The feasibility of prostate-specific membrane antigen positron emission tomography(PSMA PET/CT)-guided radiotherapy in oligometastatic prostate cancer patients.

BACKGROUND: To investigate the efficacy and toxicity of 68Ga-PSMA-HBED-CC (68Ga-PSMA) PET-CT-guided RT in the treatment of oligometastatic prostate cancer retrospectively. METHODS: A total of 23 prostate cancer patients with biochemical relapse, of which 13 were castration sensitive (CS) and 10 castration resistant (CR), were treated with intensity-modulated and image-guided RT (IMRT-IGRT) on ≤3 metastases detected by 68Ga PSMA PET-CT. Androgen deprivation therapy was continued in CR patients. RESULTS: A total of 38 metastases were treated. The involved sites were pelvic bone (n = 16), pelvic lymph nodes (n = 11), paraaortic lymph nodes (n = 6), ribs (n = 3) and vertebral body (n = 2). The median PSA prior to RT was 1.1 ng/mL (range 0.1-29.0 ng/mL). A median dose of 43.5 Gy (range 30-64 Gy) was delivered by IMRT-IGRT in 12-27 fractions. At a median follow-up of 7 months (range 2-17 months), 19 patients (83%) were in remission. Four patients (17%) developed distant recurrences. The actuarial 1-year LC, PFS and OS rates were 100, 51 (95% CI 8-83%) and 100%. Univariate analysis demonstrated a statistically significantly better PFS in CS patients as compared to CR patients (1-year PFS 67 vs. 0%, p < 0.01). One patient experienced grade 2 acute gastrointestinal toxicity. Grade 3 or more toxicity events were not observed. CONCLUSIONS: By providing optimal LC, low toxicity and a promising PFS in CS patients, the current retrospective study illustrated that 68Ga PSMA PET-CT-guided RT may be an attractive treatment strategy in patients with oligometastatic prostate cancer. Validation by randomized trials is eagerly awaited.

The impact of air pockets around the vaginal cylinder on vaginal vault brachytherapy.

OBJECTIVE: To evaluate the incidence, size and predisposing factors for air pockets around the vaginal cylinder and their dosimetric effect on the vaginal mucosa. METHODS: We investigated 174 patients with endometrial carcinoma treated with external radiotherapy (RT) and brachytherapy (BRT) (101 patients, 58%) or BRT alone (73 patients, 42%). The quantity, volume and dosimetric impact of the air pockets surrounding the vaginal cylinder were quantified. The proportions of patients with or without air pockets during application were stratified according to menopausal status, treatment modality and interval between surgery and RT. RESULTS: Air pockets around the vaginal cylinder were seen in 75 patients (43%), while 99 patients (57%) had no air pockets. Only 11 patients (6.3%) received less than the prescribed dose (average 93.9% of prescribed dose; range, 79.0-99.2%). Air pockets were significantly fewer in pre-menopausal patients or in patients treated with the combination of external RT and BRT than in post-menopausal patients or patients treated with BRT alone. A significant correlation existed between the mucosal displacement of the air gap and the ratio of the measured dose at the surface of the air gap and prescribed dose (Pearson r = -0.775; p < 0.001). CONCLUSION: Air pockets were still a frequent problem during vaginal vault BRT, especially in post-menopausal patients or in patients treated with BRT alone, which may potentially cause dose reductions at the vaginal mucosa. ADVANCES IN KNOWLEDGE: Air pockets around the vaginal cylinder remain a significant problem, which may potentially cause dose reduction in the target volume.

Simultaneous integrated boost to intraprostatic lesions using different energy levels of intensity-modulated radiotherapy and volumetric-arc therapy.

OBJECTIVE: This study compared the dosimetry of volumetric-arc therapy (VMAT) and intensity-modulated radiotherapy (IMRT) with a dynamic multileaf collimator using the Monte Carlo algorithm in the treatment of prostate cancer with and without simultaneous integrated boost (SIB) at different energy levels. METHODS: The data of 15 biopsy-proven prostate cancer patients were evaluated. The prescribed dose was 78 Gy to the planning target volume (PTV78) including the prostate and seminal vesicles and 86 Gy (PTV86) in 39 fractions to the intraprostatic lesion, which was delineated by MRI or MR-spectroscopy. RESULTS: PTV dose homogeneity was better for IMRT than VMAT at all energy levels for both PTV78 and PTV86. Lower rectum doses (V30-V50) were significantly higher with SIB compared with PTV78 plans in both IMRT and VMAT plans at all energy levels. The bladder doses at high dose level (V60-V80) were significantly higher in IMRT plans with SIB at all energy levels compared with PTV78 plans, but no significant difference was observed in VMAT plans. VMAT plans resulted in a significant decrease in the mean monitor units (MUs) for 6, 10, and 15 MV energy levels both in plans with and those without SIB. CONCLUSION: Dose escalation to intraprostatic lesions with 86 Gy is safe without causing serious increase in organs at risk (OARs) doses. VMAT is advantageous in sparing OARs and requiring less MU than IMRT. ADVANCES IN KNOWLEDGE: VMAT with SIB to intraprostatic lesion is a feasible method in treating prostate cancer. Additionally, no dosimetric advantage of higher energy is observed.