Myeloma / Plasma Cell

2026-10-04 ASTRO Annual Meeting 2026

Early signal

Ultralow-dose 4 Gy RT for myeloma bone metastases

ForMultiple myeloma, uncomplicated painful bone lesion; 79% prior chemo

TL;DRPain response 59% at 4 wks (per protocol; ITT 40/70, 57%) after 4Gy to painful MM bone lesions; 24% needed a second RT course.

Why it mattersRadiation oncology

The ITT read runs opposite to the abstract's framing: CR+PR was 40/70 (57%) at 4 wks, 33/70 (47%) at 8 wks and 37/70 (53%) at 6 mo, with 25/70 (36%) not completing the 6 mo assessment. The decision in play is 4Gy first with reRT held in reserve; 24% needed a second course.

Monday clinic

In MM with an uncomplicated painful bone lesion, this supports 4Gy as a response-adapted first step with reirradiation in reserve; it does not extend to complicated lesions or to pts who need fast relief, given a median 36 days to pain relief. The longer read

12 details

Design

Prospective, multi-institutional, single-arm phase II. 63 evaluable pts with 70 lesions from 7 institutions, treated 4/2019-9/2025. Median follow-up after RT 186 days.

Population & inclusion

Multiple myeloma with an uncomplicated painful bone lesion. Median age 66, 49% female, 89% ECOG 0-1, 79% prior chemo (median 1 line), 40% prior RT to a different area. Median baseline BPI 4.8.

Radiotherapy

4Gy total, delivered as 2Gy x 2 or 4Gy x 1 (29% received 4Gy x 1). Reirradiation with a clinician-choice regimen could be considered at 4 weeks after initial treatment for inadequately controlled pain (the inequality symbol is garbled in the source). Target volume and technique not stated in source.

Endpoints

Primary: proportion with self-reported pain response at 4 weeks. Response was scored on average BPI and oral morphine equivalent dosing per the International Consensus on Palliative RT, assessed at 4 weeks, 8 weeks and 6 months.

Results

Response rates by timepoint are in the table. Median BPI and OMED decreases were 2.25 and 5mg at 4 weeks and 2.75 and 6.2mg at 8 weeks. Median time to pain relief was 36 days, median duration 148 days, with no difference by fractionation.

Timepoint	ITT CR+PR	Per protocol CR+PR	Did not complete
4 wks	40/70 (57%)	40/68 (59%)	2/70 (2%)
8 wks	33/70 (47%)	33/52 (63%)	18/70 (26%)
6 mo	37/70 (53%)	37/45 (82%)	25/70 (36%)

Safety

No grade 3+ treatment-related toxicity. Lower-grade events and hematologic toxicity are not reported in the source, although marrow sparing was the stated rationale.

vs leading data

The source states there is no consensus on the most effective palliative dose in MM. The ultralow-dose concept comes from indolent lymphoma, where FoRT tested it against a conventional dose. With no comparator arm here, the 59% at 4 weeks cannot be ranked against conventional palliative fractionation.

Applies to

MM pts with an uncomplicated painful bone lesion, mostly ECOG 0-1 (89%) with a median of 1 prior line

Does not represent complicated bone lesions or bone metastases from solid tumors.

Limitations

Missing assessments grow from 2/70 at 4 weeks to 25/70 at 6 months, and reasons are not given, so the late per-protocol rates are vulnerable to informative dropout. Handling of reirradiated lesions in the 6 month response is not stated. Pain response is self-reported in an unblinded single-arm design.

Discussion

Best read as a strategy: 4Gy first, escalate on failure. A 63% response at 4 weeks after reirradiation suggests the low first dose did not obviously compromise salvage, at the cost of time (median 95 days to relief after reRT). It does not settle whether 4Gy matches conventional dosing up front, or whether it spares marrow.

