Adjuvant breast radiotherapy as a standard component of breast-conserving treatment for early cancer can overtreat many women. Breast MRI is the most sensitive modality to assess local tumour burden. The aim of this study was to determine whether a combination of MRI and pathology findings can identify women with truly localised breast cancer who can safely avoid radiotherapy. PROSPECT is a prospective, multicentre, two-arm, non-randomised trial of radiotherapy omission in patients selected using preoperative MRI and postoperative tumour pathology. It is being conducted at four academic hospitals in Australia. Women aged 50 years or older with cT1N0 non-triple-negative breast cancer were eligible. Those with apparently unifocal cancer had breast-conserving surgery (BCS) and, if pT1N0 or N1mi, had radiotherapy omitted (group 1). Standard treatment including excision of MRI-detected additional cancers was offered to the others (group 2). All were recommended systemic therapy. The primary outcome was ipsilateral invasive recurrence rate (IIRR) at 5 years in group 1. Primary analysis occurred after the 100th group 1 patient reached 5 years follow-up. Quality-adjusted life-years (QALYs) and cost-effectiveness of the PROSPECT pathway were analysed. This study is registered with the Australian New Zealand Clinical Trials Registry (ACTRN12610000810011). Between May 17, 2011, and May 6, 2019, 443 patients with breast cancer underwent MRI. Median age was 63·0 years. MRI detected 61 malignant occult lesions separate from the index cancer in 48 patients (11%). Of 201 group 1 patients who had BCS without radiotherapy, the IIRR at 5 years was 1·0% (upper 95% CI 5·4%). In group 1, one local recurrence occurred at 4·5 years and a second at 7·5 years. In group 2, nine patients had mastectomy (2% of total cohort), and the 5-year IIRR was 1·7% (upper 95% CI 6·1%). The only distant metastasis in the entire cohort was genetically distinct from the index cancer. The PROSPECT pathway increased QALYs by 0·019 (95% CI 0·008–0·029) and saved AU$1980 (95% CI 1396–2528) or £953 (672–1216) per patient. PROSPECT suggests that women with unifocal breast cancer on MRI and favourable pathology can safely omit radiotherapy. Breast Cancer Trials, National Breast Cancer Foundation, Cancer Council Victoria, the Royal Melbourne Hospital Foundation, and the Breast Cancer Research Foundation.

中文翻译：

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术前乳腺 MRI (PROSPECT) 后选定的早期乳腺癌患者的术后放疗遗漏：前瞻性双组研究的主要结果

辅助乳房放疗作为早期癌症保乳治疗的标准组成部分可能会对许多女性造成过度治疗。乳腺 MRI 是评估局部肿瘤负荷最敏感的方法。本研究的目的是确定 MRI 和病理学结果的结合是否可以识别患有真正局限性乳腺癌的女性，这些女性可以安全地避免放射治疗。 PROSPECT 是一项前瞻性、多中心、双臂、非随机试验，对使用术前 MRI 和术后肿瘤病理学选择的患者进行放射治疗省略。该研究正在澳大利亚的四家学术医院进行。 50 岁或以上患有 cT1N0 非三阴性乳腺癌的女性符合资格。那些患有明显单灶性癌症的患者接受了保乳手术 (BCS)，如果是 pT1N0 或 N1mi，则省略放射治疗（第 1 组）。向其他人（第 2 组）提供标准治疗，包括切除 MRI 检测到的其他癌症。所有患者均被推荐全身治疗。主要结局是第 1 组 5 年时的同侧侵袭性复发率 (IIRR)。主要分析是在第 100 名第 1 组患者达到 5 年随访后进行的。分析了 PROSPECT 途径的质量调整生命年 (QALY) 和成本效益。本研究已在澳大利亚新西兰临床试验注册中心注册 (ACTRN12610000810011)。 2011年5月17日至2019年5月6日期间，443名乳腺癌患者接受了MRI检查。中位年龄为 63·0 岁。 MRI 在 48 名患者 (11%) 中检测到 61 个与指示癌症分开的恶性隐匿性病变。在 201 名未经放疗而患有 BCS 的第 1 组患者中，5 年时的 IIRR 为 1·0%（95% CI 上限为 5·4%）。第 1 组中，第 4·5 年发生一次局部复发，第 7·5 年发生第二次局部复发。第 2 组中，9 名患者接受了乳房切除术（占队列总数的 2%），5 年 IIRR 为 1·7%（95% CI 上限为 6·1%）。整个队列中唯一的远处转移在基因上与指标癌症不同。 PROSPECT 途径将 QALY 提高了 0·019 (95% CI 0·008–0·029)，并为每位患者节省 1980 澳元 (95% CI 1396–2528) 或 953 英镑 (672–1216)。 PROSPECT 建议，MRI 上显示单灶性乳腺癌且病理结果良好的女性可以安全地省略放射治疗。乳腺癌试验、国家乳腺癌基金会、维多利亚癌症委员会、皇家墨尔本医院基金会和乳腺癌研究基金会。