Cyberknife vs IMRT - 1265255

I'm sorry to hear of your wife's diagnosis but am glad she has done so well.

My center has "stereotactic body radiation therapy" (SBRT), also known as "stereotactic ablative body radiation" (SABR), which is essentially the same cyberKnife platform of radiaiton given over 4-5 fractions. I can tell you that we readily favor SBRT/SABR over a longer course of intensity-modulated radiation therapy (IMRT) in patients who are getting a single small focus irradiated, but let me see if a radiation colleague can offer any actual data to speak to this.

One advantage of surgery is that you get tissue for doing any further molecular marker studies and/or just making sure that the histologic findings haven't changed significantly from the initial biopsy. That said, you could also just biopsy the lesion before radiating it.

Good luck.

-Dr. West

We need to get a radiation oncologist to provide input on details. We'll ask Dr. Loiselle to comment.

-Dr. West

Hi kiddoctor -

With all of the acronyms flying around regarding modern era irradiation techniques, it can be hard to sort the wheat from the chaff.

In general, local control of lung tumors is improved with high dose, short course, highly focused radiation. The local control of relatively small, isolated lung tumors is in the range of 90-95% with doses of radiation in the range of 50-60 Gy delivered in three to five fractions. The local control of the same lesion with "conventionally fractionated" radiation is closer to the range of 50% with doses of roughly 60 to 80 Gy delivered in 30-40 fractions.

Thus, the most important consideration here is dose and number of fractions. The high dose treatment is typically referred to as being "stereotactic."

Use of terms like 3DCRT and IMRT typically refer to the longer traditional dose/fractionation patterns, however, these are planning techniques which can be used to ultimately deliver both conventionally fractionated or high dose/stereotactic radiation.

More specifically in terms of equipment, modern systems are good. Varian's truebeam, cyberknife, and elekta's linear accelerators all can deliver high dose treatments well. At times, certain platforms such as cyberknife may offer some advantages. In most cases, you do not need to seek out one specific machine over the other.

I recommend meeting with your radiation oncologist and discussing these issues. Ask their experience with stereotactic radiation and the specifics of their equipment.

I hope that helps.

Dr Loiselle

I'm trying to understand the statement "he local control of relatively small, isolated lung tumors is in the range of 90-95% with doses of radiation in the range of 50-60 Gy delivered in three to five fractions. The local control of the same lesion with “conventionally fractionated” radiation is closer to the range of 50% with doses of roughly 60 to 80 Gy delivered in 30-40 fractions."

in the context of an on-going canada-wide clinical trial Stereotactic Body Radiotherapy Versus Conventional Radiotherapy in Medically-Inoperable Non-Small Lung Cancer Patients (LUSTRE),

which started at the end of 2013 and is still recruiting.

It's purpose is: A multi-centre randomized controlled open-label trial in medically inoperable patients with biopsy-proven early stage non-small cell lung cancer (NSCLC). Eligible and consenting patients will be randomly allocated to receive stereotactic body radiotherapy (SBRT) or conventional radiotherapy (CRT) in a 2:1 ratio. Radiotherapy will be administered as soon as possible following randomization and subjects will be followed for 5 years post-randomization for cancer recurrence, toxicity and survival. The primary outcome is local control (LC). The trial will be conducted at 16-20 clinical centres throughout Canada.

If the results for local control are as unambiguous and clear cut as Dr. Loiselle states then why bother with the clinical trial? It seems highly irresponsible to be subjecting people to treatment that is known to be inferior in the guise of a trial.

Hi onthemark,

I think you raise a very fair question. I can't speak for the trial sponsors, but one rational might be that the trial population is limited to a very specific set of patients with minimal disease, for whom the results may be somewhat less dramatically different. But I suspect it's more an issue of limited availability of the equipment necessary to deliver SBRT, and a resulting desire to see how important it might be to allocate funds to make that equipment more widely available.

I'd have to say, though, that I wouldn't want to opt for conventional radiotherapy over available SBRT, all other considerations being equal.

JimC
Forum moderator

Hi Jim,

Thanks for your answer but I respectfully say it is not really addressing the point I made head on. The full quote by your doctor here refers specifically to local control "In general, local control of lung tumors is improved with high dose, short course, highly focused radiation. The local control of relatively small, isolated lung tumors is in the range of 90-95% with doses of radiation in the range of 50-60 Gy delivered in three to five fractions. The local control of the same lesion with “conventionally fractionated” radiation is closer to the range of 50% with doses of roughly 60 to 80 Gy delivered in 30-40 fractions."

