Safety of Radiation Therapy for Treatment of Malignancy in Patients with Inflammatory Bowel Disease

PURPOSE/OBJECTIVE(S)

Inflammatory bowel disease (IBD) has been considered a relative contraindication to radiation therapy (RT) due to the potential greater risk of RT-induced toxicities, however, there is limited toxicity data using modern RT techniques. This study aims to assess toxicity outcomes in patients with IBD treated with abdominal or pelvic RT.

MATERIALS/METHODS

After institutional review board approval, patients with IBD who received RT to the abdomen or pelvis were filtered from an institutional research repository and their electronic medical records were reviewed. Acute toxicity was defined as that occurring within 3 months of RT. Toxicities were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 5.0. Univariable Cox proportional hazards regression was used to assess rates of grade ≥2 toxicity-free survival.

RESULTS

We identified 62 patients with median age of 69 years (interquartile range [IQR] 62-77) who received RT from 2006-2022. Median follow up was 15 months (IQR 4-33). Most patients were male (42; 68%) and had a diagnosis of ulcerative colitis (44; 71%). The most common primary malignancy was colorectal/anal (26; 42%). Intensity-modulated RT (IMRT) was most frequently used (38; 61%) followed by 3-dimensional conformal RT (3D-CRT) (12; 19%) and stereotactic body RT (SBRT)/brachytherapy (12; 19%). For IMRT/3D-CRT, median dose delivered was 50 Gy (IQR 49-59) in 25 fractions (IQR 25-30), and median maximum dose (Dmax) to bowel was 48 Gy (IQR 43-52); whereas for SBRT/brachytherapy, the median dose was 32 Gy (IQR 27-40) in 3 fractions (IQR 2-5) and median bowel Dmax was 32 Gy (IQR 20-37). The median biologically effective dose delivered with an assumed alpha/beta ratio of 10 (BED10) across all RT modalities was 63 Gy (IQR 60-72). After initiation of RT, 31 patients (50%) and 14 patients (23%) experienced grade ≥2 acute and late toxicity, respectively. Thirteen patients (21%) and 7 patients (11%) experienced grade 3 acute and late toxicity, respectively. No patients experienced grade >3 toxicity. Acute toxicity resulted in interruption to RT for 5 patients (8%), 2 of which did not resume RT. Four patients (6%) required adjustment to chemotherapy or IBD medication dosage as a result of their acute toxicity. Median time from RT start to acute toxicity onset was 41 days (IQR 32-46), whereas median time to onset of late toxicity was 9 months (IQR 5-15). The most common acute and late toxicities were diarrhea (21; 34%) and bowel obstruction/perforation/fistula (4; 6%), respectively. Rates of grade ≥2 toxicity-free survival overtime were not significantly associated with IBD status (active vs quiescent), delivered BED10, or bowel Dmax BED3.

CONCLUSION

In patients with IBD treated with abdominal or pelvic RT for malignancy, RT was feasible with acceptable rates of toxicity and active versus quiescent IBD status did not impact toxicity outcomes. Future research is needed to elucidate specific dose constraints when treating patients with IBD.

Low Dose Splenic Radiotherapy for Myeloproliferative Neoplasms prior to Allogeneic Hematopoietic Stem Cell Transplant

PURPOSE/OBJECTIVE(S)

Myeloproliferative neoplasms including primary and secondary myelofibrosis (MF) are a rare spectrum of chronic myeloproliferative disorders in which nearly 90% of patients experience splenomegaly. Importantly, splenic radiotherapy (SRT) may be used in combination with allogeneic stem cell transplant (alloSCT) to improve symptoms related to splenomegaly, though there currently is no consensus SRT dose/fractionation protocol reported in the literature for use in combination with alloSCT. We sought to report our institutional experience utilizing low dose SRT prior to alloSCT in the post-Jakafi era.

MATERIALS/METHODS

We performed a retrospective review of all patients diagnosed with MF at our institution from 2017-2022 who received reduced intensity alloHCT. Patients who underwent total lymphoid or body irradiation were excluded. Descriptive demographic and clinical characteristics of patients were summarized by means, medians, standard deviations, ranges and proportions as appropriate.

