Quantum-mechanical effects in photoluminescence from thin crystalline gold films

Luminescence constitutes a unique source of insight into hot carrier processes in metals, including those in plasmonic nanostructures used for sensing and energy applications. However, being weak in nature, metal luminescence remains poorly understood, its microscopic origin strongly debated, and its potential for unraveling nanoscale carrier dynamics largely unexploited. Here, we reveal quantum-mechanical effects in the luminescence emanating from thin monocrystalline gold flakes. Specifically, we present experimental evidence, supported by first-principles simulations, to demonstrate its photoluminescence origin (i.e., radiative emission from electron/hole recombination) when exciting in the interband regime. Our model allows us to identify changes to the measured gold luminescence due to quantum-mechanical effects as the gold film thickness is reduced. Excitingly, such effects are observable in the luminescence signal from flakes up to 40 nm in thickness, associated with the out-of-plane discreteness of the electronic band structure near the Fermi level. We qualitatively reproduce the observations with first-principles modeling, thus establishing a unified description of luminescence in gold monocrystalline flakes and enabling its widespread application as a probe of carrier dynamics and light-matter interactions in this material. Our study paves the way for future explorations of hot carriers and charge-transfer dynamics in a multitude of material systems.

Generation of entangled waveguided photon pairs by free electrons

Entangled photons are a key resource in quantum technologies. While intense laser light propagating in nonlinear crystals is conventionally used to generate entangled photons, such schemes have low efficiency due to the weak nonlinear response of known materials and losses associated with in/out photon coupling. Here, we show how to generate entangled polariton pairs directly within optical waveguides using free electrons. The measured energy loss of undeflected electrons heralds the production of counter-propagating polariton pairs entangled in energy and emission direction. For illustration, we study the excitation of plasmon polaritons in metal strip waveguides that strongly enhance light-matter interactions, rendering two-plasmon generation dominant over single-plasmon excitation. We demonstrate that electron energy losses detected within optimal frequency ranges can reliably signal the generation of plasmon pairs entangled in energy and momentum. Our proposed scheme is directly applicable to other types of optical waveguides for in situ generation of entangled photon pairs.

Nonlinear Plasmonics in Nanostructured Phosphorene

Phosphorene has emerged as an atomically thin platform for optoelectronics and nanophotonics due to its excellent optical properties and the possibility of actively tuning light-matter interactions through electrical doping. While phosphorene is a two-dimensional semiconductor, plasmon resonances characterized by pronounced anisotropy and strong optical confinement are anticipated to emerge in highly doped samples. Here we show that the localized plasmons supported by phosphorene nanoribbons (PNRs) exhibit high tunability in relation to both edge termination and doping charge polarity and can trigger an intense nonlinear optical response at moderate doping levels. Our explorations are based on a second-principles theoretical framework, employing maximally localized Wannier functions constructed from ab initio electronic structure calculations, which we introduce here to describe the linear and nonlinear optical response of PNRs on mesoscopic length scales. Atomistic simulations reveal the high tunability of plasmons in doped PNRs at near-infrared frequencies, which can facilitate the synergy between the electronic band structure and plasmonic field confinement to drive efficient high-harmonic generation. Our findings establish nanostructured phosphorene as a versatile atomically thin material candidate for nonlinear plasmonics.

Nonlocal and cascaded effects in nonlinear graphene nanoplasmonics

The ability of plasmons to focus light on nanometer length scales opens a wide range of enticing applications in optics and photonics, among which the enhancement of nonlinear light-matter interactions for all-optical modulation and spectral diversification emerges as a prominent theme. However, the subwavelength plasmonic near-field enhancement in good plasmonic materials such as noble metals is hindered by large ohmic losses, while conventional phase-matching of fields in bulk nonlinear crystals is not suitable for realizing nonlinear optical phenomena on the nanoscale. In contrast, anharmonic electron motion of free charge carriers in highly-doped graphene, which supports long-lived, highly-confined, and actively-tunable plasmons, renders the carbon monolayer an excellent platform for both plasmonics and nonlinear optics. Here we theoretically explore the enhancement in nonlinear response that can be achieved by interfacing multiple graphene nanostructures in close proximity to trigger nonlocal effects associated with large gradients in the electromagnetic near field. Focusing on second- and third-harmonic generation, we introduce a semianalytical formalism to describe interacting graphene nanoribbons with independent width, location, and electrical doping, so as to realize configurations in which plasmonic resonances may simultaneously enhance both the fundamental optical excitation frequency and harmonic intermediary and/or output frequencies. Our findings reveal the importance of both passive and active tuning in the design of atomically-thin nanostructures for nonlinear optical applications, and in particular emphasize the role played by nonlocal effects in generating an even-ordered nonlinear response that may contribute to other nonlinear optical processes through a cascaded interaction. We anticipate that our findings can aid in the design of actively-tunable nonlinear plasmonic resonators and metasurfaces.

Optoelectronic Control of Atomic Bistability with Graphene

We explore the emergence and active control of optical bistability in a two-level atom near a graphene sheet. Our theory incorporates self-interaction of the optically driven atom and its coupling to electromagnetic vacuum modes, both of which are sensitive to the electrically tunable interband transition threshold in graphene. We show that electro-optical bistability and hysteresis can manifest in the intensity, spectrum, and quantum statistics of the light emitted by the atom, which undergoes critical slow-down to steady state. The optically driven atom-graphene interaction constitutes a platform for active control of driven atomic systems in coherent quantum control and atomic physics.

Nonlinear plasmonic response in atomically thin metal films

Nanoscale nonlinear optics is limited by the inherently weak nonlinear response of conventional materials and the small light-matter interaction volumes available in nanostructures. Plasmonic excitations can alleviate these limitations through subwavelength light focusing, boosting optical near fields that drive the nonlinear response, but also suffering from large inelastic losses that are further aggravated by fabrication imperfections. Here, we theoretically explore the enhanced nonlinear response arising from extremely confined plasmon polaritons in few-atom-thick crystalline noble metal films. Our results are based on quantum-mechanical simulations of the nonlinear optical response in atomically thin metal films that incorporate crucial electronic band structure features associated with vertical quantum confinement, electron spill-out, and surface states. We predict an overall enhancement in plasmon-mediated nonlinear optical phenomena with decreasing film thickness, underscoring the importance of surface and electronic structure in the response of ultrathin metal films.

Ultracompact electro-optic waveguide modulator based on a graphene-covered λ/1000 plasmonic nanogap

The extreme field confinement and electro-optic tunability of plasmons in graphene make it an ideal platform for compact waveguide modulators, with device footprints aggressively scaling orders of magnitude below the diffraction limit. The miniaturization of modulators based on graphene plasmon resonances is however inherently constrained by the plasmon wavelength, while their performance is bounded by material loss in graphene. In this report, we propose to overcome these limitations using a graphene-covered λ/1000 plasmonic nanogap waveguide that concentrates light on length scales more than an order of magnitude smaller than the graphene plasmon wavelength. The modulation mechanism relies on interference between the non-resonant background transmission and the transmission mediated by the gate-tunable nanogap mode, enabling modulation depths over 20 dB. Since the operation of the device does not rely on graphene plasmons, the switching behavior is robust against low graphene carrier mobility even under 1000 cm²/Vs, which is desirable for practical applications.

Giant enhancement of third-harmonic generation in graphene-metal heterostructures

Nonlinear nanophotonics leverages engineered nanostructures to funnel light into small volumes and intensify nonlinear optical processes with spectral and spatial control. Owing to its intrinsically large and electrically tunable nonlinear optical response, graphene is an especially promising nanomaterial for nonlinear optoelectronic applications. Here we report on exceptionally strong optical nonlinearities in graphene-insulator-metal heterostructures, which demonstrate an enhancement by three orders of magnitude in the third-harmonic signal compared with that of bare graphene. Furthermore, by increasing the graphene Fermi energy through an external gate voltage, we find that graphene plasmons mediate the optical nonlinearity and modify the third-harmonic signal. Our findings show that graphene-insulator-metal is a promising heterostructure for optically controlled and electrically tunable nano-optoelectronic components.

Anisotropic second-harmonic generation from monocrystalline gold flakes

Noble metals with well-defined crystallographic orientation constitute an appealing class of materials for controlling light-matter interactions on the nanoscale. Nonlinear optical processes, being particularly sensitive to anisotropy, are a natural and versatile probe of crystallinity in nano-optical devices. Here we study the nonlinear optical response of monocrystalline gold flakes, revealing a polarization dependence in second-harmonic generation from the {111} surface that is markedly absent in polycrystalline films. Our findings confirm that second-harmonic microscopy is a robust and non-destructive method for probing the crystallographic orientation of gold, and can serve as a guideline for enhancing nonlinear response in plasmonic systems.