The primary outcome of the clinical trial is local control. The differences sited by Dr. Loiselle (90-95% vs 50%) local control are enormous and could not possibly justify a clinical trial to test local control in lung cancer, in my mind at least. That would already be sufficient justification for investing in more machines. I am wondering if Dr. Loiselle can address this question. If the numbers sited were really justified or not.

I appreciate your desire for a physician to address your question, but the reason we have moved to the current system is that the faculty just don't have the capacity to address individual clinical questions. The highest priority for GRACE is to have the faculty produce content that can reach and help the most people with broadly useful, general information, but it hasn't been feasible or sustainable to have faculty be available on demand to address questions for a single person, as they are all physicians who need to prioritize the care of their own clinic patients -- Dr. Loiselle has a busy clinic and treats patients nearly every day, while also trying to juggle his other commitments. For questions beyond the depth of what we've provided, we need to request that people discuss their specific concerns with their own physician/team.

Jim and Janine have been working mightily to bridge this gap, but we haven't been able to work out a perfect solution, given how busy people are.

Thanks for understanding.

-Dr. West

Might I suggest you read specifically what outcomes for which the trial in Canada is looking. It may answer the question of why. Stereotactic body radiation of lung tissue might more easily cause pneumonitis. Maybe they're looking at harm v benefit. Or looking at the areas of the lung that respond better or more safely. You can find most clinical trials worldwide on clinicaltrials.gov

Sincerely,
Janine

As I wrote the primary outcome is local control. I did get info from clinicaltrials.gov

Does the "Purpose" of the trial give any insight? What trial is it?

Hi Janine,

This is the trial: https://clinicaltrials.gov/ct2/show/NCT01968941

My thought is that SBRT has only recently (past several years) been shown to be very effective and safe in this setting, but the sponsors wanted to compare it head to head versus conventional radiation in the same patient population in order to determine not only relative percentage of local control (stated as the primary endpoint), but toxicity and survival as well. The initial concern with higher dose radiation was damage to healthy tissue.

But since the sponsors have not stated that, we can only speculate.

JimC
Forum moderator

Thanks Jim, got it.

I quoted the name LUSTRE and the purpose from clinicaltrials.gov. in my first post. You have a lot of good information on the site.

I didn't appreciate that you have moved to a current system that was different than in the past. Certainly the moderators here make an awesome contribution. I guess now any readers that hit upon this thread will know it is not a settled issue whether sbrt or conventional radiation is better for lung lesions in lung cancer in terms of local control. At least not by the researchers who are conducting the LUSTRE trial.

As far as that trial in that population is concerned, it may be an open question until the trial results are reported. But other trials have demonstrated the superiority of SBRT described by Dr. Loiselle, for example: https://www.ncbi.nlm.nih.gov/pubmed/20805737

As I stated earlier, without a statement from the trial staff, we can only speculate as to their reasons for conducting this specific trial.

JimC
Forum moderator

Hi Jim,

Thanks for pointing out that paper, which is an early phase study (LUSTRE, the study I have been referring to is phase 3) of the same patient population; stage 1, medically inoperable.

I note that the difference found in the paper you posted at 3 years for local control was not statistically significant (P=0.1).

I discovered today that most, if not all, clinical trials will have a paper describing the purpose and context in detail of the trial before the final results are in.

Indeed LUSTRE has such a paper "Canadian Phase III Randomized Trial of Stereotactic Body Radiotherapy Versus Conventionally Hypofractionated Radiotherapy for Stage I, Medically Inoperable Non?Small-Cell Lung Cancer ? Rationale and Protocol Design for the Ontario Clinical Oncology Group (OCOG)-LUSTRE Trial"

In the abstract they write: "The primary outcome of the study is 3-year local control, which we hypothesize will improve from 75% with CRT to 87.5% with SBRT."

Here CRT is conventional radiotherapy given according to the standard Canadian protocol in 3 weeks.

I guess it's a complex calculation and not all forms of CRT are equivalent but the difference in expected local control they site (87.5% vs. 75%) based on all the information they have, including the earlier trial you posted, is not anywhere close to the 90-95% vs. 50% given above.

Then they write: "Despite widespread interest and adoption of SBRT, there still remains a concern regarding long-term control and risks of toxicity (particularly in patients with centrally located lesions). The OCOG-LUSTRE study is the only randomized phase III trial testing SBRT in a medically inoperable population, and the results of this trial will attempt to prove that the benefits of SBRT outweigh the potential risks."

So the question is if the relatively small expected advantage in local control at 3 years outweigh the risk of later term complications.