Robotic Stereotactic Radiotherapy for Intracranial Meningiomas-An Opportunity for Radiation Dose De-Escalation

OBJECTIVE

To evaluate the possibility of dose de-escalation, with consideration of the efficacy and safety of robotic stereotactic CyberKnife radiotherapy in patients diagnosed with intracranial meningiomas.

METHODS

The study group consisted of 172 patients (42 men and 130 women) treated in III Radiotherapy and Chemotherapy Clinic of Maria Sklodowska-Curie National Research Institute of Oncology in Gliwice between January 2011 and July 2018. The qualification for dose de-escalation was based on MRI (magnetic resonance imaging) features: largest tumor diameter less than 5 cm, well-defined tumor margins, no edema, and no brain infiltration. The age of patients was 21-79 years (median 59 years) at diagnosis and 24-80 years (median 62 years) at radiotherapy. Sixty-seven patients (Group A) were irradiated after initial surgery. Histopathological findings were meningioma grade WHO 1 in 51 and WHO 2 in 16 cases. Group B (105 patients) had no prior surgery and the diagnosis was based on the typical features of meningioma on MRI. All patients qualified for the robotic stereotactic CyberKnife radiotherapy, and the total dose received was 18 Gy in three fractions to reference isodose 78-92%.

RESULTS

Follow-up period was 18 to 124 months (median 67.5 months). Five- and eight-year progression free survival was 90.3% and 89.4%, respectively. Two patients died during the follow-up period. Progression of tumor after radiotherapy was registered in 16 cases. Four patients required surgery due to progressive disease, and three of them were progression free during further follow-up. Twelve patients received a second course of robotic radiotherapy, 11 of them had stable disease, and one patient showed further tumor growth but died of heart failure. Crude progression free survival after both primary and secondary treatment was 98.8%. Radiotherapy was well-tolerated: acute toxicity grade 1/2 (EORTC-RTOG scale) was seen in 10.5% of patients. We did not observe any late effects of radiotherapy.

CONCLUSION

Stereotactic CyberKnife radiotherapy with total dose of 18 Gy delivered in three fractions showed comparable efficacy to treatment schedules with higher doses. This could support the idea of dose de-escalation in the treatment of intracranial meningiomas.

Thyroid remnant ablation with radioiodine activity of 30, 60, and 100 mCi in patients with differentiated thyroid cancer - a prospective comparison of long-term outcomes

INTRODUCTION

The aim of this prospective study was to evaluate long-term outcomes in differentiated thyroid cancer (DTC) patients postoperatively treated with distinct RAI activities of 30 mCi, 60 mCi, and 100 mCi.

MATERIAL AND METHODS

The analysis involved 277 low-risk and 46 intermediate-risk patients, who underwent radioiodine (RAI) ablation with 30 mCi, 60 mCi or 100 mCi under prospective, randomized clinical trials. Seventy-eight patients from the low-risk group received 30 mCi, whereas 125 and 74 patients received 60 mCi and 100 mCi, respectively. Regarding the intermediate-risk group, 20 patients were given 60 mCi, and 26 subjects were given 100 mCi. The mean time of follow-up was 11 years.

RESULTS

An excellent treatment response was obtained in 88%, 89% and 90% of low-risk patients treated with 30 mCi, 60 mCi, and 100 mCi, respectively, and in 85% of intermediate-risk patients, who were administered 60 or 100 mCi. An indeterminate response was achieved in 9.4% and 6.5%, whereas an incomplete structural response was obtained in 1.4% and 6.5% of low-risk and intermediate-risk patients, respectively. An incomplete biochemical response was observed only in 2.2% of intermediate-risk patients. The differences in treatment response regarding RAI activity were not significant.

CONCLUSIONS

RAI activity of 30 mCi demonstrates a comparable efficacy as 60 mCi and 100 mCi in low-risk DTC. RAI activity of 60 mCi seems to be effective in intermediate-risk DTC.