On the applicability of quantum-optical concepts in strong-coupling nanophotonics

Rooted in quantum optics and benefiting from its well-established foundations, strong coupling in nanophotonics has experienced increasing popularity in recent years. With nanophotonics being an experiment-driven field, the absence of appropriate theoretical methods to describe ground-breaking advances has often emerged as an important issue. To address this problem, the temptation to directly transfer and extend concepts already available from quantum optics is strong, even if a rigorous justification is not always available. In this review we discuss situations where, in our view, this strategy has indeed overstepped its bounds. We focus on exciton-plasmon interactions, and particularly on the idea of calculating the number of excitons involved in the coupling. We analyse how, starting from an unfounded interpretation of the term N/V that appears in theoretical descriptions at different levels of complexity, one might be tempted to make independent assumptions for what the number N and the volume V are, and attempt to calculate them separately. Such an approach can lead to different, often contradictory results, depending on the initial assumptions (e.g. through different treatments of V as the-ambiguous in plasmonics-mode volume). We argue that the source of such contradictions is the question itself-How many excitons are coupled?, which disregards the true nature of the coupled components of the system, has no meaning and often not even any practical importance. If one is interested in validating the quantum nature of the system-which appears to be the motivation driving the pursuit of strong coupling with small N-one could instead focus on quantities such as the photon emission rate or the second-order correlation function. While many of the issues discussed here may appear straightforward to specialists, our target audience is predominantly newcomers to the field, either students or scientists specialised in different disciplines. We have thus tried to minimise the occurrence of proofs and overly-technical details, and instead provide a qualitative discussion of analyses that should be avoided, hoping to facilitate further growth of this promising area.

Nonlinear Interactions between Free Electrons and Nanographenes

Free electrons act as a source of highly confined, spectrally broad optical fields that are widely used to map photonic modes with nanometer/millielectronvolt space/energy resolution through currently available electron energy-loss and cathodoluminescence spectroscopies. These techniques are understood as probes of the linear optical response, while nonlinear dynamics has escaped observation with similar degree of spatial detail, despite the strong enhancement of the electron evanescent field with decreasing electron energy. Here, we show that the field accompanying low-energy electrons can trigger anharmonic response in strongly nonlinear materials. Specifically, through realistic quantum-mechanical simulations, we find that the interaction between ≲100 eV electrons and plasmons in graphene nanostructures gives rise to substantial optical nonlinearities that are discernible as saturation and spectral shifts in the plasmonic features revealed in the cathodoluminescence emission and electron energy-loss spectra. Our results support the use of low-energy electron-beam spectroscopies for the exploration of nonlinear optical processes in nanostructures.

Nonlinear Graphene Nanoplasmonics

Nonlinear optics is limited by the weak nonlinear response of available materials, a problem that is generally circumvented by relying on macroscopic structures in which light propagates over many optical cycles, thus giving rise to accumulated unity-order nonlinear effects. While this strategy cannot be extended to subwavelength optics, such as in nanophotonic structures, one can alternatively use localized optical resonances with high quality factors to increase light-matter interaction times, although this approach is limited by inelastic losses partly associated with the nonlinear response. Plasmons-the collective oscillations of electrons in conducting media-offer the means to concentrate light into nanometric volumes, well below the light-wavelength-scale limit imposed by diffraction, amplifying the electromagnetic fields upon which nonlinear optical phenomena depend. Due to their abundant supply of free electrons, noble metals are the traditional material platform for plasmonics and have thus dominated research in nanophotonics over the past several decades, despite exhibiting large ohmic losses and inherent difficulties to actively modulate plasmon resonances, which are primarily determined by size, composition, and morphology. Highly doped graphene has recently emerged as an appealing platform for plasmonics due to its unique optoelectronic properties, which give rise to relatively long-lived, highly confined, and actively tunable plasmon resonances that mainly appear in the infrared and terahertz frequency regimes. Efforts to extend graphene plasmonics to the near-infrared and visible ranges involve patterning of graphene into nanostructured elements, thus facilitating the optical excitation of localized resonances that can be blue-shifted through geometrical confinement while maintaining electrical tunability. Besides these appealing plasmonic attributes, the conical electronic dispersion relation of graphene renders its charge carrier motion in response to light intrinsically anharmonic, resulting in a comparatively intense nonlinear optical response. The combined synergy of extreme plasmonic field enhancement and large intrinsic optical nonlinearity are now motivating intensive research efforts in nonlinear graphene plasmonics, the recent progress of which we discuss in this Account. We start with a description of the appealing properties of plasmons in graphene nanostructures down to molecular sizes, followed by a discussion of the unprecedented level of intrinsic optical nonlinearity in graphene, its enhancement by resonant coupling to its highly confined plasmons to yield intense high harmonic generation and Kerr nonlinearities, the extraordinary thermo-optical capabilities of this material enabling large nonlinear optical switching down to the single-photon level, and its strong interaction with quantum emitters.

Single-Plasmon Thermo-Optical Switching in Graphene

While plasmons in noble metal nanostructures enable strong light-matter interactions on commensurate length scales, the overabundance of free electrons in these systems inhibits their tunability by weak external stimuli. Countering this limitation, the linear electronic dispersion in graphene endows the two-dimensional material with both an enhanced sensitivity to doping electron density, enabling active tunability of its highly confined plasmon resonances, and a very low electronic heat capacity that renders its thermo-optical response extraordinarily large. Here we show that these properties combined enables a substantial optical modulation in graphene nanostructures from the energy associated with just one of their supported plasmons. We base our analysis on realistic, complementary classical and quantum-mechanical simulations, which reveal that the energy of a single plasmon, absorbed in a small, moderately doped graphene nanoisland, can sufficiently modify its electronic temperature and chemical potential to produce unity-order modulation of the optical response within subpicosecond time scales, effectively shifting or damping the original plasmon absorption peak and thereby blockading subsequent excitation of a second plasmon. The proposed thermo-optical single-plasmon blockade consists in a viable ultralow power all-optical switching mechanism for doped graphene nanoislands, while their combination with quantum emitters could yield applications in biological sensing and quantum nano-optics.

Nonlinear Atom-Plasmon Interactions Enabled by Nanostructured Graphene

Electrically tunable graphene plasmons are anticipated to enable strong light-matter interactions with resonant quantum emitters. However, plasmon resonances in graphene are typically limited to infrared frequencies, below those of optical excitations in robust quantum light sources and many biologically interesting molecules. Here we propose to utilize near fields generated by the plasmon-assisted nonlinear optical response of nanostructured graphene to resonantly couple with proximal quantum emitters operating in the near infrared. We show that the nonlinear near field produced by a graphene nanodisk can strongly excite and coherently control quantum states in two- and three-level atomic systems when the third harmonic of its plasmon resonance is tuned to a particular electronic transition. In the present scheme, emitter and plasmon resonances are nondegenerate, circumventing strong enhancement of spontaneous emission. We envision potential applications for the proposed nonlinear plasmonic coupling scheme in sensing and temporal quantum control.

How To Identify Plasmons from the Optical Response of Nanostructures

A promising trend in plasmonics involves shrinking the size of plasmon-supporting structures down to a few nanometers, thus enabling control over light-matter interaction at extreme-subwavelength scales. In this limit, quantum mechanical effects, such as nonlocal screening and size quantization, strongly affect the plasmonic response, rendering it substantially different from classical predictions. For very small clusters and molecules, collective plasmonic modes are hard to distinguish from other excitations such as single-electron transitions. Using rigorous quantum mechanical computational techniques for a wide variety of physical systems, we describe how an optical resonance of a nanostructure can be classified as either plasmonic or nonplasmonic. More precisely, we define a universal metric for such classification, the generalized plasmonicity index (GPI), which can be straightforwardly implemented in any computational electronic-structure method or classical electromagnetic approach to discriminate plasmons from single-particle excitations and photonic modes. Using the GPI, we investigate the plasmonicity of optical resonances in a wide range of systems including: the emergence of plasmonic behavior in small jellium spheres as the size and the number of electrons increase; atomic-scale metallic clusters as a function of the number of atoms; and nanostructured graphene as a function of size and doping down to the molecular plasmons in polycyclic aromatic hydrocarbons. Our study provides a rigorous foundation for the further development of ultrasmall nanostructures based on molecular plasmonics.

Plasmon-assisted high-harmonic generation in graphene

High-harmonic generation in condensed-matter systems is both a source of fundamental insight into quantum electron motion and a promising candidate to realize compact ultraviolet and ultrafast light sources. While graphene is anticipated to efficiently generate high-order harmonics due to its anharmonic charge-carrier dispersion, experiments performed on extended samples using THz illumination have revealed only a weak effect. The situation is further complicated by the enormous electromagnetic field intensities required by this highly nonperturbative nonlinear optical phenomenon. Here we argue that the large light intensity required for high-harmonic generation to occur can be reached by exploiting localized plasmons in doped graphene nanostructures. We demonstrate through rigorous time-domain simulations that the synergistic combination of strong plasmonic near-field enhancement and a pronounced intrinsic nonlinearity result in efficient broadband high-harmonic generation within a single material. Our results support the strong potential of nanostructured graphene as a robust, electrically tunable platform for high-harmonic generation.

