ESTRO 2024 - Abstract Book

S5340

Radiobiology - Tumour biology

ESTRO 2024

From 2015-2022, 64 prostate cancer patients with 72 oligometastatic recurrences (22 pelvis, 6 abdomen, 17 both pelvis/abdomen, and 27 bone) at a median age of 75 years old. Baseline lymphopenia was as follows: Grade 1 (8%), Grade 2 (12%), and Grade 3+4 (0%). Overall, 69.1 % of men experienced lymphopenia in the two years following SBRT for oligometastatic cancer: Grade 1 (16.9%), Grade 2 (39.4%), Grade 3 (12.7%), and Grade 4 (1.3%) The average baseline lymphocyte count of all oligometastatic patients was 1.43 k/uL which decreased to a minimum average of 0.73 k/uL at 3 months. The average baseline lymphocyte count for the site of recurrence is as follows: pelvic node- 1.64 k/uL, abdominal node- 1.38k/uL, abdominal + pelvic node- 1.51k/uL; bone- 1.43k/uL. The average lymphocyte count at 3 months for the site of recurrence is as follows: pelvic node- 1.21 k/uL; abdominal node- 0.79k/uL; abdominal + pelvic node- 0.73 k/uL; bone- 0.80 k/uL. A one-way ANOVA revealed no significant difference between the location of oligometastatic disease at each time point post-radiation (F(3,16)= [1.192], p= 0.344). Multivariant analysis was done to compare the volume of treatment to lymphopenia grade. Total RT dose received (includes Stereotactic Body Radiation Therapy (SRBT) from prior prostate cancer treatment) and RT dose received for only oligometastatic recurrence of disease with absolute lymphocyte count proved a Pearson correlation coefficient (r) of 0.0075 and 0.0069 respectively. A similar analysis was done comparing the course of treatment with absolute lymphocyte count (Pearson correlation coefficient (r) of 0.1202).

Conclusion:

RT for oligometastatic prostate cancer causes low rates of high-grade lymphopenia with most of the toxicities being low-grade (grade 1 and 2). The peak incidence was between 3 and 12 months with variation based on the location of the oligometastatic site. However, there were no significant results indicating grade of lymphopenia was dependent on the site of recurrent disease. Additionally, no correlation was found between treatment volume or course of treatment with lymphopenia grade. Resolution of lymphopenia returned in most patients 18 months after RT, except for patients receiving radiation to abdominal and pelvic sites. Only two out of the 64 patients had multiple hospitalizations for infections. It is unclear if these were caused by lymphopenia.

Keywords: Lymphopenia, prostate cancer, CyberKinfe

References:

1) Khan, Irfan, et al. “Low Incidence of Late Lymphopenia Following Stereotactic Body Radiotherapy for Localized Prostate Cancer”. Practical Radiation Oncology, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/37785339/.

2) Lischalk, Johnathon W, et al. “Stereotactic Body Radiation Therapy for Localized Prostate Cancer.” Cancer Journal (Sudbury, Mass.), U.S. National Library of Medicine, 2022, pubmed.ncbi.nlm.nih.gov/27441752/.

3) Oermann, EK, et al. “Low Incidence of New Biochemical and Clinical Hypogonadism Following Hypofractionated Stereotactic Body Radiation Therapy (SBRT) Monotherapy for Low- to Intermediate-Risk Prostate Cancer.” Journal of Hematology & Oncology, U.S. National Library of Medicine, 27 Mar. 2011, pubmed.ncbi.nlm.nih.gov/21439088/.