Retrospective Study Evaluating Outcomes Following Palliative Radiotherapy With or Without Chemotherapy for Dogs With Presumed Cardiac Hemangiosarcoma

Abstract

Canine cardiac hemangiosarcoma (cHSA) represents a complex clinical challenge in that those afflicted have an acute risk of death due to cardiac tamponade and high morbidity and mortality given the frequency of metastasis. Previous studies show that radiation therapy (RT) can decrease the risk of tamponade; however, an optimal approach has yet to be determined. The objective of this study was to evaluate the outcomes of dogs with presumptive cHSA treated with varied RT protocols and modalities, and to contrast findings with previously published literature. Secondary objectives were to assess differences in outcomes between those that received chemotherapy post-RT or did not, single fraction versus multiple-fraction RT protocols, and CT-guided versus manually calculated treatment plans. Twenty-seven dogs with echocardiographic evidence of an atrial or auricular cardiac mass that received RT were included. The frequency of pericardiocentesis before and post-RT were compared. Overall survival time was determined, along with survival time specific to those that received chemotherapy, were treated with CT-based radiation plans, and were prescribed a single fraction versus multiple fractions. Pericardiocentesis was performed an average of 1.1 times per week before RT, and an average of 0.18 times per week after RT (p = 0.01). Median overall survival time was 137 days. Plans made without CT guidance were associated with more adverse radiation events, but all were minimally impactful on quality of life. Most dogs died or were euthanized due to metastatic disease. This study shows similar benefits to previously published data in a larger cohort of dogs using a less-conformal radiation modality. As well, it highlights future directions to identify optimal systemic therapies to delay the onset of metastasis.

Keywords: hemangiosarcoma; pericardial effusion; pericardiocentesis; radiotherapy.

FIGURE 1

(a) Left, a typical dose colour wash for a 3D‐CRT plan with four static beams. Prescribed dose was 12 Gy × 1 = 12 Gy. Orange to red hues represent 10–13 Gy, green represents 4–8 Gy and blue indicates < 3.50 Gy. PTV margin (outer magenta contour) is 3 mm symmetric expansion from the GTV (inner red contour). (b) Dose colour wash for a Volumetric Modulated Arc Therapy (VMAT) plan with two 360° coplanar arcs (fields not shown). Prescribed dose was 6 Gy × 5 = 30 Gy on consecutive days. Orange to red hues represent 30.5–33.2 Gy, green represents 13–30.5 Gy and blue indicates < 13 Gy. PTV margin (outer magenta contour) is 5 mm symmetric expansion from the GTV (inner red contour).

FIGURE 2

An MV port film used for manually calculated treatment. Yellow box indicates the treatment field determined by the cardiac silhouette and adjacent landmarks.

FIGURE 3

Overall MST of all dogs was 137 days (2–652 days). Time in days was calculated from the last radiation treatment to death or euthanasia. Tick marks indicate the time point at which patient was censored.

FIGURE 4

Examples of patients with CT‐based plans that show variance in position of GTV/PTV target. Sagittal reconstructions with the dose colour wash shows 95% of the prescription dose (D95%) or higher covering the target. PTV (magenta) contour is a symmetric expansion of the GTV (red) ranging from 3 to 10 mm.