Nonlinear Plasmonic Sensing with Nanographene

Plasmons provide excellent sensitivity to detect analyte molecules through their strong interaction with the dielectric environment. Plasmonic sensors based on noble metals are, however, limited by the spectral broadening of these excitations. Here we identify a new mechanism that reveals the presence of individual molecules through the radical changes that they produce in the plasmons of graphene nanoislands. An elementary charge or a weak permanent dipole carried by the molecule are shown to be sufficient to trigger observable modifications in the linear absorption spectra and the nonlinear response of the nanoislands. In particular, a strong second-harmonic signal, forbidden by symmetry in the unexposed graphene nanostructure, emerges due to a redistribution of conduction electrons produced by interaction with the molecule. These results pave the way toward ultrasensitive nonlinear detection of dipolar molecules and molecular radicals that is made possible by the extraordinary optoelectronic properties of graphene.

Quantum Effects in the Nonlinear Response of Graphene Plasmons

The ability of graphene to support long-lived, electrically tunable plasmons that interact strongly with light, combined with its highly nonlinear optical response, has generated great expectations for application of the atomically thin material to nanophotonic devices. These expectations are mainly reinforced by classical analyses performed using the response derived from extended graphene, neglecting finite-size and nonlocal effects that become important when the carbon layer is structured on the nanometer scale in actual device designs. Here we show that finite-size effects produce large contributions that increase the nonlinear response of nanostructured graphene to significantly higher levels than those predicted by classical theories. We base our analysis on a quantum-mechanical description of graphene using tight-binding electronic states combined with the random-phase approximation. While classical and quantum descriptions agree well for the linear response when either the plasmon energy is below the Fermi energy or the size of the structure exceeds a few tens of nanometers, this is not always the case for the nonlinear response, and in particular, third-order Kerr-type nonlinearities are generally underestimated by the classical theory. Our results reveal the complex quantum nature of the optical response in nanostructured graphene, while further supporting the exceptional potential of this material for nonlinear nanophotonic devices.

Plasmonic control of nonlinear two-photon absorption in graphene nanocomposites

Nonlinear two-photon absorption in a quantum dot-graphene nanoflake nanocomposite system has been investigated. An external laser field is applied to the nanocomposite to simultaneously observe two-photon processes in the quantum dot and excite localized surface plasmons in the graphene nanodisk. This resonance condition can be achieved by tuning the plasmon resonance frequency in the graphene nanoflake via electrostatic gating. It is found that the strong local field of the graphene plasmons can enhance and control nonlinear optical processes in the quantum dot. Specifically, we show that the two-photon absorption coefficient in the quantum dot can be switched between single- and double-peaked spectra by modifying the graphene-quantum dot separation. Two-photon processes in the quantum dot can also be switched on or off by slightly changing the gate voltage applied to the graphene. Our findings indicate that this system can be used for nonlinear optical applications such as all-optical switching, biosensing and signal processing.

Switching in polaritonic-photonic crystal nanofibers doped with quantum dots

We have studied the acousto-optic effect in polaritonic nanofibers made by embedding a cylindrical polaritonic nanowire within a photonic crystal. Here the nanowire consists of either a phonon-polaritonic or an exciton-polaritonic material. The nanowire is doped with ensemble of noninteracting quantum dots. Quantum dots interact with the nanofiber via the exciton-polariton interaction. It is found that for the certain acoustic strain intensity the nanofiber has a localized-to-delocalized polariton transition similar to the metal-to-insulator transitions in doped semiconductors. It is also found that nanofiber has a transparent state due to the exciton-bound polariton coupling. The transparent state can be switched ON or OFF by the external acoustic strain intensity. These are very useful discoveries that can be used to fabricate new types of polaritonic nanoswitches and nanosensors.

Resonant Tunneling in Photonic Double Quantum Well Heterostructures

Here, we study the resonant photonic states of photonic double quantum well (PDQW) heterostructures composed of two different photonic crystals. The heterostructure is denoted as B/A/B/A/B, where photonic crystals A and B act as photonic wells and barriers, respectively. The resulting band structure causes photons to become confined within the wells, where they occupy discrete quantized states. We have obtained an expression for the transmission coefficient of the PDQW heterostructure using the transfer matrix method and have found that resonant states exist within the photonic wells. These resonant states occur in split pairs, due to a coupling between degenerate states shared by each of the photonic wells. It is observed that when the resonance energy lies at a bound photonic state and the two photonic quantum wells are far away from each other, resonant states appear in the transmission spectrum of the PDQW as single peaks. However, when the wells are brought closer together, coupling between bound photonic states causes an energy-splitting effect, and the transmitted states each have two peaks. Essentially, this means that the system can be switched between single and double transparent states. We have also observed that the total number of resonant states can be controlled by varying the width of the photonic wells, and the quality factor of transmitted peaks can be drastically improved by increasing the thickness of the outer photonic barriers. It is anticipated that the resonant states described here can be used to develop new types of photonic-switching devices, optical filters, and other optoelectronic devices.

Postoperative radiotherapy increases locoregional control of patients with stage IIIA non-small-cell lung cancer treated with induction chemotherapy followed by surgery

PURPOSE

To determine the effectiveness of postoperative radiotherapy (RT) in patients with Stage IIB and Stage IIIA non-small-cell lung cancer (NSCLC) treated with induction chemotherapy followed by surgery.

METHODS AND MATERIALS

We retrospectively reviewed the treatment records of 98 patients (58 men and 40 women; median age 61 years, range 31-91) with Stage IIB and Stage IIIA NSCLC who were treated with induction chemotherapy followed by surgery at our institution between January 1990 and December 2000. Patients were grouped by treatment (chemotherapy/surgery alone vs. chemotherapy/surgery/RT), by disease stage and nodal classification. The rates of local control (LC), disease-specific survival, disease-free survival, and overall survival (OS) were calculated using the Kaplan-Meier method.

RESULTS

Of the 98 patients, 40 had Stage IIB and 58 had Stage IIIA. The clinical disease stage and N stage were significantly greater in those patients who underwent RT than in those who did not; however, no statistically significant differences were identified in the additional characteristics between those receiving and not receiving RT within each stage or nodal group. The overall 5-year actuarial LC rate was 81% in the RT group and 54% in the chemotherapy/surgery-alone group (p = 0.07). Postoperative RT significantly improved the 5-year LC rate in patients with Stage IIIA disease (from 35% to 82%, p = 0.01). Postoperative RT did not significantly improve the 5-year OS rate (30% with RT vs. 49% without) for all patients or for patients with Stage IIIA disease. The disease-specific survival and disease-free survival rates did not differ between the treatment groups. Patients who responded to induction chemotherapy had a significantly greater 5-year OS rate (49%) than did those with stable or progressive disease (22%, p = 0.003).

CONCLUSION

Postoperative RT in patients with Stage IIIA NSCLC treated with induction chemotherapy followed by surgery significantly improved LC without improving OS. Significantly improved survival was observed in all patients who responded to induction chemotherapy compared with those with stable or progressive disease.

Biocompatible semiconductor optoelectronics

We investigate optoelectronic properties of integrated structures comprising semiconductor light-emitting materials for optical probes of microscopic biological systems. Compound semiconductors are nearly ideal light emitters for probing cells and other microorganisms because of their spectral match to the transparency wavelengths of biomolecules. Unfortunately, the chemical composition of these materials is incompatible with the biochemistry of cells and related biofluids. To overcome these limitations, we investigate functionalized semiconductor surfaces and structures to simultaneously enhance light emission and the flow of biological fluids in semiconductor microcavities. We have identified several important materials problems associated with the semiconductor/biosystem interface. One is the biofluid degradation of electroluminescence by ionic diffusion into compound semiconductors. Ions that diffuse into the active region of a semiconductor light emitter can create point defects that degrade the quantum efficiency of the radiative recombination process. In this paper we discuss ways of mitigating these problems using materials design and surface chemistry, and suggest future applications for these materials.

Randomized phase III study of chemoradiation with or without amifostine for patients with favorable performance status inoperable stage II-III non-small cell lung cancer: preliminary results

A prospective randomized study was conducted to determine whether amifostine (Ethyol) reduces the rate of severe esophagitis and hematologic and pulmonary toxicity associated with chemoradiation or improves control of non-small cell lung cancer (NSCLC). Sixty patients with inoperable stage II or III NSCLC were treated with concurrent chemoradiotherapy. Both groups received thoracic radiation therapy (TRT) with 1.2 Gy/fraction, 2 fraction per day, 5 days per week for a total dose 69.6 Gy. All patients received oral etoposide (VP-16), 50 mg Bid, 30 minutes before TRT beginning day 1 for 10 days, repeated on day 29, and cisplatin 50 mg/m(2) intravenously on days 1, 8, 29, and 36. Patients in the study group received amifostine, 500 mg intravenously, twice weekly before chemoradiation (arm 1); patients in the control group received chemoradiation without amifostine (arm 2). Patient and tumor characteristics were distributed equally in both groups. Of the 60 patients enrolled, 53 were evaluable (27 in arm 1, 26 in arm 2) with a median follow-up of 6 months. Median survival times were 26 months for arm 1 and 15 months for arm 2, not statistically significantly different. Morphine intake to reduce severe esophagitis was significantly lower in arm 1 (2 of 27, 7.4%) than arm 2 (8 of 26, 31%; P =.03). Acute pneumonitis was significantly lower in arm 1 (1 of 27, 3.7%) than in arm 2 (6 of 26, 23%; P =.037). Hypotension (20 mm Hg decrease from baseline blood pressure) was significantly more frequent in arm 1 (19 of 27, 70%) than arm 2 (1 of 26, 3.8%; P =.0001). Only 1 patient discontinued treatment because of hypotension. These preliminary results showed that amifostine significantly reduced acute severe esophagitis and pneumonitis. Further observation is required to assess long-term efficacy.

