When do you consider it too late after lumpectomy to offer adjuvant whole breast radiotherapy?

I don't know if there are studies which have looked at this - to say there is no benefit at a certain time frame. Retrospective studies have shown higher local recurrence with delay of RT with variable time period in those studies (8 weeks to 20 weeks) . The most recent one from British Columbia looking at only early breast cancer showed no difference in local recurrence up until 20 weeks, with HR of about 2 beyond 20 weeks delay. Even though they accounted for risk factors in their model, there may be bias in treating higher risk patients early on and low risk late based on resources. My personal approach for a patient with a delay > 6 months would be to consider RT on a case by case basis, with repeating imaging before any intervention. I have not treated anybody beyond a 12 month delay so far.

The phrase, "The perfect is the enemy of the good" comes to mind...This is always a tough situation, but not uncommon in the "real world", especially with underserved patients.  You hope that someone was proactive enough to place the patient on hormonal therapy if such a delay was anticipated.  There is some registry data out of Canada to suggest that patents with a delay beyond 12 weeks have poorer outcomes, but the impact on the individual patient is unclear.  The current quality metric from the American College of Surgeons Commission on Cancer states: "Radiation therapy is administered within 1 year (365 days) of diagnosis for women under age 70 receiving breast conserving surgery for breast cancer".  Yes, I know this was meant to be broad enough to cover those getting the 4-6 months of cytotoxics, but  at least you've got something to lean on here. I tend to give these patients the benefit of the doubt if they are still within the one-year time frame. If the delay is more than 6 months, I obtain a new mammogram just to rule out any residual/recurrent disease.

This is a great question. I agree with @Dr. First Last, @Dr. First Last and @Dr. First Last. Ideally, adjuvant RT within 8 weeks of surgery is optimal per a meta-analysis by Huang et al looking at timing of RT after surgery. In this meta-analysis, there were 10 studies looking at the interval between surgery and adjuvant RT in patients who underwent BCS. Eight of these studies looked at the difference in LRR in patients treated within 8 weeks and great than 8 weeks. The study fround the a 5 year LRR of 5.8% in patients treated within 8 weeks and 9.1% in those patients treated between 9 and 16 weeks after surgery that corresponded with an odds ratio of 1.62 (95% CI, 1.21 to 2.16).

I agree with @Dr. First Last's response, but I would also add that if the patient has been maintained on hormonal therapy (i.e. tam, AI, etc.), that really improves the argument for doing XRT, even if it's late.  I would argue that you've potentially kept the patient in an oncologically quiescent state in doing so (provided she is receptor positive), and that without doing even late XRT, she'll be at higher risk for recurrence once she comes off the hormonal therapy, if not sooner.  Granted, this isn't an "evidence based" rationale, but it is most certainly logic based.

Hi everyone,

All the answers have been helpful. I have a question on the same line of thought. 

If the time frame is a year since surgery and the person comes for adjuvant radiotherapy, would considering the patient's other risk factors make you inclined towards providing it (for example, very young age, high recurrence score in genetic testing, having mastectomy instead of lumpectomy)?  

I understand there may not be a clear cut answer, but was wondering if this timeframe had passed, would it be wrong to offer radiotherapy if other factors are present?