# Chronic Prostate Cancer-Related Symptoms and Toxicities Following Stereotactic Body Radiation Therapy: Implications for Future Radionuclide Therapy

## TL;DR

This study finds that many prostate cancer patients treated with SBRT experience symptoms similar to those from radionuclide therapy, suggesting the need for baseline assessments before future treatments.

## Contribution

The study introduces the use of the FACT-RNT questionnaire to assess long-term SBRT symptoms and their relevance to future RNT risk stratification.

## Key findings

- 25% of SBRT-treated patients reported mild to severe side effects, including fatigue and xerostomia.
- The FACT-RNT questionnaire can help distinguish baseline symptoms from RNT-related toxicities.
- Salivary gland dysfunction and GI issues were common, similar to RNT side effects.

## Abstract

Background

Men treated for prostate cancer can experience a high symptom burden. Stereotactic body radiation therapy (SBRT) is increasingly utilized in the management of localized prostate cancer, while radionuclide therapy (RNT) is rapidly becoming a standard treatment option for metastatic prostate cancer. The Functional Assessment of Cancer Therapy-Radionuclide Therapy (FACT-RNT) is a newly validated questionnaire assessing symptoms and toxicities among patients receiving RNT. This study aimed to characterize long-term, patient-reported symptoms in prostate cancer survivors treated with SBRT using the FACT-RNT questionnaire, and to explore whether such symptoms may inform risk stratification for future RNT candidacy.

Methodology

We conducted a cross-sectional assessment of symptoms and toxicities after prostate SBRT using the FACT-RNT, a 15-item questionnaire assessing common RNT-related symptoms and toxicities across several domains, including fatigue, salivary/lacrimal gland dysfunction, gastrointestinal (GI) difficulties, and pain. Responses to individual questions were grouped into three clinically relevant categories (i.e., absent (“not at all”), mild (“a little bit” to “somewhat”), moderate to severe (“quite a bit” to “very much”)). Standard error was calculated at a 95% confidence interval. However, there are methodological limits to linking SBRT symptoms directly with RNT tolerance.

Results

Prostate cancer patients (N = 296) who had completed SBRT a median of six years prior (range = 0-13 years) completed the FACT-RNT questionnaire at a response rate of 49.5% (296 of 598 consented patients). Patients completed prostate SBRT at a median of six years before questionnaire administration (range = 0-13 years). The median age of responders was 78 years, 76% of patients were white, and 69% were of intermediate risk disease. Overall, 25% of respondents were mildly (21%) or moderately to severely (4%) bothered by treatment side effects. Respondents endorsed at least mild fatigue (53%), xerostomia (29%), constipation (23%), and pain (20%).

Conclusions

A notable percentage of prostate cancer patients treated with SBRT report toxicities commonly associated with RNT, such as fatigue, salivary/lacrimal gland dysfunction, GI difficulties, and pain. Results of this study underscore the importance of administering the FACT-RNT before RNT treatment to obtain a baseline assessment of symptoms, evaluate pre-treatment risk for RNT toxicities (e.g., salivary gland dysfunction), and better differentiate baseline abnormalities in function from RNT-related side effects.