Long-term results with radiotherapy for Stage I-II follicular lymphomas

PURPOSE

To analyze the long-term results with radiotherapy (RT) for early-stage, low-grade follicular lymphomas.

METHODS AND MATERIALS

From 1960 to 1988, 80 patients with Stage I (n = 33) or II (n = 47), World Health Organization Grade 1 (n = 50) or 2 (n = 30) follicular lymphoma were treated with RT. The lymph nodes or spleen were involved in 97% of cases. The maximal tumor sizes ranged from 0.5 to 11.0 cm (median 2.0). The RT fields encompassed only the involved Ann Arbor nodal region (involved-field RT) in 9% of the patients. The fields also included 1-3 adjacent, grossly uninvolved nodal regions (regional RT) in 54% of patients but were smaller than mantle or whole abdominopelvic fields. Mantle or whole abdominopelvic fields encompassing up to 6 grossly uninvolved regions (extended-field RT) were used in the remaining 37% of patients. The total RT doses ranged from 26.2 to 50.0 Gy given in daily 1.0-3.0-Gy fractions.

RESULTS

The follow-up of the surviving patients ranged from 3.5 to 28.7 years (median 19.0). No recurrences were found >17.0 years after RT, with 13 patients free of disease at their last follow-up visit 17.6-25.0 years after treatment. In 58% of cases, death was not from follicular lymphoma. The 15-year local control rate was 100% for 44 lymphomas <3.0 cm treated with only 27.8-30.8 Gy (median 30.0 in 20 fractions). Progression-free survival was affected by the maximal tumor size at the start of RT (15-year rate 49% vs. 29% for lymphomas <3.0 cm vs. > or =3.0 cm, respectively, p = 0.04) and Ann Arbor stage (15-year rate 66% vs. 26% for Stages I and II, respectively, p = 0.006). Ann Arbor stage also affected the cause-specific survival (15-year rate 87% vs. 54% for Stages I and II, respectively, p = 0.01). No significant difference was found in overall survival between those treated with extended-field RT and those treated with involved-field RT or regional RT (15-year rate 49% and 40%, respectively, p = 0.51). The 15-year incidence rate of Grade 3 or greater late complications according to the Subjective, Objective, Management, and Analytical scale in patients treated with 26.2-30.8 Gy vs. 30.9-50.0 Gy was 0% and 6%, respectively.

CONCLUSIONS

RT can cure approximately one half of Stage I and one quarter of Stage II, World Health Organization Grade 1 or 2 follicular lymphomas. Follicular lymphomas <3.0 cm can be controlled locally with doses of 27.8-30.8 Gy, and there is a trend toward a higher incidence of late complications with doses of >30.8 Gy. Doses of 25-30 Gy delivered in 15-20 fractions should be examined prospectively in patients with follicular lymphomas of <3.0 cm.

Correlation between lung fibrosis and radiation therapy dose after concurrent radiation therapy and chemotherapy for limited small cell lung cancer

PURPOSE

To evaluate the relationship between physician-identified radiographic fibrosis, lung tissue physical density change, and radiation dose after concurrent radiation therapy and chemotherapy for limited small cell lung cancer.

MATERIALS AND METHODS

Fibrosis volumes of different severity levels were delineated on computed tomography (CT) images obtained at 1-year follow-up of 21 patients with complete response to concurrent radiation therapy and chemotherapy for limited small cell lung carcinoma. Delivered treatments were reconstructed with a three-dimensional treatment planning system and geometrically registered to the follow-up CT images. Tissue physical density change and radiation dose were computed for each voxel within each fibrosis volume and within normal lung. Patient responses were grouped per radiation and chemotherapy protocol.

RESULTS

A significant correlation was noted between fibrosis grade and tissue physical density change and fibrosis grade. For doses less than 30 Gy, the probability of observing fibrosis was less than 2% with conventional fractionation and less than 4% with accelerated fractionation. Physical lung density change also showed a threshold of 30-35 Gy. For doses of 30-55 Gy and cisplatin and etoposide (PE) chemotherapy, fibrosis probability was 2.0 times greater for accelerated fractionation compared with conventional fractionation (P < .005) and was correlated to increasing dose for both fractionation schedules.

CONCLUSION

Lung tissue physical density changes correlated well with fibrosis incidence, and both increased with increasing dose greater than a threshold of 30-35 Gy. With concurrent PE chemotherapy, fibrosis probability was twice as great with accelerated fractionation as with once-daily fractionation.

Comparison of two total body irradiation fractionation regimens with respect to acute and late pulmonary toxicity

BACKGROUND

Total body irradiation (TBI) is commonly used with autologous bone marrow transplantation (BMT) for treatment of hematologic malignancies. Pulmonary complications of TBI can cause long-term morbidity and mortality. The authors have compared the pulmonary toxicity and efficacy of two different TBI fractionation regimens in otherwise identical autologous BMT protocols.

METHODS

Between 1990 and 1997 patients younger than 60 years of age with low-grade lymphoma at high risk of treatment failure were enrolled on one of two sequential protocols for autologous BMT differing only in their TBI regimens. The preoperative chemotherapy regimens were identical and consisted of intravenous etoposide (1500 mg/m(2)) for 1 day, intravenous cyclophosphamide (60 mg/kg) for 2 days, and mesna (10 mg/kg). The TBI used in protocol A consisted of twice-daily fractions of 1.7 grays (Gy) for 3 days to a total of 10.2 Gy through lateral fields, with no lung shielding. In protocol B, the TBI consisted of 3 Gy once daily for 4 days to a total of 12 Gy through anteroposterior fields, with lung shielding (5 half-value layers) during the third dose. Fifty-eight patients were treated on protocol A and 24 on protocol B. The groups were equivalent with regard to age, performance status (PS) and gender. Lung function was assessed objectively by pulmonary function tests (PFTs) before and at intervals after TBI. The pulmonary function parameters assessed included forced vital capacity (FVC), forced expiratory volume in 1 second (FEV(1)), forced expiratory flow between 25% and 75% of vital capacity (FEF(25-75)), diffusing capacity for carbon monoxide (DL(CO)), and total lung capacity (TLC). Each patient's post-TBI PFTs were normalized to the corresponding pre-TBI values and analyzed using a random effects model. Clinical pulmonary function status was scored according to Radiation Therapy Oncology Group criteria for acute and late lung toxicity. All clinical pulmonary toxicities such as pneumonitis, pneumonia, and diffuse alveolar hemorrhage, whether specifically related to TBI or not, were scored. Toxicity was classified as either acute (i.e., occurring within 90 days of TBI) or late (i.e., occurring more than 90 days after TBI). The endpoints of analysis were overall survival (OS), freedom from progression, and chronic pulmonary toxicity. Survival, progression, and complication free survival were computed using the method of Kaplan and Meier.

RESULTS

Three-year actuarial OS rates were 66% and 67% for protocols A and B, respectively. Patients 50 years of age or older had a hazard ratio of death 3.5 times higher than younger patients. Freedom from progression was significantly different for the 2 TBI regimens (P < 0.001; log-rank test): 31% at 3 years in the protocol A group compared with 82% in protocol B group. Patients on protocol A had a rate of progression 4.7 times higher than patients on protocol B. The TBI protocols did not differ significantly in their effects on FVC, FEV(1), FEF(25-75), DL(CO), and TLC. Patients 45 years of age or older had lower average posttransplant values of FEV(1), FVC, and DL(CO) than younger patients. There was no significant difference in acute or late toxicity rates between patients on the two protocols. Seven of the 57 patients in the twice-daily TBI (protocol A) group had acute pulmonary events (Grade 3 or greater), compared with 6 of the 24 patients in the once-daily (protocol B) group (P = 0.19). The 3-year freedom from late complications rate was 80% in the protocol A group and 70% in the protocol B group (P = 0.45). Patients with a PS of 1 had a hazard ratio of late complications 3.2 times greater than patients with a PS of 0 (P < 0.001).

CONCLUSIONS

It is possible to intensify TBI from a total dose of 10.2 Gy delivered in 6 twice-daily fractions to 12 Gy delivered in 4 once-daily fractions without significantly increasing the risk of pulmonary toxicity. The increased dose may contribute to a decrease in the recurrence rate in these patients. (c) 2001 American Cancer Society.

Hematologic recovery after central lymphatic irradiation for patients with stage I-III follicular lymphoma

BACKGROUND

The authors previously reported that central lymphatic irradiation (CLI) can induce molecular remission in patients with Stage I-III follicular lymphoma, as measured by polymerase chain reaction analysis for t(14;18) (q32;q21). Hematologic toxicity has been considered a major consequence of CLI. This study was undertaken to analyze the patterns of hematologic recovery after CLI.

