PSMA PET Guided Salvage Radiotherapy Among Prostate Cancer Patients in the Post-Prostatectomy Setting: A Single Center Post-Hoc Analysis

PURPOSE/OBJECTIVE(S)

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) shows improved sensitivity and specificity for detection of locoregional and distant metastatic prostate cancer (PCa) compared to conventional imaging, especially at lower PSA levels as is often the case in the biochemically recurrent (BCR), post radical prostatectomy (RP) setting. Providers are now utilizing PSMA PET findings to guide their salvage radiotherapy (sRT) treatment fields and doses, although it is not well understood how PSMA PET guided sRT impacts patient outcomes.

MATERIALS/METHODS

This was a post-hoc analysis of 5 prospective studies of PSMA PET conducted at UCLA from 2016 to 2021 that included patients with recurrent PCa following RP. Patients were included in this retrospective study if they initiated sRT within 3 months of PSMA PET, had at least 12 months of follow up after sRT completion, had available sRT treatment details, and did not have distant metastases (DM) by conventional imaging on upfront staging. Patients treated with palliative RT were excluded. BCR following sRT was defined as an increase in PSA of 0.2 ng/ml above the post sRT nadir. Metastasis directed therapy (MDT) was defined as sRT to all PSMA+ N1 and M1 lesions. Baseline patient demographics, PSMA PET findings, sRT & ADT treatment details, and patient outcome data were collected.

RESULTS

A total of 176 patients were included in this study. Median time between RP and PSMA PET was 38 months (range 1-329). Median PSA at the time of the PSMA PET was 0.625 ng/mL (range 0.063-35). PSMA PET was positive in 128 patients (73%): 21 (12%) miT+N0M0, 55 (31%) miTxN1M0 and 52 (30%) miTxNxM1 with 19 (11%) miTxNxM1a, 31 (18%) miTxNxM1b, and 2 (1%) miTxNxM1c. Median number of lesions seen on positive PSMA scans was 1 (range 1-8). 39 (22%) patients were subsequently treated with sRT to the prostate bed (PB) only, 59 (34%) to PB + pelvic lymph nodes (PLNs), 33 (19%) to PLNs only, 7 (4%) to PB + PLNs + DM, 7 (4%) to PLNs + DM, and 31 (18%) to DM only. 59 (34%) patients were treated with concurrent ADT at a median duration of 6 months (range 1-39). At a median follow-up of 32 months (range 12-70) after sRT, 80 patients (45%) did not develop BCR or imaging relapse (IR) following sRT, 24 patients (14%) developed BCR but not IR, 1 patient (<1%) developed IR only, and 70 patients (40%) developed both BCR and IR. The median time to BCR and IR following sRT was 15 months (range 1-48) and 19 months (range 6-61), respectively. 1 year post sRT biochemical recurrence free survival was 77%. Of the 83 patients treated with MDT, 32 (39%) did not develop subsequent disease relapse.

CONCLUSION

This post hoc analysis assessed the outcomes of 176 patients treated with PSMA PET guided salvage RT, proving it to be an effective method for treating both pelvic and extrapelvic recurrent PCa. Further investigation is needed to assess the full extent of patient outcomes in this population.

Predictive Value of Genomic Classifier Scores and Transcriptomic Data for Prostate Cancer Distant Metastasis Risk: A Multicenter Retrospective Study

PURPOSE/OBJECTIVE(S)

Prostate-specific membrane antigen (PSMA) positron emission tomography (PET) has a greater specificity and sensitivity for detection of extraprostatic prostate cancer than conventional imaging. The Decipher genomic classifier is an established prognostic biomarker being evaluated for its ability to predict systemic treatment intensification. The relationship between Decipher scores and PSMA-based spread remains unknown, as do differences in transcriptomic patterns of PSMA PET-based spread in the de novo vs. recurrent setting.

