Letter: Whole Peritoneal Radiotherapy for Malignant Ascites: A Novel Hypothesis and Call for Research

Dear Editor:

Malignant ascites (MA) profoundly impairs quality of life and often dominates ongoing palliative care in patients with advanced cancer. Current management centers on paracentesis, diuretics, and supportive measures, particularly when disease-directed therapy is no longer feasible. ¹ Symptoms—abdominal distension, pain, nausea, dyspnea, and fatigue—drive substantial morbidity. Repeated paracenteses provide only transient relief, exacerbate protein depletion and hypoalbuminemia, and are time- and resource-intensive. Pharmacologic options, including diuretics, have limited efficacy.

Abdominal radiotherapy (RT) is established across multiple indications but has not been systematically evaluated as a dedicated symptomatic treatment for MA. Given the paucity of palliative options for MA, this gap is notable. Whole peritoneal radiotherapy (WPRT), targeting both overt and occult peritoneal infiltrates that drive effusion, represents a theoretically attractive, tumor-agnostic strategy for symptom control. Evidence remains sparse: only isolated patients with MA are described within broader series.^2–4

De Meerleer et al. reported 13 patients with chemotherapy-resistant ovarian cancer and bulky peritoneal disease treated with whole abdominopelvic RT using intensity-modulated arc therapy; among the nine patients who completed treatment, all experienced complete symptom resolution except for ascites, which showed a partial but clinically meaningful response. ² In an earlier retrospective cohort of 80 patients with ovarian carcinoma who received RT, 8 patients were treated primarily for MA; while responses were favorable, the subgroup was too small for firm conclusions. ³ Ishibashi et al. examined palliative RT for pleural (n = 9) and peritoneal (n = 13) dissemination administered for pain control and hemostasis, precluding conclusions specific to MA. ⁴ Likewise, Lee et al. demonstrated that whole-abdomen RT can eradicate small intraperitoneal deposits in endometrial adenocarcinoma without addressing MA directly. ⁵

We highlight the rationale for a randomized pilot study comparing WPRT plus best supportive care (BSC) versus BSC alone in recurrent MA secondary to radiologically confirmed peritoneal infiltration to assess feasibility, tolerability, and symptom relief. Short, logistically feasible regimens are appealing in palliative care. An initial single-dose approach (e.g., 8 Gy in 1 fraction) with optional targeted boosts to CT/MRI/PET-identified infiltrates could provide early signals of efficacy and safety, informing subsequent protocol refinement and patient selection. The workflow could include paracentesis immediately before CT simulation, followed by rapid VMAT planning and delivery to minimize the interval between drainage and therapy.

Eligibility criteria may include symptomatic ascites with imaging-confirmed peritoneal involvement, an ECOG performance status of 0–3, anticipated survival sufficient to benefit from short-course palliation, and no contraindications. Primary endpoints should include changes in quality of life (measured by standardized instruments) and symptom burden (at a minimum, pain, dyspnea, abdominal distension, and oral nutrition maintenance). Secondary endpoints could include the number and volume of paracenteses, time to next paracentesis, patient-determined need for paracentesis (symptom-driven frequency), nutritional status, treatment-related toxicity, and survival. Rigorous monitoring for gastrointestinal toxicity is essential; however, low-dose treatment is expected to minimize most risks. If signals are favorable, a larger randomized trial to refine patient selection, timing, and dose could be warranted.

This hypothesis proposes a deliberate shift from a disease-centered to a symptom-oriented paradigm, analogous to RT’s established role in palliating pain, compressive syndromes, and hemorrhage. If validated, WPRT could offer a symptom-focused option largely independent of primary tumor etiology, applicable across gynecological, gastrointestinal, pancreaticobiliary, and other malignancies complicated by MA. By reducing reliance on repeated paracentesis and potentially improving functional status, WPRT may also prove to be cost-effective.