METHODS

Thirty-three patients with Stage I-III follicular lymphoma were treated with CLI between January 1993 and February 1998. CLI consisted of irradiation to mantle, upper two-thirds of abdomen, and pelvic fields. Each field was treated to 30.0-30.6 grays (Gy) at 1.5-1.8 Gy per fraction, with a boost to 36.0-39.6 Gy at the same rate to the sites of macroscopic disease. A break of approximately 4 weeks was given after treatment of each field. Twenty-four patients who were followed for a minimum of 1 year from the end of CLI form the basis of this analysis. Fourteen patients were male. Three patients had Stage I disease, 6 patients had Stage II disease, and 15 patients had Stage III disease. The International Prognostic Index (IPI) for malignant lymphoma was 0 for 5 patients, 1 for 13 patients, and 2 for 6 patients. The Eastern Cooperative Oncology Group performance status was 0 for 21 patients and 1 for 3 patients. The median values for their pretreatment characteristics were as follows: age, 60 years (range, 34-73 years); height, 173 cm (range, 155-193 cm); weight, 79 kg (range, 57-107 kg); body surface area (BSA), 1.95 m(2) (range, 1.61-2.31 m(2)); bone marrow cellularity, 27%(range, 2-75%), platelet count, 233,000/mm(3) (range, 139,000-339,000/mm(3)), white blood cell (WBC) counts, 6400/mm(3) (range, 4200-10,900/mm(3)); and hemoglobin, 14.5 mg/dL (range, 11.8 -16.6 mg/dL). The median duration of CLI was 159 days (range, 137-345 days). Ten patients had cardiovascular disease. The number of sites receiving a boost dose of > or = 36.0 Gy was 0 sites in 1 patient, 1 site in 6 patients, 2 sites in 11 patients, 3 sites in 5 patients, and 4 sites in 1 patient. The platelet, hemoglobin, and WBC counts were followed every 3 months after completion of CLI. These counts were normalized to the pretreatment counts for statistical analyses. Univariate and multivariate analyses were performed to investigate the correlations between patient factors and hematologic status at 1 year posttreatment. Pearson correlation analysis was used for the continuous factors (patient age, height, weight, BSA, bone marrow cellularity, and duration of CLI), and the Mann-Whitney test was used for categoric factors (IPI, gender, performance status, stage, number of sites receiving > or = 36.0 Gy, and presence or absence of cardiovascular disease).

RESULTS

There was continued recovery, essentially approaching the pretreatment levels, over 3 years for platelet, WBC, and hemoglobin counts. Factors that were associated significantly with normalized platelet counts at 1 year by univariate analyses were age (P = 0.015) and cardiovascular disease (P = 0.041). Age was the only significant factor by multivariate analyses, with older patients having lower platelet counts at 1 year posttreatment. No factors were found that were associated significantly with 1-year normalized WBC or hemoglobin levels by either univariate or multivariate analyses.

CONCLUSIONS

All three of the hematologic components (platelets, WBC, and hemoglobin) essentially recover after patients undergo CLI over a 3-year period. Older age was the only significant adverse factor that affected the platelet recovery, as detected by multivariate analysis. (c) 2001 American Cancer Society.

Treatment of unicentric and multicentric Castleman disease and the role of radiotherapy

BACKGROUND

Although surgery is considered standard therapy for unicentric Castleman disease, favorable responses to radiotherapy also have been documented. The authors undertook this study to analyze the clinical factors, treatment approaches, and outcomes of patients with unicentric or multicentric Castleman disease, and to report the outcomes of patients with unicentric Castleman disease treated with radiotherapy.

METHODS

The authors reviewed the medical records of 22 patients who had received a histologic diagnosis of Castleman disease at the University of Texas M. D. Anderson Cancer Center between 1988 and 1999. One patient with a concurrent histopathologic diagnosis of nonsecretory multiple myeloma was excluded from the study. In all patients, the diagnosis of Castleman disease was based on the results of lymph node biopsies. Disease was categorized as being either unicentric or multicentric and further subdivided into hyaline vascular, plasma cell, or mixed variant histologic types. Clinical variables and outcomes were analyzed according to treatment, which consisted of surgery, chemotherapy, or radiotherapy.

RESULTS

Records from 21 patients were analyzed: 12 had unicentric disease, and 9 had multicentric disease. The mean follow-up time for the entire series was 51 months (median, 40 months). Four patients with unicentric disease were treated with radiotherapy alone: 2 remain alive and symptom free, 2 died of causes unrelated to Castleman disease and had no evidence of disease at last follow-up. Eight patients with unicentric disease were treated with complete or partial surgical resection, and all are alive and asymptomatic. All nine patients with multicentric disease were treated with combination chemotherapy: five are alive with no evidence of disease, and four are alive with progressive disease.

CONCLUSIONS

Surgery results in excellent rates of cure in patients with unicentric Castleman disease; radiotherapy can also achieve clinical response and cure in selected patients. Multicentric Castleman disease is a more aggressive clinical entity and is most effectively treated with combination chemotherapy, whereas the role of radiotherapy in its treatment remains unclear.

Treatment of unicentric and multicentric Castleman disease and the role of radiotherapy

BACKGROUND

Although surgery is considered standard therapy for unicentric Castleman disease, favorable responses to radiotherapy also have been documented. The authors undertook this study to analyze the clinical factors, treatment approaches, and outcomes of patients with unicentric or multicentric Castleman disease, and to report the outcomes of patients with unicentric Castleman disease treated with radiotherapy.

METHODS

The authors reviewed the medical records of 22 patients who had received a histologic diagnosis of Castleman disease at the University of Texas M. D. Anderson Cancer Center between 1988 and 1999. One patient with a concurrent histopathologic diagnosis of nonsecretory multiple myeloma was excluded from the study. In all patients, the diagnosis of Castleman disease was based on the results of lymph node biopsies. Disease was categorized as being either unicentric or multicentric and further subdivided into hyaline vascular, plasma cell, or mixed variant histologic types. Clinical variables and outcomes were analyzed according to treatment, which consisted of surgery, chemotherapy, or radiotherapy.

RESULTS

Records from 21 patients were analyzed: 12 had unicentric disease, and 9 had multicentric disease. The mean follow-up time for the entire series was 51 months (median, 40 months). Four patients with unicentric disease were treated with radiotherapy alone: 2 remain alive and symptom free, 2 died of causes unrelated to Castleman disease and had no evidence of disease at last follow-up. Eight patients with unicentric disease were treated with complete or partial surgical resection, and all are alive and asymptomatic. All nine patients with multicentric disease were treated with combination chemotherapy: five are alive with no evidence of disease, and four are alive with progressive disease.

CONCLUSIONS

Surgery results in excellent rates of cure in patients with unicentric Castleman disease; radiotherapy can also achieve clinical response and cure in selected patients. Multicentric Castleman disease is a more aggressive clinical entity and is most effectively treated with combination chemotherapy, whereas the role of radiotherapy in its treatment remains unclear.

Biology-based combined-modality radiotherapy: workshop report

PURPOSE

The purpose of this workshop summary is to provide an overview of preclinical and clinical data on combined-modality radiotherapy.

METHODS AND MATERIALS

The 8th Annual Radiation Workshop at Round Top was held April 13-16, 2000 at the International Festival Institute (Round Top, TX).

RESULTS

Presentations by 30 speakers (from Germany, Netherlands, Australia, England, and France along with U.S. participants and M. D. Anderson Cancer Center faculty) formed the framework for discussions on the current status and future perspectives of biology-based combined-modality radiotherapy.

CONCLUSION

Cellular and molecular pathways available for radiation modification by chemical and biologic agents are numerous, providing new opportunities for translational research in radiation oncology and for more effective combined-modality treatment of cancer.

Mantle irradiation alone for pathologic stage I and II Hodgkin's disease: long-term follow-up and patterns of failure

PURPOSE

We performed a retrospective study to determine the long-term outcome, patterns of failure, and prognostic factors for patients with pathologic Stage I or II Hodgkin's disease (HD) who were treated with mantle irradiation alone.

METHODS AND MATERIALS

The medical records of 145 patients with pathologic Stage I or II supradiaphragmatic Hodgkin's disease treated with mantle irradiation alone between June 1967 and June 1991 were reviewed. Patterns of failure, overall survival (OS) rate, and progression-free survival (PFS) rate were determined. Univariate and multivariate analyses were performed to identify adverse prognostic factors for OS and PFS. The number of adverse prognostic factors per patient was counted, and a prognostic score was assigned to each patient. The log-rank test was used to compare the OS or PFS rates among patients with prognostic scores 0, 1, and 2.

