部分乳腺放疗与全乳腺放疗10年结局相近

旧金山——由美国临床肿瘤学会主办的乳腺癌研讨会上报告的一项研究显示，经过10年随访，274例接受加速部分乳腺放疗的患者在乳腺癌局部区域性复发、远处转移或复发率方面与274例接受全乳腺放疗的匹配患者相比无显著差异。

上述数据来自3,009例于1980~2012年间在一家机构接受保乳治疗的早期乳腺癌患者。


David E. Wazer医生

在由明尼苏达州博蒙特癌症研究所的Jessica Wobb医生等人开展的这项研究中，两组均有4%的患者发生局部复发，1%发生区域性复发，6%在部分乳腺放疗后发生远处转移，3%在全乳腺放疗后发生远处转移。全乳腺放疗组（9%）与部分乳腺放疗组相比有对侧乳腺治疗失败率升高的趋势，但无统计学意义（3%，P=0.06）。部分乳腺放疗组与全乳腺放疗组的无病生存率分别为91%和93%，病因特异性生存率分别为93%和94%，总生存率分别为75%和82%，这些差异均未达到统计学意义。

这项报告是有关加速部分乳腺放疗后长期随访结果的首个报告。部分乳腺放疗后及全乳腺放疗后的平均随访时间分别为7.8年和8.1年，具有显著的统计学差异，但相差不到4个月。所有患者均随访了至少1年。两组患者在年龄、T分期以及雌激素受体状态方面均匹配；平均年龄均为63岁；均有88%的患者为ER阳性肿瘤。两组的分期分布均由18%的Tis期肿瘤、71%的T1期肿瘤以及11%的T2期肿瘤构成。部分乳腺放疗组接受辅助性激素疗法的患者人数（54%）显著少于全乳腺放疗组（68%）。进行部分乳腺放疗的患者与接受全乳腺放疗的患者相比有肿瘤缩小的趋势，两组的平均肿瘤大小分别为11.4 mm和13 mm（P=0.06）。两组患者在其他特征方面相似，其中包括阴性淋巴结的比例（接受部分乳腺放疗的患者中有91%，接受全乳放疗的患者中有86%）、最终切缘阴性的比例（分别为94%和95%）以及接受辅助化疗者的比例（分别为15%和18%）。

一项单变量分析显示，切缘接近肿瘤边缘时，两组患者的同侧乳腺癌复发风险均增加，切缘阳性使全乳腺放疗组的复发风险增加。

Wobb医生报告称无相关利益冲突。

专家点评：来自重要医疗机构的最新信息

在没有关于加速部分乳腺放疗的前瞻性随机试验数据指导临床实践的情况下，我们只能依靠医疗机构数据的积累。我认为，对扩充我们的知识库贡献最大的机构是威廉博蒙特医院。很荣幸能获得他们的最新经验，因为他们进行了一项最新的配对分析，利用组织间导管或基于球囊的短程放疗这两种不同技术观察其机构的部分乳腺放疗患者，并与其全乳腺放疗患者进行比较。在配对比较中，研究者们在局部失败、区域性失败、远处转移或总体生存率方面均未观察到组间差异的存在。

当然，我们不禁要问配对好到什么程度？他们的配对的确做得相当好，但我们也注意到，全乳腺放疗组患者的肿瘤略大，阳性淋巴结患者略多。最令人不放心的或许就是全乳腺放疗组中激素疗法的使用较多。这可能反映了两件事：其一是两个队列间预测因素的分布不平衡；其二是激素疗法对局部和区域性控制结局有影响。

当我们观察这项研究与临床变量和结局有关的结果时发现阴性切缘始终较好，无论患者是接受全乳腺放疗抑或部分乳腺放疗，这也在意料之中。值得关注的是，在部分乳腺放疗组中，年龄较小与局部失败风险较高相关。

这项分析漏掉了哪些内容？这不是研究者们的过失；只是由于这项研究是回顾性收集资料，因此有时很难获得全面的数据。我认为，分级、三阴性表型vs.其他表型、人表皮生长因子受体2状态以及淋巴血管侵犯等相关问题是2013年的热点。遗憾的是，这些相关信息均未出现在这项分析之中。

David E. Wazer医生是布朗大学放射肿瘤学教授。上述内容摘自他在本次会上的评论。Wazer医生报告与美国近距离放疗学会、高级放疗以及《美国临床肿瘤学杂志》有利益关系。

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By: SHERRY BOSCHERT, Internal Medicine News Digital Network

SAN FRANCISCO – Ten years of follow-up showed no significant difference in breast cancer locoregional recurrence, distant metastasis, or survival rates in 274 patients treated with accelerated partial breast irradiation compared with 274 matched patients treated with whole breast irradiation.

