Can Ki-67 predict radiotherapy response in neuroendocrine tumors? Retrospective analysis of a monocentric series of patients.

BACKGROUND: The impact of radiotherapy (RT) in neuroendocrine neoplasms is still unknown, and outcomes could be improved by a better insight in RT response predictors. This retrospective analysis investigates the potential correlation between Ki-67 and RT response to evaluate its role as biological marker of radiosensitivity. MATERIAL AND METHODS: Data from patients treated at an Italian NET-referral center between 2015 and 2020 were retrieved. Inclusion criteria included: histologically-proven diagnosis of NEN, Ki-67 status, indication (symptomatic and/or ablative) and at least one post-RT radiological assessment. RESULTS: Forty-two patients and 63 different treatment lines were included. Primary tumors presented Ki-67 values < 3% in 21% of cases, between 3 and 20% in 45% and >20% in the remaining 33%. Almost all patients were metastatic at the time of RT, which was performed with symptomatic purpose in 43% of cases. At a median time of three months, a complete response on the target lesion was observed in nine cases (14%), a partial response in 17 (27%), stability in 23 (37%) and local progression in 14 (22%). With median FU of 22.8 months, OS does not show statistically significant differences among three Ki-67 groups. Considering all lines of therapy, the relationship between ORR and Ki-67, did not show statistically significant differences, even following adjustments for drug types and delivered RT doses. CONCLUSION: No association between Ki67 and local tumor response to RT could be observed in the present cohort, regardless of whether the evaluation was performed on a categorical or continuous scale.

Comparison of Outcomes and Toxicity Between Extreme and Moderate Radiation Therapy Hypofractionation in Localized Prostate Cancer: A Propensity Score Analysis.

PURPOSE: To compare clinical outcomes and toxicities of 2 radiation therapy (RT) schemes for localized prostate cancer (PCa): extreme hypofractionation (EH; fractions of 6.5-7 Gy to a total dose of 32.5-35 Gy) and the moderate hypofractionation (MH; 26 fractions of 2.7 Gy to a total dose of 70.2 Gy). A propensity score method was used to compare the EH-RT and MH-RT groups. METHODS AND MATERIALS: Our analysis included a total of 421 patients divided in 2 groups: 227 treated with MH-RT and 194 treated with EH-RT (43 and 30 months median follow-up, respectively). Propensity matching created comparable cohorts. Statistical evaluations were performed on the whole cohort, stratifying the analyses by risk strata factors identified with the propensity scores, and on a subgroup of patients matched by propensity score. Multivariate proportional hazard Cox models were used to compare the 2 groups, mainly for gastrointestinal and genitourinary toxicity and secondarily for clinical progression-free survival, biochemical progression-free survival, and overall survival. RESULTS: Considering the whole population, acute genitourinary and gastrointestinal greater than grade 1 was significantly more frequent in the whole MH-RT group (P < .001 and P < .002, respectively). A borderline significantly greater late genitourinary was confirmed with the multivariate analysis (P = .07). Concerning tumor outcome, no statistically significant differences were observed. After propensity score matching, 226 patients were included in the analysis. The 2 obtained propensity score matched groups did not differ for any of the clinical and pathologic variables considered for the analysis, resulting in well-balanced cohorts. The results obtained on the whole population were confirmed in the matched groups. CONCLUSIONS: EH-RT yields a decreased risk of acute or late toxicities compared with MH-RT, and oncologic outcomes were comparable. Our data indicate that EH-RT might be considered as a treatment modality of choice for select patients with PCa.