APHINITY: What the Breast Cancer Trial Found

A trial that only just cleared its own bar

Pertuzumab was already used for HER2-positive breast cancer that had spread. APHINITY asked a different question. If you give it after surgery, to people whose cancer has been removed, do fewer of them see it come back?

The answer was yes — but only just. The p-value was 0.045, against a threshold of 0.05. Move a handful of events either way and the trial reads as negative.

Who was randomised, and what they already had

4,805 people with operable HER2-positive breast cancer took part. 2,400 were assigned pertuzumab and 2,405 placebo. Everyone also had standard chemotherapy and a year of trastuzumab, so this was one drug added on top of good treatment, not a treatment on its own.

To join, the cancer had to be node-positive or node-negative with high-risk features. 63% had cancer in their lymph nodes. 36% had hormone-receptor-negative disease. Neither the patients nor their doctors knew who was getting the real drug.

What the three-year numbers showed

Field	Detail
Trial	APHINITY
Identifier	NCT01358877
Phase	Phase 3
Design	Randomised, double-blind, placebo-controlled
Cancer type	HER2-positive early breast cancer
Comparator	Pertuzumab or placebo, added to chemotherapy plus one year of trastuzumab
Primary endpoint	Invasive disease-free survival

The cancer came back in 171 of the 2,400 people on pertuzumab (7.1%) and in 210 of the 2,405 on placebo (8.7%). The hazard ratio was 0.81 (95% CI 0.66 to 1.00, p=0.045).

At three years, 94.1% of the pertuzumab group were alive with no invasive cancer, against 93.2% on placebo. That gap is under one percentage point.

The split that decides who this is for

The overall figure hides two very different results.

Among people whose cancer had reached the lymph nodes, three-year rates were 92.0% with pertuzumab and 90.2% with placebo (hazard ratio 0.77, 95% CI 0.62 to 0.96, p=0.02).

Among people with node-negative disease, the rates were 97.5% and 98.4% — that is, slightly worse with the drug (hazard ratio 1.13, 95% CI 0.68 to 1.86, p=0.64). Nothing there suggests a benefit. The whole positive result comes from the node-positive group.

Six years, then eight: survival did not move

Two later reports followed the same people for longer.

At a median of 74 months, the benefit on recurrence held up (hazard ratio 0.76, 95% CI 0.64 to 0.91; six-year rates 91% and 88%). Survival did not reach significance: 95% of the pertuzumab group and 94% of the placebo group were alive, with 125 deaths against 147 (hazard ratio 0.85, p=0.17).

At a median of 8.4 years, eight-year survival was 92.7% and 92.0% (hazard ratio 0.83, 95% CI 0.68 to 1.02, p=0.078). In the node-positive group, eight-year rates free of invasive disease were 86.1% and 81.2% — a gap of 4.9 points. In the node-negative group, the placebo arm did well on its own.

The diarrhoea problem

Severe diarrhoea — grade 3 or worse — hit 9.8% of the pertuzumab group and 3.7% of the placebo group. It happened almost entirely during chemotherapy. Serious heart problems were uncommon in both groups, and stayed under 1% through six years.

What this trial cannot tell you

• Whether people live longer. Three separate looks at survival, the latest after more than eight years, have not shown a significant difference.
• Whether it is worth it for node-negative disease. The evidence says no, and the placebo group in that cohort did well without the extra drug.
• How large the benefit is for one person. A gap of a few percentage points across thousands of people does not translate into a personal number.
• How it compares with newer approaches. APHINITY tested one specific addition to the treatment that was standard when it opened.

Questions for a HER2-positive diagnosis

• Was cancer found in my lymph nodes, and how many?
• Given that, what does adding this drug change for me?
• What would you do about diarrhoea if it starts during chemotherapy?

Sources

This article was written from the sources below, which were checked on the source-check date shown above.

• NEJM: Adjuvant Pertuzumab and Trastuzumab in Early HER2-Positive Breast Cancer (APHINITY) (primary)
• JCO: APHINITY 6 Years' Follow-Up (primary)
• JCO: APHINITY Third Interim Overall Survival Analysis (primary)

How this article was prepared

Prepared by Cancer Explained's AI-assisted editorial system and checked against the sources listed below. This article has not been reviewed by a healthcare professional unless a named reviewer is specifically shown.

Cancer Explained is published by the National Cancer Information Foundation as a nonprofit-oriented public-interest education project. It is not a diagnostic service, does not recommend treatments, and is not for emergencies.

Found an error, a broken source link, outdated information, or wording that feels insensitive? Report it here — we log and act on material corrections.