Rationale

Single-arm phase II, 63 pts, no comparator against conventional palliative fractionation; late responses rest on a per-protocol denominator with 36% non-completion at 6 mo.

Open questions

4Gy vs conventional palliative fractionation in MM bone lesions: randomised comparison needed
Does 4Gy reduce hematologic toxicity vs higher-dose palliative RT?
Which lesions fail 4Gy and need reirradiation?

📚 Sources · 📄 1 paper

📄 PAPER L. K. Ballas; A. A. Garsa Jr; Z. He et al. · ASTRO 2026 Annual Meeting (2026-09)

Phase II Multi-Institutional Study of Ultralow-Dose (4Gy) Response-Adapted Radiotherapy for Symptomatic Bone Metastases from Multiple Myeloma

doi article →

Abstract

ASTRO 2026 abstract 10 · CT 01 - Clinical Trials Session · 2026-09-27 · presented by Leslie Ballas, MD, FASTRO Purpose/Objective(s): Palliative radiation therapy (RT) is a critical component of multiple myeloma (MM) care. Given the nature of MM, RT commonly exposes bone marrow to cytotoxic treatment. Data exists showing that a bone marrow dose of 10 Gy causes hematologic toxicity (HT). Since there is no consensus as to the most effective dose for palliation, this study hypothesized that ultralow dose RT (4Gy) could provide a pain response while minimizing HT. Materials/Methods: This prospective multi-institutional single-arm phase II trial evaluated clinical pain response, both based on the average Brief Pain Inventory (BPI) and oral morphine equivalent dosing (OMED) according to the International Consensus on Palliative RT, in patients who received 4Gy (either 2Gy x 2 or 4Gy x 1) to an uncomplicated painful bone lesion at 4, 8 weeks and 6 months. The primary endpoint was the proportion of patients with self-reported pain response at 4 weeks. Reirradiation with clinician-choice regimens could be considered at =4 weeks following initial treatment for inadequately controlled pain. Results: 63 evaluable patients with 70 lesions from 7 institutions received 4Gy from 4/2019-9/2025. 29% of patients received 4Gy x 1. 49% were female, with median age of 66 years. 89% had an ECOG performance status 0-1, 79% had prior chemo (median number of lines of therapy was 1), and 40% had prior RT to a different area. The median baseline BPI was 4.8. The median follow-up after RT was 186 days. The pain response rate in those that completed questionnaires at 4 and 8 weeks was 59% and 63% (median BPI and OMED decrease of 2.25, 5mg, and 2.75, 6.2mg, respectively), with pain response of 82% at 6 months. The median time to pain relief was 36 days with a median duration of 148 days. There was no difference in pain relief based on fractionation. 24% of patients received a second course of RT, with a median dose of 20Gy at a median of 71 days after completion of the 4Gy treatment. Following reirradiation, the pain response rate was 63% after 4 weeks with a median time to pain relief of 95 days. There was no grade 3+ treatment related toxicity. Conclusion: Ultralow dose radiation improved pain and produced durable responses in the majority of patients. The proportion of patients with improved pain increased over time. Notably, relatively few patients required a second course of RT (24%). This response-adapted approach allowed for selective augmentation of pain control with minimal toxicity. Abstract 10 - Table 1: Pain Response in patients on protocol based on intention to treat analysis and per protocol analysis (CR: complete response, PR: partial response) Assessment time point Intention to treat Per Protocol 4 wks CR+PR 40/70 (57%) 40/68 (59%) Did not complete 2/70 (2%) 8 wks CR+PR 33/70 (47%) 33/52 (63%) Did not complete 18/70 (26%) 6 mo CR+PR 37/70 (53%) 37/45 (82%) Did not complete 25/70 (36%)

📝 https://amportal.astro.org/sessions/ct-01-22948/phase-ii-multi-institutional-study-of-ultralow-dose-4gy-response-adapted-radiotherapy-for-sym-113322 10.1016/j.ijrobp.2026.06.011

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