BSA) solution.

Scaling rules for diffusive drug delivery in tumor and normal tissues.

Delivery of blood-borne molecules and nanoparticles from the vasculature to cells in the tissue differs dramatically between tumor and normal tissues due to differences in their vascular architectures. Here we show that two simple measures of vascular geometry--δ(max) and λ--readily obtained from vascular images, capture these differences and link vascular structure to delivery in both tissue types. The longest time needed to bring materials to their destination scales with the square of δ(max), the maximum distance in the tissue from the nearest blood vessel, whereas λ, a measure of the shape of the spaces between vessels, determines the rate of delivery for shorter times. Our results are useful for evaluating how new therapeutic agents that inhibit or stimulate vascular growth alter the functional efficiency of the vasculature and more broadly for analysis of diffusion in irregularly shaped domains.

Three-dimensional microscopy of the tumor microenvironment in vivo using optical frequency domain imaging.

Intravital multiphoton microscopy has provided powerful mechanistic insights into health and disease and has become a common instrument in the modern biological laboratory. The requisite high numerical aperture and exogenous contrast agents that enable multiphoton microscopy, however, limit the ability to investigate substantial tissue volumes or to probe dynamic changes repeatedly over prolonged periods. Here we introduce optical frequency domain imaging (OFDI) as an intravital microscopy that circumvents the technical limitations of multiphoton microscopy and, as a result, provides unprecedented access to previously unexplored, crucial aspects of tissue biology. Using unique OFDI-based approaches and entirely intrinsic mechanisms of contrast, we present rapid and repeated measurements of tumor angiogenesis, lymphangiogenesis, tissue viability and both vascular and cellular responses to therapy, thereby demonstrating the potential of OFDI to facilitate the exploration of physiological and pathological processes and the evaluation of treatment strategies.