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PTCOG review maps emerging roles for particle therapy in gynecologic cancers

Carbon ions show the strongest signal in radioresistant gynecologic tumors, while proton evidence centers on adjuvant treatment and reirradiation.

RadOncToday · ·2 min read

KEY POINTS

  • The PTCOG Gynecologic Subcommittee conducted a PRISMA-ScR scoping review across MEDLINE, Embase, Web of Science and Cochrane. From 414 unique records, 41 studies were included; 63.4% were published since 2018, approximately two-thirds originated from Japanese centers, 27 were cohorts/case series and 12 were phase I/II trials.
  • Carbon-ion radiotherapy dominated the evidence base, with 1,155 treatment courses across 29 studies. Twenty studies addressed locally advanced cervical cancer, with other reports covering genital-tract melanoma, medically inoperable endometrial cancer, ovarian oligometastases and pelvic/nodal reirradiation.
  • For locally advanced cervical cancer, dose-escalation experience converged around 72–74.4 Gy(RBE) in 20–24 fractions. Across heterogeneous series, reported local control ranged from 59–85% at 2 years and 53–84% at 5 years, while 5-year overall survival ranged approximately 50–72%; outcomes appeared particularly encouraging in adenocarcinoma relative to historical photon series.
  • Disease anatomy remains critical. Patients with stage IVA bladder invasion experienced vesicovaginal fistula in approximately 28%, while rectal invasion was considered an unfavorable setting for radical CIRT because of severe gastrointestinal toxicity risk. The review emphasizes bowel and rectal maximum doses below approximately 60 Gy(RBE) when feasible.
  • A notable emerging application is oligometastatic or oligoprogressive ovarian cancer. In a two-center series of 36 lesions in 26 patients, median CIRT dose was 52.8 Gy(RBE), objective response reached 97%, and local control was 92% at 1 year and 83% at 2 years, with no grade ≥3 toxicity reported.
  • Proton evidence was considerably smaller—approximately 237 patients across the included series—and concentrated mainly in postoperative treatment and recurrence/reirradiation. One comparative uterine-cancer study found less end-of-treatment diarrhea with protons than IMRT (p=0.01), with a nonsignificant signal toward less grade ≥3 GI toxicity (9% vs 31%; p=0.09).
  • Particle reirradiation also appeared feasible in selected patients. One 30-course proton series reported 1-year local control 83.5% and overall survival 65.7%, with grade 3 acute and late toxicity of 10% each; a CIRT nodal-reirradiation series reported 3-year local control 94% and overall survival 74%, without grade ≥3 late toxicity.

CLINICAL TAKEAWAY

The current gynecologic particle-therapy evidence is not uniform: carbon ions have their clearest rationale in radioresistant, unresectable and selected oligometastatic disease, while protons are primarily a toxicity-sparing strategy in postoperative and reirradiation settings. These are expert recommendations built largely on phase I/II and observational data, not randomized evidence against modern photon RT and brachytherapy.

SOURCE

International Journal of Radiation Oncology, Biology, Physics