Timing of Ga68-PSMA PETCT and patterns of recurrence after prostate radiotherapy: Implications for potential salvage.

PURPOSE: To study patterns of recurrence in Ga68-PSMA PETCT at rising serum PSA after radical radiotherapy for non-metastatic prostate cancer. METHODS: Among patients with non-metastatic prostate cancer treated with radical external beam radiotherapy and androgen deprivation therapy, those who underwent Ga68-PSMA PETCT for rising PSA during follow up were analysed. Patterns of recurrence in Ga68-PSMA PETCT were studied. Extra-prostatic recurrences ≤5 were considered oligometastases. Local and oligometastatic recurrences were deemed suitable for focal salvage therapy. Probabilities of identifying recurrent lesion and potentially salvageable recurrences in Ga68-PSMA PETCT in relation to PSA were calculated. RESULTS: Total 114 patients were included (69% high-risk). Radiotherapy was hypofractionated in 57% (moderate 40%, extreme 17%), with median prostate EQD2 78.5 Gy. Median time from radiotherapy to Ga68-PSMA PETCT was 4.3 years (IQR 2.4-6.4), with median PSA 4.7 ng/mL (IQR 2.6-10.7) at scan. Uptake suggesting recurrence was observed in 91.2% patients, with positivity of 75%, 87%, 89%, and 100% at PSA thresholds ≤2, ≤5, ≤10, and >10 ng/mL respectively. Probability of detecting recurrence in Ga68-PSMA PETCT increased with higher PSA at scan (AUC = 0.82). Uptake was local in 20 (17.5%), oligometastatic in 39 (34.2%), and polymetastatic in 45 (39.5%) patients. Recurrence was potentially salvageable in 59/104 (56.7%) patients, being 67% at PSA ≤2 ng/mL but only 38% at PSA >10 ng/mL. Probability of recurrence being potentially salvageable declined with increasing PSA at scan (AUC = 0.68). CONCLUSION: Early Ga68-PSMA PETCT for rising PSA after definitive prostate radiotherapy detected majority of recurrent lesions and identified oligorecurrences amenable to focal salvage therapy.

Evaluation of effects of porcelain firing on the marginal fit changes of porcelain­ fused-to- metal crown fabricated utilizing two different margin designs and two commercially available base metal alloys

Aim: To find the marginal fit of the porcelain fused to metal crowns by two different margin designs (shoulder and chamfer) and two commercially available base metal alloys. Material and Methods: Tooth preparation of first central incisor for porcelain-fused-to-metal crown with shoulder margin and second incisor for porcelain-fused-to-metal crown with chamfer margin was done. Wax pattern of the same was prepared. Impression of both prepared ivorine incisors was made by light body impression material and poured with pattern resin. Both the patterns were invested and casted with cobalt chromium alloy for making master dies. Two wax patterns of unprepared central incisors were fabricated, one with shoulder margin and another with chamfer margin. These patterns were then cut back to the size of the coping. Four rings were invested. In each ring ten patterns, five with shoulder margin and five with deep chamfer margin were sprued together to ensure that each group would pass through the same investing and casting procedure, followed by ceramic firing and measurement. Results: Marginal fit change or marginal discrepancy (before and after firing) between the groups was highly significant. Conclusions: Veneered crowns exhibited highly significant marginal distortion than non- veneered copings after porcelain firing. Shoulder margin is better in minimizing marginal discrepancy compared to deep chamfer margin. Marginal discrepancy is less when cerabond base metal alloy is used with shoulder margin as compared to commend base metal alloy used for shoulder margin.