Risk Factors for Symptomatic Radiation Pneumonitis after Stereotactic Body Radiotherapy (SBRT) for Early-Stage Lung Cancer

PURPOSE/OBJECTIVE(S)

To identify risk factors for symptomatic radiation pneumonitis (RP) after stereotactic body radiotherapy (SBRT) in patients with early-stage lung cancer.

MATERIALS/METHODS

We reviewed patients with clinical stage IA1-IIA non-small cell lung cancer treated by SBRT in our institution. The primary endpoint was grade ≥ 2 RP. To evaluate the relationship between clinical risk factors and grade ≥ 2 RP, the Gray test was used for univariate analysis and the Fine-Gray model for multivariate analysis. Dose parameters were univariate analyzed using the Fine-Gray model. Optimal thresholds for dose parameters were tested using receiver operating characteristic (ROC) curves.

RESULTS

Among a total of 244 patients analyzed. The median age of patients was 77 years. The median follow-up period was 48 months. The 4-year cumulative incidence of grade ≥ 2 RP was 15.3% for all patients. In univariate analysis, tumor size (p = 0.01), central tumor (p < 0.001), interstitial pneumonia (p = 0.002), biological effective dose (BED, α/β ratio of 10 Gy) (p = 0.017), lung volume (%) receiving at least 8 Gy (V8) (p = 0.012), V10 (p = 0.011), V20 (p = 0.022) and mean lung dose (MLD) (p = 0.014) were significantly associated with the risk of grade ≥ 2 RP. In multivariate analysis, central tumor (hazard ratio [HR], 3.77; 95% confidence interval [CI], 1.88-7.55; p < 0.001) and interstitial pneumonia (HR, 4.88; 95% CI, 1.77-13.43; p = 0.002) were significantly associated with the risk of grade ≥ 2 RP. ROC curve analysis showed that the optimal diagnostic thresholds for lung V8, V10, V20, and MLD were 19.5% (the area under the curve [AUC]-0.629), 16.7% (AUC-0.629), 7.9% (AUC-0.621), and 5.2 Gy (AUC-0.623). The incidence of RP2 was found to be significantly high for values higher than the ROC threshold. The 4-year cumulative incidence of grade ≥ 2 RP in the V10 ≤ 16.7% vs V10 > 16.7% groups were 10% vs. 27% (p = 0.0013).

CONCLUSION

Central tumor and interstitial pneumonia were significant risk factors for RP2 after SBRT. We recommend that lung V10 be kept below 16.7%.

Effects of Radiation Doses on Clinical Recurrence in Patients with Biochemically Recurrent Prostate Cancer after Prostatectomy

PURPOSE/OBJECTIVE(S)

Salvage radiotherapy (SRT) to the prostate bed is the only curative treatment for patients with biochemical recurrence (BCR) after radical prostatectomy (RP). Although several systematic reviews indicated that a dose escalation in the range of 60-70 Gy improved biochemical control, the effects of radiation doses on clinical relapse after SRT remain unclear. Our aim was to investigate the relationship between radiation doses and clinical relapse-free survival (cRFS) after SRT.

MATERIALS/METHODS

We identified 295 eligible patients receiving SRT for biochemically recurrent prostate cancer after RP between 2005 and 2018 at 15 institutions. Sixteen patients (5%) received short-term (< 6 months) androgen deprivation therapy (ADT) following RP and/or concurrently with SRT. SRT was delivered to the prostate and seminal vesicle bed using photon beams at a median (range) dose of 66 Gy (61-85) in 1.8-3.0 Gy fractions. The primary outcome was cRFS. Clinical relapse was identified on radiological imaging and/or biopsy and included local recurrence, lymph node metastasis, and distant metastasis. In all analyses, doses were recalculated as an equivalent dose in 2-Gy fractions (EQD2) with α/β = 1.5 Gy. Clinical RFS between the EQD2 ≥ 66 Gy (n = 229) and EQD2 < 66 Gy (n = 66) groups were compared using the Log-rank test, followed by univariate and multivariate Cox regression analyses and a subgroup analysis.