RESULTS

The median patient age was 27 years (range 10-66), with almost even male to female distribution. Every patient had splenectomy and negative laparotomy (LAP). Fifty-one patients had Stage I disease (IA-49, IB-2) and 94 Stage II (IIA-89, IIB-5). The histologic subtypes were nodular sclerosing in 110, mixed cellularity in 28, lymphocyte predominance in 5, lymphocyte depleted in 1, and unclassified in 1. Twelve patients with Stage II disease had >/= 3 sites of nodal involvement. Fifty-four patients had a prognostic score of 0, 70 of 1, and 21 of 2. The median follow-up time for the 109 surviving patients was 146 months (range 25-381). The 10- and 20-year actuarial OS rates for the whole group were 87.6% and 65.3%, respectively. The corresponding actuarial PFS rates were 75.3% and 74.2%, respectively. Thirty-six patients (9 Stage I, 27 Stage II) had relapses in a total of 41 sites. Failures by histology were 29 patients with nodular sclerosing, 6 with mixed cellularity, and 1 with lymphocyte predominance. Failures by sites were: trans-diaphragmatic, 22 (para-aortic nodes, 15; as the only site of progression in 12; visceral, 7; as the only site of progression in 5); within radiation field, 8; marginal miss, 8 (as the only site of failure in 2); and unknown, 3. The majority of the failures occurred within 5 years of diagnosis. Long-term side effects of radiation included cardiac complications in 30 patients, with 10- and 20-year actuarial cardiac complication rates of 12.6% and 35.1%, respectively; secondary solid tumors in 14, with 10- and 20-year actuarial rates of 2.3% and 25.7%, respectively; leukemia in 4; non- Hodgkin's lymphoma in 4, with the 10- and 20-year actuarial rates for leukemia and non-Hodgkin's lymphoma of 4.0% and 13.9%; and hypothyroidism in 38. Four adverse prognostic factors were identified for PFS: age > or = 40 years, > or = 3 sites of involvement, male sex, and constitutional symptoms. The prognostic score correlated with patients' outcome as indicated by PFS and OS rates. Patients with a prognostic score of 0 did significantly better than those with a score of 1 or 2.

CONCLUSION

In this select group of patients with pathologic Stage I and II Hodgkin's disease treated with mantle irradiation alone, the OS and PFS rates at 10 and 20 years were comparable to those reported in the literature. The major pattern of disease progression was relapse below the diaphragm, therefore close surveillance of the abdomen is warranted. The prognostic score used in our series may predict the patient's outcome, and might be worth testing in a prospective trial. In our series, patients with a prognostic score of 0 had excellent long-term survival, indicating adequate treatment with mantle irradiation alone. Late complications of the treatment pose a significant threat for the patient's survival with long-term follow-up.

Radiation therapy after a partial response to CHOP chemotherapy for aggressive lymphomas

PURPOSE

To analyze the results with involved-field radiotherapy after aggressive lymphomas had decreased in size by 50-99% in response to cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP)-based chemotherapy.

METHODS AND MATERIALS

From 1988 through 1996, 294 previously untreated patients with Working Formulation intermediate-grade or large-cell immunoblastic lymphomas underwent CHOP-based chemotherapy on 2 consecutive protocols at the M. D. Anderson Cancer Center. Forty-four (15%) of these patients achieved, based on international working group guidelines, a partial (50-75%) response (n = 25), or unconfirmed complete (76-99%) response (n = 19) to a median of 6 cycles of chemotherapy. These patients were treated with salvage involved-field radiotherapy (n = 32) or chemotherapy (n = 12), e.g., MINE-ESHAP, without autologous stem-cell rescue (ASCR).

RESULTS

Median follow-up was 43 months. Partial responders experienced similar outcomes to unconfirmed complete responders. Local control (4-year rates: 86% vs. 53%, p = 0.009) and progression-free survival (4-year rates: 67% vs. 8%, p < 0.0001), but not overall survival (4-year rates: 70% vs. 50%, p = 0.067) were significantly better in those who received salvage radiotherapy, which was well tolerated.

CONCLUSION

Progression-free and overall survival in aggressive lymphoma patients who underwent salvage radiotherapy were similar to results reported for high-dose chemotherapy with ASCR. The role of salvage radiotherapy in partial and unconfirmed complete responders to CHOP chemotherapy justifies examination in a large, cooperative group trial.

Bulky disease is an adverse prognostic factor in patients treated with chemotherapy comprised of cyclophosphamide, doxorubicin, vincristine, and prednisone with or without radiotherapy for aggressive lymphoma

BACKGROUND

In the current study, the authors analyzed prognostic factors in patients with aggressive lymphoma treated with a chemotherapy regimen comprised of cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) with or without radiotherapy.

METHODS

Between September 1988 and December 1996, 294 patients with newly diagnosed, clinical Ann Arbor Stage I-IV, aggressive lymphoma were enrolled on 2 protocols at The University of Texas M. D. Anderson Cancer Center. Patients on these studies had a relatively favorable prognosis; 100% had M. D. Anderson tumor scores <or= 2 and 95%% had International Prognostic Indices (IPIs) <or= 2. Treatment was comprised of 5 +/- 1 (mean +/- the standard deviation) cycles of CHOP chemotherapy with or without involved-field radiotherapy to a total dose of 40.1 +/- 3.3 grays (mean +/- the standard deviation).

RESULTS

The median length of follow-up was 61 months. Three factors were found to retain independent prognostic significance on multivariate analysis in terms of progression-free survival: > 1 extranodal site of disease (P < 0.001), bulky disease (>or= 7 cm) (P = 0.005), and an at least 10% elevation in the serum lactate dehydrogenase (LDH) level (P = 0.007). Patient age > 60 years (P = 0.001), bulky disease (P = 0.016), and an at least 10% elevation in the serum LDH level (P = 0.040) also were found to be independent prognostic factors for overall survival.

CONCLUSIONS

The independent prognostic factors in the current study suggest that either the M. D. Anderson tumor score system or the IPI can be used to select which aggressive lymphoma patients are at high risk for disease recurrence based on their having more than two adverse factors and who consequently are candidates for more intensive frontline therapy. Involved-field radiotherapy should be considered in those patients with bulky lymphomas.

Clinical stage IEA-IIEA orbital lymphomas: outcomes in the era of modern staging and treatment

BACKGROUND AND PURPOSE

The present study examines outcomes in patients with primary orbital lymphomas who underwent complete staging.

MATERIALS AND METHODS

From 1978 to 1997, 21 adult patients at the M.D. Anderson Cancer Center had stage IEA-IIEA orbital non-Hodgkin's lymphomas based on staging that included computed tomography scans. Sixteen (76%) patients had working formulation low-grade lymphomas, and five (24%) had aggressive lymphomas. Fourteen of 16 (88%) patients with low-grade lymphomas were treated with radiotherapy alone, and four of five (80%) patients with aggressive lymphomas were treated using combination chemotherapy with or without radiotherapy. Total radiotherapy doses ranged from 30.0 to 40.0 Gy using daily 1.5-2.0 Gy fractions.

RESULTS

The median follow-up was 84 months. For the low-grade lymphomas, the 5-year local control, progression-free survival, and overall survival rates were 100, 100, and 92%, respectively. For the seven low-grade lymphomas treated with radiotherapy alone to 30.0 Gy in 20 fractions, the 5-year local control, progression-free, and overall survival rates were 100, 100, and 75%, respectively. The 5-year incidence of complications, which were typically mild, in eyes irradiated to 30 Gy in 20 fractions versus higher biologically effective doses were 25 and 38%, respectively (P = 0.62). Of the five patients with aggressive lymphomas, none of the four who underwent chemotherapy with or without radiotherapy relapsed (all four remain alive), whereas the one treated with radiotherapy alone for stage IEA disease experienced a distant relapse.

CONCLUSIONS

In patients with low-grade lymphomas, a good therapeutic ratio was obtained with low-dose radiotherapy alone. In patients with aggressive lymphomas, chemotherapy with or without radiotherapy resulted in excellent local control, progression-free survival, and overall survival; however, the statistical power was limited.

Subunit-subunit interactions in trimeric arginase. Generation of active monomers by mutation of a single amino acid

The structure of the trimeric, manganese metalloenzyme, rat liver arginase, has been previously determined at 2.1-A resolution (Kanyo, Z. F., Scolnick, L. R., Ash, D. E., and Christianson, D. W., (1996) Nature 383, 554-557). A key feature of this structure is a novel S-shaped oligomerization motif at the carboxyl terminus of the protein that mediates approximately 54% of the intermonomer contacts. Arg-308, located within this oligomerization motif, nucleates a series of intramonomer and intermonomer salt links. In contrast to the trimeric wild-type enzyme, the R308A, R308E, and R308K variants of arginase exist as monomeric species, as determined by gel filtration and analytical ultracentrifugation, indicating that mutation of Arg-308 shifts the equilibrium for trimer dissociation by at least a factor of 10(5). These monomeric arginase variants are catalytically active, with k(cat)/K(m) values that are 13-17% of the value for wild-type enzyme. The arginase variants are characterized by decreased temperature stability relative to the wild-type enzyme. Differential scanning calorimetry shows that the midpoint temperature for unfolding of the Arg-308 variants is in the range of 63.6-65.5 degrees C, while the corresponding value for the wild-type enzyme is 70 degrees C. The three-dimensional structure of the R308K variant has been determined at 3-A resolution. At the high protein concentrations utilized in the crystallizations, this variant exists as a trimer, but weakened salt link interactions are observed for Lys-308.