RESULTS

We identified 39 patients with MF who underwent reduced intensity conditioning (RIC) consisting of fludarabine/melphalan in preparation for alloHCT (median age 64.5, 12/16 males, median follow up 21 months). 16 patients with Jakafi-resistant splenomegaly completed low dose SRT prior to transplant (median spleen size: 24.5cm) with a median dose of 5Gy delivered in 5 fractions. 3D conformal therapy was used for all patients. All patients completed the planned total radiation course without treatment break or dose limiting acute toxicity. Thrombocytopenia was the most reported toxicity (CTCAE v5.0; 2 patients experienced grade 1, 1 patient experienced grade 2). No patients experienced grade 3 or higher acute cytopenias nor required transfusion during radiotherapy. All patients successfully received alloHCT a median of 7 days (range: 2-11) after the completion of SRT with a 94% (15/16) engraftment rate. Median neutrophil recovery (ANC > 500 × 3 days) time was 18 days (range: 13-31); median length of hospital stay was 23 days (range: 20-129). Overall survival was 75% in the SRT cohort (12/16, 2 with persistent disease, 2 due to other causes). Symptom burden data was available for 14/16 patients; 79% (11/14) of patients reported improvement in symptoms associated with splenomegaly or reduction in splenic size on physical examination.

CONCLUSION

In the largest reported experience of a low dose SRT only cohort to date, we observe low dose SRT is feasible, safe in combination with alloHCT with high engraftment rates, and may reduce symptoms related to splenomegaly thereby improving patient quality of life without compromising transplant related outcomes. A prospective study validating this protocol is currently underway.

Impacts of Wildfire Events on California Radiation Oncology Clinics and Patients

PURPOSE/OBJECTIVE(S)

The impact of climate-related disasters such as wildfires on healthcare delivery and cancer care is a growing concern. Patients undergoing radiotherapy are particularly vulnerable to treatment interruptions which are known to have a direct impact on survival outcomes. We report results of the first pilot study characterizing the impact of wildfires on radiation oncology clinics and their patients.

MATERIALS/METHODS

A survey was sent to 415 California radiation oncologists representing 144 clinics identified using the ASTRO member directory to gather information about clinic and radiation oncologist demographics, wildfires' impacts on the clinic (physical/operational), physicians, staff, and patients between 2017 and 2022, as well as clinics' disaster preparedness efforts.

RESULTS

A total of 51 radiation oncologists completed the survey, representing 43 clinics (30% of clinics) in 24 (41%) of California counties. 35 (69%) of respondents self-identified as male, 27 (53%) worked at hospital-affiliated centers, 19 (37%) worked in academic centers, with 49 (96%) practicing in metropolitan areas. A total of 31 clinics were impacted by a wildfire between 2017 and 2020. The two rural clinics (100%) and 29 (59%) of metro practices reported being impacted by wildfires in the last 5 years, with 9 (18%) reporting a clinic closure and 15 (29%) reporting staffing shortages. 28 (55%) of respondents reported impacts on patients including having to evacuate, 27 (53%) having to cancel or reschedule treatments, and 23 (45%) experiencing physical, mental, or financial hardship due to the wildfires. Among the 25 clinics impacted by wildfires, 12 (24%) reported physical/operational impacts including being forced to evacuate patients to another treatment center, transportation interruptions (19, 37%), community and regional evacuations (18, 35%), school closures (18, 35%), and physical/mental health impacts (14, 27%) on staff due to the wildfires. Small clinics (25 staff or less) that experienced a wildfire were twice as likely to experience closures (6 of 16 clinics, 38%) but equally likely to experience staffing shortages (8 of 16, 50 %) as compared to larger practices (7 of 15, 47%). Nearly half of respondents 25 (47%) reported their workplace had a wildfire emergency preparedness plan.

CONCLUSION

The results of this study demonstrate the significant impact wildfires have on patient care in both rural and metropolitan areas. The findings emphasize the importance of emergency preparedness planning to minimize the consequences of such disasters and underscores the need for further research to explore risk factors associated with patient and community vulnerability to climate-related crises. Such research will be essential to informing and developing future emergency preparedness plans.