RESULTS

The median follow-up duration was 73 months. Among patients with BCR (n = 119), 79 of 96 (82%) in the EQD2 ≥ 66 Gy group and 21 of 23 (91%) in the EQD2 < 66 Gy group received second salvage ADT (p = 0.36). Among all patients (n = 295), clinical relapse was identified in 22 (7%) patients after SRT. Six-year biochemical relapse-free survival (bRFS), cRFS, cancer-specific survival (CSS), and overall survival (OS) rates were 58%, 93%, 98%, and 94%, respectively. Six-year cRFS rates were 94% (95% confidence interval [CI], 90-97) in the EQD2 ≥ 66 Gy group and 87% (95% CI, 75-93) in the EQD2 < 66 Gy group (p = 0.020). The multivariate analysis revealed that EQD2 < 66 Gy, Gleason score ≥ 8, seminal vesicle involvement, and PSA at BCR ≥ 0.5 ng/ml correlated with clinical relapse (p = 0.0016, 0.014, 0.011, and 0.027, respectively). The subgroup analysis showed the consistent benefit of EQD2 ≥ 66 Gy in patients across most subgroups including PSA at BCR after RP, extracapsular extension, and age at SRT.

CONCLUSION

This large multi-institutional observational study demonstrated that a higher SRT dose (EQD2 ≥ 66 Gy) resulted in superior cRFS. The present result supports the dose recommendations in the 2023 National Comprehensive Cancer Network guidelines (64-72 Gy) even in terms of clinical relapse. Prospective trial is warranted to investigate an upper threshold for optimal SRT dose.

Mode-locked laser oscillation with spectral peaks at molecular rovibrational transition lines

We demonstrate spectral peak formation in a mode-locked solid-state laser that contains a gas cell inside the cavity. Symmetric spectral peaks appear in the course of sequential spectral shaping through resonant interaction with molecular rovibrational transitions and nonlinear phase modulation in the gain medium. The spectral peak formation is explained as that narrowband molecular emissions triggered by an impulsive rovibrational excitation are superposed on the broadband spectrum of the soliton pulse by constructive interference. The demonstrated laser, which exhibits comb-like spectral peaks at molecular resonances, potentially provides novel tools for ultrasensitive molecular detection, vibration-mediated chemical reaction control, and infrared frequency standards.

Broadband background-free vibrational spectroscopy using a mode-locked Cr:ZnS laser

We demonstrate high-sensitivity vibrational absorption spectroscopy in the 2-micron wavelength range by using a mode-locked Cr:ZnS laser. Interferometric subtraction and multichannel detection across the broad laser spectrum realize simultaneous background-free detection of multiple vibrational modes over a spectral span of >380 cm^-1. Importantly, we achieve detection of small absorbance on the order of 10^-4, which is well below the detection limit of conventional absorption spectroscopy set by the detector dynamic range. The results indicate the promising potential of the background-free method for ultrasensitive and rapid detection of trace gases and chemicals.

Inherent intensity noise suppression in a mode-locked polycrystalline Cr:ZnS oscillator

We developed a diode-pumped, mode-locked polycrystalline Cr:ZnS oscillator using single-walled carbon nanotubes as a saturable absorber. The oscillator exhibits self-start mode-locking operation, generating sub-100 fs pulses with an average power of 300 mW. We found a unique feature in which the intensity noise originating from relaxation oscillation is suppressed by inherent second harmonic generation in polycrystalline Cr:ZnS. The observed noise suppression is reproduced by a theoretical model that includes an instantaneous nonlinear loss.

Direct electric-field reconstruction of few-cycle mid-infrared pulses in the nanojoule energy range

Amid the increasing potential of ultrafast mid-infrared (mid-IR) laser sources based on transition metal doped chalcogenides such as Cr:ZnS, Cr:ZnSe, and Fe:ZnSe lasers, there is a need for direct and sensitive characterization of mid-IR mode-locked laser pulses that work in the nanojoule energy range. We developed a two-dimensional spectral shearing interferometry (2DSI) setup to successfully demonstrate the direct electric-field reconstruction of Cr:ZnS mode-locked laser pulses with a central wavelength of 2.3 µm, temporal duration of 30.3 fs, and energies of 3 nJ. The reconstructed electric field is in reasonable agreement with an independently measured intensity autocorrelation trace, and the quantitative reliability of the 2DSI measurement is verified from a material dispersion evaluation. The presented implementation of 2DSI, including a choice of nonlinear crystal as well as the use of high-throughput dispersive elements and a high signal-to-noise ratio near-IR spectrometer, would benefit future development of ultrafast mid-IR lasers and their applications.