Radiation palliation of cervical cancer

Radiation is a useful modality for palliation of local-regional disease in patients with cervical cancer who require palliation because of distant metastases, extensive local-regional disease, medical consideration, or patient concerns. Two radiation schedules have been reported on for the treatment of advanced pelvic disease including cervical cancer. The large single-dose schedule consisted of 10-Gy fractions repeated at monthly intervals to a maximum of 30 Gy. This schedule has produced good palliative results with symptomatic improvement in approximately 50% of patients and objective response in 35%-80%. However, severe late toxicity was shown to be as high as 42% (actuarial). The second schedule tested by the Radiation Therapy Oncology Group consisted of 3.7-Gy fractions given twice a day for 2 days (14.8 Gy) repeated after 2-4 weeks for a maximum of 44.4 Gy. There were 284 patients accrued, and the subgroup of 61 cervical cancer patients is analyzed in this article. The subjective response (50%-100% complete response) and objective response (53%) were similar to those observed with the large single-fraction schedule. The late toxicity was significantly lower (7%-actuarial). For patients who may survive 6 months or longer, this second schedule is preferable.

Mechanistic and metabolic inferences from the binding of substrate analogues and products to arginase

Arginase is a binuclear Mn(2+) metalloenzyme that catalyzes the hydrolysis of L-arginine to L-ornithine and urea. X-ray crystal structures of arginase complexed to substrate analogues N(omega)-hydroxy-L-arginine and N(omega)-hydroxy-nor-L-arginine, as well as the products L-ornithine and urea, complete a set of structural "snapshots" along the reaction coordinate of arginase catalysis when interpreted along with the X-ray crystal structure of the arginase-transition-state analogue complex described in Kim et al. [Kim, N. N., Cox, J. D., Baggio, R. F., Emig, F. A., Mistry, S., Harper, S. L., Speicher, D. W., Morris, Jr., S. M., Ash, D. E., Traish, A. M., and Christianson, D. W. (2001) Biochemistry 40, 2678-2688]. Taken together, these structures render important insight on the structural determinants of tight binding inhibitors. Furthermore, we demonstrate for the first time the structural mechanistic link between arginase and NO synthase through their respective complexes with N(omega)-hydroxy-L-arginine. That N(omega)-hydroxy-L-arginine is a catalytic intermediate for NO synthase and an inhibitor of arginase reflects the reciprocal metabolic relationship between these two critical enzymes of L-arginine catabolism.

Probing erectile function: S-(2-boronoethyl)-L-cysteine binds to arginase as a transition state analogue and enhances smooth muscle relaxation in human penile corpus cavernosum

The boronic acid-based arginine analogue S-(2-boronoethyl)-L-cysteine (BEC) has been synthesized and assayed as a slow-binding competitive inhibitor of the binuclear manganese metalloenzyme arginase. Kinetic measurements indicate a K(I) value of 0.4-0.6 microM, which is in reasonable agreement with the dissociation constant of 2.22 microM measured by isothermal titration calorimetry. The X-ray crystal structure of the arginase-BEC complex has been determined at 2.3 A resolution from crystals perfectly twinned by hemihedry. The structure of the complex reveals that the boronic acid moiety undergoes nucleophilic attack by metal-bridging hydroxide ion to yield a tetrahedral boronate anion that bridges the binuclear manganese cluster, thereby mimicking the tetrahedral intermediate (and its flanking transition states) in the arginine hydrolysis reaction. Accordingly, the binding mode of BEC is consistent with the structure-based mechanism proposed for arginase as outlined in Cox et al. [Cox, J. D., Cama, E., Colleluori D. M., Pethe, S., Boucher, J. S., Mansuy, D., Ash, D. E., and Christianson, D. W. (2001) Biochemistry 40, 2689-2701.]. Since BEC does not inhibit nitric oxide synthase, BEC serves as a valuable reagent to probe the physiological relationship between arginase and nitric oxide (NO) synthase in regulating the NO-dependent smooth muscle relaxation in human penile corpus cavernosum tissue that is required for erection. Consequently, we demonstrate that arginase is present in human penile corpus cavernosum tissue, and that the arginase inhibitor BEC causes significant enhancement of NO-dependent smooth muscle relaxation in this tissue. Therefore, human penile arginase is a potential target for the treatment of sexual dysfunction in the male.

The significance of molecular response of follicular lymphoma to central lymphatic irradiation as measured by polymerase chain reaction for t(14;18)(q32;q21)

BACKGROUND

More than 80% of the patients with follicular lymphoma have a characteristic chromosomal translocation, t(14;18)(q32;q21), at the major breakpoint region (MBR) or minor cluster region (MCR) involving the bcl-2 oncogene. This study was undertaken to assess the significance of the molecular response rate measured by the polymerase chain reaction (PCR) evidence of translocation among patients with Stage I to III follicular lymphoma treated with central lymphatic irradiation (CLI).

METHODS AND MATERIALS

Thirty-three patients with Stage I-III follicular lymphoma were treated with CLI on a prospective protocol. Bone marrow and peripheral blood samples were obtained before CLI for PCR analysis of t(14;18)(q32; q21). PCR-positive patients were followed by PCR analysis at regular intervals during and after CLI, and the results were correlated with clinical outcome. The following pretreatment factors were also investigated for their relationship to relapse and molecular response: gender, age, lactate dehydrogenase (LDH) and beta-2 microglobulin (beta2M) levels, Ann Arbor stage, and International Prognostic Index (IPI) for malignant lymphoma.

RESULTS

The subjects were 19 men and 14 women, with a median age of 52 years (range 30-69), who started CLI between January 1993 and February 1998. Median follow-up was 44 months (range 12-67), and all but 2 patients were still alive at the last follow-up. Four patients were Stage IA, 8 were Stage IIA, 19 were Stage IIIA, and 2 were Stage IIIB. Two patients had abnormal LDH levels (> 618 U/dL) and 7 patients had abnormal beta2M levels (> 2 mg/dL). Nine patients had IPI = 0, 16 had IPI = 1, and 8 had IPI = 2. All patients achieved complete response (CR). Twelve patients have relapsed to date. The median overall time to relapse was 54 months. The actuarial proportion of patients free from relapse at 3 years was 87% (95% confidence interval [CI] 69-95%). A total of 287 PCR results were available, 64 from bone marrow and 223 from peripheral blood. Pretreatment PCR data were available for 27 patients, of whom 21 were positive and 3 were unambiguously negative (in blood and bone marrow for both MBR and MCR). For the 19 PCR positive patients for whom we had post-treatment results, there was a clear and steady decreasing trend toward loss of PCR positivity (49% positive for bone marrow and 32% positive for peripheral blood at 3 years). There was a clear trend for increasing PCR positivity with increasing IPI: 10% for IPI = 0, 31% for IPI = 1, and 63% for IPI = 2 at 3 years for blood. The same trend was also observed for bone marrow. The IPI was the only statistically significant predictor for relapse with a relapse-free survival of 91% at 3 years for IPI < 2 and 75% for IPI = 2 (p = 0.024, log-rank test).

CONCLUSION

Molecular response to CLI occurs gradually over years. High IPI is a negative predictor for molecular response and relapse-free survival.

Localized non-Hodgkin lymphoma involving the thyroid gland

BACKGROUND

The current study was undertaken to define the natural history and patterns of failure of localized non-Hodgkin lymphoma (NHL) involving the thyroid gland.

METHODS

A retrospective review of 51 patients with Ann Arbor Stage I or II NHL involving the thyroid gland was performed. The median age of the patients was 59 years. There were 33 females. There were 21 patients with Stage I disease and 30 patients with Stage II disease. The International Prognostic Index (IPI) was known for 43 patients (it was 0 in 16 patients and > or = 1 in 27 patients). Fifteen patients had mediastinal involvement. Four patients underwent thyroidectomy, 18 patients received radiation therapy, 5 patients received chemotherapy, and 24 patients received combined modality therapy (CMT) with chemotherapy and radiation therapy. Treatment modality, patient gender, IPI, disease stage, and mediastinal involvement were examined for significance with regard to overall survival (OS) and failure free survival (FFS).

RESULTS

The 5-year OS and FFS rates were 64% and 76%, respectively. The 5-year FFS rates by treatment regimen were 76% for radiation therapy, 50% for chemotherapy, and 91% for CMT (P = 0.15). IPI was found to be the only significant predictor of OS. The 5-year OS rates were 86% and 50%, respectively, for IPIs of 0 and > or = 1 (P = 0.02). None of the 5 variables were found to correlate significantly with FFS, although the 5-year FFS rates were 93% and 68%, respectively, for IPIs of 0 and > or = 1 (P = 0.08). Eleven patients failed treatment. Nine patients had a component of distant failure across the diaphragm.