MATERIALS/METHODS

We retrospectively identified patients who (a) had undergone staging with a PSMA PET prior to treatment or for evaluation of recurrence post-radical prostatectomy (RP) at two institutions and (b) had transcriptomic data available from the Genomics Resource for Intelligent Discovery (GRID) database from either biopsy or RP specimens. We classified the PSMA PET pattern of spread using molecular imaging (mi) staging as localized (miT+N0M0), node-positive (miN1M0), distant metastasis (miM1a-c), or negative/non-diagnostic. We used logistic regression to calculate the odds ratios (OR) with 95% confidence intervals (CI) for distant metastasis risk based on Decipher score both pre-treatment and post-RP. As an exploratory analysis, we compared each of the staging groups for differences in important transcriptomic signatures. Kruskal-Wallis and Pearson chi-squared tests were used for continuous and categorical variables, respectively.

RESULTS

A total of 315 patients were included in this analysis (n = 164 pre-treatment, n = 151 post-RP). Eighty PSMA PET scans were negative, while 147 were miT+N0M0, 45 were miN1M0, and 43 were miM1a-c. A higher Decipher score was associated with distant metastasis (miM1a-c) on PSMA PET both pre-treatment (OR 1.3 [95% CI: 1.0-1.7] per 0.1 increase in Decipher score, P = 0.05) and post-RP (OR 1.2 [1.0-1.4] per 0.1 increase in Decipher score, P = 0.04). There were higher TP53 mutation (P = 0.01) and cell cycle progression (P = 0.04) signature scores in miM1a-c patients compared to miN1M0 or miT+N0M0 patients. Basal subtype was more prevalent per PAM50 in miM1a-c or miN1M0 patients (36%) than miT+N0M0 patients (19%, P=0.01). Patients with de novo miN1M0 or miM1a disease (n = 19) had higher Decipher scores (0.85 vs 0.57, P = 0.10) and IFNa response (P = 0.08) than patients with recurrent miN1M0 or miM1a disease (n = 35).

CONCLUSION

Higher Decipher scores were associated with distant metastasis on PSMA PET in both the de novo and recurrent setting. Transcriptomic differences in pathways related to proliferation, p53 status, and PAM50 classification were seen when comparing localized, node-positive, and distant metastatic disease. Patients with de novo miN1M0 or miM1a disease may harbor more aggressive disease than those with miN1M0 or miM1a disease at recurrence.

First Measurement of Hard Exclusive π^{-}Δ^{++} Electroproduction Beam-Spin Asymmetries off the Proton

The polarized cross-section ratio σ_{LT^{'}}/σ_{0} from hard exclusive π^{-}Δ^{++} electroproduction off an unpolarized hydrogen target has been extracted based on beam-spin asymmetry measurements using a 10.2  GeV/10.6  GeV incident electron beam and the CLAS12 spectrometer at Jefferson Lab. The study, which provides the first observation of this channel in the deep-inelastic regime, focuses on very forward-pion kinematics in the valence regime, and photon virtualities ranging from 1.5  GeV^{2} up to 7  GeV^{2}. The reaction provides a novel access to the d-quark content of the nucleon and to p→Δ^{++} transition generalized parton distributions. A comparison to existing results for hard exclusive π^{+}n and π^{0}p electroproduction is provided, which shows a clear impact of the excitation mechanism, encoded in transition generalized parton distributions, on the asymmetry.

First Measurement of Λ Electroproduction off Nuclei in the Current and Target Fragmentation Regions

We report results of Λ hyperon production in semi-inclusive deep-inelastic scattering off deuterium, carbon, iron, and lead targets obtained with the CLAS detector and the Continuous Electron Beam Accelerator Facility 5.014 GeV electron beam. These results represent the first measurements of the Λ multiplicity ratio and transverse momentum broadening as a function of the energy fraction (z) in the current and target fragmentation regions. The multiplicity ratio exhibits a strong suppression at high z and an enhancement at low z. The measured transverse momentum broadening is an order of magnitude greater than that seen for light mesons. This indicates that the propagating entity interacts very strongly with the nuclear medium, which suggests that propagation of diquark configurations in the nuclear medium takes place at least part of the time, even at high z. The trends of these results are qualitatively described by the Giessen Boltzmann-Uehling-Uhlenbeck transport model, particularly for the multiplicity ratios. These observations will potentially open a new era of studies of the structure of the nucleon as well as of strange baryons.

