Update on Kaiser Study

At my appointment on Tues., Dr. Jeske mentioned a retrospective study [1] which looked at all 17,000+ breast cancer patients treated at Kaiser Permanente Northern California during the time period 2000-2006.  They divided those patients into subgroups to study the recurrence rates for women with very small Her2+ invasive tumors but no lymph node involvement.  To better understand my specific risk, I contacted the study’s authors requesting additional information.  One of the researchers called me back this morning and here are the facts pertaining to my case (0.3cm tumor, ER-/PR-).

Of the 17,000 patients, 116 had invasive Her2+ tumors <=0.5cm in largest dimension (<1%!).

Of the 116 patients, 18 had tumors <0.1cm and 98 had tumors >= 0.1cm and <= 0.5cm.

Of the 98 patients, 7 had chemo, 8 had chemo + Herceptin, and 83 had neither chemo nor Herceptin.

Of the 83 patients, 36 were ER+ and 47 were ER-.

Of the 47 patients in a 5 year period, 3 had local/regional recurrences, 1 had a distant recurrence, and 43 had no recurrence.

Of the 3 local/regional recurrences, 2 had tumors>0.3cm and 1 had tumor=0.2cm (but had declined part of the recommended treatment – radiation to treat an unclean margin).

The single distant recurrence occurred in a patient whose tumor was 0.5cm.

So of this tiny subset of 47 [Her2+, ER-, >=0.1cm, <=0.5cm] patients like me, foregoing adjuvant chemo and/or Herceptin treatment resulted in 1 distant recurrence and 3 local recurrences.  With the exception of the 1 case where the patient chose a suboptimal follow-up treatment, all 3 remaining recurrences occurred in patients with tumors 33-66% larger than mine.  Even if we include those 4 recurrences,

P(5 Year Recurrence Free Interval | [T1aN0M0, ER-, Her2+, No Chemo, No Herceptin]) = 1-(4/47) = 0.915, so there would be an 8.5% chance of my having a recurrence (local or distant) in the first 5 years if I choose no adjuvant treatment.

Clearly, if you discount the recurrences where the original tumor size was larger than mine, you get an even more favorable number:

P(5 Year Recurrence Free Interval | [>=0.1cm, <=0.3cm, N0M0, ER-, Her2+, No Chemo, No Herceptin]) = 1-(1/44)=0.977, so a 2.3% likelihood of recurrence (local or distant) in the first 5 years if I choose no adjuvant treatment.

Dr. Jeske contends that neither 2.3% nor 8.5% warrants the risk of significant side effects from chemotherapy or Herceptin.  I will be asking the other oncologists whether they agree.

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