Real world experience of intraoperative radiation therapy (IORT) during lumpectomy for early-stage breast cancer: retrospective data from a single large institutional observational study.

BACKGROUND

We report outcomes of patients who received intraoperative radiation therapy (IORT) using 50 kV after lumpectomy and sentinel lymph node biopsy.

METHODS

Women with age > 45 and post-menopausal status, localized, unifocal, invasive breast carcinoma were included in the study. Patients were diagnosed by needle biopsy, and suitable for wide local excision of invasive ductal carcinoma without nodal involvement on conventional examination (cT1 and small cT2 ≤ 3.5 cm, cN0, M0). Overall, 489 patients who received adjuvant IORT after breast-conserving surgery were identified between March 2016 to June 2023. The median age was 68 years (range 49-93). The median tumor size was 8 mm (0-40 mm). Adjuvant whole breast adiation therapy (WBRT), chemotherapy and endocrine were additionally offered in 36 patients (7.4%), 12 (2.4%) and 384 patients (78.5%) respectively.

RESULTS

After a median follow-up of 36 months (range, 0-100), the 3-year LR was 1.4% (95% CI 0.6-3.1%). The 3-year LRFS, LRRFS, and PFS were each 97.1% (95% CI 94.6-98.5%), while the 3-year MRFS and OS were both 98.3% (95% CI 96.1-99.2%). The 3-year outcomes did not differ significantly between the IORT and IORT + WBRT cohorts. Patients who did not receive ET (n = 104) experienced a significantly higher rate of local recurrence compared with those who received ET (n = 384) (3-year LR 4.0% vs. 0.7%; p = 0.01). LRFS and LRRFS showed borderline significance (5-year LRFS 96.9% vs. 100%; p = 0.05). MRFS, PFS, and OS did not differ significantly between the two groups.

CONCLUSIONS

Preliminary 3-year results show that IORT with 50 kV achieves excellent local control in selected early-stage breast cancer patients. Endocrine therapy reduced local recurrence, while WBRT added no significant benefit, underscoring the need for longer follow-up.