Observation of Correlations between Spin and Transverse Momenta in Back-to-Back Dihadron Production at CLAS12

We report the first measurements of deep inelastic scattering spin-dependent azimuthal asymmetries in back-to-back dihadron electroproduction in the deep inelastic scattering process. In this reaction, two hadrons are produced in opposite hemispheres along the z axis in the virtual photon-target nucleon center-of-mass frame, with the first hadron produced in the current-fragmentation region and the second in the target-fragmentation region. The data were taken with longitudinally polarized electron beams of 10.2 and 10.6 GeV incident on an unpolarized liquid-hydrogen target using the CLAS12 spectrometer at Jefferson Lab. Observed nonzero sinΔϕ modulations in ep→e^{'}pπ^{+}X events, where Δϕ is the difference of the azimuthal angles of the proton and pion in the virtual photon and target nucleon center-of-mass frame, indicate that correlations between the spin and transverse momenta of hadrons produced in the target- and current-fragmentation regions may be significant. The measured beam-spin asymmetries provide a first access in dihadron production to a previously unexplored leading-twist spin- and transverse-momentum-dependent fracture function. The fracture functions describe the hadronization of the target remnant after the hard scattering of a virtual photon off a quark in the target particle and provide a new avenue for studying nucleonic structure and hadronization.

Observation of Azimuth-Dependent Suppression of Hadron Pairs in Electron Scattering off Nuclei

We present the first measurement of dihadron angular correlations in electron-nucleus scattering. The data were taken with the CLAS detector and a 5.0 GeV electron beam incident on deuterium, carbon, iron, and lead targets. Relative to deuterium, the nuclear yields of charged-pion pairs show a strong suppression for azimuthally opposite pairs, no suppression for azimuthally nearby pairs, and an enhancement of pairs with large invariant mass. These effects grow with increased nuclear size. The data are qualitatively described by the gibuu model, which suggests that hadrons form near the nuclear surface and undergo multiple scattering in nuclei.These results show that angular correlation studies can open a new way to elucidate how hadrons form and interact inside nuclei.

Improved Λp Elastic Scattering Cross Sections between 0.9 and 2.0 GeV/c as a Main Ingredient of the Neutron Star Equation of State

Strange matter is believed to exist in the cores of neutron stars based on simple kinematics. If this is true, then hyperon-nucleon interactions will play a significant part in the neutron star equation of state. Yet, compared to other elastic scattering processes, there is very little data on Λ-N scattering. This experiment utilized the CEBAF Large Acceptance Spectrometer (CLAS) detector to study the Λp→Λp elastic scattering cross section in the incident Λ momentum range 0.9-2.0  GeV/c. These are the first data on this reaction since the 1970s. The new cross sections have significantly better accuracy and precision than the existing world data, and the techniques developed here can also be used in future experiments.

First Measurement of Timelike Compton Scattering

We present the first measurement of the timelike Compton scattering process, γp→p^{'}γ^{*}(γ^{*}→e^{+}e^{-}), obtained with the CLAS12 detector at Jefferson Lab. The photon beam polarization and the decay lepton angular asymmetries are reported in the range of timelike photon virtualities 2.25<Q^{'2}<9  GeV^{2}, squared momentum transferred 0.1<-t<0.8  GeV^{2}, and average total center-of-mass energy squared s=14.5  GeV^{2}. The photon beam polarization asymmetry, similar to the beam-spin asymmetry in deep virtual Compton scattering, is sensitive to the imaginary part of the Compton form factors and provides a way to test the universality of the generalized parton distributions. The angular asymmetry of the decay leptons accesses the real part of the Compton form factors and thus the D-term in the parametrization of the generalized parton distributions.

Intraoral leukoplakia, abrasion, periodontal breakdown, and tooth loss in a snuff dipper

Dentists should be aware that snuff dipping or chewing is increasing in southern states and perhaps in other sections of the United States. These habits can lead to clinical leukoplakia, gingival recession, tooth abrasion, and periodontal bone destruction. The possibility also exists that a malignant transformation of leukoplakia can develop in persons who use snuff and other forms of tobacco.