CONCLUSIONS

The prognosis of patients with localized NHL involving the thyroid gland appears to be very good, especially when CMT is used. Distant recurrences appear to account for the majority of treatment failures. The IPI was found to be a significant prognostic factor for OS and a marginal one for FFS.

c-MYC induces mammary tumorigenesis by means of a preferred pathway involving spontaneous Kras2 mutations

Although the process of mammary tumorigenesis requires multiple genetic events, it is unclear to what extent carcinogenesis proceeds through preferred secondary pathways following a specific initiating oncogenic event. Similarly, the extent to which established mammary tumors remain dependent on individual mutations for maintenance of the transformed state is unknown. Here we use the tetracycline regulatory system to conditionally express the human c-MYC oncogene in the mammary epithelium of transgenic mice. MYC encodes a transcription factor implicated in multiple human cancers. In particular, amplification and overexpression of c-MYC in human breast cancers is associated with poor prognosis, although the genetic mechanisms by which c-MYC promotes tumor progression are poorly understood. We show that deregulated c-MYC expression in this inducible system results in the formation of invasive mammary adenocarcinomas, many of which fully regress following c-MYC deinduction. Approximately half of these tumors harbor spontaneous activating point mutations in the ras family of proto-oncogenes with a strong preference for Kras2 compared with Hras1. Nearly all tumors lacking activating ras mutations fully regressed following c-MYC deinduction, whereas tumors bearing ras mutations did not, suggesting that secondary mutations in ras contribute to tumor progression. These findings demonstrate that c-MYC-induced mammary tumorigenesis proceeds through a preferred secondary oncogenic pathway involving Kras2.

Dose-response analysis for radiotherapy delivered to patients with intermediate-grade and large-cell immunoblastic lymphomas that have completely responded to CHOP-based induction chemotherapy

PURPOSE

To test the hypothesis that prechemotherapy tumor size affects the dose of radiation that should be delivered to intermediate-grade and large-cell immunoblastic lymphomas that have completely responded to cyclophosphamide, doxorubicin, vincristine and prednisone (CHOP)-based induction chemotherapy.

METHODS AND MATERIALS

From September 1988 through December 1996, 294 patients with newly diagnosed, Stage I-IV, intermediate-grade or large-cell immunoblastic lymphomas were enrolled on 2 prospective protocols at the M. D. Anderson Cancer Center. Treatment consisted of CHOP-based chemotherapy with or without involved field radiotherapy. One hundred seventy-two patients, with 178 nodal sites and 87 nonbony, extranodal sites of disease achieved a complete response to 2-6 cycles of chemotherapy and underwent involved field radiotherapy. Total radiation doses ranged from 30.0 to 50.4 Gy (mean +/- standard deviation: 39.7 +/- 2.5 Gy) over 22-49 days using a daily fraction size of 1.3-2.3 Gy. Because various fraction sizes were delivered, the linear-quadratic model was used to convert total radiation doses to biologically equivalent doses given at 1.8 Gy per fraction (D1.8). An alpha/beta ratio of 10 Gy was used for the lymphomas, resulting in D1.8 ranging from 29.1 to 50.8 Gy. Regression tree analysis was performed on nodal sites of disease to determine which of the following factors were predictive of local control: age, tumor size, D1.8, total radiation dose, and duration of radiotherapy. Based on the results of the regression tree analysis, Kaplan-Meier analysis was used to determine the probability of local control per site as a function of tumor size and D1.8. Regression tree analysis was also performed on patients with nonbony disease who received D1.8 = 29.1-39.1 Gy to determine if small lymphomas could be locally controlled with relatively low doses of radiation. The log-rank test was used to compare local control curves.

RESULTS

The median length of follow-up among survivors was 63 months. Regression tree analysis of nodal sites identified 3 distinct groups: (a) lymphomas < or = 10 cm and D1.8 = 29.1-39.1 Gy; (b) lymphomas < or = 10 cm and D1.8 = 39.2-50.8 Gy; and (c) lymphomas > 10 cm. For nonbony lymphomas that measured < 3.5 cm, low doses of radiation resulted in excellent local control (5-year rates: 96% vs. 97% for D1.8 = 29.1-39.1 Gy vs. D1.8 = 39.2-50.8 Gy; p = 0.610). For 3.5-10.0 cm lymphomas, higher doses of radiation resulted in better local control (5-year rates: 40% versus 98% for D1.8 = 29.1-39.1 Gy versus D1.8 = 39.2-50.8 Gy, p < 0.0001). A narrow dose range (D1.8 = 39.2-40.7 Gy) was delivered to the 8 lymphomas measuring > 10 cm that completely responded to 6 cycles of chemotherapy, resulting in a 5-year local control rate of only 70%. There was no difference in local control for nodal versus nonbony, extranodal sites of disease.

CONCLUSION

D1.8 ranging from 29.1 to 39.1 Gy yielded excellent local control for nonbony lymphomas measuring < 3.5 cm that had completely responded to a median of 3 cycles of CHOP-based chemotherapy. D1.8 ranging from 39.2 to 50.8 Gy yielded excellent local control for nonbony lymphomas measuring 3.5-10.0 cm that completely responded to either 3 or 6 cycles of chemotherapy. For nonbony lymphomas measuring > 10 cm that completely responded to 6 cycles of chemotherapy, D1.8 ranging from 39.2 to 40.7 Gy yielded suboptimal local control, suggesting that higher doses of radiation are indicated.

Recursive partitioning analysis of 1999 Radiation Therapy Oncology Group (RTOG) patients with locally-advanced non-small-cell lung cancer (LA-NSCLC): identification of five groups with different survival

PURPOSE

Survival of patients with locally-advanced non-small-cell lung cancer (LA-NSCLC) is predicted by the stage of the disease and other characteristics. This analysis was undertaken to identify these characteristics in a large cooperative group patient population, as well as to define subgroups of the population with differing outcomes.

PATIENTS AND METHODS

Analysis included 1,999 patients treated in 9 RTOG trials between 1983 and 1994 with thoracic irradiation (RT) with (n = 355) or without chemotherapy (CT).

RESULTS

In univariate analysis, the following characteristics were significantly associated with an improved survival: use of CT, CT delivered without major deviation, abnormal pulmonary function tests, normal hemoglobin, protein, LDH and BUN, presence of dyspnea, hemoptysis, cough or hoarseness, uninvolved lymph nodes, T1 or T2 stage, no malignant pleural effusion (PE), weight loss of < 8%, Karnofsky performance status (KPS) of at least 90, adenocarcinoma histology, female gender, and age less than 70 years. Recursive partitioning analysis (RPA) was subsequently applied to identify 5 patient subgroups with significantly different median survival times (MST): Group I, KPS of > or = 90, who received chemotherapy (MST 16.2 months); Group II, KPS of > or = 90, who received no CT, but had no PE (MST 11.9 months); Group III, KPS < 90, younger than 70 years, with non-large cell histology (MST 9.6 months); Group IV, KPS > or = 90, but with PE, or KPS < 90, younger than 70 years, and with large cell histology, or older than 70 years, but without PE (MST 5.6-6.4 months); Group V, older than 70, with PE (MST 2.9 months).

CONCLUSION

Cisplatinum-based CT improves survival, for excellent prognosis of LA-NSCLC patients, over RT alone. The presence of a malignant pleural effusion is a major negative prognostic factor for survival. The identification of RPA prognostic groups among patients with LA-NSCLC provides prognostic information and may serve as a basis of stratification in future trials.

Structural influence of hydrophobic core residues on metal binding and specificity in carbonic anhydrase II

Aromatic residues in the hydrophobic core of human carbonic anhydrase II (CAII) influence metal ion binding in the active site. Residues F93, F95, and W97 are contained in a beta-strand that also contains two zinc ligands, H94 and H96. The aromatic amino acids contribute to the high zinc affinity and slow zinc dissociation rate constant of CAII [Hunt, J. A., and Fierke, C. A. (1997) J. Biol. Chem. 272, 20364-20372]. Substitution of these aromatic amino acids with smaller side chains enhances Cu(2+) affinity while decreasing Co(2+) and Zn(2+) affinity [Hunt, J. A., Mahiuddin, A., & Fierke, C. A. (1999) Biochemistry 38, 9054-9062]. Here, X-ray crystal structures of zinc-bound F93I/F95M/W97V and F93S/F95L/W97M CAIIs reveal the introduction of new cavities in the hydrophobic core, compensatory movements of surrounding side chains, and the incorporation of buried water molecules; nevertheless, the enzyme maintains tetrahedral zinc coordination geometry. However, a conformational change of direct metal ligand H94 as well as indirect (i.e., "second-shell") ligand Q92 accompanies metal release in both F93I/F95M/W97V and F93S/F95L/W97M CAIIs, thereby eliminating preorientation of the histidine ligands with tetrahedral geometry in the apoenzyme. Only one cobalt-bound variant, F93I/F95M/W97V CAII, maintains tetrahedral metal coordination geometry; F93S/F95L/W97M CAII binds Co(2+) with trigonal bipyramidal coordination geometry due to the addition of azide anion to the metal coordination polyhedron. The copper-bound variants exhibit either square pyramidal or trigonal bipyramidal metal coordination geometry due to the addition of a second solvent molecule to the metal coordination polyhedron. The key finding of this work is that aromatic core residues serve as anchors that help to preorient direct and second-shell ligands to optimize zinc binding geometry and destabilize alternative geometries. These geometrical constraints are likely a main determinant of the enhanced zinc/copper specificity of CAII as compared to small molecule chelators.