A prospective study on the early evaluation of response to androgen receptor-targeted agents with 11C-Choline, 68Ga-PSMA, and 18F-FACBC PET in metastatic castration-resistant prostate cancer: a single-center experience.

BACKGROUND: The early identification of responsive and resistant patients to androgen receptor-targeting agents (ARTA) in metastatic castration-resistant prostate cancer (mCRPC) is not completely possible with prostate-specific antigen (PSA) assessment and conventional imaging. Considering its ability to determine metabolic activity of lesions, positron emission tomography (PET) assessment might be a promising tool. PATIENTS AND METHODS: We carried out a monocentric prospective study in patients with mCRPC treated with ARTA to evaluate the role of different PET radiotracers: 49 patients were randomized to receive 11C-Choline, Fluorine 18 fluciclovine (anti-1-amino-3-18F-fluorocyclobutane-1-carboxylic acid - FACBC) (18F-FACBC), or Gallium-68-prostate-specific-membrane-antigen (68Ga-PSMA) PET, one scan before therapy and one 2 months later. The primary aim was to investigate the performance of three novel PET radiotracers for the early evaluation of response to ARTA in metastatic CRPC patients; the outcome evaluated was biochemical response (PSA reduction ≥50%). The secondary aim was to investigate the prognostic role of several semiquantitative PET parameters and their variations with the different radiotracers in terms of biochemical progression-free survival (bPFS) and overall survival (OS). The study was promoted by the Italian Department of Health (code RF-2016-02364809). RESULTS: Regarding the primary endpoint, at log-rank test a statistically significant correlation was found between metabolic tumor volume (MTV) (P = 0.018) and total lesion activity (TLA) (P = 0.025) percentage variation among the two scans with 68Ga-PSMA PET and biochemical response. As for the secondary endpoints, significant correlations with bPFS were found for 68Ga-PSMA total MTV and TLA at the first scan (P = 0.001 and P = 0.025, respectively), and MTV percentage variation (P = 0.031). For OS, statistically significant correlations were found for different 68Ga-PSMA and 18F-FACBC parameters and for major maximum standardized uptake value at the first 11C-Choline PET scan. CONCLUSIONS: Our study highlighted that 11C-Choline, 68Ga-PSMA, and 18F-FACBC semiquantitative PET parameters and their variations present a prognostic value in terms of OS and bPFS, and MTV and TLA variations with 68Ga-PSMA PET a correlation with biochemical response, which could help to assess the response to ARTA.

Use of 65Zn as a tracer for the assessment of purification in the 68Ga-DOTANOC synthesis.

In the last years (68)Ga has got into the focus of researchers and clinicians especially for radio-labeling of biomolecules; an important characteristic of this positron emitting isotope is its availability via the (68)Ge/(68)Ga generator system: the long-lived (68)Ge (t1/2=270.8 d) produces the short-lived (68)Ga (t1/2=67.63 min) which decays to stable (68)Zn. (68)Ge breakthrough compromises (68)Ga radionuclidic purity, while (68)Zn might affect the specific activity of the radiopharmaceutical. In this paper we investigated the weight of these impurities in (68)Ga-DOTANOC synthesis. (65)Zn (t1/2=244.26d; decay mode: EC 98.3%, ß(+) 1.7%) was used as a radiotracer of stable (68)Zn; samples of the purification columns, wastes and product were recovered and measured with a calibrated HPGe gamma-ray spectrometry system. The results showed that (68)Zn competes with (68)Ga in labeling DOTANOC with a (95±2)% labeling yield; they also proved the effectiveness of the STRATA X-C cationic post-processing of the generator eluate in lowering the amount of this impurity to less than 1%. Moreover this approach, along with the purification of the final product through a STRATA X cartridge, effectively removes (68)Ge breakthrough providing a (68)Ga-DOTANOC radionuclidic purity of (99.9999986±0.0000006)%, superior to 99.9% required by the Pharmacopoeia Monograph on (68)Ga Edotreotide injection.

Automation synthesis modules review.

The introduction of (68)Ga labelled tracers has changed the diagnostic approach to neuroendocrine tumours and the availability of a reliable, long-lived (68)Ge/(68)Ga generator has been at the bases of the development of (68)Ga radiopharmacy. The huge increase in clinical demand, the impact of regulatory issues and a careful radioprotection of the operators have boosted for extensive automation of the production process. The development of automated systems for (68)Ga radiochemistry, different engineering and software strategies and post-processing of the eluate were discussed along with impact of automation with regulations.

Effective production of 65Zn with a PET cyclotron.

Cyclotrons dedicated to the production of PET radiopharmaceuticals for clinical use can be a resource also for research in other fields of science. In the present study we assessed the feasibility of (65)Zn production via the (65)Cu(p,n)(65)Zn reaction using a 16.5 MeV GE-PETtrace biomedical cyclotron. The radioisotope (65)Zn (t(1/2)=244.26 zd; decay mode: EC 98.3%, ß(+) 1.7%) has a wide range of applications, especially in botany and agriculture; its long half life allows storage and delivery to research centers without a cyclotron on site. Natural copper foils (thickness: 100 µm; purity: >99.9%) were irradiated in a solid target station developed in our institution. The EXFOR and IAEA cross sections databases were carefully studied to optimize the irradiation setup in order to maximize the yield of the radionuclide of interest and minimize the production of isotopic impurities. We performed production runs at 20 µA for 30 min. Activity was measured using a calibrated HPGe gamma ray detector and an ionization chamber radionuclide activity meter. These measures showed the presence of two main contaminants: (63)Zn (t(1/2)=38.47 min) and (64)Cu (t(1/2)=12.7h); we produced (65)Zn with a saturation yield of (1.06 ± 0.07) GBq/µA (E(p)=12.65→10.48 MeV). The irradiated target was dissolved in 1 ml of 6N HNO(3) at the temperature of 90°C and then purified through anion exchange chromatography with BIO RAD AG 1×8 resin. The radionuclidic purity of the final solution of (65)Zn in HCl 0.005 N, expressed in activity, resulted superior to (99.921 ± 0.003) %.

[Prognostic factors and results of surgical treatment of pelvic recurrence of rectal cancer]. / Fattori prognostici e risultati del trattamento chirurgico delle recidive pelviche da cancro del retto.

From 1990 to 2003 have been admitted 105 patients with pelvic recurrence from rectal cancer. Fifty-nine patients have been selected and 25 patients underwent surgery. We evaluate the prognostic factors and the 3 years disease-free survival. The 60% of the patients after R0 resection and the 20% of the patients who underwent R1-R2 resection are alive. The evaluation of the prognostic factors allows early diagnosis of recurrence with a better long time survival.