Evaluation of the hemostatic effect of a combination of hemostatic agents and fibrin glue in a rabbit venous hemorrhage model

BACKGROUND

In neurosurgery, it is important to use local hemostatic agents. We have explored a more powerful method of hemostasis by the combination of commercially available hemostatic agents with fibrin glue in the hopes of synergistic effects.

METHOD

A bleeding model was constructed by puncturing the rabbit posterior vena cava with a needle. After applying the sample to the bleeding point, compression was performed for 10 s. If temporary hemostasis was achieved after pressure release, a 30 s wash was performed to confirm that ultimate hemostasis was achieved. Up to three hemostasis attempts were performed on the same bleeding point until hemostasis was achieved, and the number of attempts required for hemostasis was counted. If hemostasis was not achieved after three attempts, it was counted as four times. Four groups were evaluated: (1) gelatin sponge alone, (2) gelatin sponge + fibrin glue, (3) oxidized cellulose alone, and (4) oxidized cellulose + fibrin glue; each group was tested 16 times.

RESULTS

The median value (range minimum value-maximum value) of the number of hemostatic attempts in Group 1 to Group 4 was 3 (1-4), 1 (1-1), 4 (4-4), and 4 (2-4). In Group 2, there were two test exclusions owing to deviations of the test procedure.

CONCLUSIONS

The compatibility of gelatin sponge and fibrin glue was very good, with a very strong and rapid hemostatic effect compared to other methods, showed its usefulness. This combination method may be effective for a variety of venous hemorrhages in neurosurgery.

Ultrafast saturable absorption of large-diameter single-walled carbon nanotubes for passive mode locking in the mid-infrared

We study the saturable absorption properties of single-walled carbon nanotubes (SWCNTs) with a large diameter of 2.2 nm and the corresponding exciton resonance at a wavelength of 2.4 µm. At resonant excitation, a large modulation depth of approximately 30 % and a small saturation fluence of a few tens of µJ/cm² are evaluated. The temporal response is characterized by an instantaneous rise and a subpicosecond recovery. We also utilize the SWCNTs to realize sub-50 fs, self-start mode locking in a Cr:ZnS laser, revealing that the film thickness is an important parameter that affects the possible pulse energy and duration. The results prove that semiconductor SWCNTs with tailored diameters exceeding 2 nm are useful for passive mode locking in the mid-infrared range.

Self-starting mode-locked Cr:ZnS laser using single-walled carbon nanotubes with resonant absorption at 2.4 μm

We develop a mode-locked Cr:ZnS polycrystalline laser using single-walled carbon nanotubes (SWCNTs) that have resonant absorption at the wavelength of 2.4 μm. The laser generates ultrashort pulses of 49 fs duration, a 2.4 μm center wavelength, and a 9.2 THz (176 nm) spectral span at a repetition rate of 76 MHz. We also confirm self-starting of the mode-locked operation. SWCNTs, if appropriately controlled in terms of their diameters, prove to be useful as ultrafast saturable absorbers in the mid-infrared region.

Effect of nerve growth factor on the transplacental induction of neurinomas by ethylnitrosourea in Sprague-Dawley rats

Administration of nerve growth factor (NGF) to the offspring of Sprague-Dawley rats transplacentally exposed to 50 mg/kg ethylnitrosourea on the 20th day of gestation resulted in a significant reduction of trigeminal and peripheral nerve neurinomas. Forty, 60, and 80 micrograms of NGF was administered in five s.c. doses, one dose on each of days 12-16, 90-94, and 210-214 postnatally. Of the 34 rats in the NGF-treated group, 11 animals were affected with trigeminal nerve neurinomas as compared to 18/34 in the NGF-untreated group (P less than 0.05). In the peripheral nerves (spinal cord nerve roots) there were five and 11 neurinomas, respectively, in each group of 34 rats. When the total numbers of neurinomas (trigeminal and peripheral nerves) between these groups were compared (16/34 versus 29/34), the significance of neurinoma reduction was P less than 0.01. Five trigeminal and two peripheral neurinomas in the NGF-untreated group were shown by immunohistochemical staining to contain nerve growth factor receptor protein, whereas none of the neurinomas in the NGF-treated group were positive for the receptor protein. The results obtained from this experiment lend support to the hypothesis that NGF has the capability to reduce the oncogenic consequences of ethylnitrosourea exposure perhaps by the process of maturation and/or differentiation of the transformed cells, and that this effect may depend upon the presence of receptor binding sites.