The data came from records on 3,009 patients with early-stage breast cancer who were treated with breast-conserving therapy at one institution between 1980 and 2012.

Four percent in each group developed local recurrence, 1% in each group had a regional recurrence, and 6% had distant metastases after partial breast irradiation and 3%, after whole breast irradiation. There was a nonsignificant statistical trend toward a higher rate of contralateral breast failure in the whole breast irradiation group (9%) compared with the partial breast irradiation group (3%, P = .06), Dr. Jessica Wobb reported in a poster presentation at a breast cancer symposium sponsored by the American Society of Clinical Oncology.

Rates of disease-free survival were 91% in the partial breast irradiation group and 93% in the whole breast irradiation group. Cause-specific survival rates were 93% and 94%, respectively, and overall survival rates were 75% and 82%, reported Dr. Wobb of the Beaumont Cancer Institute, Royal Oak, Mich. None of these differences reached statistical significance.

This is one of the first reports on prolonged follow-up after accelerated partial breast irradiation, she noted. Mean follow-up was 7.8 years after partial breast irradiation and 8.1 years after whole breast irradiation, a difference that was statistically significant, but amounted to less than 4 months. All patients were followed for at least 1 year.

Patients in the cohorts were matched by age (within 3 years); T stage (Tis, T1, or T2); and estrogen receptor (ER) status. The mean age was 63 years of age in both groups. Eighty-eight percent in both groups had ER-positive tumors. The stage distribution in both groups consisted of 18% with stage Tis tumors, 71% with T1 tumors, and 11% with T2 tumors.

Significantly fewer patients in the partial breast irradiation group received adjuvant hormonal therapy (54%) compared with those in the whole breast irradiation group (68%). There was a trend toward smaller tumors in patients undergoing partial breast irradiation than in those receiving whole breast irradiation, with mean tumor sizes of 11.4 mm and 13 mm (P = .06).

Other characteristics were similar between the groups, including the proportion with negative lymph nodes (91% of patients undergoing partial breast irradiation and 86% of those who got whole breast irradiation), the proportion with negative final margins (94% and 95%, respectively), and the proportion who received adjuvant chemotherapy (15% and 18%).

Close tumor margins increased the risk for ipsilateral breast tumor recurrence in both groups, and positive margins increased the recurrence risk in the whole breast irradiation group, a univariate analysis found.

Dr. Wobb reported having no relevant financial disclosures.

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Helpful update from key institution

In the absence of prospective, randomized trial data on accelerated partial breast irradiation to guide us, we are left with the accumulation of institutional data. The institution that, in my opinion, has contributed most to our knowledge base is the group at William Beaumont Hospital. We’re fortunate to have an update of their experience in that they’ve performed an updated a matched-pair analysis looking at their partial breast irradiation patients (using interstitial catheter or balloon-based brachytherapy two different techniques), compared with their whole breast irradiation patients.

In this matched-pair comparison, the investigators saw no difference in local failure, regional failure, distant metastases, or overall survival.
 
Of course, we have to ask, in a matched pair, how good is the match? We do notice that in their group it’s a pretty good match, but we see that for whole breast irradiation, there are slightly larger tumors in that cohort and slightly more positive-node patients. Perhaps the most unsettling aspect is that there is more hormonal therapy in the whole breast irradiation group. This could reflect two things: One is an imbalance in prognostic factors between the two cohorts; the other is an impact of hormonal therapy on local and regional control outcomes.

When we look at their results related to clinical variables and outcome, not surprisingly we find that a negative margin is always better irrespective of whether the patient is getting whole breast irradiation or partial breast irradiation. Interestingly, in the partial breast irradiation group, younger age was associated with a higher risk of local failure.

What’s missing from this analysis? Again, this is not a fault of the investigators; just by virtue of this being a retrospective collection of data, it’s sometimes hard to get all this data. The questions that I think are pertinent in 2013 relate to grade, triple-negative phenotype versus other phenotypes, human epidermal growth factor receptor 2 status, and lymphatic vascular invasion. Unfortunately, none of that information is present in this analysis.

Dr. David E. Wazer is a professor of radiation oncology at Brown University, Providence, R.I. These are excerpts of his remarks as the discussant of Dr. Wobb’s study at the meeting. Dr. Wazer reported financial associations with the American Brachytherapy Society, Advanced Radiation Therapy, and American Journal of Clinical Oncology.