Abstract PS15-09: Adverse events in breast cancer patients treated with concurrent or sequential radiation therapy and CDK 4/6 inhibitors in metastatic setting

Background. Radiation therapy (RT) is important modality in MBC patients, however, there is paucity of data on safety and feasibility in combining radiation and a cyclin-dependent kinase 4 and 6 inhibitors (CDK 4/6i). No sufficient data were gathered in clinical trials and a few small retrospective series were published; it is important to extend these data. Theoretically, concerns pertain both the augmentation of effect (toxicity) or decrease of treatment effectiveness. Methods. 116 patients with MBC were treated in our center with CDK 4/6i (ribociclib n=59, palbociclib n=57) between 2018-2020. 26 patients were also treated with RT and were included into further analysis. 10 patients were treated with concurrent RT and 16 patients with sequential RT. Median age of patients was 55 years (range 23-78). 11 patients (42%) were diagnosed with de novo MBC, whereas 15 patients (57%) with recurrent breast cancer. 16 patients received prior chemotherapy, 6 of them less than 1 year before CDK 4/6i treatment. 73% of patients received CDK 4/6i in first line setting. Bones were the main metastatic site in the majority of patients, whereas visceral metastasis were diagnosed in 9 patients (35%). Overall 32 RT treatments in 26 patients were performed. Various RT regimens were used, including 8 Gy in 1 fraction (n=10), 20 Gy in 5 fractions (n=9), 30 Gy in 10 fractions (n=3). SBRT was performed in 5 patients and chest wall irradiation in 3 patients. The majority of patients received palliative radiotherapy to the bones, including 6 patients (23%) with RT to the pelvic area. Results. Nineteen patients (73%) experienced G2 and G3 neutropenia, with no G4 case. Neutropenia G≥2 occurred during first cycle of CDK 4/6i treatment in 50% of patients (n=8) after sequential RT and signicantly more often in patients after concurrent RT (all treated, n=10; p= 0.0095). No neutropenia was observed in 7 patients after sequential RT (27%). 4 patients (15%) had CDK 4/6i dose reduction, including 1 patient treated with concurrent RT and 3 patients treated with sequential RT. In all 4 patients the cause of dose reduction was prolonged G3 neutropenia. Patients were treated as follows: 60yo patient received RT 8 Gy in 1 fraction for bone metastases in lumbar and thoracic spine and ribs; 31yo patient received RT 20 Gy in 5 fractions for central nervous system, then 20 Gy in 5 fractions for bone metastases in thoracic, lumbar and sacral spine (all of these treatments were performed during 4 weeks before CDK 4/6i first dose). The following two patients received additionally doxorubicin-based chemotherapy shortly before CDK 4/6i treatment. At median follow up of 17 months (range 9-20 months) none of these patients discontinued treatment because of toxicity: one patient continue ribociclib at first dose reduction level, two patients continue ribociclib at second dose reduction level and one patient continued ribociclib treatment for 11 consecutive months and then CDK 4/6i treatment was ended because of disease progression. There was no difference in neutropenia rate in patients treated previously with chemotherapy (n=16) and chemo-naïve patients (n=10; p=0.6680). No cases of acute radiation-induced enterocolitis or enhanced dermatologic toxicity were found. No other serious adverse events were observed. Conclusions. We found that concurrent RT leads to more frequent neutropenia than sequential RT, although it did not change treatment course in the majority of patients and appeared well-tolerated. Potential risk factors for radiation-induced CDK4/6i dose reduction might be extensive radiation fields and previous chemotherapy in metastatic setting. Until now, combined RT is not a part of adjuvant CDK 4/6i clinical trials protocols. Excellent tolerance of this combination supports future consideration of this scenario in clinical trial setting.

Citation Format: Marcin Kubeczko, Agnieszka Badora-Rybicka, Anna Polakiewicz-Gilowska, Aleksandra Leśniak, Katarzyna Świderska, Marta Mianowska-Malec, Barbara Grandys, Barbara Łanoszka, Magdalena Stankiewicz, Marzena Gawkowska, Elżbieta Nowicka, Grzegorz Woźniak, Dorota Gabryś, Rafał Tarnawski, Leszek Miszczyk, Michał Jarząb. Adverse events in breast cancer patients treated with concurrent or sequential radiation therapy and CDK 4/6 inhibitors in metastatic setting [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS15-09.